telomeres

Chris Fields cjfields at jove.acs.unt.edu
Wed Apr 29 14:42:48 EST 1998


Patrick J. Maher wrote:
> 
> > do bacteria have telomeres?
> >
> > skyamsen
> Linear chromosomes, due to the nature of DNA polymerase, shorten after
> every successive replication by a couple bases.  Therefore those organisms
> with linear chromosomes have an enzyme call telomerase which adds
> repetative sequences onto the ends of the chromosomes called telomeres so
> no genes are lost by the shortening of the chromosomes.
> Since it's the eucaryotes that have the linear chromosomes not the
> eubacteria (ie bacteria) which have circular chromosomes,
> bacteria do not have telomeres.
> 
> Patrick Maher

Actually, there are several bacteria that have linear chromosomes and
have telomeres. Streptomyces, a high G+C Gram-positive soil bacterium
that produces antibiotics, has a very large (~8Mb) linear chromosome
with proteins attached to the ends.  The end of the chromosome are
thought to be telomeres.  As for proof of telomeres, the parasitic
Borrelia burgdorferi has linear chromosomes as well as linear plasmids,
both of which have been conclusively proven to have telomeres!  The
entire chromosome has been sequenced and published (in Nature, I
think).  Agrobacterium tumefaciens is also thought to have a linear
plasmid with a circular chromosome.  I believe that Hinnebusch and
Hopwood are the main researchers of bacterial telomeres.

Don't fall into the false assumption that because one bacterium has a
circular chromosome (E. coli was the paradigm-builder) that ALL bacteria
have circular chromosomes.  Paradigms can be a dangerous thing.  Look at
the state of the Five Kingdoms (now the three Domains of Life, acc. to
C. Woese).
-- 
C. J. Fields

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