Cellulolytic bacteria employ a variety of different strategies for the degradation of cellulose. Our laboratory is interested in biofilm-mediated breakdown of cellulose and possible roles of exopolysaccharides in this process. As part of an effort to isolate new strains of biofilm-forming, cellulolytic bacteria, soil samples were collected from sites rich in decaying vegetation and used to inoculate a minimal growth medium containing a MOPS/Tris buffer (pH 7.4), a combination of inorganic salts, 0.05% yeast extract, and 1% microcrystalline cellulose (MCC) as the primary source of carbon and energy (MSYE-MCC media). These cellulose-enrichment cultures were grown aerobically at 30C for 2 weeks in a shaking incubator, and culture samples were then spread over the surface of tryptic soy agar (TSA) plates. Colonies on TSA were streaked onto agar plates containing the MSYE basal medium plus either 1% carboxymethyl-cellulose (MSYE-CMC media) or 1% filter paper cellulose (MSYE-FPC). Over one dozen new, cellulose-degrading strains were isolated and initially characterized according to colony morphologies, relative cell size, cellular arrangements, Gram stain reaction, and other outstanding features. Approximately one quarter of the new strains were Gram-negative, and large inclusion bodies were noted in some. The remainder of the strains were either Gram-positive or Gram-variable. Many Gram-positive strains were bacilli arranged in chains (streptobacilli) and one strain exhibited filamentous growth. Phase-contrast microscopy was used to observe cultures grown in MSYE-MCC media, and strains which attached to MCC particles, aggregated on and around the particles, and grew as biofilms on the surfaces of the particles were selected for further study. These strains were also screened for the production of extracellular material as detected by phase-contrast microscopy. A few strains produced possible glycocalyx layers during biofilm formation and utilization of cellulose. These extracellular layers, and any exopolysaccharides associated with them, will be the primary focus of future research.


University of West Georgia

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