Characterization and Identification of Tetragenococcus halophilus and Tetragenococcus muriaticus Strains from Fish Sauce (Nam-pla)

Eighty strains of homofermentative tetrad-forming lactic acid bacteria were isolated from fish sauce fermentation in Thailand. These bacteria were divided into three groups based on the phenotypic and chemotaxonomic characteristics including DNA relatedness. Forty strains (Group I) showed high degrees (70.0% to 109.1%) DNA-DNA homology with Tetragenococcus halophilus ATCC 33315. They were identified as T. halophilus. Thirty-eight strains (Group II) showed high degrees (70.9% to 105.6%) of DNA-DNA homology with Tetragenococcus muriaticus JCM 10006. They were identified as T. muriaticus. Two strains (Group III) showed low degrees (3.7% to 16.3%) of DNA-DNA homology with T. halophilus ATCC 33315, T. muriaticus JCM 10006, and Aerococcus uiridans TISTR 393. Then they were left unidentified. Group I and Group II strains are halophilic which grew in 25% NaCl. All the strains tested produced L-lactic acid and contained cellular fatty acids with C18:1 as the major component. Some of the selected strains produced histamine ranging from 0.04 to 52.29mg/100 ml. The differentiation of Tetragenococcus strains is discussed.