Diversity ofnifHgene pools in the rhizosphere of two cultivars of sorghum (Sorghum bicolor) treated with contrasting levels of nitrogen fertilizer

Abstract

The diversity of nitrogen-fixing bacteria was assessed in the rhizospheres of two cultivars of sorghum (IS 5322-C and IPA 1011) sown in Cerrado soil amended with two levels of nitrogen fertilizer (12 and 120 kg ha(-1)). The nifH gene was amplified directly from DNA extracted from the rhizospheres, and the PCR products cloned and sequenced. Four clone libraries were generated from the nifH fragments and 245 sequences were obtained. Most of the clones (57%) were closely related to nifH genes of uncultured bacteria. NifH clones affiliated with Azohydromonas spp., Ideonella sp., Rhizobium etli and Bradyrhizobium sp. were found in all libraries. Sequences affiliated with Delftia tsuruhatensis were found in the rhizosphere of both cultivars sown with high levels of nitrogen, while clones affiliated with Methylocystis sp. were detected only in plants sown under low levels of nitrogen. Moreover, clones affiliated with Paenibacillus durus could be found in libraries from the cultivar IS 5322-C sown either in high or low amounts of fertilizer. This study showed that the amount of nitrogen used for fertilization is the overriding determinative factor that influenced the nitrogen-fixing community structures in sorghum rhizospheres cultivated in Cerrado soil.

Impacts of Organic and Conventional Crop Management on Diversity and Activity of Free-Living Nitrogen Fixing Bacteria and Total Bacteria Are Subsidiary to Temporal Effects

“…DeLuca et al, [22] compared the use of cattle manure and urea fertilizers and found that both fertilizer types inhibited nitrogen fixation (measured by acetylene reduction assay) and that pH was correlated with nitrogen fixation ability. Previous studies, looking at the effect of individual attributes of farm management on the rhizospheric nitrogen fixing community, suggested that the application of increased amounts of nitrogen fertilizer (normally associated with conventional fertility management) would result in decreased diazotrophic diversity and activity [4], [52]. Rather our data suggests that many different factors affect the nitrogen fixing community (Table 3 and S3).…”

Comparative molecular analysis of chemolithoautotrophic bacterial diversity and community structure from coastal saline soils, Gujarat, India

“…Among the Betaproteobacteria two OTUs (22 clones, AS) were very closely related to Limnobacter thiooxidans (99%), which can grow chemolithoheterotrophically by oxidation of thiosulphate to sulphate [49]. One phylotype was related (96%) to Azohydromonas australica - nitrogen and hydrogen utilizing bacteria [50]. Two OTUs from AS clone library belonged to the phylum Nitrospira , which are facultative chemolithoautotrophic nitrite oxidizing bacteria [51].…”

Analysis of nifH gene diversity in red soil amended with manure in Jiangxi, south China

“…The scale bar indicates five changes per 100 amino acid positions. ration (Table 2), indicating that all clone libraries could represent the four environmental samples, although the number of the clones in each clone library was less than that of previous research (Zhang et al, 2006;Rodrigues Coelho et al, 2008). The proportions of each nifH clusters were shown in Fig.…”