Discovery of a Novel Cellobiose Dehydrogenase from Cellulomonas palmilytica EW123 and Its Sugar Acids Production

Cellobiose dehydrogenases (CDHs) are a group of enzymes belonging to the hemoflavoenzyme group, which are mostly found in fungi. They play an important role in the production of acid sugar. In this research, CDH annotated from the actinobacterium Cellulomonas palmilytica EW123 (CpCDH) was cloned and characterized. The CpCDH exhibited a domain architecture resembling class-I CDH found in Basidiomycota. The cytochrome c and flavin-containing dehydrogenase domains in CpCDH showed an extra-long evolutionary distance compared to fungal CDH. The amino acid sequence of CpCDH revealed conservative catalytic amino acids and a distinct flavin adenine dinucleotide region specific to CDH, setting it apart from closely related sequences. The physicochemical properties of CpCDH displayed optimal pH conditions similar to those of CDHs but differed in terms of optimal temperature. The CpCDH displayed excellent enzymatic activity at low temperatures (below 30°C), unlike other CDHs. Moreover, CpCDH showed the highest substrate specificity for disaccharides such as cellobiose and lactose, which contain a glucose molecule at the non-reducing end. The catalytic efficiency of CpCDH for cellobiose and lactose were 2.05 x 105 and 9.06 x 104 (M-1 s-1), respectively. The result from the Fourier-transform infrared spectroscopy (FT-IR) spectra confirmed the presence of cellobionic and lactobionic acids as the oxidative products of CpCDH. This study establishes CpCDH as a novel and attractive bacterial CDH, representing the first report of its kind in the Cellulomonas genus.

A New Saharan Strain of Streptomyces sp. GSB-11 Produces Maculosin and N-acetyltyramine Active Against Multidrug-Resistant Pathogenic Bacteria

Multi-resistant bacterial pathogens are a major public health problem for treating nosocomial infections owing to their high resistance to antibiotics. The objective of this research was to characterize the bioactive molecules secreted by a novel moderately halophilic actinobacterium strain, designated GSB-11, exhibiting a strong antagonistic activity against several multidrug-resistant pathogenic bacteria. This potential strain was identified by phenotypic, genotypic (16S rRNA), and phylogenetic analyses. GSB-11 was related to "Streptomyces acrimycini" NBRC 12736 ^T with 99.59% similarity. Molecular screening by PCR assay demonstrated that the strain possesses two biosynthetic genes coding for NRPS and PKS-II. Two active compounds GSB11-6 and GSB11-7 were extracted from the cell-free culture supernatant of Bennett medium and purified using reversed-phase HPLC. According to spectrometric (mass spectrum) and spectroscopic (¹H NMR, ¹³C NMR, ¹H-¹H COSY, and ¹H-¹³C HMBC) spectra analyses, the compounds GSB11-6 and GSB11-7 were identified to be maculosin and N-acetyltyramine, respectively. Their minimum inhibitory concentrations (MIC) revealed interesting values against certain multidrug-resistant pathogenic bacteria. They were between 5 and 15 mg/mL for GSB11-6, 10 and 30 mg/mL for GSB11-7. To our best knowledge, this is the first study of these active substances isolated from "Streptomyces acrimycini" showing an interesting antibacterial activity. Therefore, these essential compounds could be candidates for future research against multidrug-resistant bacteria.

Streptomyces spinosus sp. nov. and Streptomyces shenzhenensis subsp. oryzicola subsp. nov. endophytic actinobacteria isolated from Jasmine rice and their genome mining for potential as antibiotic producers and plant growth promoters

