Mesophilic Cellulolytic Clostridia from Freshwater Environments
AUTOR(ES)
Leschine, S. B.
RESUMO
Eight strains of obligately anaerobic, mesophilic, cellulolytic bacteria were isolated from mud of freshwater environments. The isolates (C strains) were rod-shaped, gram negative, and formed terminal spherical to oval spores that swelled the sporangium. The guanine plus cytosine content of the DNA of the C strains ranged from 30.7 to 33.2 mol% (midpoint of thermal denaturation). The C strains fermented cellulose with formation primarily of acetate, ethanol, CO2, and H2. Reducing sugars accumulated in the supernatant fluid of cultures which initially contained ≥0.4% (wt/vol) cellulose. The C strains resembled Clostridium cellobioparum in some phenotypic characteristics and Clostridium papyrosolvens in others, but they were not identical to either of these species. The C strains differed from thermophilic cellulolytic clostridia (e.g., Clostridium thermocellum) not only in growth temperature range but also because they fermented xylan and five-carbon products of plant polysaccharide hydrolysis such as d-xylose and l-arabinose. At 40°C, cellulose was degraded by cellulolytic mesophilic cells (strain C7) at a rate comparable to that at which C. thermocellum degrades cellulose at 60°C. Substrate utilization and growth temperature data indicated that the C strains contribute to the anaerobic breakdown of plant polymers in the environments they inhabit.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=239342Documentos Relacionados
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