Genetically modified leaven

[The Leaven – exploring the relationship between science and religion (cont)]

Advances in technology can bring significant medical or agricultural benefits but they are also exploited for commercial gain sometimes with a disregard to any negative impact they may have. In general the introduction of new drugs has benefited human health. The early 1900s witnessed many great advances in chemical therapy. Ehrlich developed a treatment for syphilis in 1907; Fleming discovered the first antibiotic, penicillin in 1920; Domagk found that sulphanilamide could cure septicaemia in 1932. Life expectancy has improved as a consequence of these drugs, in 1935 there were 3,690 deaths in Britain from scarlet fever and diptheria compared to just one death in 1970. Thalidomide was introduced hot on the heels of these discoveries when huge profits could be made from a new drug. Especially in Britain were there was very little regulation of pharmaceuticals.

Ironically, because of extensive screening and restrictions now in place to prevent a reoccurrence of an episode like the thalidomide tragedy, it has become increasingly difficult to bring new drugs on to the market. Therefore, re-evaluating harmful or ineffective drugs for other uses has become an ever increasing trend with pharmaceutical companies. The mechanism behind the teratogenicity of thalidomide has still not been established yet this drug is currently being researched as a possible therapeutic agent for other diseases, such as cancer. Celegene are currently remarketing thalidomide to treat the symptoms of leprosy. It is also effective in the treatment of some myeloma. In the documentation they produce to promote the drug, ‘Thalomid (thalidomide): Balancing the benefits and the risks’, they admit that birth defects still occur in countries where controls and monitoring plans have been inadequate. This brings about another form of controversy, where there is tension between the victim of a disease and a social goal to obliterate thalidomide. The Sunday Times article that the High Court tried to ban ended with this emotional statement:

Many of the main characters who figured in this narrative are now in other employment, thalidomide is only a painful memory. Of the original cast of the tragedy only the victims still occupy the stage.

Thalidomide still retains the ability to promote controversy and to raise issues by the public concerned with the morality of scientists under the influence of commercial gain.

So metaphorically speaking, whose leaven should modern society now be aware of? There are a number of candidates that can permeate a corruptive influence in science, including the media, researchers, commercial companies (pharmaceutical, agricultural), academics, and politicians. The majority of science is fairly mundane and straightforward occurring without grabbing news headlines but occasionally something attracts media attention and becomes headline news. On several occasions in the past, trust in science has been challenged by controversy.

The introduction of genetically manipulated or modified (GM) products into the environment before all research has been effectively collated and publicly distributed, can manifest into controversy. The public may be justifiably cautious of GM food, if there is no benefit in eating it why take a risk? An experiment that is restricted to a laboratory can be controlled and environmental conditions can be manipulated. Once the experiment leaves this controlled confinement of a laboratory it is at the mercy of a number of influencing and unpredictable factors, including commercial profit. It was exactly these factors, combined with the lack of governmental policy, that contributed to thalidomide entering the marketplace.

Following the impact of the BSE crisis, Britain is very cautious about the introduction of GM crops. In the United States GM crops are fairly prevalent, accounting for over 90% of all soybean and rapeseed production. Mostly GM crops are resistant to glyphosate herbicides but there are also GM pest resistant crops. In the US 90% of cotton production is GM for pest resistance. In 2010, 10% of the worlds crop production was GM most of which is grown in the US. Invariably, most of us are unwittingly eating some form of GM food.

Peanut plant containing a bacterial pesticide gene. Lesser cornstalk borer larvae damage the leaves of the unmodified peanut plant (top) but die on the GM plant (bottom). Image: Herb Pilcher

In food production, GM yeasts are available for wine production and in baking. In the UK two products have been approved for commercial use. One in baking to reduce leavening time and the other in  brewing to produce low calorie beer. No GM yeast are currently in use in EU countries. In the US and Canada a GM yeast called ML01 is used to improve taste and colour of wine and to reduce the production of histamines. Additionally, a GM yeast that has been produced to reduce the production of ethylcarbamate, a compound that has carcinogenic properties, has been labelled generally recognised as safe for use in the US. Mostly GM yeasts have non-food usage,they are grown in controlled environments to produce pharmaceticals, chemical compounds and enzymes. They are also increasingly being developed to produce biofuels.

Very little research has been carried out on the safety of consuming GM products. The consequence of eating pesticide containing GM crops, such as maize, is largely unknown. Perhaps scientists are wary about publishing research because they face being academically ostracised.  In 1998, researcher Árpád Pusztai reported changes in the intestines of rats who had eaten a GM potato containing snowdrop lectin, to confer pest resistance. Other scientists argued that there were insufficient controls to determine that the toxin and not the potatoes were detrimental to the rats. As a consequence of his research, Puszatai was suspended from his post and his contract was not renewed. This incident,  known as the Pusztai affair, highlights the extent at which scientists and their research are influenced by corruptive factors.

