Steven Sanyal <steven.sanyal at utoronto.ca> wrote:
>I am a third year Molecular Biology student at the university of Toronto
>and am also taking a microbiology course out of general interest.
>>I am curious as to the proposed origin of plasmids. I have heard that
>bacteria can actually scavenge their surroundings for useful pieces of
>DNA.
>>Most plasmids I have come across thus far have dealt with antibiotic
>resistance genes - used for selections. Did these genes evolve only
>since the advent of antibiotics this century, or is it believed that they
>existed before? ie: were their natural antibiotic agents that existed
>before - a sort of interbacterial warfare.
>>Steve
>>steven.sanyal at utoronto.ca>
Most, if not all, were probably already around in one form or another,
but not necessarily dominant in the community except where selective
pressures gave "owners" an advantage. Not only that, it doesn't have to
be interbacterial "warfare" (although that does occur - look up
bacteriocins) - penicillin is a natural product of fungi (although most
precribed modern penicillins have been chemically modified - hence the
term "semi-synthetic penicillin"). Indeed, the oldest known herbals
describe the use of bread mould as a good way of treating infected
wounds.
Lesley Robertson
