Identification of Acetobacter strains from Thai fermented rice products based on the 16S rRNA gene sequence and 16S-23S rRNA gene internal transcribed spacer restriction analyses

BACKGROUND

Fermented rice flour (khao-khab, a non-glutinous rice) and related products are Thai traditional products. The types of acetic acid bacteria (AAB) microflora in khao-khab have not been reported. In this study, Acetobacter strains were isolated and identified based on the phenotypic and chemotaxonomic characteristics and molecular aspects.

RESULTS

Twenty-five acetic acid bacteria isolated from fermented rice products and a starter for sweetened rice in Thailand by an enrichment culture approach, were assigned to the genus Acetobacter by phenotypic and chemotaxonomic characterisations. On the basis of the 16S rRNA gene sequence and 16S-23S rRNA gene ITS restriction analyses, 25 isolates were divided into six groups and identified at the specific level: (1) Group 1 included five isolates, which were identified as A. indonesiensis; (2) Group 2 included two isolates, which were identified as A. lovaniensis; (3) Group 3 included one isolate, which was identified as A. orientalis; (4) Group 4 included eleven isolates, which were identified as A. pasteurianus; (5) Group 5 included three isolates, which were identified as A. syzygii and (6) Group 6 included three isolates, which were unidentified and considered to constitute a new species.

CONCLUSION

Results revealed that various Acetobacter species were distributed in Thai fermented rice flour and related products. A novel Acetobacter species was isolated from the product.

Application of the Chinese steamed bun starter dough (CSB-SD) in breadmaking

The application of Chinese steamed bun starter dough (CSB-SD) in breadmaking was investigated. The activation of CSB-SD to activate the growth of lactic acid bacteria (LAB) and to increase the number of yeast, prior to making bread, was conducted by mixing CSB-SD with wheat flour and water and then incubating for 24 h. Wheat flour was then substituted by this activated CSB-SD (aCSB-SD) at 10%, 30%, and 50% (w/w) to make bread. Dough and bread properties were studied comparing to the control (without aCSB-SD). From the farinograph results, a high aCSB-SD substitution level resulted in a less stability in dough with a higher degree of softening. Extensigraph results suggested that after aging, all the substituted dough yielded a greater resistance to extension with lower extensibility values than the control. Substitutions with 30% and 50% (w/w) aCSB-SD significantly increased the total CO(2) gas generation. Scanning electron microscopy SEM images of the 30% and 50% (w/w) substituted dough showed a well-developed gluten matrix. The 50% (w/w) substituted breads obtained a greater risen volume, finer crumb grain, and retained more softness after 5-d storage than the control. In addition, both the 30% and 50% (w/w) substituted breads showed a slightly increased mold stability, as compared to the 0% and 10% (w/w) substituted breads.

Gluconobacter nephelii sp. nov., an acetic acid bacterium in the class Alphaproteobacteria

Three strains, RBY-1T, PHD-1 and PHD-2, were isolated from fruits in Thailand. The strains were Gram-negative, aerobic rods with polar flagella, produced acetic acid from ethanol and did not oxidize acetate or lactate. In phylogenetic trees based on 16S rRNA gene sequences and 16S–23S rRNA gene internal transcribed spacer (ITS) sequences, the strains formed a cluster separate from the type strains of recognized species of the genus Gluconobacter. The calculated 16S rRNA gene sequence and 16S–23S rRNA gene ITS sequence similarities were respectively 97.7–99.7 % and 77.3–98.1 %. DNA G+C contents ranged from 57.2 to 57.6 mol%. The strains showed high DNA–DNA relatedness of 100 % to one another, but low DNA–DNA relatedness of 11–34 % to the tested type strains of recognized Gluconobacter species. Q-10 was the major quinone. On the basis of the genotypic and phenotypic data obtained, the three strains clearly represent a novel species, for which the name Gluconobacter nephelii sp. nov. is proposed. The type strain is RBY-1T ( = BCC 36733T = NBRC 106061T = PCU 318T), whose DNA G+C content is 57.2 mol%.