Two endophytic actinobacteria, strains SBTS01^T and W18L9^T, were isolated from leaf sheath and leaf tissue, respectively, of Jasmine rice (Oryza sativa KDML 105) grown in a rice paddy field in Roi Et Province, Thailand. A polyphasic taxonomic study showed that both strains belong to the genus Streptomyces; they are aerobic, forming well-developed substrate mycelia and aerial mycelia with long chains of spores. Strain SBTS01^T shares high 16S rRNA gene sequence similarity with Streptomyces rochei NRRL B-2410 ^T (99.0%) and Streptomyces naganishii NRRL ISP-5282 ^T (99.0%). Strain W18L9^T shares high 16S rRNA gene sequence similarity with Streptomyces shenzhenensis DSM 42034 ^T (99.7%). The genotypic and phenotypic properties of strains SBTS01^T and W18L9^T distinguish these two strains from the closely related species with validly published names. The genome analysis showed the dDDH, ANIb and ANIm values of the draft genome between strain SBTS01^T and its close neighbour in the phylogenomic tree, Streptomyces corchorusii DSM 40340^T to be 54.1, 92.6, and 94.3%, respectively; similarly for strain W18L9^T and the closely related species S. shenzhenensis DSM 42034 ^T values were 72.5, 95.1 and 97.0%. The name proposed for the new species represented by the type strain SBTS01^T is Streptomyces spinosus (= NRRL B-65636 ^T = TBRC 15052^T). The name proposed for the novel subspecies of strain W18L9^T is Streptomyces shenzhenensis subsp. oryzicola (= NRRL B-65635 ^T = TBRC 15051^T). Recognition of this subspecies also permits the description of Streptomyces shenzhenensis subsp. shenzhenensis. Strains SBTS01^T and W18L9^T can produce antibiotic against rice and human pathogens and showed plant growth promoting properties such as production of indole acetic acid, cytokinin, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, siderophores and cellulase. Genomic data mining of these two strains confirmed their potential as antibiotic producers and plant growth promoters. Their genomes contain multiple biosynthetic gene clusters including those for terpene, type 1, 2 and 3 polyketide synthase, Non-ribosomal peptide synthetase and lanthipeptides. Genes encoding plant growth promoting traits such; nitrogen fixation, ACC deaminase, siderophore production and stress-related adaption may have ecological significance.

Identification of molecular basis that underlie enzymatic specificity of AzoRo from Rhodococcus opacus 1CP: A potential NADH:quinone oxidoreductase

Azo dyes are important to various industries such as textile industries. However, these dyes are known to comprise toxic, mutagenic, and carcinogenic representatives. Several approaches have already been employed to mitigate the problem such as the use of enzymes. Azoreductases have been well-studied in its capability to reduce azo dyes. AzoRo from Rhodococcus opacus 1CP has been found to be accepting only methyl red as a substrate, surmising that the enzyme may have a narrow active site. To determine the active site configuration of AzoRo at atomic level and identify the key residues involved in substrate binding and enzyme specificity, we have determined the crystal structure of holo-AzoRo and employed a rational design approach to generate AzoRo variants. The results reported here show that AzoRo has a different configuration of the active site when compared with other bacterial NAD(P)H azoreductases, having other key residues playing a role in the substrate binding and restricting the enzyme activity towards different azo dyes. Moreover, it was observed that AzoRo has only about 50% coupling yield to methyl red and p-benzoquinone - giving rise to the possibility that NADH oxidation still occurs even during catalysis. Results also showed that AzoRo is more active and more efficient towards quinones (about four times higher than methyl red).

nov., an actinobacterium isolated from the root of Callitris preissii with potential for plant growth-promoting properties

An endophytic actinobacterium, strain CAP261^T was isolated from the surface sterilized root of Callitris preissii (Australian native pine tree). As a result of a polyphasic taxonomy study, this strain was identified as a member of the genus Streptomyces. This strain was an aerobic actinobacterium with well-developed substrate mycelia with loop spore chains and the spore surfaces are verrucose. The closest phylogenetic members which shared the highest 16S rRNA gene sequences similarity was Streptomyces bottropensis ATCC 25435 ^T at 98.1%. Chemotaxonomic data including cell wall components, major menaquinones, and major fatty acids confirmed the affiliation of strain CAP261^T to the genus Streptomyces. The results of the phylogenetic analysis, including physiological and biochemical studies in combination with genome comparison study, allowed the genotypic and phenotypic differentiation of strain CAP261^T and the closest species with validly published names. ANIb, ANIm and dDDH values of strain CAP261^T and S. bottropensis ATCC 25435 ^T were 86.7%, 89.2% and 33.9%, respectively. The name proposed for the new species is Streptomyces adelaidensis sp. nov. The type strain is CAP261^T (= DSM 42026 ^T = NRRL B-24814 ^T).

