🚀 go-pugleaf

Maybe it doesn't like the media you put it in or the atmosphere is wrong for
the organism.

-- 
John Gentile                                    Rhode Island Apple Group
yjgent@home.com                                      President
 "I never make mistakes, I only have unexpected learning opportunities"

> From: "craig" <craig6109@remove-this.yahoo.com>
> Organization: ntlworld News Service
> Newsgroups: sci.bio.microbiology,bionet.microbiology
> Date: Thu, 13 Sep 2001 22:45:12 +0100
> Subject: Microbial lag phases
> 
> Hi,
> 
> I've been given an assignment to calculate the lag phases of several
> microorganisms from graphs of their growth.
> 
> I don't have any problem with this, but what do I do if the organism begins
> to decline in numbers almost from time 0?  Do I assume there is no lag phase
> at all (as there is no increase in numbers), or can an organism have a
> negative lag phase?
> 
> Help!
> Craig
> 
> 

Negative lag means that your organism really doesn't like what it finds
itself in. If it eventually 'recovers' it may mean that the organism has
underwent a beneficial mutation, or reconstructed/switched certain rare gene
cassettes on. In both cases, the experiment is invalid as far as the
original intent is concerned.

A.G.E.
"John Gentile" <yjgent@home.com> wrote in message
news:B7C6E34E.2AAC%yjgent@home.com...
> Maybe it doesn't like the media you put it in or the atmosphere is wrong
for
> the organism.
>
> --
> John Gentile                                    Rhode Island Apple Group
> yjgent@home.com                                      President
>  "I never make mistakes, I only have unexpected learning opportunities"
>
> > From: "craig" <craig6109@remove-this.yahoo.com>
> > Organization: ntlworld News Service
> > Newsgroups: sci.bio.microbiology,bionet.microbiology
> > Date: Thu, 13 Sep 2001 22:45:12 +0100
> > Subject: Microbial lag phases
> >
> > Hi,
> >
> > I've been given an assignment to calculate the lag phases of several
> > microorganisms from graphs of their growth.
> >
> > I don't have any problem with this, but what do I do if the organism
begins
> > to decline in numbers almost from time 0?  Do I assume there is no lag
phase
> > at all (as there is no increase in numbers), or can an organism have a
> > negative lag phase?
> >
> > Help!
> > Craig
> >
> >
>

Hi again,

Thanks to all who helped (John, Artem, Bob), I understand that the organism
obviously doesn't like the media, but the question was asked from a results
point of view.  I have to give a value for the lag, but I'm not sure whether
its possible to calculate it (organism appears to 'lag' then begin death
phase - never recovering).

Do I put "lag phase: n/a" in my results or are negative lag phases valid?

Thanks again,
craig

I'd put 'incompatible medium'.

Good luck,

A.
"craig" <craig6109@remove-this.yahoo.com> wrote in message
news:Xxjo7.7013$mj6.683558@news6-win.server.ntlworld.com...
> Hi again,
>
> Thanks to all who helped (John, Artem, Bob), I understand that the
organism
> obviously doesn't like the media, but the question was asked from a
results
> point of view.  I have to give a value for the lag, but I'm not sure
whether
> its possible to calculate it (organism appears to 'lag' then begin death
> phase - never recovering).
>
> Do I put "lag phase: n/a" in my results or are negative lag phases valid?
>
> Thanks again,
> craig
>
>

During the lag phase, the culture is accommodating to the new environment
(pH, temperature, medium composition, etc.).  Growth will start, possibly,
from a very small number of cells which have adapted.  If you are following
growth by means of OD, then the non-growing cells contribute background and
make the start of the new growth phase difficult to see until enough
actively growing cells accumulate.  If you are counting viable cells, the
apparent start of the new growth phase may be sooner than if you follow OD.

As to a decline in numbers of viable cells, this can be explained by the
different environment rendering cells non-viable (killing them).  If the
culture never recovers and never starts to grow actively, there is no
meaning to the term "lag phase."

Rich Mateles

--
---

Candida Corporation
Suite 1310
220 South State Street
Chicago, IL 60604

Tel: (312) 431-1601
Fax: (312) 431-1605
e-mail: rmateles@candida.com
"Artem Evdokimov" <AEVDOKIMOZ@cinci.rr.com> wrote in message
news:z8Ao7.130454$nh4.16754364@typhoon.neo.rr.com...
> I'd put 'incompatible medium'.
>
> Good luck,
>
> A.
> "craig" <craig6109@remove-this.yahoo.com> wrote in message
> news:Xxjo7.7013$mj6.683558@news6-win.server.ntlworld.com...
> > Hi again,
> >
> > Thanks to all who helped (John, Artem, Bob), I understand that the
> organism
> > obviously doesn't like the media, but the question was asked from a
> results
> > point of view.  I have to give a value for the lag, but I'm not sure
> whether
> > its possible to calculate it (organism appears to 'lag' then begin death
> > phase - never recovering).
> >
> > Do I put "lag phase: n/a" in my results or are negative lag phases
valid?
> >
> > Thanks again,
> > craig
> >
> >
>
>

Dear Craig,

Lag phase is defined as a phase of sustained growth as a result of
environmental change for a microorganizm where it is getting accustomed with
new growth contitions.
It is a phase during which a number of m.o. does not multiply but lots of
methabolic activities take place as increased protein and  DNA quantity,
etc.
Therefore, I asume that your m.o. did not even went through lag phase (I
don't think that you can use the therm of a negative lag phase) but it
entered a
log phase of decreased growth (or dying) where the speed of
growth is negative (the phase is reverse of the 1 st log phase where m.o.
has an
increase growth).
So, I would skipp all the phases (lag, 1.st log and stationary phase) and go
right to the 2.nd log phase which presents a declined growth.

Miroslava Turina-Mihelj, B.Sci. in food technology

>
>

Hi,

As defined in Microbiology (Brock, Harley and Klien)Lag phase is a
phenomenon which is associted with the inoculation and growth of cells
in batch (or related) culture. Lag phase, or the period when cells are
introduced into fresh liquid culture medium, is often related to the
type of medium used and the species of bacteria introduced into it. It
does not matter if the cells take a long period to grow or even if a
percentage become no longer viable, as long as you get exponential
growth following the lag period. This is a common phenomenon when
examining the growth characteristics of bacteria from oligotrophic
environments (ie growing freshwater bacteria in say R2A medium). All
you are essentially doing is "training" the bacteria to grow in a
different type of medium (ie selecting for a particular sub-population
in the original inoculum to grow in you defined/complex medium).

Hope this helps,

Alex

Dr. Alex Rickard
University of Manchester
School of Pharmacy
UK