Leaven continues to evolve

[The Leaven – exploring the relationship between science and religion (cont)]

Yeast has also made a valuable impact in evolutionary biology as it has allowed the mechanisms of evolution to be scrutinised at the molecular level and over short time-scales. In evolutionary terms, fungi, including yeasts, precede mammals and other bilatarians. Bilaterians possess a left and right symmetry of body plan. The two predominate groups, deuterostomes and protostomes, differ from one another in skeletal development. They are believed to have separated in an early stage of evolution estimated to be 670 million years ago. Humans are likely to have diverged from apes only 4 to 5 million years ago. Plants and fungi are thought to have moved from water to land together, the earliest fossils of fungi are in Precambrian rocks dating back 900 million years. Comparing conserved DNA motifs between species of yeasts allows geneticists to estimate the evolution rate of proteins. Yeast can be compared with other yeasts and then with other model organisms such as nematodes or fruit flies. Comparative genomics evaluates the evolution of certain proteins and the processes and complicated pathways that they participate in.

Antibiotic resistance test: Antibiotic impregnated discs are placed on a lawn of Staphylococcus aureus. The width of the halo around each disc represents the efficiency of the antibiotics in clearing the bacterial cells. Image Don Stalons.

Fungal species are susceptible to disease and parasites that they control by producing antibiotics, such as, penicillin. In fact, the microbial world is full of toxins secreted by bacteria and fungi many being used as insecticides and other biological control  agents. Yeast can also be used to study antibiotic resistance. Resistance to antibiotics and other stresses in yeast is often called rapid evolution. As yeast cells can evolve rapidly to overcome environmental challenge they provide a means to study the mechanisms of evolution. In addition the yeast cell susceptibility to mutagens make it an ideal organism to study the effects of mutagenesis and adaptation.

Yeast therefore provides a molecular tool to study cell biology and a model system that can add to our knowledge of evolution. In contrast to yeast in the biblical era, the molecular era now knows a great deal about this organism. In addition to great improvements in disease management, advances in genetics have led to new arguments surrounding the creation of living things, especially in respect to evolution and cloning. Yet, even though it exists as a simple single-celled organism that thousands of researchers have been studying intensely for centuries, a lot remains to be discovered.

Life on earth has evolved over millions of years through a complex network of processes that will take many years to unravel. Whether the molecular information we have derived from yeast is comparable to the corrupt leaven of the Pharisees or the leaven that the women kneaded into the dough to represent the kingdom of heaven (see previous post) has yet to be established.

Yeast produces not only bread and wine

[The Leaven – exploring the relationship between science and religion (cont)]

The last post established why yeast is used as a model organism to study molecular biology but how and what is it used for? The last century saw a molecular enlightenment, yeast was cemented as a key component of that movement. In the 1950’s, molecular biologists constructed a  Saccharomyces cerevisiae strain containing biochemical markers (antibiotic  resistance or amino acid selection) known as S288C from the fig strain mentioned in the previous post, EM93. It was soon discovered that self-replicating elements of DNA found in bacteria called plasmids could also be made to function in yeast. Yeast cells multiply rapidly and the overall effect of a mutation in a certain gene can be measured biochemically or by observation under the microscope. If DNA fused to reporter genes is inserted into the self replicating DNA from bacteria and then introduced into the yeast cell, it can be propagated and then extracted. This technique is called cloning as it replicates an identical copy of a gene, has been used to mass-produce proteins and vaccines. In yeast, cloning was used as early as 1980 to produce Hepatitis B vaccine. Since then it has produced a multitude of proteins and vaccines including: insulin, growth hormone, haemoglobin, oestrogen receptor and interferons.

Cloning can also take place in bacteria such as Escherichia coli, these cells divide faster than mammalian cells but are a lot smaller so there is a limit in the size of the protein that can be cloned. As a consequence of this other cells types are now also used for cloning such as those derived from mammals, insects and viruses. Cloning provides an extremely economical way to reproduce human proteins. They replace the need for animal production and reduce the risk of transferring unwanted diseases, such as, CJD from growth factor. Although great advances have been made, the systems are still not perfect and have their limitations according to the type of protein that can be cloned, as some are toxic to the cell, and introduction of unwanted mutations occurs far more frequently when selection is not acting on the protein. Most organisms, including bacteria, have their own DNA repair systems that detect mutations. Foreign DNA has a higher chance of retaining mutations in a host cell as it is not detected through normal cell function, a problem to biotechnology that is successfully addressed in natural systems by selection. The use of these systems with limitations causes uncertainty and increases risk factors, subjects which are discussed  in future posts. It seems yeast occasionally retains its Biblical ability to behave in a corrupt way.

Protein interactions: Ribonuclease-inhibitor protein grabbing and surrounding the ribonuclease A enzyme. Image by Dcrjsr.

