An inventive mechanism: A DNA 'Shapiro change' (Evolution)

by David Turell , Sunday, November 27, 2016, 15:23 (2916 days ago) @ dhw

A marine microorganism appears to have changed its metabolic machinery to reduce stress by removing some enzymes. Enzymes are enormous molecules and take lots of energy to produce:

https://www.sciencedaily.com/releases/2016/11/161115150109.htm

"Researchers from David Karl's laboratory at the University of Hawai'i at Mānoa (UHM) and from Professor Jens Nielsen's laboratory at Chalmers University of Technology in Göteborg, Sweden, developed a computer model which takes into account hundreds of genes, chemical reactions, and compounds required for the survival of Prochlorococcus, the most abundant photosynthetic microbe on the planet. They found that Prochlorococcus has made extensive alterations to its metabolism as a way to reduce its dependence on phosphorus, an element that is essential and often growth-limiting in the ocean.

***

"Microbes are known to employ three basic strategies to compete for limiting elemental resources: cell quotas may be adjusted, stressed cells may synthesize molecules to make more efficient use of available resources, and cells may access alternatives or more costly sources of the nutrient.

"In the case of phosphorus, a limiting resource in vast oceanic regions, the cosmopolitan Prochlorococcus thrives by adopting all three strategies and a fourth, previously unknown strategy.

"'By generating the first detailed model of metabolism for an ecologically important marine microbe, we found that Prochlorococcus has evolved a way to reduce its dependence on phosphate by minimizing the number of enzymes involved in phosphate transformations, thus relieving intracellular demands"

***

"Prochlorococcus has an extremely minimal genome. If it were to lose the function of any one metabolic gene, its survival would be nearly a coin toss. To their surprise, Casey and co-authors discovered that the world's most abundant microbe has performed, through a process called "genome streamlining" -- the concerted loss of frivolous genes over evolutionary time -- a comprehensive re-design of the core metabolic pathways in response to the persistent limitation of phosphorus.

"'The dramatic and widespread change in the metabolic network is really a shock," said Casey. "However, we're seeing that these changes provide a substantial growth advantage for this ubiquitous microbe in phosphorus-limited regions of the ocean, so it seems that where there's a will there's a way."

***

"'We're interested in the underlying principles guiding metabolism and physiology in marine microbes, and that is going to require a deep understanding of not only the 1-dimensional genetic code, but also the 4-dimensional product it codes for," said Casey. "So we're looking to a systems-level approach to incorporate a great variety of physiological and 'omics studies all in one computational structure, with the hope that we can start to learn from the design and interactions of these complex systems.'"

Comment: This modification is just what Shapiro has championed. A dramatic editing of DNA removing the metabolic stress of producing enzymes by finding a simpler way of manufacturing photosynthesis products. Still the same species! Doesn't show how speciation occurs and is no support for Darwin's original thesis.