RESUMO
Eighteen aerobic endospore forming strains were isolated from sugarcane rhizosphere in N-free medium. A phenotypic description and analysis of the 5' end hypervariable region sequences of 16S rRNA revealed a high diversity of Bacillus and related genera. Isolates were identified, and four genera were obtained: seven strains belonged to Bacillus (Bacillaceae family), four belonged to Paenibacillus, six belonged to Brevibacillus and one strain was identified as Cohnella (Paenibacillaceae family). Four Brevibacillus strains showed in vitro inhibitory activity against plant pathogens fungi Curvularia and Fusarium. Seventy-four percent of the isolated bacteria grew on pectin as the only carbon source, showing polygalacturonase activity. Pectate lyase activity was detected for the first time in a Brevibacillus genus strain. All isolates showed endoglucanase activity. Calcium phosphate solubilisation was positive in 83.3% of the isolates, with higher values than those reported for Bacillus inorganic phosphate solubilising strains. High ethylene plant hormone secretion in the culture medium was detected in 22% of the bacteria. This is the first report of ethylene secretion in Paenibacillaceae isolates. Indole-3-acetic acid production was found in a Brevibacillus genus isolate. It was reported for the first time the presence of Cohnella genus strain on sugarcane rhizosphere bearing plant growth promoting traits. The sugarcane isolate Brevibacillus B65 was identified as a plant growth inoculant because it showed wider spectra of plant stimulation capabilities, including an antifungal effect, extracellular hydrolases secretion, inorganic phosphate solubilisation and plant hormone liberation. In this work, sugarcane was shown to be a suitable niche for finding aerobic endospore forming 'Bacilli' with agriculture biotechnological purposes.
Assuntos
Antibiose , Bacillales/isolamento & purificação , Bacillales/fisiologia , Rizosfera , Saccharum/microbiologia , Microbiologia do Solo , Agricultura/métodos , Bacillales/classificação , Bacillales/genética , Técnicas de Tipagem Bacteriana , Análise por Conglomerados , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Fungos/crescimento & desenvolvimento , Filogenia , Reguladores de Crescimento de Plantas/metabolismo , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
An online scheme to assign Stenotrophomonas isolates to genomic groups was developed using the multilocus sequence analysis (MLSA), which is based on the DNA sequencing of selected fragments of the housekeeping genes ATP synthase alpha subunit (atpA), the recombination repair protein (recA), the RNA polymerase alpha subunit (rpoA) and the excision repair beta subunit (uvrB). This MLSA-based scheme was validated using eight of the 10 Stenotrophomonas species that have been previously described. The environmental and nosocomial Stenotrophomonas strains were characterised using MLSA, 16S rRNA sequencing and DNA-DNA hybridisation (DDH) analyses. Strains of the same species were found to have greater than 95% concatenated sequence similarity and specific strains formed cohesive readily recognisable phylogenetic groups. Therefore, MLSA appeared to be an effective alternative methodology to amplified fragment length polymorphism fingerprint and DDH techniques. Strains of Stenotrophomonas can be readily assigned through the open database resource that was developed in the current study (www.steno.lncc.br/).
Assuntos
DNA Bacteriano/genética , Tipagem de Sequências Multilocus/métodos , RNA Ribossômico 16S/genética , Stenotrophomonas/genética , Técnicas de Tipagem Bacteriana , RNA Polimerases Dirigidas por DNA/genética , Humanos , FilogeniaRESUMO
An online scheme to assign Stenotrophomonas isolates to genomic groups was developed using the multilocus sequence analysis (MLSA), which is based on the DNA sequencing of selected fragments of the housekeeping genes ATP synthase alpha subunit (atpA), the recombination repair protein (recA), the RNA polymerase alpha subunit (rpoA) and the excision repair beta subunit (uvrB). This MLSA-based scheme was validated using eight of the 10 Stenotrophomonas species that have been previously described. The environmental and nosocomial Stenotrophomonas strains were characterised using MLSA, 16S rRNA sequencing and DNA-DNA hybridisation (DDH) analyses. Strains of the same species were found to have greater than 95 percent concatenated sequence similarity and specific strains formed cohesive readily recognisable phylogenetic groups. Therefore, MLSA appeared to be an effective alternative methodology to amplified fragment length polymorphism fingerprint and DDH techniques. Strains of Stenotrophomonas can be readily assigned through the open database resource that was developed in the current study (www.steno.lncc.br/).
Assuntos
Humanos , DNA Bacteriano , Tipagem de Sequências Multilocus/métodos , Stenotrophomonas , Técnicas de Tipagem Bacteriana , RNA Polimerases Dirigidas por DNA , FilogeniaRESUMO
Beijerinckia derxii, a free-living nitrogen-fixing bacterium, maintained an increasing nitrogenase specific activity during the stationary growth phase. To verify the destination of the nitrogen fixed during this phase, intra and extracellular nitrogenated contents were analyzed. Organic nitrogen and amino acids were detected in the supernatant of the cultures. An increase in intracellular content of both nitrogen and protein occurred. Cytoplasmic granules indicated the presence of arginine. The ability of a non-diazotrophic bacterium (E. coli) to use B. derxii proteins as a source of nitrogen was observed concomitantly with E. coli growth. There is a suggestion that B. derxii contributes to the environment by both releasing nitrogenated substances and accumulating substances capable of being consumed after its death.