Streptomonospora mangrovi sp. nov., isolated from mangrove soil showing similar metabolic capabilities, but distinct secondary metabolites profiles.

A novel actinomycete, designated strain S1-112 T, was isolated from a mangrove soil sample from Hainan, China, and characterized using a polyphasic approach. Strain S1-112 T showed the highest similarity of the 16S rRNA gene to Streptomonospora nanhaiensis 12A09T (99.24%). Their close relationship was further supported by phylogenetic analyses, which placed these two strains within a stable clade. The highest values of digital DNA-DNA hybridization (dDDH, 41.4%) and average nucleotide identity (ANI, 90.55%) were detected between strain S1-112 T and Streptomonospora halotolerans NEAU-Jh2-17 T. Genotypic and phenotypic characteristics demonstrated that strain S1-112 T could be distinguished from its closely related relatives. We also profiled the pan-genome and metabolic features of genomic assemblies of strains belonging to the genus Streptomonospora, indicating similar functional capacities and metabolic activities. However, all of these strains showed promising potential for producing diverse types of secondary metabolites. In conclusion, strain S1-112 T represents a novel species of the genus Streptomonospora, for which the name Streptomonospora mangrovi sp. nov. was proposed. The type strain is S1-112 T (= JCM 34292 T).

Actinophytocola gossypii sp. nov. and Streptomyces gossypii sp. nov., two novel actinomycetes isolated from rhizosphere soil of cotton.

Two Gram-positive, aerobic and non-motile actinomycetes, designated S1-96T and N2-109T, were isolated from soils collected from a cotton field. They are described as representing two novel species of genera Actinophytocola and Streptomyces through a polyphasic approach. Analysis of 16S rRNA gene sequences revealed that strains S1-96T and N2-109T showed highest similarity to Actinophytocola xinjiangensis CGMCC 4.4663T (99.10 %) and Streptomyces iconiensis BNT558T (98.21 %), respectively. Phylogenetic analyses based on 16S rRNA and core genes confirmed the close relationships of these strains. Genomic analyses further supported the novel taxonomic delimitation of these two species based on digital DNA-DNA hybridization and average nucleotide identity. Strains S1-96T and N2-109T contained MK-9(H4) and MK-9(H6) as the most abundant menaquinone, respectively. High abundances of iso-fatty acids were detected in both strains, which was similar to their close relatives. Physiological and polar lipid analyses also revealed differences between these strains and their phylogenetic neighbours, supporting their taxonomic delimitation as novel species. The names Actinophytocola gossypii sp. nov. (type strain S1-96T=JCM 34412T=CGMCC 4.7707T) and Streptomyces gossypii sp. nov. (type strain N2-109T=JCM 34628T=CGMCC 4.7717T) are proposed.

Occultella gossypii sp. nov., an alkali-resistant isolate from soil sampled in a cotton field.

A non-spore-forming, motile and alkali-resistant actinobacterium, designated N2-46T, was isolated from an alkaline soil sample collected from a cotton field in the Xinjiang region of PR China. Strain N2-46T formed creamy colonies on tryptone soy agar and managed to survive in extreme alkaline conditions at a pH value of 11. Strain N2-46T displayed the highest 16S rRNA gene similarity of 99.65 % to Haloactinobacterium kanbiaonis HY164T, followed by Occultella aeris F300T (99.61%) and Occultella glacieicola T3246-1T (98.54 %). 16S rRNA-directed phylogenetic analysis showed that strain N2-46T was embedded in a subclade with O. aeris F300T with a bootstrap value of 71.8 %. The phylogenetic tree based on core genes of genome sequences showed that strain N2-46T formed a unique subclade next to H. kanbiaonis HY164T and O. aeris F300T with a bootstrap value of 100 %. Digital DNA-DNA hybridization and the average nucleotide identity analyses showed that strain N2-46T displayed the highest values of 67.1 % (63.2-70.7 %) and 91.82 % with H. kanbiaonis HY164T, respectively. Comparative genomic analysis indicated that strain N2-46T and its three closest neighbours exhibited comparable distribution patterns in heavy metal resistance genes and biosynthetic gene clusters, while displaying distinctions probably related to ecological adaptation. MK-8(H4) was identified as the predominant isoprenoid quinone. The main fatty acids were identified as iso-C14 : 0 and anteiso-C15 : 0. Polar lipids are composed of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, mono and diacylated phosphatidylinositol dimannosides, as well as several uncharacterized polar lipid, glycolipid, and phospholipids. Genotypic and physiological analyses support the view that strain N2-46T (=JCM 34413T=CGMCC 1.18819T) should be classified as a novel species of the genus Occultella, for which the name Occultella gossypii sp. nov. is proposed.

Pseudonocardia humida sp. nov., an Actinomycete Isolated from Mangrove Soil Showing Distinct Distribution Pattern of Biosynthetic Gene Clusters.

