Hi All/Mike
 
Mike - you asked if bacteria could transfer genes without mating. (an
interesting question)
 
The short answer is yes they can - even between very unrelated
species and even between gram positive and gram negative bacteria - a
bit like a human picking up a gene from a mushroom or tortoise.
 
There are two main ways genes are spread - sexually and horizontally.
 
Horizontal gene transfer is the very important one in bacteria. The
basic genetic control in a bacterium is it's chromosome - which it
can diversify in mating with closely related bacteria (usually within
the same species, sometimes same genus).
 
However - many bacteria, and some yeast, have things called plasmids
which they can contain. The plasmid usually does not contain genes
for essential functions - but it can give the bacterium an advantage
over it's competitors.
 
Plasmids are usually a small circular strand of DNA with one or two
genes making a product and a few controlling that product. An example
is one of the universal plasmids for Tetracycline resistance that
have been isolated - it has a TetResistance gene and I think a
regulator gene. If a bacterium dies it can burst releasing many
copies of this plasmid into the environment - another bacterium may
be near by and a whole range of factors lead to it either
intentionall or accidentally picking up the plasmid. Now it is say
TetResistant. Sometimes something goes wrong and that gene gets
incorporated onto the bacterial chromosome - and you now have a
permanantly resistant strain.
 
Usually there is at least a small
percentage of bacteria that have a resistance plasmid to any
antibiotic you apply - these will thrive when one gives the treatment
- but after one stops there is no real reason for the majority to
keep the plasmid and they lose it again. BUT - if the gene
incorporates onto the chromosome it takes a lot longer for it to be
lost.
 
A beautiful example of horizontal gene transfer is the sequence of
genes responsible for producing Penicillin. Bacteria (Streptomycetes)
and fungi (Penicillium and Aspergillus to name a few) make these
products. The order of genes on the genome and even the structure of
the genes are almost identical. Researchers have even shown that it
is possible to take the gene sequence from a bacteria and get it to
incorporate onto the chromosome of Aspergillus (a fungi) showing that
the original transfer of the ability to make penicillin into these
completely unrelated life forms was probably by horizontal gene
transfer.
 
So in conclusion - bacteria treat the world as their tool box - they
live in an environment full of broken cells with genes floating
around - the occasional 'expand your genome hippie bacteria' tries
out a new gene to see what it does and sometimes the effects 'expand
it's niche man!'. (After all DNA is just information - we swop ideas
that let us use new products and make them, bacteria swop DNA which
lets them do the same - we'll have to see who evolves the fastest.)
 
Keep well
 
Garth
Garth Cambray           Camdini Apiaries
15 Park Road
Grahamstown             Apis mellifera capensis
6139
South Africa
 
Time = Honey
 
If you are not living on the edge you are taking up too much space!!