This is the first in an ongoing series about recent discoveries and commentaries concerning aspects of evolution that affect our everyday lives. On the one hand, it’s a fun way to showcase some of the recent goings-on in the literature, and on the other, it’s a way to rebut the occasional creationist claim that evolution isn’t important to biology or to science at large. That assertion is false, and would be irrelevant even if true, but in my opinion (and I suspect this is true of most of us here), the aspects of evolution that affect our day-to-day lives are the most fascinating.
Consider the existence of man-made pollutants. Since the advent of modern chemistry, humans have found ways of making new and useful chemicals that can’t be found in nature. Unfortunately, part of what makes a chemical useful is its ability to resist breaking-down. And if it happens that such a chemical gets produced in huge quantities, and that some of this quantity manages to make its way out into our environment, it can be quite a hazard to human and environmental health. The resistance to degradation becomes a part of the problem, because these chemicals can accumulate over many years to the point where they become toxic. It’s therefore important for us to understand methods by which these compounds can be eliminated.
Fortunately, our bacterial friends have evolved ways of dealing with many of the persistent pollutants that have been dumped into the environment. In a just published review in the Journal of Biological Chemistry, Lawrence Wackett of the University of Minnesota describes some of the enzymes that microbes have evolved to digest these man-made chemicals. Unlike enzymes that evolved gillions of years ago, many of which have histories that are impossible to reconstruct, these enzymes show signs of having evolved quite recently. Wackett notes:
Another lesson being learned from biodegradation studies is that functionally significant enzyme evolution occurs on shorter time scales than previously appreciated; weeks, months and years rather than eons.
9 Comments
Nick · 24 June 2004
Spiffy post Steve. Folks who want to investigate further can look at the the articles "Related To" Wackett's article on PubMed.
Nick · 24 June 2004
Just skimmed the paper. He hits several of the good examples -- PCP degradation, atrazine degradation, etc. The only weird bit is Wackett's analogy between the immune system and the global "system" of bacterial metabolism. There are some similarities but overall the analogy is swamped by disanalogies. Bacteria will pump out poisons as happily as they degrade them -- oxygen in the atmosphere 2.5 billion years ago being exhibit A, resulting in a great many prokaryote lineages being reduced to refugees in tiny anoxic niches in the modern world (and perhaps provoking several "snowball earth" events to boot). It all depends on your perspective...
cs · 25 June 2004
I'm curious, why would a newly-evolved gene be expected to lose its regulatory apparatus? Wouldn't it be most likely to keep the regulatory apparatus of the "original" gene that it evolved from?
Tom H. · 25 June 2004
Nice article.
steve · 25 June 2004
PubMed should really be celebrated. I have access to all these expensive databases through the university, yet I keep returning to pubmed for papers, sequences, etc. Good Job NIH!
steve · 25 June 2004
"Posted by cs on June 25, 2004 09:59 AM
I'm curious, why would a newly-evolved gene be expected to lose its regulatory apparatus? Wouldn't it be most likely to keep the regulatory apparatus of the "original" gene that it evolved from?"
Good question. I just glanced at the literature and couldn't find an answer. Hopefully one of the bio guys will give us a good answer.
Ian Menzies · 26 June 2004
While IANAB, I think they're talking about new genes which come about when existing genes are duplicated. A gene duplication would not necessarily include the regulatory apparatus, since that is a seperate stretch of DNA. This is especially true in the case of transcribed RNA being re-inserted into the genome since the regulatory apparatus itself is never transcribed into RNA.
I think.
michael · 26 June 2004
I haven't read the article but a brief (and thoroughly undergraduate ) hypothesis may be to do with selectivity for regulation.
first of all I would assume that the bacteria would have evolved in highly PCP saturated areas where there would be no need to turn off the regulation (except at certain times in the cell cycle)
secondly It is unlikely that the regulatory system would be 'in tune' with the demands related to PCP metabolism, and despite the inefficencies of not having proper regulation, unregulated genes would have more efficency in metabolising PCP's than 'regulated' ones that are being turned on and off in response to other stimulii
Steve Reuland · 28 June 2004