Effect of sodium chloride concentration on growth and degradation of eicosane by the marine halotolerant bacterium Marinobacter hydrocarbonoclasticus

The extremely halotolerant marine species Marinobacter hydrocarbonoclasticus presents an absolute requirement for NA(+) ions. When grown on acetate or eicosane, lag phase of cultures and generation time of cells increased exponentially at NaCl concentrations greater than or equal to 1.0 M whereas the final biomass did not vary significantly (p less than or equal to 0.05) when salinity increased from 0.2 to 2.5 M NaCl. The increase in salinity induced morphological changes with increased cell size. Scanning electron microscopy revealed extracellular vesicles on cells grown on eicosane. High salinity did not modify hydrocarbon biodegradation rates (80-90% biodegraded eicosane). This bacterium produced an extracellular emulsifying agent and adhered to hydrocarbon, but did not solubilize it before uptake. Both emulsification and adherence took place during growth on eicosane, achieving contact between cells and hydrocarbon. An increase in external NaCl concentration modified emulsifying activity and adherence ability, but not the biodegradation rates.