RESUMO
Andosols comprise one of the most important soil groups for agricultural activities in Japan because they cover about 46.5% of arable upland fields. In this soil group, available phosphorus (P) is accumulated by application of excessive fertilizer, but little is known about the influence of increasing P availability on microbial community diversity at large scales. We collected soil samples from 9 agro-geographical sites with Andosol soils across an available P gradient (2048.1-59.1 mg P2O5·kg(-1)) to examine the influence of P availability on the fungal community diversity. We used polymerase chain reaction - denaturing gradient gel electrophoresis to analyze the fungal communities based on 18S rRNA genes. Statistical analyses revealed a high negative correlation between available P and fungal diversity (H'). Fungal diversity across all sites exhibited a significant hump-shaped relationship with available P (R(2) = 0.38, P < 0.001). In addition, the composition of the fungal community was strongly correlated with the available P gradient. The ribotype F6, which was positively correlated with available P, was closely related to Mortierella. The results show that both the diversity and the composition of the fungal community were influenced by available P concentrations in Andosols, at a large scale. This represents an important step toward understanding the processes responsible for the maintenance of fungal diversity in Andosolic soils.
Assuntos
Biodiversidade , Fungos/classificação , Fungos/isolamento & purificação , Fósforo/análise , Microbiologia do Solo , Solo/química , Produtos Agrícolas , DNA Fúngico/análise , Eletroforese em Gel de Gradiente Desnaturante , Fertilizantes , Fungos/genética , Japão , Reação em Cadeia da Polimerase , RibotipagemRESUMO
Anaerobic degradation of phenol, p-cresol, 4-n-propylphenol (n-PP), 4-i-propylphenol (i-PP), 4-n-butylphenol (n-BP) and 4-sec-butylphenol (sec-BP) was observed in a paddy soil supplemented with nitrate. We detected the metabolites 4'-hydroxypropiophenone (HPP) from n-PP, 4-i-propenylphenol from i-PP, and 4-(1-butenyl)phenol and 4'-hydroxybutyrophenone (HBP) from n-BP. Compared with the original soils, Betaproteobacteria became predominant in the microcosm during the degradation of phenol and p-cresol whereas no remarkable change was observed in the community degrading propylphenols and butylphenols. The microcosm, however, did not degrade 4-t-butylphenol (t-BP), 4-t-octylphenol (t-OP) and 4-n-octylphenol (n-OP). Paddy soil supplemented with sulfate or iron (III) as electron acceptors did not degrade phenol and 4-alkylphenols with the exception of the degradation of p-cresol in sulfate-reducing conditions. It was demonstrated for the first time that anaerobic microbial degradation of alkylphenols, in a paddy soil supplemented with nitrate as an electron acceptor, occurred via oxidation of the alpha carbon in the alkyl chain.