Pisciglobus halotolerans gen. nov., sp. nov., isolated from fish sauce

Two strains of Gram-stain-positive, catalase-negative, tetrad-forming cocci, C01T and C02, were isolated in Thailand from fish sauce. They were facultatively anaerobic, non-motile and non-spore-forming bacteria. These strains produced l-lactic acid from glucose. They grew at pH 5.0–9.0, at 15–40 °C and in the presence of 10 % (w/v) NaCl. The dominant fatty acid was C18 : 1ω9c. The DNA G+C contents of strains C01T and C02 were 38.6 and 38.7 mol%, respectively. Strain C01T was related most closely to Desemzia incerta DSM 20581T, with a 16S rRNA gene sequence similarity of 96.9 %. The strains could be distinguished clearly from D. incerta DSM 20581T based on cell morphology, physiological and biochemical characteristics and low levels of DNA–DNA relatedness. On the basis of the data presented, strains C01T and C02 are considered to represent a novel species of a new genus in the Bacillus–Lactobacillus cluster, for which the name Pisciglobus halotolerans gen. nov., sp. nov. is proposed. The type strain of Pisciglobus halotolerans is C01T ( = KCTC 13150T  = TISTR 1958T  = PCU 316T).

Micromonospora humi sp. nov., isolated from peat swamp forest soil

A novel actinomycete, strain P0402T, was isolated from peat swamp forest soil collected in Thailand. Its taxonomic position was determined by using a polyphasic taxonomic approach. The chemotaxonomic characteristics of this strain matched those of the genus Micromonospora, i.e. the presence of meso-diaminopimelic acid and N-glycolyl muramic acid in the peptidoglycan, whole-cell sugar pattern D, phospholipid type II, and cellular fatty acid type 3b. Phylogenetic analysis based on 16S rRNA gene sequences revealed a close relationship between strain P0402T and Micromonospora coxensis JCM 13248T (99.0 % similarity), Micromonospora eburnea JCM 12345T (99.0 %), Micromonospora marina JCM 12870T (98.9 %), Micromonospora halophytica JCM 3125T (98.7 %), Micromonospora chalcea JCM 3031T (98.7 %), Micromonospora purpureochromogenes JCM 3156T (98.6 %) and Micromonospora aurantiaca JCM 10878T (98.5 %). It could be clearly distinguished from these type strains based on low levels of DNA–DNA relatedness and phenotypic differences. On the basis of the data presented, strain P0402T is suggested to represent a novel species of the genus Micromonospora, for which the name Micromonospora humi sp. nov. is proposed. The type strain is P0402T ( = JCM 15292T  = PCU 315T  = TISTR 1883T).

Agromyces tropicus sp. nov., isolated from soil

Two actinomycete strains, CM9-9T and AK2-48, which produced straight rod-shaped, non-motile cells, were isolated from soils in Chiang Mai and Phuket provinces, respectively, Thailand. The morphological and chemotaxonomic characteristics of the isolates coincided with those of the genus Agromyces. Phylogenetic analysis using 16S rRNA gene sequences also indicated that the isolates were clearly separated from their closest relative, Agromyces aurantiacus YIM 21741T, and should be classified in the genus Agromyces. Furthermore, a combination of DNA–DNA hybridization results and physiological and biochemical properties indicated that the isolates could be distinguished from all recognized members of the genus Agromyces. The isolates therefore represent a novel species, for which the name Agromyces tropicus sp. nov. is proposed. The type strain is CM9-9T (=JCM 15672T =BCC 34764T).

Identification of moderately halophilic bacteria from Thai fermented fish ( pla-ra ) and proposal of Virgibacillus siamensis sp. nov

Forty-one isolates of moderately halophilic bacteria were isolated from fermented fish (pla-ra) in Thailand. On the basis of their phenotypic and chemotaxonomic characteristics, DNA-DNA relatedness and 16S rRNA gene sequences analyses, they were divided into six groups. The isolates in Group I to V were Gram-positive rod-shaped bacteria. They contained meso-diaminopimelic acid in the cell-wall peptidoglycan and menaquinone with seven isoprene units (MK-7). An isolate in Group VI was a Gram-negative rod-shaped bacterium. The DNA G+C contents of tested strains ranged from 36.5-63 mol%. Ten strains (Group I) were identified as Virgibacillus dokdonensis, 13 isolates (Group II) as V. halodenitrificans, 14 isolates (Group III) as V. marismortui, 1 isolate (Group IV) as Virgibacillus sp., 2 isolates (Group V) as Bacillus vietnamnensis, and 1 isolate (Group VI) as Chromohalobacter salexigens. Isolate MS3-4 in Group IV was closely related to V. carmonensis KCTC 3819(T) (95.9%). This strain contained anteiso-C(15:0) (55.8%) and anteiso-C(17:0) (17.7%) as major cellular fatty acids and had phosphatidylglycerol, diphosphatidylglycerol and an unidentified glycolipid as polar lipids. The DNA G+C content of MS3-4 was 38.0 mol%. The strain from Group IV is proposed as Virgibacillus siamensis sp. nov. and MS3-4(T) is the type strain (JCM 15395(T) =PCU 312(T) =TISTR 1957(T)).

