When I grow the colonies in R2A medium, I saw clear halos surrounding the colonies. The medium is prepared with seawater and maybe some salts are precipitated after sterilization. Could this be related with the halos?.
Hi Leandro A Sanchez,
It is important for us to know what type of bacteria you cultured in R2A saline medium. It could be that the bacterial strains you are talking about came from seawater and the intestines of benthonic organisms. Cultivable bacteria could be characterized and classified as either psychrotolerant or psychrophiles. Presence of halos around bacterial colonies when they grow in mediums, such as R2A saline medium, could be attributed to protease production. Studies show that more protease-producing strains (around 67%) are detected from the isolated bacteria coming from benthic invertebrates as compared to those obtained from seawater (around 33%), with protease production under neutral conditions resulting in milk protein hydrolysis halos between 27 and 30 ± 2 mm in diameter (2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).
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