I have cultured a strain of marine bacteria in Nutrient Broth with 2% NaCl with pH adjusted between 2.0-10.0 in individual tubes to check the tolerance of bacteria towards various pH. After 48 hrs I have observed that pH of the broth of all the tubes which has growth had adjusted between 7.0 to 8.5 but the control tubes didn't change.
Does bacteria alter /adjust the pH of the liquid media itself while growing?
Does this mean anything?
Yes, many bacteria change the pH of their medium. Most common is the secretion/excretion of organic acids such as lactic acid, by the well-known lactic acid bacteria, or acetic acid by the microbes responsible for vinegar fermentation. Less common is the secretion of ammonia and other basic compounds, but it does happen in some bacteria.
Yes, they do. Please see this recent publication from some of my former colleagues: http://pubs.rsc.org/en/content/articlelanding/2016/ra/c6ra06468j#!divAbstract
Dear Jordan R. Yaron,
I don't have access to the publication link you have given. Can you kindly send me the full text article. It would be helpful.
Yes, many bacteria change the pH of their medium. Most common is the secretion/excretion of organic acids such as lactic acid, by the well-known lactic acid bacteria, or acetic acid by the microbes responsible for vinegar fermentation. Less common is the secretion of ammonia and other basic compounds, but it does happen in some bacteria.
As Greg has mentioned above, the type of metabolic processes the bacteria are undergoing can lead to the secretion of different compounds which can then alter the media's pH. The different (non-marine) bacteria we have worked with in my lab would cause the change of pH if the bacteria were in the presence of the proper carbohydrate. In our setup we looked at the ability to ferment lactose, glucose, or sucrose, and different bacteria could metabolize different carbohydrates. We only ever used an indicator, phenol red in our phenol red broth, to determine if the pH was changing. I would assume that since different bacteria can metabolize different carbohydrates, they would also change the pH differently from bacteria to bacteria.
yes, they do, see our paper Romanowski et al. BMC Microbiology 2011, 11:212,
Prevention of siderophore- mediated gut-derived sepsis due to P. aeruginosa can be achieved without iron provision by maintaining local phosphate abundance: role of pH
I accept that the pH will change due to release of metabolites produced into the liquid broth. What I have observed is that the bacteria is adjusting the pH to its optimum growth conditions. Because initially they were not growing in the tubes with pH 2.5, 3.0 and 3.5 but after 2 days they started growing where I have found that the pH is adjusted to 7.0 which is an optimal for that particular bacteria. Same with case of higher pH. Initially no growth at pH 9.0, 9.5 and 10.0 but after 36 hrs I have observed the growth with pH adjusted to 8.5. Does it mean that the bacteria releases certain metabolites to neutralize the pH to its favorable conditions and then starts growing vigorously. Is there any more literature available on this.
Dear Dr. Azeez,
here it is. Please let me know if you can open it
With the warmest wishes
Olga
http://www.ncbi.nlm.nih.gov/pubmed/21943078
Yes, the products, byproducts, and waste produced by the bacteria during growth and metabolism will alter pH of the medium
As everyone has said, bacteria can clearly modify the pH of their environment. However, it seems to me that no one has truly addressed your particular question or situation.
Do bacteria sense the pH of their environment and in response produce acids/bases that alter the pH to a preferred level? Unfortunately, I don't have an answer to this. It could be that under different pH conditions, the metabolism is different such that the set of excreted products is different. Thus the metabolism under acidic conditions produces more basic compounds and the metabolism under basic conditions produces more acidic compounds. I hope this help you in finding more useful literature.
Good luck!
I have cultured PSB bacteria in NB medium to check the tolerance of bacteria towards various pH(5.5-6.5-7.5-8.5-9.5).after two days I saw the medium pH adjusted to 8.5-8.8.
also i saw the pH related to growth of bacteria.
could every one address me for this situation?
why pH adjusted to 8.5-8.8?
Mostafa: hope you read answers 1-11?,
Best wishes and regards....
NB: if you find specific literature by a thorough literature search (e. g. using Google, or any other search machine; Google scholar =www.scholargoogle.com (especially for the literature which might available already..., or even PubMed) using appropriate keywords/search phrases....
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