In the present study, Streptomyces sp. CW1 was isolated from a constructed wetland system mesocosm and identified as such based on 16S rDNA analysis, and additional biochemical properties were evaluated. This isolate was found to be halotolerant (up to 11% NaCl) and able to grow and utilize biopolymers such as: agarose, agar, gellan gum (a bacterial polysaccharide), polypectate and chitin as the sole carbon and energy source. Since the primary isolation was performed based on its capability to degrade phenol, the high cell yield coefficient showed rapid growth on phenol (0.82–0.98 mg dry biomass/mg phenol). Its halotolerance and the capability to biodegrade biopolymers found mainly in the marine environments, suggest on its primordial oceanic origin. In the present study some of its characteristics are described and discussed along with its beneficial use for wastewater purification processes in constructed wetland systems.
During a study of the distribution of actinomycetes in a subtropical zone in Japan, two strains forming short sporangiophores on the substrate mycelium were isolated from soil. The 16S rRNA gene sequences of the isolates indicated that these organisms formed a monophyletic cluster with members of the genus Virgisporangium in the family Micromonosporaceae. These strains formed narrow sporangia on short sporangiophores directly above the substrate mycelium. The sporangia contained motile spores. The strains contained 3-OH-diaminopimelic acid in the cell wall and glucose, ribose, mannose, galactose, xylose and 3-O-methylmannose as whole-cell sugars. The predominant menaquinones were MK-10(H4) and MK-10(H6). The diagnostic phospholipid was phosphatidylethanolamine. Cis 9 C17:1 and C17:0 were detected as the major cellular fatty acids. The G+C content of the DNA was 71.7 mol%. DNA–DNA relatedness analysis showed that the two isolates represented the same genomic species. The results of morphological, chemotaxonomic and 16S rRNA gene sequence analyses, as well as DNA–DNA hybridization studies, confirmed that these isolates certainly belonged to a new species of the genus Virgisporangium. We propose a novel taxon of the genus Virgisporangium as Virgisporangium aliadipatigenens sp. nov., with the type strain IR20-55T (= NBRC 105644T).
The eshA gene was originally found to encode a protein required for the extension of sporogenic hyphae during submerged spore formation in Streptomyces griseus NRRL B-2682. An eshA-disrupted strain of S. griseus IFO13189 was reported to be conditionally deficient in streptomycin production and aerial mycelium formation. Our previous transcriptomic analyses indicated that AdpA, a global transcriptional regulator of morphological and physiological differentiation, induced eshA (SGR1270) transcription in S. griseus IFO13350. Here, we examined the transcriptional regulation of eshA by AdpA and the involvement of eshA in the morphological and physiological differentiation of S. griseus IFO13350. Transcriptional analysis by S1 nuclease mapping showed that eshA was transcribed throughout growth on solid medium. In contrast, no eshA transcription was detected in an adpA deletion mutant. Recombinant His-tagged AdpA bound to a region upstream from the eshA promoter in vitro. However, mutation of the AdpA-binding sequence did not affect the transcription of eshAin vivo, indicating that AdpA indirectly activates eshA transcription. Streptomycin production by an eshA deletion mutant grown on TSB plates was lower than that of the wild-type strain. However, the eshA deletion mutant grew and formed aerial mycelia and spores following the same time course as the wild-type strain on various media.
Virginiamycin M1 (VM1), produced by Streptomyces virginiae, is a polyunsaturated macrolactone antibiotic belonging to the streptogramin family. The 10-kb regulatory gene cluster of VM1 production contains the varM gene, which encodes the type II ATP-binding cassette (ABC) transporter. This transporter is presumably involved in self-resistance to avoid suicide of the producer strain. Northern blot analyses revealed that varM expression is transcriptionally controlled by the VM1 molecule, but not by virginiamycin S, which is simultaneously produced to form a synergistic pair of the streptogramin family. Sequential addition of VM1 at increasing concentrations secured constitutive activation of varM expression, which suggested that the varM expression reflected an intracellular concentration of VM1. Heterologous expression of varM in Streptomyces lividans generated strains with no significant VM1 resistance. The mechanism underlying varM function in VM1 production is discussed.
In this study, we investigated the taxonomic diversity of actinomycetes isolated from swine manure compost that had undergone self-heating. Pretreatment with sodium dodecyl sulfate and subsequent cultivation of the compost sample on humic acid-vitamin agar at 30 and 50°C resulted in the selective isolation of 125 actinomycete strains. These isolates were classified using a combination of morphological characterization and 16S rDNA sequence analysis, with sequence similarities of ≥97% and ≥99% used to identify isolates at genus and species level, respectively. The isolated actinomycete assemblage consisted of a diverse array of species, with the 125 isolates falling into 10 families, 15 genera, and 22 species. The most dominant thermophilic actinomycetes were Saccharomonospora (Sam.) viridis and Thermobifida fusca, followed by Actinomadura spp. Other species that were frequently isolated at 30°C included Glycomyces spp., Nocardiopsis (Nop.) alba, Nop. composta, Rhodococcus rhodochrous, and Sam. azurea.
Sinefungin is a nucleoside antibiotic in which L-ornithine is covalently bound to adenosine. 14C-Incorporation studies indicate that L-Arg and ATP are precursor substrates. To identify the biosynthetic intermediates in the sinefungin biosynthetic pathway, a shunt metabolite accumulated in a resting cell system was isolated from the cell suspension broth, and identified as ornithine-lactam (OrnLcm). The enzyme that catalyzes the formation of OrnLcm was purified from the lysed cell extract of Streptomyces incarnatus NRRL8089 by four-steps of column chromatography using DEAE-Toyopearl, Sephacryl S-200 HR gel filtration, Butyl-Toyopearl and hydroxy-apatite. The molecular mass of the purified protein was determined to be 43 kDa by SDS-PAGE. The N-terminal sequence MKVGIRP was identical to those of L-alanine dehydrogenases (40 kDa) encoded in the genomes of Streptomyces griseus, Streptomyces avermitilis, Streptomyces coelicolor, and other Gram-positive bacteria. The purified enzyme catalyzed the NAD-dependent oxidation of L-Ala, as well as the formation of OrnLcm from L-Arg. It did not show any activity towards L-Orn or D-Arg. Although it has not yet been clarified whether OrnLcm serves as a direct substrate for enzymatic C-C bond formation intracellularly, the lactam intermediate has the advantage of facile transport across the cell membrane as well as the enhanced nucleophilicity at the C5 carbon.
The dereplication of isolates is an important step in the search for microorganisms that are producers of novel bioactive compounds. We have tested the RiboPrinter system, an automated ribotyping instrument, for the detection of polyketide synthase (PKS) genes and checking of strain similarity. Using a 1.1 kb probe derived from the ketosynthase (KS) domain of eryAIII instead of the standard ribosomal probe, the system was able to detect PKS genes in Streptomyces strains. Band patterns were similar among four Streptomyces violaceoruber strains harboring similar PKS genes. Conversely, some strains taxonomically identified as the same species showed different band patterns. Two unknown isolates were appropriately discriminated from their closest strains by band patterns. These results demonstrate that an automated Southern hybridization method employing a KS-probe will enable easy and rapid dereplication based on an index of PKS genes.
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