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Streptomyces tyrfis sp. nov., an actinobacterium isolated from Thai peat swamp forest soil and its promising secondary metabolites
(2026-12-01)
Kottip, Penkawee
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Klanbut, Khanungkan
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Fukasem, Poowadon
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Pittayakhajonwut, Pattama
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Intaraudom, Chakapong
An actinomycete strain, PTD5-9T, was isolated from peat swamp forest soil in Narathiwat Province, Thailand. Chemotaxonomic features and phylogenetic analysis based on the 16S rRNA gene sequence placed this strain within the genus Streptomyces. It exhibited the highest sequence similarity to Streptomyces gelaticus NRRL B-2928ᵀ (99.38%) and Streptomyces sanglieri NBRC 100784ᵀ (99.31%). However, the average nucleotide identity based on MUMmer (ANIm) values (88.48–88.56%), the average amino acid identity (84.37–84.97%), and digital DNA–DNA hybridization (dDDH) estimates (31.2–36.5%) were significantly below the accepted thresholds for species demarcation, supporting its classification as a new species within the genus. Accordingly, the name Streptomyces tyrfis sp. nov. is proposed. The crude extract derived from the culture broth of strain PTD5-9ᵀ exhibited potent antibacterial activity against Gram-positive bacteria (MIC ≤ 250 µg/mL). Subsequent chemical analysis led to the identification of ten bioactive secondary metabolites: isocycloheximide (1), (2R,4S,6E)-anhydrocycloheximide (2), actiphenol (3), (−)-phenatic acid A (4), 8-O-methyltetrangomycin (5), 8-O-methylrabelomycin (6), 4-hydroxy-8-O-methylrabelomycin (7), tetrangulol methyl ether (also known as X-14881 E) (8), (−)-elmonin (9), and 2-phenylacetamide (10). Among these, compounds 3, 6, 7, and 8, which were isolated in sufficient quantities, exhibited notable inhibitory activity against Mycobacterium tuberculosis, with MIC values ranging from 3.13 to 25.0 µg/mL. Furthermore, compounds 6, 7, and 8 demonstrated pronounced cytotoxicity against human small cell lung cancer (NCI-H187) cells (IC₅₀: 1.10–7.80 µM), and against human breast cancer (MCF-7) cells (IC₅₀: 1.21–24.6 µM).
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Streptomyces odontotermitis Odt1-20BT, an actinobacterium isolated from the fungus-growing Odontotermes formosanus
(2026-08-01)
Supong, Khomsan
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Niemhom, Nantawan
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Suriyachadkun, Chanwit
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Tanasupawat, Somboon
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Pittayakhajonwut, Pattama
A novel culturable insect-derived actinobacterium, designated strain Odt1-20BT, was isolated from Odontotermes formosanus. The cells exhibited aerobic, Gram-stain-positive, and filamentous characteristics. Strain Odt1-20BT formed well-developed substrate and aerial mycelia, with straight spore chains borne on the aerial mycelium. Strain Odt1-20BT grew at 20–40 °C (optimum 30 °C), 0˗4% (w/v) NaCl, and pH 5˗10 (optimum 7−8). The l,l-diaminopimelic acid was determined in the whole-cell hydrolysate of strain Odt1-20BT. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine, whereas the detected major quinones were MK-9(H<inf>4</inf>), MK-9(H<inf>6</inf>), and MK-9(H<inf>8</inf>). Whole-cell sugars were galactose, glucose, mannose, ribose, and xylose. Summed feature C<inf>18:1</inf> ω6c/ω7c, C<inf>16:0</inf>, anteiso-C<inf>15:0</inf>, and iso-C<inf>16:0</inf> were the main fatty acids. The draft genome size was 10,091,787 nucleotides, with a G + C content of 71.5%. Comparative phylogenetic analysis based on 16S rRNA gene sequence demonstrated that strain Odt1-20BT belonged to the genus Streptomyces, and shared the highest similarity with S. davaonensis JCM 4913 T (98.55%). Furthermore, phylogenomic analysis showed that strain Odt1-20BT was clearly distinguished from the closely related Streptomyces species. The average nucleotide identity analyses based on BLAST (ANIb) and MUMmer (ANIm) between strain Odt1-20BT and its related species ranged below 87%, and the digital DNA-DNA hybridization (dDDH) values ranged from 21.2% to 29.9%, all of which are below the species delimitation thresholds. The results of polyphasic taxonomy clearly indicated that strain Odt1-20BT represents a novel species, proposed as Streptomyces odontotermitis sp. nov. with the type strain Odt1-20BT (= NBRC 116112 T = TBRC 16156 T).
