Study of Red Halophilic Bacteria in Solar Salt and Salted Fish: I. Effect of Bacto-Oxgall

Bacto-oxgall has shown a differential effect on the red halophilic bacteria commonly found in solar salt and in contaminated salted fish. Pseudomonas salinaria was inhibited by low oxgall concentrations while Sarcina littoralis tolerated high ones. When this differentiating test is applied to a larger number of strains it will be possible to determine if Bacto-oxgall can be used as the basis of a selective medium to distinguish one genus from the other. The clearing of bacterial suspensions and microscopical examination have shown that the inhibition of Ps. salinaria was produced by the lysis of the cells. The inhibition of Ps. salinaria was effective and rapid. It was not affected by pH variations but was reduced by the presence of proteins. When compared similarly to other bile products, Bacto-oxgall was found to have the same inhibitory power as sodium taurocholate. Bacto-oxgall, diluted to the equivalent of fresh bile, was also found to be three times more effective than fresh cod bile. From the evidence gathered it was concluded that the inhibition of Ps. salinaria by Bacto-oxgall is due to a mechanical disruption of the bacterial cytoplasm.