SULFONOLIPID CONTENT OF CYTOPHAGA AND FLEXIBACTER SPECIES ISOLATED FROM SOIL AND CULTURED UNDER DIFFERENT NUTRIENT AND TEMPERATURE REGIMES

Gliding bacteria of the genera Cytophaga and Flexibacter contain an un usual sulfonolipid in their outer membrane that may be a potential bio chemical marker for these organisms in soil. The precision with which a marker provides information about biomass varies with the range in m arker content within the cells of the taxon under study. To evaluate t his, Cytophaga and Flesibacter spp. were isolated from earthworm fecal pellets and soil, batch cultured with [S-35]sulfate, and extracted fo r lipids. Sulfonolipid S was measured using isotope dilution technique s and Lipid phosphate was determined by colorimetry. Ratios of sulfono lipid S to protein and to phospholipid P were compared among isolates grown under various conditions. Ratios of sulfonolipid S to phospholip id P from 0.22 to 0.98 confirmed sulfonolipids as major cell component s of Cytophaga and Flexibacter spp. Two criteria essential to the succ ess of sulfonolipids as a biomarker for these organisms in soil were m et: (i) sulfonolipid concentration among the noncellulolytic isolates, with one exception, spanned a narrow range (40-60 mu mol S/g cell pro tein), and (ii) this range in sulfonolipid concentration was maintaine d under the range of growth conditions studied here. Cellulolytic cyto phagas, however, could be clearly differentiated from other Cytophaga and Flexibacter spp. on the basis of sulfonolipid content, 85-164 mu m ol S/g cell protein. This dichotomy in sulfonolipid content between ce llulolytic and noncellulolytic isolates must be considered when interp reting data where sulfonolipids are used as a quantitative biomarker f or Cytophaga and Flexibacter spp. in habitats where cellulolytic cytop hagas are dominant.