Paenibacillus xylanisolvens sp. nov., a xylan-degrading bacterium from soil

A xylan-degrading bacterium, strain X11-1T, was isolated from soil collected in Nan province, Thailand. The strain was characterized based on its phenotypic and genotypic characteristics. Strain X11-1T was a Gram-stain-positive, facultatively anaerobic, spore-forming, rod-shaped bacterium. It contained meso-diaminopimelic acid in the cell-wall peptidoglycan. The major menaquinone was MK-7, anteiso-C15 : 0 (56.6 %) and C16 : 0 (14.0 %) were the predominant cellular fatty acids and diphosphatidylglycerol, phosphatidylmonomethylethanolamine, phosphatidylethanolamine and phosphatidylglycerol were the major phospholipids. The DNA G+C content was 51.6 mol%. Phylogenetic analysis using 16S rRNA gene sequences showed that strain X11-1T was affiliated to the genus Paenibacillus and was closely related to Paenibacillus naphthalenovorans KACC 11505T and Paenibacillus validus CCM 3894T, with 96.5 % sequence similarity. Therefore, the strain represents a novel species of the genus Paenibacillus, for which the name Paenibacillus xylanisolvens sp. nov. is proposed. The type strain is X11-1T (=KCTC 13042T =PCU 311T =TISTR 1829T).

Cohnella xylanilytica sp. nov. and Cohnella terrae sp. nov., xylanolytic bacteria from soil

Two xylan-degrading bacteria, strains MX15-2T and MX21-2T, were isolated from soils collected in Nan province, Thailand. Cells were Gram-reaction-positive, facultatively anaerobic, spore-forming and rod-shaped. They contained meso-diaminopimelic acid in the cell-wall peptidoglycan. The major menaquinone was MK-7. iso-C16 : 0 and anteiso-C15 : 0 were the predominant cellular fatty acids. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and lysyl-phosphatidylglycerol were the major polar lipids. The genomic DNA G+C contents of strains MX15-2T and MX21-2T were 63.0 and 65.1 mol%, respectively. Phylogenetic analysis using 16S rRNA gene sequences showed that strains MX15-2T and MX21-2T were affiliated with the genus Cohnella and were closely related to Cohnella thermotolerans CCUG 47242T, with 96.5 and 95.6 % sequence similarity, respectively. The strains could be clearly distinguished from each other and from all known species of the genus Cohnella based on their physiological and biochemical characteristics as well as their phylogenetic positions and levels of DNA–DNA hybridization. Therefore, these two strains represent novel species of the genus Cohnella, for which the names Cohnella xylanilytica sp. nov. (type strain MX15-2T =KCTC 22294T =PCU 309T =TISTR 1891T) and Cohnella terrae sp. nov. (type strain MX21-2T =KCTC 22295T =PCU 310T =TISTR 1892T) are proposed.

Dactylosporangium tropicum sp. nov., isolated from soil

Two novel actinomycete strains, designated KB2-4(T) and KB9-2, were isolated from soil samples. Both isolates formed finger-shaped sporangia on short sporangiophores that emerged directly from substrate hyphae. The cell-wall peptidoglycan contained glutamic acid, glycine, alanine and meso-diaminopimelic acid; the whole-cell sugars were galactose, glucose, mannose, rhamnose, ribose and xylose. The diagnostic phospholipid was phosphatidylethanolamine. The predominant menaquinones were MK-9(H(8)) and MK-9(H(6)). Mycolic acids were not detected. The predominant cellular fatty acids (>20 %) were iso-C(16 : 0) and anteiso-C(17 : 0). For both strains, the G+C content of the genomic DNA was about 72 mol%. The morphological and chemotaxonomic characteristics of the two strains were typical of members of the genus Dactylosporangium. Phylogenetic analysis using 16S rRNA gene sequences also indicated that these strains should be classified in the genus Dactylosporangium and showed that the closest relative was Dactylosporangium salmoneum NRRL B-16294(T) (99.1 % 16S rRNA gene sequence similarity). DNA-DNA relatedness and some physiological and biochemical properties indicated that the isolates could be readily distinguished from their closest phylogenetic relatives. On the basis of these phenotypic and genotypic data, the isolates represent a novel species, for which the name Dactylosporangium tropicum sp. nov. is proposed. The type strain is strain KB2-4(T) ( = BCC 34760(T)  = JCM 15673(T)).

