Bacterial Flocculation: Focus on Bioengineering Applications
Final rept. 1 Jul 1999-31 Dec 2002
HAMPTON UNIV VA DEPT OF CHEMISTRY
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Subsurface microbial activity is critical in many bioengineering processes such as enhanced oil recovery, in-situ or enhanced bioremediation, and biomass plugging operations. To investigate biofilm formation, strain PHOO2 of the Azoarcus genus, which produces flocs in stationary growth phase was studied. Flocculation occurs as this gram-negative, denitrifying strain is grown anaerobically on a phenol carbon source. As stationary phase is approached, the phenol concentration diminishes and the hydrophilic cells become hydrophobic. When grown in a comparable manner, aerobically with succinate as the carbon source, flocculation does not occur and the cells remain hydrophilic. The main thrust of the research was to understand the molecular basis of flocculation in this strain by comparing the molecules most likely to contribute hydrophobicity to the bacterial surface. In this research, the outer membrane proteins from anaerobically and aerobically grown cells were extracted, separated by gel electrophoresis and compared. Reproducible results were not obtained from the outer membrane experiments. Cellular lipopolysaccharides were also extracted and separated by gel electrophoresis. Differences in lipopolysaccharides bands were observed between hydrophobic and hydrophilic cells but a complete study was not done. Further work remains to adequately study the outer membrane proteins and lipopolysaccharide components of strain PHOO2 as causative factors in flocculation.
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