| Thauera sp. strain MZ1T is a floc-forming bacterium isolated from the wastewater treatment plant of Eastman Chemical Company. Its overabundance was positively correlated to episodes of poor dewatering of activated sludge (Lajoie 2000). The specific cause of this problem was thought to be due to the production of large quantities of exopolysaccharide (EPS) by MZ1T.; EPS was extracted from pure cultures of MZ1T. Subsequent investigation of the physical properties of the purifed EPS found that the polymer was highly soluble in water but not in organic solvents. Investigations into the interaction of the EPS with metal cations revealed that the EPS showed a capacity for binding uranium ions in both aqueous and non-aqueous solutions. Additionally, the EPS was found to precipitate from solution in the presence of calcium chloride.; The glycosyl composition of the EPS was determined by gas chromatography-mass spectroscopy (GC-MS) of both the alditol acetate and per-O-trimethylsilyl methyl glycoside (TMS) derivatives. By these methods, the EPS was found to include: rhamnose, N-acetylfucosamine, galacturonic acid, N-acetylglucosamine, and trace amounts of glucose.; Several mutants of MZ1T incapable of, or reduced in, their capacity for floc formation in liquid media were isolated following chemical mutagenesis. Investigations of EPS extracted from these mutants revealed that all of the monosaccharides previously detected in the wild type EPS could also be identified in the mutants. Spectroscopic analysis by FT-IR of the EPS extracted from true floc− mutants did, however, reveal conserved alterations in the spectra of the mutant EPS relative to that from the wild type. These data suggest that alteration of the linkage or the substitution of the EPS is responsible for the loss of floc-forming capacity in the mutants.; Additionally, it was found that floc and floc-reduced isolates, unlike the wild type, were competent to receive broad host range plasmids by conjugal transfer. Colonies of these mutants also exhibited altered colony texture and differential responses to dyes than did the wild type. Taken together, these data suggest a protective role for the EPS of MZ1T, and that mutations resulting in alterations of the EPS have broad phenotypic effects. |