Following the heady days of protein engineering, yeast laboratories, through intra-science communication, successfully completed the enormous challenge to complete the first fully sequenced eukaryotic genome. This was achieved using strain S288C and relatively archaic apparatus compared to the robotic systems used to decode the human genome. Eventually, over 6,000 genes were unravelled from the yeast nucleus. The yeast genome is 200 times smaller than the human genome but almost four times larger than that of E. coli. This achievement marked a milestone in biological history. Yeast biologists did not stop at just sequencing the genome. In a striking example of inter-organisation collaboration, nominated laboratories began deleting single genes from individual yeast cells through advances in polymerase chain reaction (PCR), a technique that can amplify a single gene from the cells DNA. A marker/reporter gene flanked by target DNA is amplified by PCR technique and then inserted into the yeast cell. Non-homologous recombination replaces the genomic gene with the introduced marker/reporter gene. Biochemical tests were then carried out on the mutant yeast strains to uncover the functional analysis of hundreds of different gene products. This work elucidated many gene functions and undoubtedly contributed to the discovery of many analogous human genes. This information has been collated into several databases to provide a plethora of data available for bioinformatics across the internet. Genes placed on microarray slides and subjected to various environmental conditions and variations of DNA recombination techniques have increased the quantity of this information, enabling researchers to compose complicated hypotheses and uncover new cell processes without even entering a laboratory.

Many would expect yeast’s contribution to scientific research to stop at this point. Exhausted by constant, investigative probing. In contrast, the yeast story continues. It has also been used as a vehicle to investigate protein interactions first with native yeast proteins and then later with proteins from any other organism. Genes can be fused to protein tags, introduced into yeast cells and reporter genes within the cell can detect if the proteins produced from the introduced DNA interact. This procedure is known as the yeast 2-hybrid technique. Several variations to this technique exist, again modifying it to be used in other in cell cultures from other organisms. These techniques, in a rudimentary way, can also be used to evaluate post-translational modifications in proteins, to see how gene products are modified by the cell. Compared to the amount of gene sequencing data available the amount of protein interaction data is still fairly incomplete with the function of many gene products still unknown.

From figs trees to laboratories

[The Leaven – exploring the relationship between science and religion (cont)]

The development of yeast molecular biology can literally be used to assess the impact that the application of scientific research has had on 21st century society. Scientific researchers often describe yeast as the workhorse of eukaryotic molecular biology with many laboratories devoted to studying this single-celled organism, as much of the information derived from it can be equally applied to the study of human cells.

Most modern laboratory strains of yeast originate from one particular Saccharomyces cerevisiae strain, EM93, isolated from dried figs in Merced, California in the 1930’s by Emil Mrak. This strain turned out to be heterothallic, meaning that cells existed as two types of sterile haploids, with a single copy of each gene, that when fused together formed a fertile diploid that could perform meiosis in a similar way to that seen in human cells. Up until this point most strains studied were homothallic, this meant that all haploid cells were of the same mating type and capable of fusing together to form a fertile cell known as a zygote. The emergence of a heterothallic strain meant that the genetic stability of a culture could be placed under greater control, as it would remain haploid until the other haploid type was introduced and then through the production of mating phermones followed by cell fusion a diploid cell could be created.

Green Fluorescent reporter gene in yeast cells. Image: bio+ve

So why has yeast become such a popular organism to study molecular biology and why is this microbe chosen in favour of others microorganisms? Firstly, Saccharomyces is non-pathogenic and does not present a threat to human safety. Therefore laboratory workers do not require expensive protective equipment to practice research. Saccharomyces is also easy to contain as is not usually airborne unless transported involuntarily by animals and insects. Another reason  is the ease by which it is cultured. Yeast can be grown easily and only requires a suitable carbon source, nutrients and appropriate physical conditions to continue multiplying. Additionally, these requirements can also be used to control the rate of cell division, for instance, by altering temperature or by creating metabolic mutants. Mutants are generated either through using a mutagen or by manipulating DNA through genetic engineering. Genes involved in yeast metabolism can be mutated and then used as molecular markers. For instance if the genes for the requirement of an essential amino acid are defective then the yeast will not grow without that amino acid added to its immediate environment. If the defective gene is artificially replaced by a functional one then the yeast cell will be able to continue growing without the need for that particular amino acid. Armed with this knowledge researchers are able to introduce fragments of DNA fused to these marker or reporter genes. If the yeast is able to grow without the selected amino acid this means that the DNA of interest to the researcher has been successfully introduced into the cell. This approach has led to the characterisation of countless genes and proteins in yeast and from other organisms.

Another reason why yeast is used as a molecular model system alongside other well-known microbes, such as Escherichia coli, is because it is a eukaryote. E. coli and other bacteria are prokaryotes, in contrast to eukaryotes they only have one chromosome housed in a cell without a nucleus. In yeast cells, DNA is packaged in chromosomes stored in a nucleus in a similar way as in human cells. Yeast has 16 individual chromosomes compared to 23 in humans. Surprisingly, there are only four chromosomes in the multi-celled fruit fly Drosophila another model organism used for biological research. Yeast also has the advantage of being able to grow just as happily with one set of chromosomes, in haploid cells, as with two or more sets of chromosomes, diploid and polyploid respectively. Additionally, as yeast is a single celled organism without the complexity of cellular differentiation it can be used to study the cell-cycle at a fundamental level. It can be used to study mitosis and meiosis. Many mutations that cause human disease are introduced during meiosis. Following cell fusion or mating, two haploid cells form diploids which can produce four individual haploid cells known collectively as an ascospore. After microscopic dissection of the ascospores, researchers can study recessive mutations and the complicated exchange of genetic material during meiosis by counting the numbers of surviving progeny. The information derived from yeast studies aids the study of genes involved in tissue development and cell differentiation in higher eukaryotes, such as Drosophila. Adding to all these factors many of the biochemical and cellular functions in yeast are conserved in human cells. Yeast therefore is a simple and practical system to study the mechanism of human cell division.

