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Mesophilic Cellulolytic Clostridia from Freshwater Environments

By S. B. Leschine and E. Canale-Parola


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, CO(2), and H(2). 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

Topics: General Microbial Ecology
Year: 1983
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Provided by: PubMed Central
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