title: Determination of the hydrogenase status of individual legume nodules by a methylene blue reduction assay.
abstract: We adapted a method for the rapid screening of colonies of free-living Rhizobium japonicum for hydrogenase activity to determine the hydrogenase status of individual soybean nodules. Crude bacteroid suspensions from nodules containing strains known to be hydrogen uptake positive (Hup) caused a localized decolorization of filter paper disks, whereas suspensions from nodules arising from inoculation with hydrogen uptake-negative (Hup) mutants or strains did not decolorize the disks. The reliability of the method was demonstrated by its successful application to 29 slow-growing rhizobia. The Hup phenotype on methylene blue filters agreed with that determined amperometrically with either methylene blue or oxygen as the electron acceptor.
authors.affiliation: Laboratory for Nitrogen Fixation Research, Oregon State University, Corvallis, Oregon 97331.
authors.forename: G R
authors.initials: GR
authors.lastname: Lambert
authors.forename: F J
authors.initials: FJ
authors.lastname: Hanus
authors.forename: S A
authors.initials: SA
authors.lastname: Russell
authors.forename: H J
authors.initials: HJ
authors.lastname: Evans