saline vs. peptone water - (Mar/25/2009 )
In class, I was taught to use saline for serial dilution and plate count of microbes. However, my current lab use 0.1% peptone water for this purpose. I wonder what are the pros and cons of these two.
Thank you.
why on Mar 25 2009, 11:05 AM said:
Thank you.
why,
do they always use the peptone solution ? (for any micro-organim)
and do they just use it to make the dilution and then count it? (meaning: they trow away the dilution,plates when counted) or?
I do wonder why do would use peptone water just to make a dilution to count, you can simply use water for that (but also depends on the micro-organisms)
the pro's and cons depend mostly on wich micro-organism you use , well sometimes anyway.
http://aem.asm.org/cgi/reprint/5/1/21.pdf ; take a look at this text, here they speak about what dilutant to use and they also speak about peptone versus saline... (page 24 ,or 4/5 pfd, under discussion)
They also speak about bacteria that can die rapidly when using saline ...
and be sure to check page 24 (4/5in the pdf pages) at the bottom, starting with: Destruction of bacteria during dilution can be avoided.....
this might be helpfull..
i support the fact that saline destroy the growth of certain bacteria. While carrying out an environmental studies, i isolated an unknown specie for acclimatization in a specific medium. i found out that the isolate did not grow on saline soln but on innoculating it in 0.1% peptone medium, the growth was very massive. Its very advisable to use0.1% peptone in dilution to avoid eliminating some strains of bacteria
I think the question was regarding dilution - not gowth. None of us expects to grow bugs in saline.
Dear Pito,
Yes, we use 0.1% peptone water as diluent to dilute the samples and then plate on suitable agar for grow and cell count later. The seniors in the lab told me that they tested with distilled water as diluent and found that the cell count was lower than compared with peptone water as diluent, means that water has destructive effect on the microbes. Therefore, they use peptone water for all their samples since then.
Thanks for the paper. It is very useful to me.
why on Apr 9 2009, 05:23 AM said:
Yes, we use 0.1% peptone water as diluent to dilute the samples and then plate on suitable agar for grow and cell count later. The seniors in the lab told me that they tested with distilled water as diluent and found that the cell count was lower than compared with peptone water as diluent, means that water has destructive effect on the microbes. Therefore, they use peptone water for all their samples since then.
Thanks for the paper. It is very useful to me.
Dear why,
It could also be the other way around.
In stead of saying that the demiwater (I was speaking of demineralized water, not distilled, however I do not think this should make a big difference) has bad effects on the micro-organisms, you could say that the peptone water has a positive effect on the micro-organisms... maybe the peptone induces better growth?
Or you are indeed correct, if you check the article I allready posted here, you can indeed read that water has also a bad effect on some micro-organisms.
PS. add what lab do you work why?
I do wonder if there are no other articles on the subject, it does indeed seem odd that there hasnt been a study on what dilutant to use.
(I havent seen any other article then the one I posted here, maybe I should look for other articles)
@GeorgeWolf, I understand your point of view, however I have one question then:
No one expects to grow bacteria on saline, but what if you use saline to make dilutions and then you plate out those dilutions so check the growth on , lets say, common agar.
Is it by any change possible that you have killed or slowed growth then by using saline as a dilutant?
(according to the text I posted here I would say yes... but to what extend?)
If there is a question, just do the experiment.
If there's a question , just do the experiment(s) 
i would go with the theory that different diluent probably will affect the population of viable + culturable bacteria.
if u look at the paper from AEM . the experiment was extended for like 20+ min.
the key is to plate the bacteria as soon as possible.
for diversity sake, u probably could use a range of diluent to improve the diversity of culturable bacteria.
hanming86 on Apr 13 2009, 04:37 AM said:
i would go with the theory that different diluent probably will affect the population of viable + culturable bacteria.
if u look at the paper from AEM . the experiment was extended for like 20+ min.
the key is to plate the bacteria as soon as possible.
for diversity sake, u probably could use a range of diluent to improve the diversity of culturable bacteria.
Exactly - a range - as in the experiment.
Dear Pito,
I am working in a microbial biotech lab. I am running fermentation for my yeast clones and want to do viable plate count for that. My labmates use peptone water as diluent for their environmental samples too.