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Characterization, comparative genomics, and metabolome analysis of Streptomyces tuberiscabiei sp. nov., a novel actinomycete causing potato scab disease in Long Khot, Chiang Mai Province, Thailand
(2026-07-01)
Inthong, Tanchanok
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Wannawong, Thippawan
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Mhuantong, Wuttichai
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Hongprasit, Aphinan
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Tanasupawat, Somboon
Three actinomycete strains, WSLK1–3T, WSLK1–4, and WSLK1–5, associated with scabby potato tuber, were characterized using polyphasic and genome-based taxonomy. All strains were found to be Gram-stain-positive, filamentous bacteria, including LL-diaminopimelic acid in cell-wall peptidoglycan. Whole-cell sugars were glucose, mannose, rhamnose, and ribose. MK-9(H<inf>6</inf>) and MK-9(H<inf>10</inf>) were major menaquinones; C<inf>16:0</inf>, isoC<inf>16:0</inf>, ante iso-C<inf>15:0</inf>, and anteiso -C<inf>17:0</inf> were major cellular fatty acids; diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, and phosphatidylinositol mannoside were major phospholipids; and DNA G + C contents were 71.5 mol%. Phylogenetic analysis based on 16S rRNA gene and genome sequences indicated that strains WSLK1–3T, WSLK1–4, and WSLK1–5 are closely related to Streptomyces canus DSM 40017T (=JCM 4212T), and S. pseudovenezuelae DSM 40212T (=JCM 11516T), respectively. The 16S rRNA gene sequences, average nucleotide identity based on BLAST (ANIb) and MUMmer (ANIm), and digital DNA-DNA hybridization (dDDH) values among the three strains were 100%, 99.12%, 99.33%, and 94.3%, respectively, indicating that these strains belong to the same species. Strains WSLK1–3T, WSLK1–4, and WSLK1–5 showed 88.54–90.62% ANIb, 90.99–92.27% ANIm, and 40.4–45.1% to their closely related type strains: S. canus JCM 4212T, and S. pseudovenezuelae JCM 11516T. All novel strains were pathogenic, causing necrosis on potato tuber slices, inhibiting plant seedlings, and inducing superficial to raised scab lesions on potato tubers. Based on the phenotypic, chemotaxonomic, pathogenic, and genomic data, strains WSLK1–3T, WSLK1–4, and WSLK1–5 could be assigned to the novel species within the genus Streptomyces for which the name Streptomyces tuberiscabiei sp. nov. is proposed. The type strain is WSLK1–3T (=TBRC 19150T = LMG 33893T).
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Integrative genome analysis of bacteriocin-producing Lactiplantibacillus pentosus LNP1-39 and its synbiotic role in suppressing food-borne pathogens
(2026-06-01)
Jirakanjanasit, Thanadol
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Choovet, Natladda
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Booncharoen, Auttaporn
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Kingkaew, Engkarat
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Poothong, Saranporn
Lactic acid bacteria were isolated from traditional Thai-fermented foods. Among these, the strain LNP1-39, closely related to Lactiplantibacillus pentosus, was selected for further study because of its non-pathogenic profile. The bacteriocins produced by L. pentosus LNP1-39 were proteinaceous substances that exhibited strong antimicrobial activity across a wide pH range (pH 2–11; 6400–2400 AU/mL) and thermal stability at 100 °C for 40 min (400 AU/mL). These bacteriocins showed a narrow antimicrobial spectrum, effectively targeting Gram-positive pathogens, such as Kocuria rhizophila MIII, Enterococcus faecalis JCM 5803 T, and Listeria monocytogenes ATCC 19115. Comprehensive safety assessments, including whole-genome analysis and in vitro tests, confirmed a low risk of antibiotic resistance and the absence of virulence factors. Strain LNP1-39 was confirmed to be closely related to L. pentosus DSM 20314 T via digital DNA‒DNA hybridization (dDDH; 75.4%), with average nucleotide identity (ANI) at 96.56% ANIb and 97.22% ANIm values. Additionally, LNP1-39 produces pediocin with notable similarity (76.29% identity to pediocin) and presents low risks for antibiotic-resistance genes or transfer genes while providing antioxidant properties. Strain LNP1-39 survived harsh gastrointestinal tract conditions and exhibited a favorable prebiotic index and positive prebiotic activity score when paired with polydextrose or isomalto-oligosaccharide. These findings support L. pentosus LNP1-39 as potential bacteriocin-producing lactic acid bacteria for further application in food preservation and pathogen control or as a synbiotic.