A novel actinomycete strain, designated S2-4T, was isolated from a mangrove soil sample, and a polyphasic approach was employed to determine its taxonomic position. Phylogenetic analysis based on 16S rRNA gene indicated that strain S2-4T formed a unique clade next to that harboring Pseudonocardia dioxanivorans CB1190T, which shared the highest sequence similarity (98.20%) with the new isolate. Phylogenetic analysis based on core genes of genomic sequences displayed a different scenario, exhibiting closer phylogenetic relationship of strain S2-4T with several species with 16S rRNA gene sequence similarities ranging from 96.95 to 98.06%, which was confirmed by the phylogenetic tree reconstructed based on genomic sequences. Further, substantial differences between the genotypic properties of strain S2-4T and its closest neighbors, including digital DNA-DNA hybridization, average nucleotide identity, and distribution patterns of biosynthetic gene clusters (BGC), indicated the taxonomic position of strain S2-4T as a novel species of the genus Pseudonocardia. Accordingly, strain S2-4T was observed to show a different distribution pattern of a predicted BGC encoding ectoine by comparative genomic analysis, which could be strongly linked to its unique habitat distinct from where its close neighbors were isolated. The major cellular fatty acids were iso-C15:0, C21:0, and iso-C16:0. The predominant menaquinone was MK-8(H4). The polar lipids were composed of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidyl-N-monomethylethanolamine, phosphatidylcholine, phosphatidylinositol, phosphatidylinositol mannosides, and two unidentified glycolipids. Here, we propose a novel species of the genus Pseudonocardia: Pseudonocardia humida sp. nov. with the type strain S2-4T (= JCM 34291T = CGMCC 4.7706T).

Steroidobacter gossypii sp. nov., isolated from cotton field soil.

A Gram-negative bacterium, designated S1-65T, was isolated from soil samples collected from a cotton field located in the Xinjiang region of PR China. Results of 16S rRNA gene sequence analysis revealed that strain S1-65T was affiliated to the genus Steroidobacter with its closest phylogenetic relatives being 'Steroidobacter cummioxidans' 35Y (98.4 %), 'Steroidobacter agaridevorans' SA29-B (98.3 %) and Steroidobacter agariperforans KA5-BT (98.3 %). 16S rRNA-directed phylogenetic analysis showed that strain S1-65T formed a unique phylogenetic subclade next to 'S. agaridevorans' SA29-B and S. agariperforans KA5-BT, suggesting that strain S1-65T should be identified as a member of the genus Steroidobacter. Further, substantial differences between the genotypic properties of strain S1-65T and the members of the genus Steroidobacter, including average nucleotide identity and digital DNA-DNA hybridization, resolved the taxonomic position of strain S1-65T and suggested its positioning as representing a novel species of the genus Steroidobacter. The DNA G+C content of strain S1-65T was 62.5 mol%, based on its draft genome sequence. The predominant respiratory quinone was ubiquinone-8. The main fatty acids were identified as summed feature 3 (C16:1ω6c/C16:1ω7c), C16 : 0 and iso-C15 : 0. In addition, its polar lipid profile was composed of aminophospholipid, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. Here, we propose a novel species of the genus Steroidobacter: Steroidobacter gossypii sp. nov. with the type strain S1-65T (=JCM 34287T=CGMCC 1.18736T).

Genomic molecular signatures determined characterization of Mycolicibacterium gossypii sp. nov., a fast-growing mycobacterial species isolated from cotton field soil.

A Gram-positive, acid-fast and rapidly growing rod, designated S2-37 T, that could form yellowish colonies was isolated from one soil sample collected from cotton cropping field located in the Xinjiang region of China. Genomic analyses indicated that strain S2-37 T harbored T7SS secretion system and was very likely able to produce mycolic acid, which were typical features of pathogenetic mycobacterial species. 16S rRNA-directed phylogenetic analysis referred that strain S2-37 T was closely related to bacterial species belonging to the genus Mycolicibacterium, which was further confirmed by pan-genome phylogenetic analysis. Digital DNA-DNA hybridization and the average nucleotide identity presented that strain S2-37 T displayed the highest values of 39.1% (35.7-42.6%) and 81.28% with M. litorale CGMCC 4.5724 T, respectively. And characterization of conserved molecular signatures further supported the taxonomic position of strain S2-37 T belonging to the genus Mycolicibacterium. The main fatty acids were identified as C16:0, C18:0, C20:3ω3 and C22:6ω3. In addition, polar lipids profile was mainly composed of diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol. Phylogenetic analyses, distinct fatty aids and antimicrobial resistance profiles indicated that strain S2-37 T represented genetically and phenotypically distinct from its closest phylogenetic neighbour, M. litorale CGMCC 4.5724 T. Here, we propose a novel species of the genus Mycolicibacterium: Mycolicibacterium gossypii sp. nov. with the type strain S2-37 T (= JCM 34327 T = CGMCC 1.18817 T).

Chemical structure, properties and potential applications of surfactin, as well as advanced strategies for improving its microbial production.

Surfactin, a cyclic lipopeptide produced by microbes belonging to the genus Bacillus, is one of the most effective biosurfactants available in many industrial fields. However, its low production and high cost have intensively constrained its commercial applications. In this review, we first summarize the molecular structure, biological properties, beneficial roles and potential applications of surfactin in the fields of medical care and food safety, highlighting the great medical and commercial values of making its industrial production into reality. Further, genetic regulation for surfactin biosynthesis and advanced strategies for enhancing its microbial production, including optimizing fermentation conditions, rational genetic engineering and synthetic biology combined with metabolic engineering approaches, are elucidated. Finally, prospects for improving surfactin biosynthesis are discussed, and the establishment of suitable chassis hosts for exogenous production of surfactin might serve as an important strategy in future research.