Leaven in a molecular era.

[The Leaven – exploring the relationship between science and religion (cont)]

Not only does yeast now serve as one of the most important organisms throughout domestic history, in recent years it has also substantially contributed to biological research. The numerous molecular techniques that have evolved in yeast have allowed it to make an important contribution to a number of areas in science. Through studying various types of yeast and other microbes, scientists now know a great deal about the molecular processes involved in cell division, rapid evolution and disease.

Fortunately, individuals with skin diseases are no longer thought of as unclean and are normally treated within the community. Scientists have greater understanding of disease management and although quarantine and hygiene are still practiced they are now carried out in order to reduce disease transmission. In the majority of cases, people are not ostracised when they are infected by disease, although fears and anxieties can still be generated through sensational media coverage. Nevertheless, even in this molecular age, some transmissible diseases are still associated with sins of the flesh and can lead to social ostracisation.

Yeast colonies in an array. Each spot contains thousands of yeast cells. The plate shows synthetic lethal interactions when the interaction of 2 or more genes cause cell death (shown by colonies with reduced/no growth colonies). Image uploaded by Masur

There are still many diseases that generate fear because they are untreatable. Some of these have evolved through human activities, such as Bovine spongiform encepthalopathy (BSE) which gives rise to a human form of spongiform encepthalopathy called variant Creutzfeldt-Jakob Disease (CJD). The causative agent of BSE is a defective version of a protein called prion that is similar to one found in the brains of sheep with Scrapies. The prion protein is transmitted horizontically and causes disease through disrupting the normal function of the native protein. Studying the molecular mechanisms by which proteins change conformation to become prions in yeast has led to a greater understanding in the pathology of this disease. Many other human diseases, especially cancers, can be researched by studying molecular processes first in yeast.

Cancers arise when cells begin to divide abnormally due to mutations in DNA. Cancer research investigates the mechanisms that encourage these mutations to arise. The mechanism of cell division is often studied in fission yeast, Schizosaccharomyces pombe. Unlike Saccharomyces cerevisiae, which divides by budding, S. pombe divides symmetrically in a similar way to human cells. Fission yeast originates from Africa were it is found growing on banana skins and is used to ferment beer. Through research in this area scientists have reached many milestones in the mechanisms that have caused various cancers leading to greatly improved clinical treatments. Work yeast genetics has greatly contributed to our understanding of cell cycle research and has led to the award of a Nobel prize in 2001 to three scientists who led pioneering work in this area: Paul Nurse, for his work in S. pombe and human model systems; Leland Hartwell, for his work in S. cerevisiae; and Tim Hunt who used sea urchins as a model system. Researchers later found similar cell division genes in human genomes.

Scanning electron micrographs of Fission yeast (Schizosaccharomyces pombe). Image by David O Morgan.

In addition to investigating diseases, yeast is also used as a model system to research ageing. Saccharomyces cells can divide by budding a number of times but the new bud is always physiologically younger than the mother cell. Each cell produces about thirty buds depending on the environmental conditions and other factors. About thirty genes in yeast have already been found to be involved in ageing. The main factors seem to be related to metabolic capacity, resistance to stress, gene dysregulation and genetic stability. Encountering certain environments that would overload any of these factors would also affect longevity. For instance, excessive oxidative damage or radioactivity would lead to a high level of mutations that will reduce the number of times that a cell can bud. Excessive oxidation is associated with the consumption of calories; so caloric restriction should result in increased longevity. This has been demonstrated in yeast, limiting the amount of nutrients and carbohydrates available in growth medium leads to a longer generation time and life span.

Be filled with the spirit

[The Leaven – exploring the relationship between science and religion (cont)]

The words for wine used in the New Testament are oinos, a Greek term for completely fermented wine, and gleukos, used to denote new or sweet wine with less alcohol content. Gleukos as a reference to wine that has been drunk is only mentioned one time in the New Testament [Acts 2.13]. In the context of this passage the apostles were behaving in an unusual way because they were full of the Holy Spirit. Onlooker’s accused them of behaving as if they were drunk on gleukos because of how their behaviour had changed with no alcohol being present.