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Functional and genomic characterization of Pediococcus pentosaceus NR4-4 reveals a safe bacteriocinogenic probiotic with strong anti-listerial activity and prebiotic metabolism
(2026-05-01)
Ratthanachot, Natnarin
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Woraprayote, Weerapong
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Janyaphisan, Thitiphorn
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Tanasupawat, Somboon
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Ochaikul, Duangjai
The growing interest in bacteriocin-producing lactic acid bacteria from traditional fermented foods has highlighted the value of strains that combine antimicrobial activity, probiotic functionality, and genome-supported safety. This study presents an integrated functional and probiogenomic characterization of Pediococcus pentosaceus NR4-4 isolated from Thai fermented mustard greens. The strain was found to produce a heat-stable class IIa bacteriocin with pronounced inhibitory activity against Listeria monocytogenes . In addition, NR4-4 exhibited strong tolerance to simulated gastrointestinal conditions and demonstrated effective adhesion to Caco-2 intestinal epithelial cells. In vitro safety evaluations confirmed that the strain was non-hemolytic and did not exhibit cytotoxic effects toward AGS or Caco-2 cell lines. Whole-genome sequencing verified species identity and revealed the presence of pediocin-related gene clusters, carbohydrate-active enzymes associated with fructooligosaccharide utilization, and a favorable genome-based safety profile. Notably, no virulence factors, biogenic amine biosynthesis pathways, plasmids, or transferable antimicrobial resistance determinants were detected. The preferential metabolism of fructooligosaccharides further suggests compatibility with synbiotic formulations. Overall, these findings indicate that P. pentosaceus NR4-4 is a genomically supported, safe, and multifunctional probiotic candidate with potential applications in food biopreservation and functional food development.
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Genomic insights into arsenic and antibiotic resistance in Comamonas thiooxydans strains F1-6 and A7-5
(2026-04-01)
Sitlaothaworn, Kanchana
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Phongsopitanun, Wongsakorn
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Chitpirom, Kitja
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Kingkaew, Engkarat
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Lee, Jung Sook
Two arsenic-resistant, Gram-negative, aerobic rod-shaped bacterial strains, F1-6 and A7-5, which were isolated from agricultural soil in Thailand, were systematically studied. They grew at 30 °C, pH 5–11, and in 3% (w/v) NaCl. Ubiquinone with eight isoprene units (Q-8) and the cellular fatty acids C1<inf>6:0</inf>, C<inf>18:1</inf> ω7c, and C<inf>17:0</inf> CYCLO were the major components. Phylogenetic analysis via 16S rRNA gene sequences revealed that strains F1-6 and A7-5 were affiliated with the genus Comamonas and closely related to C. thiooxydans DF2T and C. testosteroni KCTC 2990T, with 99.79% and 99.86% similarity, respectively. The average nucleotide identity and digital DNA-DNA hybridization values between F1-6 and C. thiooxydans DF2T were 97.89% and 85.7%, respectively, whereas those between A7-5 and C. thiooxydans DF2T were 97.23% and 81.3%, respectively. Thus, both the F1-6 and A7-5 were identified as C. thiooxydans. The draft genome sizes of F1-6 and A7-5 were 5.2 and 5.3 Mb, comprising 87 and 84 contigs, with DNA G+C contents of 61.5% and 61.4%, respectively. The genomes of both strains contained ars cluster genes and many genes for growth and resistance to heavy metals and antibiotics, similar to those of C. testosteroni ATCC 11996T, C. thiooxydans CNB-1 substr. CNB-2 Chr, and C. terrae NBRC 106524T. Nevertheless, the acr3, qacG, and vanH genes in the vanO cluster were found only in C. terrae NBRC 106524T. This study provides more comprehensive insight into As-resistant bacteria and could be applied to the bioremediation of As and other heavy metals in the future.
