CULTIVATION OF A MIXED BACTERIAL POPULATION OF SEWAGE ORIGIN IN THE CHEMOSTAT

Bacteria of distinctive colony morphology isolated from the biological stage of two typical sewage treatment works have been continuously cultured in a complex nutrient medium. Changes in the composition of the mixed population have been monitored by viable counts on casein, glycerol yeast extract agar and Christensen's agar. A selection of suitable species was attempted upon the basis of growth in pure and mixed batch culture. A reproducible mixed bacterial population has been cultured continuously for 170 h at a dilution rate of 0.166 h-1. An increase in the dilution rate to 0.2 h-1 did not prevent the maintenance of a mixed bacterial population, but caused changes in the population size, of individual species. © 1979.