Abstract
Facultative spore-forming bacteria, fermenting lactose with gas production, have been encountered on a number of occasions in water supplies. As these bacteria are gram negative and frequently do not show spores on carbohydrate media, they have been a source of confusion in the interpretation of bacterial water analysis for the incidence of members of the colon group. Such organisms, which were isolated for the first time in Iowa from the chlorinated drinking water at Iowa City in 1921 by Hinman and Levine, were thought to be rare; but evidence is accumulating to indicate that they are quite ubiquitous, having since been isolated from soil, animal and human feces, decaying and canned vegetables, sewage, grains, and eggs.
There is considerable confusion in the literature concerning the identity and differentiation of species allocated to this group of bacteria. This report presents, briefly, a study of all strains described in the literature, which are available, together with a number of freshly isolated cultures.
The study included 63 freshly isolated strains and authentic cultures of all described strains except 2 which apparently are extinct.
There was considerable variation in the size of the bacteria on different culture media. In a few cases terminal oval spores were seen within the sporangia, but generally they were observed free. All strains were actively motile.
Culturally, the strains showed very little difference. On nutrient agar at 37°C, growth was slight, effuse, and transparent. On sugar-containing agar, growth was spreading and slimy. Growth in nutrient broth was slight and with some sediment; in sugar broth the medium frequently became very viscous.
Colony characteristics vary with the medium. On nutrient agar, well isolated colonies are small and transparent. On sugar-containing media, colonies are extremely variable, but are transparent and usually very slimy.
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