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Optimization of astaxanthin production by Rhodotorula toruloides CB6-10/1 using response surface methodology and its genome analysis
(2026-02-01)
Butsararattanagomen, Pornthipa
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Tanasupawat, Somboon
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Kingkaew, Engkarat
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Kotatha, Ditpon
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Soontorngun, Nitnipa
Astaxanthin is a valuable carotenoid with potent antioxidant properties and has broad applications in the pharmaceutical, nutraceutical, and cosmetic industries. In this study, Rhodotorula toruloides CB6-10/1, isolated from Canna indica L. flowers, was evaluated for astaxanthin production. The orange-red pigment was confirmed as astaxanthin via thin-layer chromatography and high-performance liquid chromatography, with quantification performed by spectrophotometry. Comprehensive genome analysis and production optimization of R. toruloides CB6-10/1 confirmed the presence of key astaxanthin biosynthesis genes, such as CrtYB, CrtI, CrtW, CrtZ, and CrtR, which facilitate the conversion of β-carotene to astaxanthin through hydroxylation and ketolation. The key parameters, including carbon and nitrogen sources, their concentrations, trace elements, agitation speed, and pH, were systematically evaluated to optimize production. Although copper appeared beneficial in the Plackett–Burman screening, its effect and those of other metals were not significant. Optimization using Response Surface Methodology for cost-effective nitrogen sources determined that a combination of 1.10 g/L yeast extract, 10.0 g/L peptone, and 0.50 g/L ammonium sulfate yielded the maximum astaxanthin production of 4.728 mg/L, under cultivation conditions of pH 4.5, 200 rpm, and 30 g/L glucose, representing a fourfold increase compared with the basal medium. This optimization not only enhances pigment production efficiency but also reduces dependency on costly trace elements, improving process scalability and economic feasibility. Overall, these results demonstrate R. toruloides CB6-10/1 as a promising microbial source for sustainable astaxanthin production with potential further applications.
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Genomic Assessment, Metabolic Profile Mapping, and Anti-Helicobacter pylori Activity of Lactococcus lactis SK2-659 from Thai Fermented Green Mustard (Pak-kad-dong)
(2026-01-01)
Kingkaew, Engkarat
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Woraprayote, Weerapong
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Sitdhipol, Jaruwan
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Vilaichone, Ratha Korn
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Visessanguan, Wonnop
Probiotics play crucial roles in promoting gut health, enhancing immunity, and combating pathogenic microorganisms, with increasing interest in their applications in the food and therapeutic industries. Lactococcus lactis, a well-known lactic acid bacterium, has emerged as a promising candidate owing to its probiotic traits and safety profile. In this study, we investigated the probiotic potential and genomic profile of Lactococcus lactis SK2-659, a strain isolated from Thai fermented green mustard (Pak-kad-dong). Genomic analysis revealed numerous genes associated with probiotic traits, including stress tolerance, adhesion, and antimicrobial activity, with a particular focus on bacteriocin SK2-659, which was effective against pathogenic bacteria such as Helicobacter pylori. The bacteriocin produced by L. lactis SK2-659, identified as nisin Z, disrupts bacterial membranes via pore formation, leading to cell lysis. Metabolomic profiling further highlighted its ability to increase carbohydrate and amino acid metabolism, supporting cell growth and survival in acidic environments. Also, amino acid metabolism (elevated tryptophan, tyrosine, histidine) supports acid tolerance and immune modulation. Tryptophan metabolism produces indole derivatives, which are known to benefit gut health and immunity. Additionally, strain SK2-659 demonstrated strong tolerance to gastrointestinal conditions, high adhesion capacity to intestinal cells, and immunomodulatory effects, contributing to gut health. Safety assessments confirmed the absence of virulence factors, pathogenic traits, and antibiotic resistance genes, along with a lack of biogenic amine production, underscoring its suitability for food and health applications. These findings establish L. lactis SK2-659 as a promising probiotic candidate with potential industrial applications in functional foods, food preservation, and therapeutic products. Given its probiotic properties, antimicrobial activity, and safety profile, this strain is particularly suited for the food industry as a functional food ingredient and natural bio-preservative, as well as the healthcare and pharmaceutical industries for use in therapeutic probiotics and gut health formulations.