Biblical society viewed wine in a similar way to how it is currently perceived. They were aware that over indulgence could be harmful  but generally it was socially accepted. The New Testament attempts to rescue individuals from a drunken abyss by suggesting that they should be filled with a different kind of spirit:

Do not get drunk with wine, which will only ruin you; instead, be filled with the Spirit.
[Eph. 5.18]

In a comparatively brutal manner the Old Testament illustrates and blatantly condemns the consequences of intoxication:

The Lord God said to me, “Jeremiah, tell the people of Israel that every wine-jar should be filled with wine. They will answer that they know every wine-jar should be filled with wine. Then tell them that I, the Lord, am going to fill the people in the land with wine until they are drunk: the kings, who are David’s descendants, the priests, the prophets, and all the people of Jerusalem. Then I will smash them like jars against one another, old and young alike. No pity, compassion, or mercy will stop me from killing them.”
[Jer. 13.12-15]

The Roman’s took wine very seriously, to the extent that they even had a deity assigned to it, Bacchus. Even so some social groups were discouraged from drinking alcohol. For instance, women, in the early day of the Republic, were forbidden from drinking ordinary wine but were permitted to drink those with low alcohol content. There were a number of ways that the alcoholic content of wine could be reduced. Fermentation could be inhibited by increasing sugar content. The Romans called this beverage defrutum. Grape juice with enough sweetness to remain unfermented can be made by pressing dried grapes. Pliny refers to a raisin-wine, made from grapes dried to half their weight. Roman women also drank a wine alternative made of raisins called passum. Another method to reduce wine alcoholic content was to prevent the yeast from growing. Vinous fermentation occurs only within a certain temperature range, the lower limit is about 15°C. If cooled wine were allowed to sit undisturbed, the clear juice could be removed from the sediment and would remain unfermented. Another method of making a nonalcoholic wine was by adding salt, a process favoured by the Greeks and described by several classical authors (Cato, Columella and Pliny), this method was also used to preserve the must. Alcohol evaporates at below 100°C, so could be physically removed from the wine by heating. Pliny describes another drink called adynamon, made by adding water to wine and boiling the mixture until the quantity was considerably reduced. This provided a fortifying drink for invalids.

Bacchus, Roman God of Wine. Caravaggio, 1596

It is believed that the Hebrews were also familiar with preserving wine by boiling down grape juice to a thick syrup like molasses. The boiling process would also remove any microbial contaminants from the grapes. The syrup would be diluted with water as a drink or added to wine must.  Some of the Biblical references to honey debash could be referring to a sweet grape syrup. The Hebrew debash is similar to Arabic dibs, a sweet syrup made by boiling down the juice of grapes, raisins or dates.

In moderate use the social impact of yeast is beneficial but alcoholism is becoming a modern scourge of the 21st century replacing the problems caused by microbial diseases. In a recent study conducted by the World Health Organisation, the long-term health burden of alcohol related disease surpasses smoking and malnutrition. The countries that produce the highest quota of alcohol last century were the USA (beer), China (spirits) and France (wine). The leading exporter of alcohol was Great Britain, which exports nearly twice as much as France in second place. The total consumption of alcohol increased in Great Britain between the 1970’s and 1990’s while in France it decreased. However, in the 1990’s the French were still more likely to consume more alcohol per capita than the British, 14% compared to 9%.  In general, the Bible portrays the message that drinking wine is an acceptable part of every day life  but its increased accessibility by modern preservation and production methods seem to have created new social challenges.

Is wine considered leavened?

[The Leaven – exploring the relationship between science and religion (cont)]

As leaven was seen as an impurity that symbolised corruption only unleavened bread is used to celebrate the Passover and to symbolise the body of Christ. The symbolic use of wine in the present Eucharist originated from the words of Jesus at the last supper, which occurred during the feast of unleavened bread:

As the disciples were eating, Christ took bread and blessed it, he broke it and shared it amongst the disciples saying “Take and eat it,” he said; “ this is my body.” He then took the cup, gave thanks to God and passed it to them. “Drink ye all of it; for this is my blood of the covenant, which is shed for many for the remission of sins. But I say unto you, I will not drink henceforth of this fruit of the vine, until that day when I drink it new with you in my Father’s kingdom.”
[Mt. 26.26-29; Mk. 14.22-26; Lk. 22.14-20; 1 Cor. 11.23-25]

At this stage Jesus was committed to his fate, he would be condemned to death. He persistently associated with people that were unclean; he did not observe strict ritual procedures such as hand washing; he disrupted the traditions of the Temple; and was constantly defamatory towards the policies of the Pharisees and Sadducees. He was a negative influence that had to be eliminated. It was the role of the High Priest to sanction and condemn those that had not obeyed the Torah. Jesus already knew that one of his disciples had betrayed him to the high priest so took it upon himself to play the role of Passover sacrificial lamb. It is evident from Biblical accounts that Jesus was condemned before the Passover as it was against Jewish tradition to execute during a religious festival or on the Sabbath:

Then the chief priests and the elders met together in the palace of Caiaphas, the High Priest, and made plans to arrest Jesus secretly and put him to death. “We must not do it during the festival,” they said, “or the people will riot.”
[Mt. 26.3-5; Mk. 14.1-2; Lk. 22.1-2; Jn. 11.45-53]

