the common mode of bacterial motility

arlin at ac.dal.ca arlin at ac.dal.ca
Sun Apr 24 11:16:37 EST 1994


In article <timi-210494183304 at kustu1.berkeley.edu>, timi at mendel.berkeley.edu (Tim Ikeda) writes:
> In article <1994Apr21.190914.23337 at dal1>, arlin at ac.dal.ca wrote:
> [...]
>> If these and a few other important characters (circular chromosomes,
>> operons, shine-dalgarno sites, etc) were present in the common
>> ancestor, as is likely, then archaebacteria and eubacteria have a
>> common heritage that I would call "bacterial." [...]
> 
> Just an aside...
> It's time to throw out the "bacteria only have circular chromosomes" idea.
> 
> See:  Davidson BE; MacDougall J; Saint Girons I. 1992.
>   Physical map of the linear chromosome of the bacterium Borrelia
>   burgdorferi 212, a causative agent of Lyme disease, and localization
>   of rRNA genes. J. Bacteriol.174:3766-74.
> 
> The cool question is: What system/s does a bacterium use to maintain a
> linear chromosome?
> 
> - Tim Ikeda (timi at mendel.berkeley.edu)

Certainly its a cool question, but saying (as I did) that bacteria 
*ancestrally* have circular chromosomes is not the same as saying
"bacteria only have circular chromosomes" (Tim's words, not mine).  
Linear bacterial chromosomes are, as far as I know, restricted to 
members of the spirochete genus _Borrelia_, and the inference that
circular chromosomes are ancestral is therefore a sound one.

Arlin



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