Influence of Aeration Speed on Bacterial Colony Forming Unit (CFU) Formation Capacity

Bacterial homeostasis depends on an array of physical and chemical stimulants. Current investigation assessed the impact of one of such factors, the speed of aeration, on cell viability and culturability of Escherichia coli, Pseudomonas spp. and Bacillus spp. Each of the bacterial strain was incubated at 37°C with a shaking speed of 0, 100 or 200 rotation per minute (rpm) separately up to 72 hours, with a simultaneous monitoring of morphological changes and cell culturability. All bacterial species were found to optimally grow at 100 rpm whereas at 0 rpm growths of E. coli and Pseudomonas spp. were bit slower compared to that of Bacillus spp. The capacity to form colony forming units (CFUs) of E. coli and Pseudomonas spp. on Luria Burtani (LB) agar plates were observed to be inhibited after 36 hours of growth at 200 rpm; i.e., approximately 3-log reduced CFUs than those formed by Bacillus spp. Besides, morphologically impaired cells were observed for the former two bacteria cultivated at 200 rpm. Taken together, it is assumed that the high speed shaking might evolve the oxidative stress endogenously which possibly rendered the cells lose their culturability.