ABSTRACT
Within the aquatic environment, bacteria can be found either attached to various substrates or existing as free-living single or aggregated cells in the water column. Substrates to which bacteria are likely to attach include marine snow, fecal and detrital particles in the water column, sediment particles, and aquatic plants. The sample preparation method delineated overcomes the problems by utilizing a combination of chemical and physical procedures for dispersing the bacteria from their attached sites or aggregated forms. The method involves initial fixation and strengthening of bacteria in the sample with formaldehyde, followed by addition of dispersant, tetrasodium pyrophosphate (PPi), and an application of ultrasound for physical separation of the bacterial cells. The method allows for bacterial enumeration from aquatic substrates that are difficult or impossible to enumerate via the use of standard methods. The sample preparation method disperses bacteria evenly and thereby decreases variance in bacterial counts between microscopic fields.