Ironically, this meal is far more poignant as it takes place just before a festival that commemorates the Jews freedom from persecution. Jesus refers to himself as the sacrificial animal used in the traditional ceremony and to the wine as the sacrificial blood but in this instance the destroyer did not pass over (see previous post). Following the meal, Jesus and his disciples retired to the Mount of Olives . Here, the High Priest’s servants apprehended Jesus  after being  led to him by the disloyal disciple Judas Iscariot. He was brought before the High Priest and the Sanhedrin, the Jewish court that tries those who disobey the Torah, and charged with threatening to destroy the Temple and with blasphemy

Behold the man. Bosch c1475

The Sanhedrin delivered Jesus to the Roman procurator, Pontius Pilate, on the grounds that he was claiming to be the King of the Jews and a potential rebel. Roman and Jewish religions would probably have had a very contrasting outlook and therefore Pilate was reluctant to condemn Jesus. Perhaps Pilate shared many viewpoints with Jesus in regard to the Jewish religion and therefore asked the crowd if he should be set free. The crowd responded unfavourably. He was condemned to death by crucifixion, a Roman method of execution. Fearing  retribution the disciples denied their beliefs when interrogated by the Pharisees, but following the death of Jesus continued to preach his teachings in exile.

The modern Eucharist was established to serve as a reminder of how Jesus gave his life in return for his convictions. In many aspects this religious ceremony seems to go against the philosophies of Jesus by its ritual connotations and sectarian exclusiveness. Perhaps serving  more as a means of retaining ceremonial sacrifices and symbolic worship favoured by the Pharisees that were originally rejected in the teachings of Jesus. In the Eucharist, wine is used to symbolise the blood of Christ but grape juice is sometimes substituted on moral grounds. Many disagree with this principle and regard grape juice as a leavened drink because it has the potential to ferment. Some believe it  is  impure and it gives rise to objections when it is used symbolically to represent the blood of Christ. Their argument is that wine that has fermented is physically separated from the yeast containing sediment. It is seen as having had the leaven removed and no longer has the potential to ferment, it is predominately thought of as unleavened. Those that follow the doctrines of a Christian religion but strongly object to the moral use of alcohol put forward the argument that the wine used by Christ to represent his blood is a non-alcoholic grape juice.

In the New Testament messages are communicated so that they are accessible to those that they are expected to influence. If there were a spiritual objection to drinking alcoholic wine than surely these ideals would be put forward in Biblical teachings? Additionally, if this were the case,  why not  use water as the pure and sinless drink in the last supper? The Hebrews seemed to have an innate sense of disease prevention. In sacrifices they used animals that had no blemishes, they ostracised those individuals that were viewed as unclean, they removed potential microbial contaminants, such as leaven, from food. Water in that era would have been the source of many contaminants and likely to contain as many microbes as leaven, therefore wine would be less likely to cause disease. Water could therefore be interpreted, as a disease-causing agent in contrast wine would have been  associated with disease prevention. As the processes behind diseases were unknown they were attributed to acts of retribution by angry deities. In the disease-ridden Biblical era,  a gift of wine to the Lord would perhaps have been perceived as more suitable than a gift of murky water.

The Blood of Christ

[The Leaven – exploring the relationship between science and religion (cont)]

In the molecular era, it is now known that fermentation is not only responsible for the leavening of bread but it is also the principle process in brewing and wine making. It ‘s worthwhile taking time to consider how wine was perceived in the biblical era and how its use is viewed in current religious ceremony. Present society now understands that the intoxicating agent of wine is alcohol, a by-product of the yeast fermentation process. It is also understood that unfermented fresh grape juice, or must, is relatively free from alcohol. These principles were not understood by ancient societies, as the knowledge behind the biology of fermentation did not exist. When leaven is used in making bread it is viewed as an impurity and therefore omitted from many sacrificial ceremonies. In contrast wine, which is also produced by a similar fermentation process involving yeast, was not only permitted in sacrifices but was sometimes a principal component.

Monk drinking wine. Grod c1800.

Wine production occurs naturally in the environment. Grape skins are covered with yeasts and bacteria, mainly members of  the yeast family Saccharomyces. When grapes are crushed they ferment, especially in warm climates as yeast fermentation occurs between 20 and 40°C with an optimum growth temperature of around 30°C. The main fermentation is aerobic and takes a few days. It then  continues anaerobically at a slower rate for some time. When fermentation is complete the resulting wine is racked from the sediment, a substance containing precipitated organic matter and yeast. In the biblical era wine is produced in animal skins or in jars designed specifically for the fermentation process. In the New Testament the fermentative characteristics of wine were well recognised as is evident in some of the passages. The following parable uses the properties of fermentation to describe how a flexible way of thinking was needed to accept new and fresh ideas:

Nor does anyone pour new wine into used wineskins, for the skins will burst, the wine will pour out, and the skins will be ruined. Instead, new wine is poured into fresh wineskins, and both will keep in good condition
[Matt. 9.17; Mk. 2.22; Lk. 5.37]