Cohnella thailandensis sp. nov., a xylanolytic bacterium from Thai soil

A xylanolytic bacterium, strain S1-3T, was isolated from soil collected in Nan province, Thailand. It was characterized taxonomically based on phenotypic characteristics and 16S rRNA gene sequence comparison. The strain was a Gram-stain-positive, facultatively anaerobic, spore-forming, rod-shaped bacterium. It contained meso-diaminopimelic acid in the cell-wall peptidoglycan. The major menaquinone was MK-7. Iso-C16 : 0 (39.5 %) and anteiso-C15 : 0 (26.8 %) were predominant cellular fatty acids. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and lysyl-phosphatidylglycerol were the major polar lipids. The DNA G+C content was 53.3 mol%. Phylogenetic analysis using 16S rRNA gene sequences showed that strain S1-3T was affiliated to the genus Cohnella, and was closely related to Cohnella ginsengisoli GR21-5T and Cohnella thermotolerans CCUG 47242T with 95.7 and 95.3 % sequence similarity, respectively. Strain S1-3T could be clearly distinguished from related species of the genus Cohnella by its physiological and biochemical characteristics as well as by its phylogenetic position. Therefore, the strain represents a novel species of the genus Cohnella, for which the name Cohnella thailandensis sp. nov. is proposed. The type strain is S1-3T (=KCTC 22296T =TISTR 1890T =PCU 306T).

Bacillus siamensis sp. nov., isolated from salted crab (poo-khem) in Thailand

A Gram-positive, endospore-forming, rod-shaped bacterium, strain PD-A10T, was isolated from salted crab (poo-khem) in Thailand and subjected to a taxonomic study. Phenotypic and chemotaxonomic characteristics, including phylogenetic analyses, showed that the novel strain was a member of the genus Bacillus. The novel strain grew in medium with 0–14 % (w/v) NaCl, at 4–55 °C and at pH 4.5–9. The predominant quinone was a menaquinone with seven isoprene units (MK-7). The major fatty acids were anteiso-C15 : 0 and anteiso-C17 : 0. Polar lipid analysis revealed the presence of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, lysylphosphatidylglycerol, glycolipid and unknown lipids. The DNA G+C content was 41.4 mol%. The 16S rRNA gene sequence similarities between strain PD-A10T and Bacillus amyloliquefaciens NBRC 15535T, Bacillus subtilis DSM 10T, Bacillus vallismortis DSM 11031T and Bacillus mojavensis IFO 15718T were 99.5, 99.4, 99.4 and 99.2 %, respectively. Strain PD-A10T showed a low degree similarity of rep-PCR fingerprints and low DNA–DNA relatedness with the above-mentioned species. On the basis of the data gathered in this study, strain PD-A10T should be classified as representing a novel species of the genus Bacillus, for which the name Bacillus siamensis sp. nov. is proposed. The type strain is PD-A10T (=BCC 22614T=KCTC 13613T).

Proteinase-producing halophilic lactic acid bacteria isolated from fish sauce fermentation and their ability to produce volatile compounds

Halophilic lactic acid bacteria were isolated from fish sauce mashes fermented at 1 to 12 months. Seven out of sixty-four isolates were selected according to their proteolytic activity and growth at 25% NaCl for characterization and investigation of volatile compound production. All selected isolates were Gram-positive cocci with pairs/tetrads and grew at 0-25% NaCl, pH 4.5-9.0. Results of 16S rRNA gene sequence analysis showed 99% homology to Tetragenococcus halophilus ATCC 33315. The restriction fragment length polymorphism (RFLP) patterns of all isolates were also similar to those of T. halophilus ATCC 33315. These isolates were, thus, identified as T. halophilus. All isolates hydrolyzed fish protein in the medium containing 25% NaCl. Intracellular aminopeptidase of 7 isolates exhibited the highest activity of 2.85-3.67 U/ml toward Ala-p-nitroanilide (Ala-pNA). T.halophilus strains MS33 and M11 showed the highest alanyl aminopeptidase activity (P<0.05), and produced histamine in mGYP broth containing 5 and 25% NaCl in the level of 6.62-22.55 and 13.14-20.39 mg/100ml, respectively. Predominant volatile compounds of fish broth containing 25% NaCl inoculated with T. halophilus MS33 and MRC5-5-2 were 1-propanol, 2-methylpropanal, and benzaldehyde, corresponding to major volatile compounds in fish sauce. T.halophilus appeared to play an important role in volatile compound formation during fish sauce fermentation.

