Physiological Characteristics of Three Oligotrophic Soil Bacteria, Aeromonas sp. Y26,Aeromonas sp. Z06,and Chromobacterium sp. Y95,in Low Concentration of Nutrient Broth

The characteristics of three oligotrophic bacteria (Aeromonas sp. Y26, Aeromonas sp. Z06, and Chromobacterium sp. Y95) isolated from soil were studied and compared with those of the eutrophic bacteria, Escherichia coli and Bacillus subtilis. The Km values of the three oligotrophic bacteria for D-glucose and L-leucine were 0.3-1.8 and 1.5-7.8μM, respectively, while those of E. coli were 1.6μM for D-glucose and 0.6μM for L-leucine. There were no significant differences of uptake kinetics between the three oligotrophic bacteria and E. coli. The oligotrophic bacteria grew in 104-fold dilution of nutrient broth (NB/104) with doubling times of 1.5 to 3 days and reached final yields of 5.2 to 8.6×106 colony-forming units (CFU) per ml. During exponential growth in NB/104, the oligotrophic bacteria maintained a high level of adenylate energy charge. The viability of the oligotrophic bacteria when they were incubated in 10mM sodium phosphate buffer (pH 7.0) decreased exponentially from 5 to 15 days of culture. However, after 60 days of culture in ultra pure water, 8-26% of the oligotrophic cells were viable.