Calcium and the biological activities of two Streptomyces species isolated from the rhizosphere of soybean plants

Abstract

Careful examination of the characteristics of both organisms revealed that we are dealing with Streptomyces violaceochromogenes and Streptomyces glaucescens. Calcium chloride decreased the permeability of both organisms as indicated by the low total nitrogen content of their media compared to the controls. Small doses of calcium nitrate suppressed the permeability of S. violaceochromogenes and increased that of S. glaucescens whereas the larger doses were stimulatory for both organisms. Calcium nitrate had similar effects on S. violaceochromogenes only without affecting S. glaucescens. The stimulatory effects of calcium gradually faded with increased concentration. Calcium chloride increased the proteolytic activity in S. violaceochromogenes media ; a phenomenon that was apparent in S. glaucescens media only in the case of the larger doses. Calcium nitrate suppressed the proteolytic activity in S. glaucescens media. The cellulolytic activity of both organisms was suppressed by calcium but amylases were initiated in S. glaucescens media. Those of S. violaceochromogenes were arrested with the lower levels of calcium but the larger doses restored or stimulated their activity.The metabolic activities of rhizospheric microflora play an important role in the growth of plants through supplying them with the mineralization products of organic matter. They may produce degrading enzymes, growth promoting or growth retarding substances for higher as well as lower plants (RAo 1977, HEcco 1984.The role of rhizospheric actinomycetes has received little attention. Streptomyces species are relatively good decomposers of organic matter (ALEXANDER 1977). KUSTER (1979) reported that a large number of actinomycetes, exhibiting different kinds of unusual physio-

Dinâmica das populações bacterianas em solos de Cerrados

“…Entretanto, as alterações do pH e da disponibilidade de nutrientes podem influenciar a comunidade microbiana de maneira direta através da atuação sobre processos microbianos, fisiológicos e bioquímicos específicos, ou indiretamente através da disponibilidade de nutrientes e da neutralização de elementos tóxicos (Kamel et al, 1989).…”

População microbiana em solo cultivado com soja e tratado com diferentes herbicidas em área de cerrado no estado de Roraima

“…Esta heterogeneidade observada entre os perfis de bandeamento, provavelmente, é decorrente do preparo do solo, uma vez que as práticas agrícolas de manejo do solo como a aração, adubação e a calagem alteram a aeração do solo, a decomposição da matéria orgânica, a disponibilização de nutrientes e o pH do solo. E, estas alterações influenciam nos processos bioquímicos do solo e por conseqüência a estrutura da comunidade bacteriana do solo (Kamel et al, 1989;Pereira et al, 1999). Oito das bandas ocorridas nos géis de DGGE (Figuras 4 e 5) foram isoladas, reamplificadas, seqüenciadas e submetidas à análise de homologia com seqüências do rDNA depositadas no National Center for Biotechnology Information (NCBI), através do programa BLAST (Altshul et al, 1997).…”