| 著者 |
Ishikawa M, Tanasupawat S, Nakajima K, Kanamori H, Ishizaki S, Kodama K, Okamoto-Kainuma A, Koizumi Y, Yamamoto Y, Yamasato K.
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| Abstract |
We describe 10 new strains of marine lactic acid bacteria isolated from decaying marine algae, decaying seagrass, raw fish, salted fish and salted and fermented shrimp paste ('ka-pi') collected from a temperate area of Japan and Thailand. The isolates are Gram-positive and non-sporulating. They have motility with peritrichous flagella depending on the strains. They lack catalase and quinones. Under anaerobic conditions, lactate yields were 64-93 % of the glucose consumed; residual products were formate, acetate and ethanol with a molar ratio of approximately 2 : 1 : 1. The pH of the fermentation medium markedly affected the product composition; at higher pH, the yield of lactate decreased (15-48 % at pH 9.0) and yields of other products increased, retaining the molar ratio. Under aerobic conditions, acetate and lactate were produced from carbohydrates and related compounds. The isolates were slightly halophilic, highly halotolerant and alkaliphilic. The optimum NaCl concentration for growth ranged between 0.5 and 4.0 % (w/v), depending on the strain, with a growth range of between 0 and 17-21 % (11 % for one isolate). The optimum pH for growth ranged between 8.0 and 9.5, with a growth range of 6.0-11.0, depending on the strains. Comparative sequence analysis of the 16S rRNA genes revealed that the isolates occupied three phylogenetic positions within the genus Alkalibacterium, showing 97.1-99.8 % similarity to Alkalibacterium indicireducens. DNA-DNA hybridization values (<46 %) among the 10 isolates and phylogenetically related taxa resulted in the identification of four genomic species (designated groups GS1-GS4). The G+C contents of the DNA were 41.7 mol% (group GS1), 42.2 mol% (group GS2), 41.0-43.0 mol% (group GS3) and 38.4-39.4 mol% (group GS4). The cell-wall peptidoglycan was type A4beta, Orn-d-Asp, for three genomic species (groups GS1, GS2 and GS3), and type A4beta, Orn-d-Glu, for the remaining species (group GS4). The major components of cellular fatty acids were C(16 : 0), C(16 : 1)omega9c and C(18 : 1)omega9c (oleic acid). On the bases of phenotypic characteristics, genetic distinctiveness and phylogenetic affiliations, the four genomic species, groups GS1, GS2, GS3 and GS4, were classified as four novel species within the genus Alkalibacterium, for which the names Alkalibacterium thalassium sp. nov., Alkalibacterium pelagium sp. nov., Alkalibacterium putridalgicola sp. nov. and Alkalibacterium kapii sp. nov., respectively, are proposed. The respective type strains are T117-1-2(T) (=DSM 19181(T)=NBRC 103241(T)=NRIC 0718(T)), T143-1-1(T) (=DSM 19183(T)=NBRC 103242(T)=NRIC 0719(T)), T129-2-1(T) (=DSM 19182(T)=NBRC 103243(T)=NRIC 0720(T)) and T22-1-2(T) (=DSM 19180(T)=NBRC 103247(T)=NRIC 0724(T)).
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