We have observed Bacillus subtilis micro-colony by using scanning electron microscope and optical microscope. In the previous report, a cell on a agar plate grew drawing the curved string without cut off one string. Shapes of micro colony formed on agar plates were changed in response to agar concentration, nutrient concentration and other environments. In this report, we took notice of relationships between agar concentration and micro colony morphology. A cell string had a small amount of curvature under low agar concentrations. Under high concentrations curvatures increase in size. Under all concentrations tested filament chains of cells were twisted, especially under medium concentrations double stranded helical structures were observed at many parts of the peripheral domain of the colony. Furthermore, we discussed the ecological meanings of one string and twisted growth of this bacteria.
A scanning electron microscopic (SEM) image analysis system was used to measure bacterial biovolume in fresh water. Halation, which is a problem encountered in epifluorescence microscopy, is avoided in SEM image analysis. The biovolume-to-carbon and nitrogen conversion factors, which are used to estimate bacterial biomass, were determined in four standard strains and five river water isolates. These factors for carbon and nitrogen were 0.34±0.06pg C/μm3 and 0.094±0.014pg N/μm3 respectively. There was no noticeable difference among bacterial species or growth phases. Bacterial size and biomass were measured in polluted and unpolluted river water. The average volume of bacterial cell was twice as high in polluted water, while the bacterial biomass was 35 times higher than in unpolluted water.