Prevalence and distribution of antibiotic-producing actinomycetes

Streptomyces enissocaesilis L-82 has broad-spectrum antibacterial activity and promotes growth for Carassius auratus

Aeromonas is the main pathogen causing bacterial diseases in fish. The disadvantages of chemical drugs to control fish diseases have been highlighted, and it is urgent to find an eco-friendly control method. In this study, an actinomycete strain with antibacterial activity against fish pathogenic bacteria was screened from soil samples. Combined with morphological characteristics, physiological and biochemical characteristics, and gyrB gene and whole genome comparison analysis, it was identified as a new strain of Streptomyces enissocaesilis, named Streptomyces enissocaesilis L-82. The strain has broad-spectrum antibacterial activity against fish pathogens. A substance with a mass-to-charge ratio of 227.20 [M + H] + was isolated and purified by high-performance liquid chromatography and mass spectrometry. It was presumed to be a derivative of 5-dimethylallylindole-3-acetonitrile. The strain is safe and non-toxic to crucian carp, and can stably colonize crucian carp and inhibit the proliferation of A. hydrophila. After feeding the feed containing 1 × 108 CFU/mL strain concentration, the weight growth rate and specific growth rate of crucian carp increased, the activity of ACP and SOD in serum increased, and the survival rate of crucian carp increased after challenge. Genome-wide analysis showed that the strain had strong ability to metabolize and tolerate extreme environments. And has a strong potential for disease resistance. Therefore, the strain is expected to be developed as a feed additive for fish farming. KEY POINTS: • The new Streptomyces enissocaesilis L-82 has a broad spectrum and stable antibacterial activity and meets the safety standards of feed additives. • Strain L-82 can colonize crucian carp, improve the growth, antioxidant, and immune performance of the host, and improve the survival rate after being infected with A. hydrophila. • Genome-wide analysis suggests that the strain has great disease resistance potential and is expected to be developed as a feed additive for fish culture.

Nyuzenamide C, an Antiangiogenic Epoxy Cinnamic Acid-Containing Bicyclic Peptide from a Riverine Streptomyces sp

A new nonribosomal peptide, nyuzenamide C (1), was discovered from riverine sediment-derived Streptomyces sp. DM14. Comprehensive analysis of the spectroscopic data of nyuzenamide C (1) revealed that 1 has a bicyclic backbone composed of six common amino acid residues (Asn, Leu, Pro, Gly, Val, and Thr) and four nonproteinogenic amino acid units, including hydroxyglycine, β-hydroxyphenylalanine, p-hydroxyphenylglycine, and 3,β-dihydroxytyrosine, along with 1,2-epoxypropyl cinnamic acid. The absolute configuration of 1 was proposed by J-based configuration analysis, the advanced Marfey's method, quantum mechanics-based DP4 calculations, and bioinformatic analysis of its nonribosomal peptide synthetase biosynthetic gene cluster. Nyuzenamide C (1) displayed antiangiogenic activity in human umbilical vein endothelial cells and induced quinone reductase in murine Hepa-1c1c7 cells.

Calcium carbonate precipitation by cave bacteria isolated from Kashmir Cave, Khyber Pakhtunkhwa, Pakistan

The participation of numerous physicochemical and biological functions maintains the evolution and expansion of the remarkable nature. Due to its vast applicability in several engineering disciplines, naturally occurring bio-mineralization or microbially induced calcium carbonate (MICP) precipitation is attracting more interest. Cave bacteria contribute to the precipitation of calcium carbonate (CaCO₃ ). In the present study, soil sediments were collected from Kashmir cave, KPK, Pakistan, and plated on B4 specific nutrients limited medium for bacterial isolation and the viable bacterial count was calculated. Three bacterial strains named GSN-11, TFSN-14, and TFSN-15 were capable of precipitating CaCO₃ . These bacterial isolates were identified through 16S rRNA gene sequencing and strain GSN-11 was identified as Bacillus toyonensis, TFSN-14 as Paracoccus limosus and TFSN-15 as Brevundimonas diminuta. Enhanced CaCO₃ precipitation potential of these bacteria strains was observed at 25°C and pH 5. The precipitated CaCO₃ was confirmed by scanning electron microscopy, X-ray powder diffraction, and Fourier transform infra-red spectroscopy. The findings showed that the precipitates were dominated by calcite, aragonite, and nanosize vaterite. Current research suggests that precipitation of CaCO₃ by proteolytic cave bacteria is widespread in Kashmir cave and these bacterial communities can actively contribute to the formation of CaCO₃ by enhancing the pH of the microenvironment.