Gentamicin and sisomicin are two different aminoglycoside antibiotics. The comparison of their chemical structure and biosynthetic gene clusters, coupled with bioinformatic analysis, suggested that the gntK gene would be associated with methylation. The gntK gene fragment in M. purpurea G1008 was inactivated by genetic engineering and its mutant strain M. purpurea GK1101 (ΔgntK) was screened. The metabolites of G1008 and GK1101 was analyzed by HPLC-MS, which revealed that GK1101 no longer produced gentamicin C1 or C2, while mainly synthesizing gentamicin C1a, and the production of C1a increased significantly. This indicated that the metabolic flow for the gentamicin C1 and C2 biosynthesis was blocked by disrupting the gntK gene, which substantiated that the gntK gene encoded the enzyme that catalyzes the methylation of purpurosamine C-6′. The mutant GK1101 has good prospects for industrial application. In addition, our study provides information that can be used to clarify the function of a single gene and simplify the targeted genetic breeding of important pharmaceutical microorganisms.
A Gram-negative, rod-shaped, aerobic, non-motile, bacterium (YG-17T) was isolated from eutrophic Taihu lake sediment. Colonies grown on YG agar plates were circular, convex, and yellow-colored. On the basis of 16S rRNA gene sequence similarity, strain YG-17T was shown to be closely related to Novosphingobium aromaticivorum (97.9%), followed by Novosphingobium stygium (97.5%), Novosphingobium subterranea (96.9%) and Novosphingobium taihuense (96.7%). The DNA-DNA relatedness values of strain YG-17 T to the most phylogenetically related species N. aromaticivorum and N. stygium were 14% and 21%, respectively. The G+C content of the genomic DNA was 63.2 mol%. The major respiratory quinone was ubiquinone-10 and major fatty acids were C18:1ω7c, C17:1ω6c and C14:02-OH. Sphingoglycolipids were present, and spermidine was detected as the major polyamine. According to comparative physiological and chemotaxonomic analysis, strain YG-17T is proposed to be a novel species of the genus Novosphingobium, with the name of Novosphingobium sediminis sp. nov. The type strain is YG-17T (NBRC 106119T= CGMCC 1.9114T).
Although members of the genus Streptomyces are useful producers of secondary metabolites, Streptomyces turgidiscabies, a cause of potato scab, has not been investigated for this purpose. To examine the potential of S. turgidiscabies as a secondary metabolite producer, its polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) gene clusters, conferring major biosynthetic pathways in actinomycetes, were surveyed using whole genome analysis of S. turgidiscabies NBRC 16081. This strain possessed seventeen PKS and NRPS gene clusters composed of two type-I PKS, two type-II PKS, seven NRPS, and six PKS/NRPS hybrid clusters. Abundance of these gene clusters was not only comparable to those of industrially useful strains such as S. avermitilis MA-4680 and S. griseus subsp. griseus NBRC 13350, but also superior to those of genetically well-studied S. coelicolor A3(2) and potato scab-causing S. scabiei 87.22. Remarkably, its PKS/NRPS gene clusters were more diverse in their module organization than those of other Streptomyces strains, although it possessed the lowest number of type-I PKS gene clusters. Our results suggest that S. turgidiscabies, unlike S. scabiei, harbors considerable genetic potential for producing diverse polyketide and peptide compounds.
A bacterial strain, designated PS9T, was isolated from soil in the Ryukyu Archipelago, Japan. The bacterium grew with racemic phenylsuccinate as the sole carbon and energy source. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain PS9T was closely related to Citricoccus muralis, C. alkalitolerans and C. nitrophenolicus with sequence similarities of 97.5, 97.8, and 98.3%, respectively, suggesting that the strain belonged to the genus Citricoccus. Strain PS9T was a Gram-positive, non-motile, circular-shaped and aerobic bacterium. The major respiratory quinone was MK-8 (H2) and the predominant cellular fatty acid was C15:0 anteiso, C17:0 anteiso, and C15:0 iso. The G+C content was 72.4 mol%. Based on the phylogenetic and phenotypic traits, it was concluded that the organism represents a new species in the genus Citricoccus, with the name Citricoccus yambaruensis. The type strain is PS9T (=NBRC102121T = DSM18783T).
Polyphasic taxonomic investigation was conducted on a strictly aerobic, Gram-negative, non-motile, pale-yellow-pigmented, rod-shaped strain designated HJ24T which was isolated from an unidentified orange-colored marine sponge. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the novel isolate could be affiliated with the family Flavobacteriaceae of the phylum Bacteroidetes and that it showed highest sequence similarity (88.6%) with Pseudozobellia thermophila KMM 3531T. The novel isolate is phenotypically and physiologically different from other related genera. The DNA G+C contents were 41 mol%, MK-6 was the major menaquinone and iso-C15:0, iso-C15:1 and iso-C17:0 3-OH were the predominant fatty acids. On the basis of polyphasic taxonomic studies, it was concluded that the novel strain represents a new genus and a novel species of the family Flavobacteriaceae. We propose the name Spongitalea numazuensis gen. nov., sp. nov. for this strain; its type strain is HJ24T (= DSM 21243T).