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Characterization of red pigmented yeasts and genes associated with astaxanthin synthesis in Rhodotorula mucilaginosa HL26-1 and Rhodotorula paludigena LL69-1
(2026-01-01)
Hoondee, Patcharaporn
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Tedsree, Nisachon
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Phuengjayaem, Sukanya
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Kingkaew, Engkarat
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Sritularak, Boonchoo
Background: Astaxanthin, a red xanthophyll carotenoid, is a powerful antioxidant, anticancer, and glucose and lipid homeostasis regulator. Some pigmented yeasts belonging to the genus Rhodotorula, the well-known yeast for beta-carotene production, have been reported as natural astaxanthin producers. However, the lack of genomic data on astaxanthin-producing strains within these species hinders the identification of biosynthetic routes, molecular characterization of these pathways, and gene editing applications. Methods: This study explored the diversity and astaxanthin production capability of cultivable pigmented yeast in flower samples. The astaxanthin production ability was inspected by three consecutive methods, including thin-layer chromatography (TLC) for the preliminary step, followed by quantitative spectrophotometry and high-performance liquid chromatography (HPLC) for qualitative validation. The draft genome sequence and astaxanthin-producing genes of astaxanthin-producing yeasts were examined. Results: Twelve of 23 yeasts from floral samples exhibited natural pigmentation, with colors ranging from pinkish-orange to red, and exhibited the potential for astaxanthin synthesis. These yeasts were Rhodotorula paludigena (three strains) and Rhodotorula mucilaginosa (nine strains). Among R. mucilaginosa strains, HL26-1 had the greatest astaxanthin content (104.98 ± 0.13 μg/g DCW) and yield (0.9280 ± 0.0012 mg/L). Strain LL69-1 has the greatest astaxanthin content (251.78 ± 0.27 μg/g DCW) and yield (1.8632 ± 0.0023 mg/L) among R. paludigena strains. The 18.78 Mbp R. mucilaginosa HL26-1 genome includes 5,711 protein-coding genes. Conversely, the R. paludigena LL69-1 genome was 20.99 Mbp, encompassing 6,782 predicted genes. A comprehensive investigation of draft genome sequences of these two strains identified CrtE, CrtYB, CrtI, CrtS, and CrtR as potential astaxanthin transcription genes. Conclusion: Here, our results highlight the outstanding potential of two naturally pigmented yeasts, R. mucilaginosa HL26-1 and R. paludigena LL69-1, for astaxanthin production. Furthermore, our findings provide information on the whole genome and protein-encoded genes associated with astaxanthin production, which serve as valuable biological resources for various biotechnological applications.
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Genomic Characterization and Hydrolysis Enzyme of Piscibacillus salipiscarius RBU1-1ᵀ and Allobacillus salarius SKP4-8ᵀ Isolated from Fermented Fish Products
(2026-01-01)
Namwong, Sirilak
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Chaimongkol, Apichai
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Kingkaew, Engkarat
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Phongsopitanun, Wongsakorn
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Chamroensaksri, Nitcha
Two halophilic bacterial strains, Piscibacillus salipiscarius RBU1-1ᵀ and Allobacillus salarius SKP4-8ᵀ, were isolated from traditional Thai fermented foods, namely pla-ra from Ratchaburi, Thailand, and ka-pi from Samut Sakhon, Thailand, respectively. Comparative genomics confirmed their taxonomic distinctiveness, with RBU1-1ᵀ representing a novel species and SKP4-8ᵀ showing clear genomic separation from its closest relatives. The draft genomes were 2.99 Mb (36.7 mol% G+C) for RBU1-1ᵀ and 2.59 Mb (38.8 mol% G+C) for SKP4-8ᵀ. Both strains encoded hydrolytic enzymes and secondary metabolite pathways, with SKP4-8ᵀ displaying higher protease activity and RBU1-1ᵀ harboring ectoine biosynthetic and stress-response genes. RBU1-1ᵀ encoded the biosynthesis pathways for ectoine, tryptophan, and thiamine, while SKP4-8ᵀ encoded thiamine, riboflavin, coenzyme A, and menaquinone, indicating their potential contributions to postbiotic and nutritional value. Safety assessment revealed the absence of biogenic amine, antibiotic biosynthesis, and major virulence genes in both strains. Although antimicrobial resistance-associated genes were detected, no complete clusters were identified, suggesting low phenotypic risk. Computational pathogenicity prediction indicated a low probability for RBU1-1ᵀ (0.242) and a higher probability for SKP4-8ᵀ (0.945), though these require cautious interpretation. Overall, genomic evidence and enzymatic activity support RBU1-1ᵀ and SKP4-8ᵀ as safe, functional starter culture candidates, with RBU1-1ᵀ showing strong potential through postbiotic biosynthesis and SKP4-8ᵀ through proteolytic activity.

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