Isolation and identification of aerobic denitrifying bacterium Defluvibacter lusatiensis strain DN7 and its heterotrophic nitrification ability. Screening and Denitrification Characteristics of an Aerobic Denitrifying-Heterotrophic Nitrification Bacterium Denitrification characteristics of an aerobic denitrifying bacterium Defluvibacter lusatiensis str. DN7 using different sources of nitrogen