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Author Topic:   AIG has an article up on the nylon-digesting bacteria
Trixie
Member (Idle past 3706 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004


Message 9 of 27 (98976)
04-09-2004 7:26 PM
Reply to: Message 8 by Loudmouth
04-09-2004 12:58 PM


Re: Random Mutation
I can't believe that I've spent a Friday evening (Good Friday at that) doing literature searches and Entrez and Blast searches on this blasted bug!!! Also on Pseudomonas. Ho hum, what fun!!! Anyway, first thing to say is that some of the information in the AIG article and some of the interpretations don't make a lot of sense. I had intended to disect it, but my DNA analysis software has led me a merry dance on the sequence alignments and translations in all three reading frames and I don't have time tonight. Hopefully I'll get back to it tomorrow (toddler and his disease permitting).
One thing I will say with regards to the genes in question residing on plasmids and not the Chromosome is that the effects of selection pressure on plasmids in bugs are so much more readily seen. Carrying a plasmid is a bioburden on a bug - it has to use valuable resources copying the pasmid as well as the chromosome when it divides. In an environment devoid of nylon, those bugswhich have the nylon digesting enzyme gene on a plasmid are at a distinct reproductive disadvantage and so become less numerous in the population. However, possession of the pasmid in these conditions is not lethal and so the odd one or two will still carry copies. If all other carbon and nitrogen sources run out and only nylon remains, these very few are now at a distinct advantage, even with their bioburden and so they become more numerous. Under these conditions the non-possession of the plasmid IS lethal because the bugs will starve. Eventually, the entire population in the given environment will contain the plasmid. So, although the bug doesn't change into another species or become extinct, evolution can be seen in the behaviour of the plasmid withn the bugs, even although the plasmid doesn't change its DNA sequence. There is no mutation involved, as no offspring will contain information that the parent didn't, since the parent MUST have the plasmid for the offspring to have it (I believe this plasmid is non-conjugative). The whole thing is population dynamics.
To complicate matters, the presence of a number of transposons on the plasmid CAN cause DNA rearrangements. These jumping genes can jump to new locations in the plasmid, possibly inactivating genes that they jump into and leaving a copy of themselves in the original position. They can also jump into the chromosome under certain circumstances.
The bottom line is that I'm going to have to do a lot more reading before I can explain this in a less garbled manner, but my opinion is that the behaviour of this plasmid and its nylon-digesting gene is a wonderful example of selection pressures acting on a population and demonstrates perfectly the mechanisms behind the ToE.

This message is a reply to:
 Message 8 by Loudmouth, posted 04-09-2004 12:58 PM Loudmouth has replied

Replies to this message:
 Message 11 by Brad McFall, posted 04-12-2004 6:08 PM Trixie has not replied
 Message 14 by Sylas, posted 04-15-2004 9:43 PM Trixie has replied
 Message 16 by Loudmouth, posted 04-16-2004 6:29 PM Trixie has not replied

  
Trixie
Member (Idle past 3706 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004


Message 21 of 27 (100748)
04-18-2004 4:40 PM
Reply to: Message 14 by Sylas
04-15-2004 9:43 PM


Re: Random Mutation
I haven't forgotten about this thread, but I haven't had time to write anything about plasmids and the selection pressures on bugs to keep or get rid of them. I've been wandering around the sequence databases looking at the nylB sequence and comparing it to other sequences. Last night I pulled out some interesting information from all of this which has left me astounded and puzzled. I'll try to sort out my brain on this tonight and get something written and then I'll get something written about plasmids in general. Thanks for being patient.
By the way, toddler STILL not well! (yeuch)

This message is a reply to:
 Message 14 by Sylas, posted 04-15-2004 9:43 PM Sylas has not replied

  
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