Polyphasic taxonomy of a novel Halobacillus, Halobacillus thailandensis sp. nov. isolated from fish sauce.
In order to speed up fish sauce production, a more complete understanding of the microorganisms associated with the fermentation was needed. This study was undertaken to meet that need. A bacterium was isolated from a fish sauce production line containing 25% NaCl. It is a Gram-positive, rod-shaped bacillus with pointed ends, occurring as single cells, pairs, or short chains. Endospores are produced on a low nutrient medium and, in old cultures, the cells round up, even when undergoing division. The cell wall is relatively amorphous and similar to that of Gram-positive bacteria in structure and composition. Cells grown in a medium containing 10-20% salt possess thicker cell walls than those grown in a medium with 3% salt. Based on 16S rRNA sequence and DNA/DNA hybridization data, we conclude that the bacterium is a species of Halobacillus. This bacterium shares 99.2% and 97.2% 16S rRNA similarity with Halobacillus litoralis and Halobacillus halophilus respectively and DNA/DNA homology was lower than 70%, considered indicative of species similarity. Three highly expressed extra-cellular proteolytic enzymes with M(r) of approximately 100 kDa, 42 kDa and 17 kDa, respectively, were detected by gelatin-polyacrylamide gel electrophoresis. Activity of the 100 kDa and 17 kDa proteases was inhibited by phenylmethanesulphonyl fluoride (PMSF), without being affected by L-trans epoxysuccinyl-leucylamide 4-guanidino-butane (E-64), pepstatin, EDTA, or 1, 10-phenanthroline, leading to the conclusion that these enzymes are serine proteases. The 42-kDa protease was inhibited by EDTA and 1,10-phenanthroline, but not by PMSF, thus, being classified a metalloprotease. The strain has been successfully employed to improve fermentation in industrial production of fish sauce in Thailand.
Chaiyanan
S
S
Center of Marine Biotechnology, Columbus Center, University of Maryland, Baltimore.
Chaiyanan
S
S
Maugel
T
T
Huq
A
A
Robb
F T
FT
Colwell
R R
RR
D000818:Animals; D003470:Culture Media / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D005399:Fishes / Q000382:microbiology*; D005516:Food Microbiology; D005519:Food Preservation; D005780:Gelatin; D016987:Gram-Positive Rods / Q000145:classification* / Q000166:cytology / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D008666:Metalloendopeptidases / Q000032:analysis / Q000378:metabolism; D008854:Microscopy, Electron; D009693:Nucleic Acid Hybridization; D010802:Phylogeny; D012329:RNA, Bacterial / Q000032:analysis; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D012689:Sequence Homology, Nucleic Acid; D012697:Serine Endopeptidases / Q000032:analysis / Q000378:metabolism; D012965:Sodium Chloride; D013696:Temperature
D003470:Culture Media; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012965:Sodium Chloride; D005780:Gelatin; D012697:Serine Endopeptidases; D008666:Metalloendopeptidases