Identification of the diazotrophic bacteria previously referred to as Protomonas-like bacteria, and their capacity for nitrogen fixation.

Abstract

This study was undertaken to clarify the taxonomy of the pink-pigmented nitrogen-fixing bacteria isolated from the rhizosphere of rice and previously referred to as Protomonas-like bacteria (Oyaizu-Masuchi, Y. and Komagata, K., J. Gen. Appl. Microbiol., 34, 127-164 (1988)); also to investigate their capacity for nitrogen fixation. The ability of the isolates to grow anaerobically under photoheterotrophic conditions as well as aerobic chemotrophic conditions demonstrate that they are a member of anoxygenic phototrophic purple bacteria. Based on the phenotypic and chemotaxonomic tests and DNA-DNA hybridization assays, it was concluded that the isolates should be assigned to Rhodopseudomonas palustris. All these isolates grew with Nz as the sole nitrogen source under both anaerobic-light and microaerobic-dark conditions, and showed significant in vivo nitrogenase activity.