title: Comparison of two direct-count methods for determining metabolizing bacteria in freshwater.
abstract: Planktonic bacteria collected from several freshwater environments and cultured bacteria were used to compare two methods for determining the numbers of metabolizing bacteria. The methods used were (i) reduction of 2-(rho-iodophenyl)-3-(rho-nitrophenyl)-5-phenyl tetrazolium chloride 2-(rho-iodophenyl)-3-(rho-nitrophenyl)-5-phenyl to tetrazolium chloride-formazan and (ii) elongation of cells by using yeast extract and nalidixic acid. No statistically significant difference was found between methods in determining metabolizing bacteria, although significant differences (P < 0.05) were found when comparing numbers of total bacteria. A combination of the two methods yielded significant changes, both positive and negative, in the numbers of metabolizing bacteria.
authors.affiliation: Center for Great Lakes Studies, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201.
authors.forename: J S
authors.initials: JS
authors.lastname: Maki
authors.forename: C C
authors.initials: CC
authors.lastname: Remsen