[extropy-chat] What is the smallest genome possible?

[Robert Bradbury]

On 10/15/06, John K Clark <jonkc at att.net> wrote:
>
>  It might be worthwhile to study it to find the bare minimum needed
> for life, perhaps they could try removing one of its 182 genes to see if
> they could get something even smaller.
>

Careful, careful, careful.  As the article points out, it may be a bacteria
in the process of becoming an organelle!  You could view a mitochondria as
being the smallest bacteria if you allow for bacteria to import proteins
essential for self-replication.  The previous minimal genome size for
bacteria was thought to be in the 350-450 gene range so a 2-3x reduction is
not simply trimming around the edges.

The question is whether or not *all* the genes required for self-replication
are in those 182 genes?  I would tend to doubt it.  If you are importing
RNAs or proteins to accomplish complete replication then you are violating
the "rules".  I suspect this could be extended if you are importing anything
other than simple molecules to produce a copy of yourself.  (E.g. does the
bacteria do the synthesis of its cell membrane and/or wall or is relying on
the host to do the heavy lifting?)

This is going to cause rather loud discussions as to *what* precisely is a
bacteria? [And we thought the "what is a planet?" discussions were bad.]  As
at least one virus has recently been found with a multi-thousand base genome
so I think the virus and bacteria definitions are starting to get very
fuzzy.

Where is Humpty Dumpty when you need him?

Robert
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