Comparison of homogenization and ultrasonication as techniques in extracting attached sedimentary bacteria

Uncertainty of complete recovery of attached bacteria during extraction is a major problem in the enumeration of these microorganisms. Homogenization and ultrasonication are the most commonly used physical techniques of extraction, and each is used on the assumption that it gives maximum yield. Ultrasonication of formalin-fixed sandy sediments using an ultrasonication bath with a frequency range varying between 40 and 50 kHz, and with a power output simultaneously varying between 100 and 200 W, was more effective than homogenization at 23000 rpm. Ultrasonication destroyed many bacteria and, for the sediment under study, it was estimated that counts obtained after an optimum treatment of 2.5 min are corrected for inadequacies in the extraction process when multiplied by a factor of 1.44.