Hydrogenase in Rhizobium japonicum Increases Nitrogen Fixation by Nodulated Soybeans

Abstract

Some Rhizobium strains synthesize a unidirectional hydrogenase system in legume nodule bacteroids; this system participates in the recycling of hydrogen that otherwise would be lost as a by-product of the nitrogen fixation process. Soybeans inoculated with Rhizobium japonicum strains that synthesized the hydrogenase system fixed significantly more nitrogen and produced greater yields than plants inoculated with strains lacking hydrogen-uptake capacity. Rhizobium strains used as inocula for legumes should have the capability to synthesize the hydrogenase system as one of their desirable characteristics.

Insights learned from pBTAi1, a 229-kb accessory plasmid from Bradyrhizobium sp. strain BTAi1 and prevalence of accessory plasmids in other Bradyrhizobium sp. strains

“…Comparative expression of BTAi1 hydrogenase genes Some rhizobia induce uptake hydrogenases during symbiotic growth in order to reduce energy losses associated with nitrogen fixation (Albrecht et al, 1979). The multiplicity of phylogenetically distinct uptake hydrogenases, and the presence of a plasmidborne hydrogenase gene cluster in strain BTAi1, warranted assessment of the functional capacity of these enzymes and their potential role in symbiosis.…”

“…Several Rhizobium and Bradyrhizobium species contain uptake hydrogenases, which reduce energy loss associated with symbiotic nitrogen fixation (Albrecht et al, 1979;Evans et al, 1987). Generally, the hydrogen uptake (hup) genes are arranged in at least three operons with conserved gene composition and organization (Baginsky et al, 2002).…”

Symbiotic Hydrogenase Activity in Bradyrhizobium sp. ( Vigna ) Increases Nitrogen Content in Vigna unguiculata Plants

“…Consequently, incorporation of the hydrogen oxidation capability into rhizobial strains has been proposed as a way to improve symbiotic nitrogen fixation (11). However, enhancement of legume host productivity associated to the activity of the hydrogenase enzyme has been reported only for certain symbiotic associations, such as Bradyrhizobium japonicum/soybean (1,8).To date, a detailed molecular characterization of hydrogenase gene clusters has been reported for Rhizobium leguminosarum bv. viciae, B. japonicum, and Azorhizobium caulinodans (3,11,16).…”

“…Consequently, incorporation of the hydrogen oxidation capability into rhizobial strains has been proposed as a way to improve symbiotic nitrogen fixation (11). However, enhancement of legume host productivity associated to the activity of the hydrogenase enzyme has been reported only for certain symbiotic associations, such as Bradyrhizobium japonicum/soybean (1,8).…”

Activities, Occurrence, and Localization of Hydrogenase in Free-Living and Symbiotic Frankia

“…Not only energy is gained (1), but also 02 is scavenged from the 02-sensitive nitrogenase (6,9). H2 is also known to inhibit nitrogenase activity, is debatable whether the in vivo situation will create H2 concentration high enough to inhibit nitrogen fixation (7).…”