Genome sequences and functional analysis of Levilactobacillus brevis LSF9-1 and Pediococcus acidilactici LSF1-1 from fermented fish cake (Som-fak) with gamma-aminobutyric acid (GABA) production.

Gamma-aminobutyric acid (GABA) is a crucial inhibitory neurotransmitter in the sympathetic nervous system that exerts regulatory effects on the blood, immune, and nervous systems. GABA production in som-fak, a traditional fermented fish of Thailand, has been attributed to the activity of lactic acid bacteria (LAB). The present study aims to characterize the LAB isolates and compare the genomes and GABA synthesis genes of selected isolates capable of GABA production. Thirteen isolates demonstrating GABA synthesis capability were identified based on their phenotypic and genotypic characteristics. Seven isolates (group I: LSF3-3, LSF8-3, LSF9-1, LSF9-3, LSF9-6, LSF9-7, and LSF10-14) were identified as Levilactobacillus brevis with 99.78-100% similarity. LSF2-1, LSF3-2, LSF5-4, and LSF6-5 (group II) were identified as Lactiplantibacillus pentosus with 99.86-100% similarity. Strain LSF1-1 (group III) was identified as Pediococcus acidilactici (99.47%), and LSF10-4 (group IV) was identified as Pediococcus pentosaceus with 99.93% similarity. The GABA production of isolates ranged from 0.087 to 16.935 g/L. The maximum production of 16.935 g/L from 3% monosodium glutamate was obtained from strain LSF9-1. Gene and genome analysis revealed that L. brevis LSF9-1 has multiple gad genes in the genome, such as gadB1, gadB2, gadC1, and gadC2, making it the potential strain for GABA production. Additionally, the genome analysis of P. acidilactici LSF1-1 consists of gadA, gadB, and gadC, which respond to controlling GABA production and export. Furthermore, strain LSF1-1 was considered safe, containing no virulence factors. Thus, Levilactobacillus brevis LSF9-1 and Pediococcus acidilactici LSF1-1 have the potential for GABA production and probiotic use in future studies.

Salinicoccus siamensis sp. nov., isolated from fermented shrimp paste in Thailand.

Fifteen strains of moderately halophilic, Gram-positive cocci were isolated from a traditional fermented shrimp paste ('ka-pi') produced in Thailand. These bacteria were strictly aerobic, non-motile, non-sporulating and catalase- and oxidase-positive. They produced orange pigment and grew in the presence of 1.5-25 % (w/v) NaCl. They grew optimally in 10 % (w/v) NaCl, at pH 8.5 and at 37 degrees C. The cell-wall peptidoglycan was of l-Lys type. Menaquinone with six isoprene units (MK-6) was a major component. The dominant cellular fatty acids were anteiso-C(15 : 0) and iso-C(15 : 0). DNA G+C contents were in the range 44.5-47.5 mol%. Comparative 16S rRNA gene sequence analyses indicated that representative strain PN1-2(T) was related most closely to Salinicoccus roseus JCM 14630(T), with 97.3 % similarity. The other novel strains were included in the same species based on their levels of DNA-DNA relatedness to strain PN1-2(T) (> or =76.6 %) but showed low DNA-DNA relatedness to S. roseus JCM 14630(T) (21.7 %). On the basis of the phenotypic and molecular data presented, the 15 novel strains are suggested to represent a single novel species of the genus Salinicoccus, for which the name Salinicoccus siamensis sp. nov. is proposed. The type strain is PN1-2(T) (=JCM 12822(T) =PCU 242(T) =TISTR 1562(T)).

Identification of lactic acid bacteria from fermented tea leaves (miang) in Thailand and proposals of Lactobacillus thailandensis sp. nov., Lactobacillus camelliae sp. nov., and Pediococcus siamensis sp. nov.