Haloarcula salaria sp. nov. and Haloarcula tradensis sp. nov., isolated from salt in Thai fish sauce

Two red-pigmented, strictly aerobic, pleomorphic rod-shaped and extremely halophilic archaea, designated strains HST01-2R(T) and HST03(T), were isolated from salt in a fish sauce sample from Thailand. The novel strains grew optimally at 37 °C, pH 7.0, and in the presence of 20-25 % (w/v) NaCl. The DNA G+C contents of the isolates were 61.6-62.2&emsp14;mol%. Phylogenetic analysis based on a comparison of 16S rRNA gene sequences revealed that strains HST01-2R(T) and HST03(T) were placed in the radiation of species of the genus Haloarcula. The chemotaxonomic properties of the two strains, i.e. the presence of MK-8 and MK-8(H(2)) as the major menaquinone components and C(20)C(20) derivatives of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and a triglycosyl diether as major polar lipids, supported the assignment of the two strains to the genus Haloarcula. Nevertheless, several phenotypic features and the low DNA-DNA relatedness between the two strains and related species of the genus Haloarcula (13.4-46.9 %) enabled the strains to be distinguished from each other and from recognized species. Therefore, strains HST01-2R(T) and HST03(T) represent two novel species in the genus Haloarcula, for which the names Haloarcula salaria sp. nov. and Haloarcula tradensis sp. nov. are proposed, respectively. The type strains are HST01-2R(T) (=BCC 40029(T)=JCM 15759(T)=PCU 313(T)) and HST03(T) (=BCC 40030(T)=JCM 15760(T)=PCU 314(T)).

Actinaurispora siamensis gen. nov., sp. nov., a new member of the family Micromonosporaceae

Two actinomycete strains, CM2-8(T) and CM2-12, were isolated from temperate peat swamp forest soil in Chiang Mai Province, Thailand. Their taxonomic positions were determined using a polyphasic approach. Chemotaxonomic characteristics of these strains coincided with those of the family Micromonosporaceae, i.e. cell wall chemotype II, N-glycolyl type of muramic acid, and type II phospholipids. Phylogenetic analysis based on 16S rRNA gene sequence data also indicated that these strains fell within the family Micromonosporaceae and formed a distinct taxon in the Micromonosporaceae phylogenetic tree. On the basis of phylogenetic analysis, characteristic patterns of 16S rRNA gene signature nucleotides and chemotaxonomic data, it is proposed that the novel isolates belong to a new genus, Actinaurispora gen. nov. The type species of the genus is proposed as Actinaurispora siamensis sp. nov., with strain CM2-8(T) (=JCM 15677(T)=BCC 34762(T)) as the type strain.

Gracilibacillus thailandensis sp. nov., from fermented fish (pla-ra)

A novel strain, designated TP2-8(T), was isolated from fermented fish (pla-ra) in Thailand. It stained Gram-positive and the cells were aerobic, endospore-forming rods. The strain grew at pH 6-8 (optimum pH 7), 15-55 degrees C (optimum 37 degrees C) and 1-22 % (w/v) NaCl (optimum 5-10 %). It contained meso-diaminopimelic in the cell-wall peptidoglycan. MK-7 and cellular fatty acids anteiso-C(15 : 0), iso-C(15 : 0) and anteiso-C(17 : 0) were major components. Polar lipids diphosphatidylglycerol and phosphatidylglycerol and unidentified lipids were detected. The DNA G+C content was 37.6 mol%. Comparison of the 16S rRNA gene sequence of strain TP2-8(T) with those of other members of the family Bacillaceae indicated that it was a member of the genus Gracilibacillus (94.9-99.2 % sequence similarity) and was closely related to Gracilibacillus saliphilus YIM 91119(T) (99.2 % similarity), G. lacisalsi BH312(T) (98.6 %), G. orientalis XH-63(T) (97.7 %), 'G. quinghaiensis' YIM C229 (97.7 %) and G. boraciitolerans T-16X(T) (97.2 %). Strain TP2-8(T) showed low DNA-DNA relatedness (< or = 49%) to G. saliphilus YIM 91119(T), G. lacisalsi DSM 19029(T), G. orientalis CCM 7326(T), 'G. quinghaiensis' DSM 17858 and G. boraciitolerans JCM 21714(T). On the basis of the physiological and biochemical characteristics and molecular data presented, strain TP2-8(T) is proposed to represent a novel species, Gracilibacillus thailandensis sp. nov. (type strain TP2-8(T) =JCM 15569(T) =PCU 304(T) =TISTR 1881(T)).

