[Distribution of heterotrophic aerobic microflora and specially denitrifying and free-living nitrogen-fixing bacteria in the rhizosphere of rice (author's transl)].
The distribution of heterotrophic aerobic bacteria, actinomycetes and fungi was estimated in three samples (rhizospherical soil (SR), rhizoplane (R) and endorhizosphere (ER)) obtained from one rice seedling which had grown in pot during four mounths in a Casamance grey soil. The number of microbial populations were about the same from one sample to another: 1.1 to 2 X 10(8) bacteria, 3.3 to 8.6 X 10(6) actinomycetes and 0.2 to 8.9 X 10(4) fungi per gram of dry soil (SR) or dry roots (R and ER). The denitrifying and free-living nitrogen fixing bacteria were numerous (10(7) bacteria/g) but lower for ER where the number of actinomycetes remained high. Thirty-six bacterial strains have been isolated from every sample with the use of a grid of isolation. The Gram-negative bacteria were dominant in SR and R where they represented respectively 70 and 94% of total count. The major groups were non-sporulated Gram-variable rods (SR) and Alcaligenes-like bacteria (ER). The pseudomonads represented quite 15% of total count in the three samples. On the other hand, the frequency of endospore-forming Gram-positive bacteria was high only in R where the Bacillus group was estimated to 45% of total count. Only 5 free-living nitrogen-fixing bacterial strains had shown a denitrifying ability.
D000332:Aerobiosis; D001419:Bacteria / Q000302:isolation & purification* / Q000378:metabolism; D009586:Nitrogen Fixation; D012275:Oryza; D012675:Senegal; D012988:Soil Microbiology
Distribution de la microflore hétérotrophe aérobie et en particulier des bactéries dénitrifiantes et fixatrices d'azote libres dans la rhizosphère du riz.