Comparison of two direct count techniques for enumerating aquatic bacteria

Abstract

Planktonic bacteria from an estuary were concentrated on membrane filters and counted with both a scanning electron microscope and an epi-illuminated fluorescent microscope. Counts on 0.2-μm Nuclepore filters (polycarbonate) were significantly higher (P<0.001) than counts on 0.2-μm Sartorius filters (cellulose). In contrast, there was not a statistically significant difference between the two techniques when Nuclepore filters were used (0.5