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.

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