Non-nodular endorhizospheric nitrogen fixation in wetland rice

Abstract

Diazotrophic Alcaligenes faecalis strain A15 isolated from rice roots is associated with rice roots and resides in the mucilage layer. On examination by light and electron microscopy, about 10% of the bacteria that accumulated on the surface entered the root cells. Some bacteria were observed to penetrate the cell wall. By using a 10B α-track technique, the presence of bacteria inside the root was also demonstrated after the rice plants were inoculated with A. faecalis. This was further supported by results of an immunofluorescence study. Both single cells and protoplasts were isolated from rice root and its callus. Transmission and scanning electron microscopy showed that A. faecalis grew inside the root cell. Callus, developed from rice root cells inoculated with this bacterium, grew well in nitrogen-free culture medium, while it died within 30 days without inoculation. Nitrogen fixation in the callus was confirmed by 15N tracer methodology and the rate ranged from 18.5 to 35.5 μg N fixed/g dry weight callus per day.Key words: Alcaligenes faecalis, endorhizospheric nitrogen fixation, rice–bacteria symbiont.

Root colonization and systemic spreading of Azoarcus sp. strain BH72 in grasses

“…From (4). Intracellular ingress has also been claimed to accompany colonization of rice roots by Alcaligenes faecalis A15 (59). The sporadic occurrence of the diazotrophic Enterobacter agglomerans Cl in the stele of gnotobiotically grown wheat seedlings was accompanied by an infection intensity close to a pathogenic relationship (33).…”

Isolation and characterization of endophytic bacteria from wild and traditionally cultivated rice varieties

“…Through these studies, several species of diazotrophs, such as Klebsiella (Ladha et al 1983;Fujii et al 1987), Alcaligenes (You and Zhou 1989), and Azospirillum (Bald ani and Dobereiner 1980), have been isolated from the rhizosphere of wetland rice. However, the recent discovery of endophytic N 2 -fixing bacteria within the roots and shoots of sugarcane and kallar grass suggests that unique diazotrophic bacteria (e.g., Acetobacter diazotrophicus, Herbaspirillum spp., and Azoarcus spp.)…”

Nitrogen fixation island and rhizosphere competence traits in the genome of root-associated Pseudomonas stutzeri A1501

“…stutzeri A1501 can survive in the soil, colonize the root surface, and invade the superficial layers of the root cortex (7,8,14). This is why it was also reported as being an endophyte (14,15). We report here the analysis of the complete genome of A1501 and compare it with other Pseudomonas species.…”