Strain CCMM B554, also known as FSM-MA, is a soil dwelling and nodule forming, nitrogen-fixing bacterium isolated from the nodules of the legume Medicago arborea L. in the Maamora Forest, Morocco. The strain forms effective nitrogen fixing nodules on species of the Medicago, Melilotus and Trigonella genera and is exceptional because it is a highly effective symbiotic partner of the two most wid...

Soil microbial communities are continuously exposed to H2 diffusing into the soil from the atmosphere. N2-fixing nodules represent a peculiar microniche in soil where H2 can reach concentrations up to 20,000 fold higher than in the global atmosphere (0.530 ppmv). In this study, we investigated the impact of H2 exposure on soil bacterial community structure using dynamic microcosm chambers simul...

The symbiotic plasmid (pSym) of Rhizobium leguminosarum bv. trifolii 4S5, which carries Tn5-mob, was successfully transferred into Agrobacterium tumefaciens A136 by using a conjugation method. The resulting transconjugants induced the development of ineffective nitrogen-fixing nodules on the roots of white clover seedlings. Depending on the manner in which the pSym was retained, the transconjug...

Patterns in nitrogen-fixing activity by Inga jinicuil Schl., a leguminous shade tree in Mexican coffee plantations, were monitored over a three-and-half year period using acetylene reduction. Year to year variation was unexpectedly large; mean annual fixation equalled 35 kg N ha yr, which constitutes a significant nitrogen input to the coffee ecosystem. Nitrogen-fixing activity occurred through...

In previous publications (4, 6), the preparation and properties of a particulate enzyme complex from Rihizobiumn japonicutm cells isolated from the nodules of soybean plants (Glycine max Merr.) have been described. It has been established that the particles catalyze the reduction of nitrate to nitrite and that either DPNH or succinate serves as effective electron donor. Evidence indicates that ...

The NAD(+)-dependent malic enzyme (DME) and the NADP(+)-dependent malic enzyme (TME) of Sinorhizobium meliloti are representatives of a distinct class of malic enzymes that contain a 440-amino-acid N-terminal region homologous to other malic enzymes and a 330-amino-acid C-terminal region with similarity to phosphotransacetylase enzymes (PTA). We have shown previously that dme mutants of S. meli...

Why do rhizobia expend resources on fixing N(2) for the benefit of their host plant, when they could use those resources for their own reproduction? We present a series of theoretical models which counter the hypotheses that N(2) fixation is favoured because it (i) increases the exudation of useful resources to related rhizobia in the nearby soil, or (ii) increases plant growth and therefore th...

In this study, the nitrogen fixing bacteria VIT SS 1-6 were screened from the root nodules of Groundnut (Family: Fabaceae, Species: Arachis hypogaea) collected from Vellore district were examined for their plant growth promoting properties. Of the six isolates obtained, five were fast growing and one was slow growing. The slow growing species VIT SS5 was further examined for its nitrogen fixing...

This study was performed to assess the N2-fixing capability of the native actinorhizal species Ochetophila trinervis (sin. Discaria trinervis) and Discaria chacaye (Rhamnaceae) in Northwest Patagonia. We measured the N concentration and N natural abundance in leaves and nodules of O. trinervis and D. chacaye, in leaves of associated non-actinorhizal vegetation, and in the soils under each sampl...

Endophytes MQ23 and MQ23R isolated from Sophora alopecuroides root nodules were characterized by observing their ability to promote plant growth and employing molecular analysis techniques. Results showed that MQ23 and MQ23R are potential N2-fixing endophytes and belong to the same species as Bacillus cereus. MQ23 was shown to be able to produce siderophores, IAA, and demonstrate certain antifu...