The isolation and enumeration of cytophagas

Abstract

A comparison of 20 media based on degraded milk protein or tryptone, yeast extract, and sodium acetate snowed that various new formulae were superior to standard media for enumeration of cytophagas from aquatic habitats, for their isolation, and for maximum expression of the spreading characteristic. The use of 0.1 μliter/liter Tween 20 in dilution blanks increased counts of cytophagas up to threefold, but incorporation of Tween 20 into the plating agar had no significant effect on the numbers recovered. Sodium lauryl sulfate (S.L.S.) was examined as a possible screening agent for identification of cytophagas. A concentration of 0.1% S.L.S. inhibited the growth of 97% of the 66 cytophagas tested, but more than 80% of the other 41 organisms tested were also affected. However, 91% of the cytophagas were sensitive to S.L.S. and showed proteolysis on skim acetate medium compared to 53% of the Flavo-bacteria and 50% of the other organisms tested. None of the third group of organisms could be confused morphologically with the cytophaga group; thus it is suggested that S.L.S. susceptibility performed on skim acetate medium could be a useful screening test for cytophagas.