Stress: a factor to be considered in heterotrophic microorganism enumeration from aquatic environments.

Heterotrophic microorganisms in water samples are susceptible to the transient stress of warmed agar used in the standard methods pour plate procedure, causing significantly decreased recoveries in comparison with a spread plate technique. Microbial starvation can increase susceptibility to a transient warming stress. The standard plate count procedure, as presently described, should not be considered for quantitation of microorganisms from aquatic environments.