Hi Simon
The problem lies in your definition of viability. If you think of
reproductive growth as the sole definition of viability than
you have to accept that - if you have no children - you are in a
viable but non culturable state. However if you are
'metabolically' active you might at least have to consider the
possibility of having children, e.g demonstrating reproductive
growth. In some cases a little help (like little blue pills) might be
required to achieve the desired activity, leading to
reproduction, whilst other metabolic functions are fully intact.
However, if you had 'the snip' you had it despite normal
metabolic activity. For a more detailed discussion on viability see
Nebe-von-Caron et al in one of the October issues of the
Journal of Microbiol. Methods. or, for an older text on
http://www.cyto.purdue.edu/flowcyt/research/micrflow/gerhard/genmic10.h
tm
Depending what you amplify you will eventually find that there is a
definite lifetime of nucleic acid for up to several
months as people have shown in marine environment. However, even the
synthesis of message can occur in intact bacteria
that are not necessarily capable of multiplication. From a safety
point of view the only safe cell is a truly dead cell with an
irreversible permeabilised cell membrane. A lot of stressed or injured
cells only fail to reproduce under the
conditions we offer. Before Koch developed the culture techniques
actually all bugs were VBNC.
I have speculated for some time that for example irradiated cells
might be a good example to investigate the expression of
virulence factors and the transfer of genes by non-culturable cells.
Whilst they can not demonstrate reproductive viability
but are still metabolically active for weeks. However, due to the
influence of the culture conditions, mainly oxidative stress,
(see: Stephens, P.J.; Druggan, P.; Nebe-von Caron, G., Stressed
Salmonella are exposed to reactive oxygen species from two
independent sources during recovery in conventional culture media.
International Journal Of Food Microbiology, Vol: 60,
Issue: 2-3, September 25, 2000, pp. 269-285) non- culturability has to
be
investigated using optimised recovery media like the Oxoid SPRINT
system first.
Regards
Gerhard
In article <8qkp9f$832$1 at nereid.worldonline.nl>,
"fey" <velds at worldonline.nl> wrote:
> Hi there,
>> Does anyone know something about the virulence of Legionella when
this
> organism is in a viable but non culturable phase. We cultivate
Legionella by
> the standard culture method on BCYE-agar and with PCR. Often we found
the
> PCR positive and the culture method negative to Legionella. There are
a lot
> of articles about the phenomenon viable but non culturable but I
didn't find
> anything about the virulence. Can someone tell me more about what
will
> happen when a viable but non culturable Legionella is inhalated.
>> Simon
>>
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