Wine is not referred to in the Bible as leaven or unleavened although it does feature in sacrifices and rituals. In the Old Testament it is used in large quantities as part of a daily sacrificial offering that also included animals and unleavened bread [Ex.29.38-46; Num. 28.1-8]. Wine is also offered on the Sabbath and on the first day of the month, where the quantity varies depending on the type of animal used in the sacrifice . Most notably, wine was offered in the daily sacrifice during the festival of the unleavened bread:

The proper wine-offering is two measures of wine with each bull, one and a half measures with the ram, and one measure with each lamb.
[Num. 28.9-15]

It does seem, in respect to sacrifices, that leaven was not associated with wine in the same way as it is associated with bread. Perhaps this is because the process of wine production was not as accessible to the overall population as bread making, therefore it is less likely to be used in domestic ceremonies due to lack of availability. Also as wine is intoxicating and bread is not,  perhaps fermentation in bread was simply thought of as a different process. In addition wine is rarely associated with food poisoning although it is possible for some microbial toxins to be found in wine. Generally if wine becomes contaminated during fermentation it is undrinkable and becomes cloudy, perhaps at this stage it might have been viewed as impure and corrupt. Pathogenic microbes usually require an optimal pH similar to that found in animals, this is why ethanol with a high pH is normally used in sterilisation. In fact this could be the reason why alcohol, similarly to salt, is used in these sacrifices, for its ability to sterilise and remove contamination.

…heavenly bread making

[The Leaven – exploring the relationship between science and religion (cont)]

Leaven when used figuratively in the bible is most often used to denote something that is corrupt. The initial conception of it in the leaven parable (see previous post) is of a favourable component in the dough, this implies that Jesus is contradicting its symbolic use in the Bible.

The Leaven Parable. Illustration by Jan Luyken from the Bowyer Bible.

This parable could be interpreted in many ways. The leaven is taken by the woman and hidden in the meal or flour. The leaven may represent the subtle way that evil can permeate through the dough. In this manner leaven still represents something that corrupts, disintegrates and breaks up. The woman is impregnating the pure symbol of heaven symbolised by the meal with evil symbolised by the leaven. The first indication that leaven was associated with corruption in the Bible was when Lot baked unleavened bread for the angels:

But he insisted so strongly that they did go with him and entered his house. He prepared a meal for them, baking bread without leaven, and they ate.
[Gen. 19.3].

Lot did not give leavened bread to the angels because he did not want to offer them anything containing impurities. The next reference to leaven is in the book of Exodus when the Hebrews left Egypt. They received a command from the Lord, through Moses, not to eat leavened bread for seven days. Similar sentiments occur in later sections of the Bible when the Lord demands that leaven should not be offered in sacrifices to him.

Do not offer bread made with leaven when you sacrifice an animal to me. Do not keep until morning any part of an animal killed at the Passover festival.
[Ex. 34.25].

Leaven was excluded from any sacrifice because it was thought of as a contaminant that did not reflect sinlessness. Leaven  during the Biblical era would have contained many undesirable elements in addition to microbes that fermented bread dough. It’s unlikely that the primitive baking processes used at that time would have destroyed all pathogenic microbes and therefore there was the potential for leaven in bread to transmit diseases. This is perhaps why it earned such a bad reputation and why people tended not to offer it to guests during festivals or at other times. Perhaps one person’s leaven was another person’s poison. Interestingly, animal sacrifices were disposed of before they started to decompose or they could become contaminated also. Perhaps there was the additional fear that Egyptians would look unfavourably upon this practice and there would be consequences for  the Hebrews if they were caught with animal remains:

If we use these animals and offend the Egyptians by sacrificing them where they can see us, we will be stoned  to death. We must travel three days into the desert to offer sacrifices to the Lord our God, just as he commanded us.
[Ex. 8.26-27]

The words leaven and unleavened occur over sixty times in the Old Testament and nearly twenty times in the New Testament. In every instance, except for in the leaven parable, it is used to denote something corrupt or sinful. Mostly, Jesus  uses leaven  figuratively in the same way as it is used in the Old Testament to denote corruption. For instance, Jesus compares the doctrines of the Pharisees with leaven:

Be on guard against the leaven of the Pharisees, I mean their hypocrisy.
[Lk. 12.1]

In Mark’s gospel  “and the leaven of Herod” is added to the above quote [Mk 8.14-15].  According to Lockyer the leaven of the Pharisees can be interpreted to represent the hypocritical formality and ritual of their beliefs. The leaven of the Sadducees was rationalism and the denial of supernatural events. The leaven of Herod was the consequence of these two doctrines, a departure from God and his teachings to a devotion of secularism and indulgence.

