[Development of bacteria and their activity in an aqueous surface film under experimental conditions]

The formation and number of bacteria in the surface film of water depend on the content of organic substances in water. In flasks containing distilled water after 1-2 days, a bacterial film 5-7 mcm thick is formed at the surface; in flasks with water taken from reservoirs, the film is 5-15 mcm thick; in flasks with water containing organic substances, the film is 15-50 mcm thick. A distinct bacterial band of growth is formed on glasses semisubmerged in water in this layer. At the beginning, bacterial rodshaped cells are oriented by their side surface to the surface layer of water. Judging by the assimilation of protein labeled hydrolysate, the total activity of bacterial population in a film is much higher than in deep water layers. In the course of time, the number of bacteria changes, they begin to die off, and their species are substituted by other bacterial species. Numerous motile forms and various Caulobacterial forms are found in the surface layer of water. The dimensions of bacterial cells growing on glass are much larger than in dry preparations obtained from this film on membrane filters.