Denitrification by a novel halophilic fermentative bacterium

Abstract

A novel halophilic heterotrophic bacterium, designated strain DN34, was isolated from seawater in Nanwan Bay of Renting National Park, Taiwan. It was Gram negative and facultatively anaerobic. Cells in late exponential to early stationary phase of growth were predominantly straight or curved rods, but Y- or V-shaped forms were also observed; straight and curved rods achieved motility by one to several lateral or subpolar flagella. The G+C content of the DNA was 51.7 mol%. Strain DN34 grew optimally at about 30 °C and pH 8.0. Growth depended on the presence of NaCl with optimal concentration at about 3%. Aerobically, strain DN34 grew much better and tolerated NaCl at a greater range of concentration with sufficient Mg2+and Ca2+than under deficient conditions; Mg2+or Ca2+was indispensable for growth under anaerobic conditions. The strain was capable of anaerobic growth by carrying out denitrifying metabolism using nitrate, nitrite, or nitrous oxide as terminal electron acceptors or, alternatively, by fermenting glucose or mannose as substrates. Halophilic heterotrophic bacteria capable of both denitrification and fermentation have not been reported previously.Key words: denitrification, denitrifying bacteria, halophilic bacteria, fermentative bacteria.