Throughout history the nature of leaven has led it to be seen with similar connotations. A rabbi reportedly said “Trust not a proselyte till twenty-four generations, for he holds his leaven.” Here leaven is used as a symbol of hostile infidelity. It was also used by the Talmund to signify “Evil affections and the naughtiness of the heart.” The ancient interpretation of leaven by the Greek historian, Plutarch, presented a figurative meaning that had similar connotations:

Leaven is both generated by corruption, and also corrupts the mass with which it is mingled.

Paul‘s also uses leaven to illustrate corruption[1 Cor. 5.6].  Paul encouraged the purging of a sinful man because if his sins remained unpunished they would spread amongst the group. This statement by Paul cements the traditional meaning associated with leaven of being  a corruptive persuasive and a permeating influence.

Of the leaven parable Martin Luther states that:

Our Lord wishes to comfort us with this similitude, and gives us to understand that, when the Gospel, as a piece of new leaven, has once mixed itself with the human race, which is the dough, it will never cease till the end of the world, but will make its way through the whole mass of those who are to be saved, despite of all the gates of Hell. Just as it is impossible for the sourness, which it has once mingled itself with the dough, ever again to be separated from it, because it has changed the nature of the dough, so it is also impossible for Christians to be ever torn from Christ. For Christ, as a piece of leaven, is so incorporated with them that they form with Him one body, one mass… leaven is also the Word which renews men.

Martin Luther assumes that leaven is used merely for its permeating quality and not in relation to corruption. He has interpreted leaven in this parable as depicting faith rather than corruption. Christ is the piece of leaven that is incorporated into the dough, which is portrayed as the human race. Once the leaven has mingled into the dough it can never be separated.

The Leaven Parable

[The Leaven – exploring the relationship between science and religion (cont)]

Then the disciples came to Jesus and asked him, “Why do you use parables when you talk to the people?” Jesus answered, “The knowledge about the secrets of the Kingdom of heaven have been given to you, but not to them. For the person who has something will be given more, so that he will have more than enough; but the person who has nothing will have taken away from him even the little he has. The reason I use parables in talking to them is that they look, but do not see, and they listen, but do not hear or understand. So the prophecy of Isaiah applies to them:

‘This people will listen and listen, but not understand; they will look and look, but not see, because their minds are dull, and they have stopped up their ears and have closed their eyes. Otherwise, their eyes would see, their ears would hear, their minds would understand, and they would turn to me, says God, and I would heal them.’

As for you, how fortunate you are! Your eyes see and your ears hear. I assure you that many prophets and many of God’s people wanted very much to see what you see, but they could not, and to hear what you hear, but they did not [Mk 4.10-12; Lk 8.9-10; Matt 13.10-16].”

Jesus’ teachings and philosophies are predominately analogical; he tried to encourage new insights by allowing people to draw comparisons with familiar situations. Perhaps this is why simple foodstuffs and domestic chores feature so many times in the Bible. It is fairly evident that his preferred audience are not the wealthy or powerful so many of the terms he uses are familiar to them. By using parables he is encouraging freedom of thought in an imaginative style that would appeal to this audience. Parables encourage self-assessment, are memorable and others could pass the stories through the community. Moreover, they would permeate through society in a leaven-like manner.

Return of the prodigal son. Rembrandt, 1665.

The parables also tend to be grouped together by subject manner. For instance the parable of the Lost Sheep is grouped with the parable of the Lost Coin and the parable of the Lost Son [Lk.15]. These parables all deal with the issue of finding belief when it has been lost. In the Lost Sheep Jesus describes how joyous a shepherd is when one of his sheep strays and is found even though he has several that are not lost. Similarly, in the parable of the Lost Coin a woman loses one of her few coins searches frantically for it and rejoices when it is rediscovered. In the final parable a father celebrates when a sinful son repents, he was lost and then was found. Some of the parables are told within the context of life at that particular time in history, perhaps referring to a current or political situation. Therefore, the parables are sometimes difficult to interpret accurately.

The Leaven parable, mentioned by Mathew and Luke, is grouped with several parables describing the Kingdom of Heaven, such as the parable of Weeds [Matt. 13.24-47] and the parable of the Mustard Seed [Mk. 4.30-32, Matt. 13.31-32; Lk. 13.18-19]. In each of these parables the coming of heaven could be interpreted as the end product resulting from the growth of all these items; the leavened loaf of bread, the weed-free harvest and the fully-grown tree from a mustard seed. The parable of Weeds describes how the Kingdom of Heaven is compared to a field sown only with good seed. Any weeds that grow represent evil and are separated from the crop to be destroyed by the harvesters. In the context of the era leaven may have had a different connotation. The parable of the Leaven consists of just two sentences:

“The Kingdom of heaven is like this. A woman takes some leaven and hid it in three measures of meal until the whole batch of dough rises”
[Matt. 13.33; Lk. 13.20]

To many this parable is thought to illustrate how the Gospel will slowly permeate through society until all is converted to Christianity. This is in contradiction to how leaven is usually interpreted in the bible, to symbolically represent corruption. The leaven parable can be divided into three component parts: the leaven, the woman and the meal or flour. Each of these component parts plays a different role in the message being conveyed within the parable and are discussed separately in following posts.