Eighteen rod-shaped homofermentatives, six heterofermentatives, and a coccal homofermentative lactic acid bacteria were isolated from fermented tea leaves (miang) produced in the northern part of Thailand. The isolates were placed in a monophyletic cluster consisting of Lactobacillus and Pediococcus species. They were divided into seven groups by phenotypic and chemotaxonomic characteristics, DNA-DNA similarity, and 16S rRNA gene sequences. Groups I to VI belonged to Lactobacillus and Group VII to Pediococcus. All of the strains tested produced DL-lactic acid but those in Group IV produced L-lactic acid. The strains tested in Groups I, II and V had meso-diaminopimelic acid in the cell wall. Six strains in Group I were identified as Lactobacillus pantheris; five strains in Group II as Lactobacillus pentosus; and four strains in Group V as Lactobacillus suebicus. Two strains in Group VI showed high DNA-DNA similarity for each other and MCH4-2 was closest to Lactobacillus fermentum CECT 562(T) with 99.5% of 16S rRNA gene sequence similarity. Five strains in Group III are proposed as Lactobacillus thailandensis sp. nov., and MCH5-2(T) (BCC 21235(T)=JCM 13996(T)=NRIC 0671(T)=PCU 272(T)) is the type strain which has 49 mol% G+C of DNA. Two strains in Group IV are proposed as Lactobacillus camelliae sp. nov., and the type strain is MCH3-1(T) (BCC 21233(T)=JCM 13995(T)=NRIC 0672(T)=PCU 273(T)) which has 51.9 mol% G+C of DNA. One strain in Group VII is proposed as Pediococcus siamensis sp. nov., and MCH3-2(T) (BCC 21234(T)=JCM 13997(T)=NRIC 0675(T)=PCU 274(T)) is the type strain which has 42 mol% G+C of DNA.

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

Two strains of strictly aerobic, moderately halophilic Gram-positive rods were isolated from fermented shrimp paste ('ka-pi') produced in Thailand. They produced a red pigment and grew optimally in the presence of 5-30 % NaCl. The diagnostic diamino acid in the cell-wall peptidoglycan was meso-diaminopimelic acid. The predominant menaquinone was MK-7. The major cellular fatty acid was anteiso-C(15 : 0). Phosphatidylglycerol, diphosphatidylglycerol and two unidentified glycolipids were found to be the major polar lipid components. The DNA G+C content was 41.2-41.6 mol%. Comparative 16S rRNA gene sequence analyses showed that strain PN7-6T was most closely related to Lentibacillus salarius KCTC 3911T with 96.5 % sequence similarity. On the basis of phenotypic and molecular properties, the two isolates represent a novel species of the genus Lentibacillus, for which the name Lentibacillus kapialis sp. nov. is proposed. The type strain is PN7-6T (=JCM 12580T=PCU 259T=TISTR 1551T).

Lentibacillus halophilus sp. nov., from fish sauce in Thailand.

Fifteen strains of extremely halophilic bacteria were isolated from fish sauce (nam-pla) collected in Thailand at various stages of the fish-fermentation process. The isolates were strictly aerobic, spore-forming, Gram-positive rods. They grew optimally in the presence of 20-26 % NaCl. The cell-wall peptidoglycan contained meso-diaminopimelic acid. The predominant menaquinone was MK-7. The major cellular fatty acids were anteiso-C(15 : 0) and anteiso-C(17 : 0). Polar lipid analysis revealed the presence of phosphatidylglycerol, diphosphatidylglycerol and two unidentified glycolipids. The DNA G+C content was 42.1-43.1 mol%. On the basis of the 16S rRNA gene sequence, a representative strain, PS11-2(T), was found to be closely related to Lentibacillus juripiscarius JCM 12147(T) (97.3 % similarity). The 15 strains were included in the same species on the basis that the levels of DNA-DNA relatedness with strain PS11-2(T) were greater than 70 %. They could be distinguished from L. juripiscarius and other Lentibacillus species on the basis of several phenotypic characteristics and low levels of DNA-DNA relatedness (