Microcultural Study of Bacterial Size Changes and Microcolony and Ultramicrocolony Formation by Heterotrophic Bacteria in Seawater

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Abstract
With a microculture technique and time-lapse, phase-contrast photomicrography, it was possible to follow the division of individual cells and the development of microcolonies of bacteria in freshly collected marine water samples. A certain number of marine bacteria, upon inoculation onto a nutrient rich agar surface, displayed an increase in size and a high growth rate. Other bacteria were identified as very small marine bacteria (ultramicrobacteria). These had a very slow growth rate when inoculated onto a nutrient-rich agar surface. These latter cells formed very small microcolonies (ultramicrocolonies) and cell size did not increase significantly. These 2 types of marine heterotrophs could be described in terms of zymogenous and autochthonous bacteria, a concept used by Winogradsky for describing soil microorganisms.