Influence of maize mucilage on the diversity and activity of the denitrifying community

Abstract

In order to understand the effect of the maize rhizosphere on denitrification, the diversity and the activity of the denitrifying community were studied in soil amended with maize mucilage. Diversity of the denitrifying community was investigated by polymerase chain reaction (PCR) amplification of total community DNA extracted from soils using gene fragments, encoding the nitrate reductase (narG) and the nitrous oxide reductase (nosZ), as molecular markers. To assess the underlying diversity, PCR products were cloned and 10 gene libraries were obtained for each targeted gene. Libraries containing 738 and 713 narG and nosZ clones, respectively, were screened by restriction fragment analysis, and grouped based on their RFLP (restriction fragment length polymorphism) patterns. In all, 117 and 171 different clone families have been identified for narG and nosZ and representatives of RFLP families containing at least two clones were sequenced. Rarefaction curves of both genes did not reach a clear saturation, indicating that analysis of an increasing number of clones would have revealed further diversity. Recovered NarG sequences were related to NarG from Actinomycetales and from Proteobacteria but most of them are not related to NarG from known bacteria. In contrast, most of the NosZ sequences were related to NosZ from alpha, beta, and gammaProteobacteria. Denitrifying activity was monitored by incubating the control and amended soils anaerobically in presence of acetylene. The N2O production rates revealed denitrifying activity to be greater in amended soil than in control soil. Altogether, our results revealed that mucilage addition to the soil results in a strong impact on the activity of the denitrifying community and minor changes on its diversity.

Diversity and Abundance of Nitrate Reductase Genes ( narG and napA ), Nitrite Reductase Genes ( nirS and nrfA ), and Their Transcripts in Estuarine Sediments

“…This cluster was comprised of narG sequences from Hythe and Alresford sediments only. A further 10 clones (cluster II) were most closely related to narG sequences derived from agricultural soils (11,41). Four clones were related to narG sequences derived from agricultural soils (Fig.…”

Identification and isolation of active N2O reducers in rice paddy soil

“…Similar nosZ clones have also been obtained from other paddy fields (for example, GenBank Accession No. ACI48848) and maize rhizospheric soils (Mounier et al, 2004;Dambreville et al, 2006;Henry et al, 2008). Considering the general agreement between the 16S rRNA gene and nosZ phylogenies (Jones et al, 2008;Palmer et al, 2009), these results suggested that Herbaspirillum and other Burkholderiales bacteria may be important players in N 2 O reduction, not only in rice paddy soils but also in other environments.…”

Quantitative Detection of the nosZ Gene, Encoding Nitrous Oxide Reductase, and Comparison of the Abundances of 16S rRNA, narG , nirK , and nosZ Genes in Soils

“…The second cluster encompassed (1,9). Although several authors reported the diversity of the N 2 O-reducing community (10,18,23,24,28), no studies were performed to estimate its actual density. The isolation and characterization of denitrifiers based on their N 2 O-reducing abilities (2) are hampered by cultivation-dependent bias and the extensive manual effort due to the fact that denitrifiers represent a low percentage of the total FIG.…”