Factors influencing the cultivability of lake water bacteria

Counting bacteria in natural water samples by cultivation yields only low recovery efficiencies ca. 1%., compared to total counts obtained after 4,6-diamidino-2-phenylindol DAPI.staining. In order to optimize the cultivation of heterotrophic planktonic bacteria from Lake Constance Germany., selected parameters of the medium composition were modified. The most important factor was the concentration of organic substrate nutrient broth plus yeast extract., which significantly influenced the Amost probable numberB obtained in liquid growth medium. Reduced oxygen concentrations 3 12%. lowered the Amost probable numberB. Addition of N-acyl homoserine lactones to the medium increased the cultivability slightly. Low substrate concentrations w0.03 0.06% wrv.x, an incubation atmosphere of 21% oxygen at 16 8C for 4 weeks were optimal and increased the cultivability ("most probable number" related to total bacterial counts.to an average cultivability of 1811%, ns8.. The results indicate that cultivabilities of heterotrophic bacteria from lakewater samples can be significantly increased by modifying the cultivation methods