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An accurate most-probable-number enumeration method was developed for counting the number of Beggiatoa trichomes from various freshwater sediments. The medium consisted of extracted hay, diluted soil extract, 0.05% acetate, and 15 to 35 U of catalase per ml. The same enrichment medium, but without the acetate, was the best enrichment medium from which to obtain pure cultures because it supported good growth of the beggiatoas without allowing them to be overgrown by other bacteria. A total of 32 strains of Beggiatoa were isolated from seven different freshwater habitats and partially characterized. The strains were separated into five groups based on several preliminary characteristics. Four of the groups contained cells with trichomes of approximately the same diameter (1.5 to 2.7 mum) and may be Beggiatoa leptomitiformis or an unnamed species. The fifth group appeared to be Beggiatoa alba. With the exception of three strains, all of the strains deposited sulfur in the presence of hydrogen sulfide, and all strains grew heterotrophically and deposited poly-beta-hydroxybutyrate and volutin when grown on acetate supplemented with low concentrations of other organic nutrients. Thin sections of sulfur-bearing trichomes indicated that the sulfur granules were external to the cytoplasmic membrane and that they were surrounded by an additional membrane.
Strohl et al. (Wed,) studied this question.