Studies of Freshwater Bacteria

Abstract

It has long beenknown that the standard methods of bacteriology pure culture isolation and observation upon artificial media-often yield only an incomplete knowledge of a particular microbic flora. Both in numbers of individuals and numbers of species, plate cultures from mouth, intestines, or vagina fall far below expectations based upon direct microscopic examination, and the same is often true of saprophytic habitats as well. This fact has been explained in part by the assumption that many of the organisms observed in smears are dead, more satisfactorily on the ground that many of them are incapable of growing upon the artificial media so far devised. From time to time we succeed in cultivating organisms which were previously known only in their natural habitat, but such accomplishments become progressively rarer. It is the author's opinion that only a minor portion of the species of bacteria existing have been cultivated and described. Soil microbiologists have succeeded perhaps better than any other group in bringing a wide variety of organisms under artificial cultivation. The number of bacterial forms which may be isolated from soil seems to be limited only by the imagination and ingenuity of the investigators in concocting special media having a selective action. But here also one finds that after suimmarizing all of the information obtained by such pure culture studies, one is left without any adequate conception of the soil microflora as a whole. It is not possible, from the bacteriological analysis, to synthesize a picture of the various organisms living