During the course of evolution, for functional (enzymatic proteins) which has been selected more favorably ? An enzyme with low to high catalytic activity (kinetics, rate, promiscuity and substrate selectivity) or multiple enzymes/ proteins (isoforms, neofunctionalized forms as a compensatory mechanisms) are favored across/ during evolution? Both, -OMICS (genomic, transcriptomic and proteomic) and core-biochemical "thoughts" are welcome as long as they reflect on a genome-wide/ evolutionary perspective.
Dr. Teo's answer was brilliant. We can build in labs enzymes with higher catalytic activities than we found in nature, making small changes in native sequences. So of course this enzyme not evolved to the maximum catalytic activity. Many microorganisms, especially pathogenic ones, instead of to pursue the best performance in one enzyme, has three or four isoforms. This evolutionary strategy overcomes the immune system tricking the defenses.
Interesting question. I am no evolutionary geneticist, but I would have thought that the answer depends upon the selection pressures at the time, the type of "insult", the speed and extent of changing environment (eg rapid change of substrate availability, new substrates etc), life cycle and replication times, the mutation rate, whether the organism can remain dormant for long periods eg in spore forms, is unicellular or multicellular.
There are examples of redundancy eg in DNA repair where maintaining an intact genome is paramount. I guess at the end of the day it is survival of the fittest at the time of sampling. We have no real measure of what we may have lost in terms of genetic / protein variability in the past and what may have been advantageous in terms of protein activity 10 million years ago under different selection pressures could well have been lost by selection since. Redundancy is a good insurance if as an organism you can bear the "genetic burden". If you are constrained by genome size (eg viruses) then the options are more limited.
Off to the Waffle House.......
Dr. Teo's answer was brilliant. We can build in labs enzymes with higher catalytic activities than we found in nature, making small changes in native sequences. So of course this enzyme not evolved to the maximum catalytic activity. Many microorganisms, especially pathogenic ones, instead of to pursue the best performance in one enzyme, has three or four isoforms. This evolutionary strategy overcomes the immune system tricking the defenses.
The field of marine microbiology provides excellent support for Dr Teo's answer that it is dependent on selection pressure. There, we see organisms that encode many proteins with layers of regulatory control (e.g. Vibrio, Roseobacters, Bacteroidetes etc). They tend to be boom-and-bust organisms - opportunitrophs that deal with the extra cost of encoding additional function. They also tend to do well in coastal, nutrient-rich water. When you head out to the ocean gyres, where nutrients are much more limiting, you see far fewer of these organisms. Instead, organisms which have 'streamlined' their genome to reduce replication cost dominate. Such organisms like SAR11 have lost much of their regulatory mechanisms and have incomplete metabolic pathways, relying instead on 'communal goods' (making them much harder to culture axenically). Interestingly, we are now starting to see both of these strategies within the same clades. Coastal SAR11 strains can encode for glycolysis, whereas open ocean strains do not. Indeed, single cell genomics is now finding 'streamlined' versions of Roseobactes and bacteroidetes. This would suggest that such adaptations are not ancient, but are lost and regained as required by the environment. I've attached a couple of papers that you might find interesting.
Article Implications of streamlining theory for microbial ecology
Article Prevalent genome streamlining and latitudinal divergence of ...
Interesting answers Zaira and Ben. Re Ben's 2nd last line" This would suggest that such adaptations are not ancient, but are lost and regained as required by the environment" I have a daft question. When I still had my own teeth, eyes and hair and worked with enthusiasm in the lab, we were always told that it was essential to maintain antibiotic treatment to retain plasmids. As far as I know, no one deviated from this and withheld antibiotics to see how long it was before the plasmids and antibiotic resistance were actually lost completely in the absence of selection pressure (presumably it would depend on differential growth rates). Antibiotic resistance can be acquired by either mutation or horizontal gene transfer and is an increasing problem. If we were to withdraw whole classes of antibiotics, would we get to a stage after x years in the absence of selection pressures, that those defunct antibiotics would again be useful.(i.e how rapidly can loss of function occur when it poses no selective advantage in a unicellular organism). One assumes that with mutation this could take millennia, but with horizontal gene transfer??
Another manifestation of my ignorance - do organism that exist in symbiosis or work co-operatively evolve at the same rate?
- Badges
- Science topic
- Similar topics
- Chemistry
- General Biochemistry
- Proteomics