Micromonospora marina sp. nov., isolated from sea sand

Two actinomycete strains, JSM1-1(T) and JSM1-3, were isolated from sea sand collected in Thailand. Their taxonomic position was determined using a polyphasic approach. The chemotaxonomic characteristics of these strains coincided with those of the genus Micromonospora, i.e. the presence of meso-diaminopimelic acid and N-glycolyl muramic acid in the peptidoglycan, whole cell sugar pattern D, phospholipids type II, and cellular fatty acid type 3b. Phylogenetic analysis of 16S rRNA gene sequences revealed a close relationship between strains JSM1-1(T) and JSM1-3 (99.8 %), and between JSM1-1(T) and Micromonospora aurantiaca JCM 10878(T) (99.3 %), Micromonospora chalcea JCM 3031(T) (99.0 %), and Micromonospora coxensis JCM 13248 (T) (99.0 %). However, strains JSM1-1(T) and JSM1-3 could be clearly distinguished from these type strains by a low DNA-DNA relatedness and by phenotypic differences. On the basis of the data presented, a new species, Micromonospora marina sp. nov., is proposed. The type strain is JSM1-1(T) (=JCM 12870(T) =PCU 269(T) =TISTR 1566(T)).

Oceanobacillus kapialis sp. nov., from fermented shrimp paste in Thailand

A Gram-positive, rod-shaped, strictly aerobic, spore-forming, moderately halophilic bacterium, designated strain SSK2-2T, was isolated from fermented shrimp paste (ka-pi) produced in Thailand. It contained MK-7 as the predominant menaquinone and meso-diaminopimelic acid in the cell-wall peptidoglycan. The isolate grew at 8-43 degrees C, pH 6-9 and in 0.5-24% (w/v) NaCl (optimum, 6-14% NaCl). The major cellular fatty acids were anteiso-C15:0 and anteiso-C17:0. Phosphatidylglycerol and diphosphatidylglycerol were the major polar lipid components. The DNA G+C content was 39.7 mol%. Comparative 16S rRNA gene sequence analyses showed that strain SSK2-2T was most closely related to Oceanobacillus picturae KCTC 3821T with 98.7% sequence similarity. Based on phenotypic and molecular features combined with DNA-DNA hybridization results (<or=24.9% with O. picturae KCTC 3821T), this strain represents a novel species of the genus Oceanobacillus for which the name Oceanobacillus kapialis sp. nov. is proposed; the type strain is SSK2-2T (=KCTC 13177T=PCU 300T=TISTR 1858T).

Salinivibrio siamensis sp. nov., from fermented fish (pla-ra) in Thailand

A Gram-negative, facultatively anaerobic, moderately halophilic bacterium, strain ND1-1(T), was isolated from fermented fish (pla-ra) in Thailand. The cells were curved rods, motile and non-endospore-forming. The novel strain grew optimally at 37 degrees C, at pH 8 and in the presence of 9-10 % (w/v) NaCl. The predominant respiratory lipoquinone was Q-8. The major cellular fatty acids were C(16 : 0) and C(12 : 0). Polar lipid analysis revealed the presence of phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The DNA G+C content was 49.0 mol%. Comparative 16S rRNA gene sequence analyses indicated that strain ND1-1(T) was closely related to Salinivibrio costicola, which comprises three subspecies, and Salinivibrio proteolyticus with gene sequence similarities of 98.3-98.6 %. Strain ND1-1(T) showed low levels of DNA-DNA relatedness with S. costicola subsp. costicola JCM 15095(T) (33.2 %), S. costicola subsp. alcaliphilus DSM 16359(T) (38.4 %), S. costicola subsp. vallismortis JCM 15096(T) (59.7 %), and S. proteolyticus AF-2004(T) (42.1 %). On the basis of the physiological and biochemical characteristics and the molecular data presented, strain ND1-1(T) should be classified as a novel species of the genus Salinivibrio for which the name Salinivibrio siamensis sp. nov. is proposed. The type strain is ND1-1(T) (=JCM 14472(T)=PCU 301(T)=TISTR 1810(T)).