nov., an endophytic actinobacterium with antibacterial potential

An endophytic actinobacterium, strain CAP215^T was isolated from the root sample of a native pine tree (Callitris preissii), Adelaide, South Australia. This strain was a Gram stain-positive, aerobic actinobacterium with well-developed substrate mycelia. It produced spiral chains of spores. The closest phylogenetic members which shared the highest 16S rRNA gene sequence similarity were Streptomyces marinus DSM 41968^T, Streptomyces haliclonae DSM 41970^T and Streptomyces karpasiensis K413^T at 98.2%, 98.0% and 97.9%, respectively. The major cellular fatty acid of this strain was anteiso-C_15:0 and major menaquinone was MK-9(H₄). Polar lipids of strain CAP215^T contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol dimannoside and two unknown glycolipids. Chemotaxonomic data confirmed strain CAP215^T belonged to the genus Streptomyces. Genome of strain CAP215^T was 6.65 Mb with 69.8% DNA G + C content and contains 5992 coding sequences (CDS). Biosynthesis Genes Clusters (BGCs) comprised post-translationally modified peptides (RiPPs) cluster, genes encoding enzyme relating to antibiotic production; actinorhodin, surfactin and tetracenomycin. Genome mining of this strain identified genes encoding proteins relating to plant growth promotion such as pyrophosphatase, ectoine synthase, superoxide dismutase and siderophore production; penibactin and desferrioxamine E. Genes encoding beneficial enzymes; amylase, β-xylosidase, chitinase, lipase and protease were detected. The genome of this strain contained genes encoding enzymes degrading xenobiotic compounds such as 2,4-dichlorophenol 6-monooxygenase, nitroreductase and epoxide hydrolase. Also, genes encoding squalene, hopene and betacarotenoid production were observed. Digital DNA-DNA (dDDH) hybridization, Average Nucleotide Identity BLAST (ANIb), ANI-MUMmer (ANIm) between strain CAP215^T and S. marinus DSM 41968^T were 25.4 %, 82% and 86.4%, respectively. The data on the genotypic and phenotypic characteristics and genome analysis recognized the differentiation of strain CAP215^T with the closest species with valid names. The name Streptomyces albidus sp. nov. was proposed for which the type strain is CAP215^T (= DSM 42025^T = NRRL B-24815^T).

Geodermatophilus marinus sp. nov., isolated from the marine sponge Leucetta chagosensis

A novel actinobacterium, designated LHW52908^T, was isolated from a marine sponge, Leucettachagosensis, collected in the South China Sea. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain LHW52908^T was member of the family Geodermatophilaceae, with highest similarities to Geodermatophilus obscurus DSM 43160^T (97.7 %), Geodermatophilus siccatus CF6^T (97.6 %) and Geodermatophiluschilensis B12^T (97.5 %). Multilocus sequence analysis confirmed that the strain should be a member of genus Geodermatophilus. Chemotaxonomic characteristics confirmed the genus-level affiliation of strain LHW52908^T. Based on phylogenetic data, average nucleotide identity and digital DNA-DNA hybridization results, strain LHW52908^T could be distinguished from its closest neighbours, representing a novel species of the genus Geodermatophilus, for which the name Geodermatophilusmarinus sp. nov. is proposed, with the type strain LHW52908^T (=DSM 106570^T=CCTCC AA 2018014^T).

A new flavonoid derivative and a new 5-hydroxyanthranilic acid derivative from the sea urchin-derived Streptomyces sp. HDa1

One new flavonoid derivative flavoside A (1), one new 5-hydroxyanthranilic acid derivative crassilin (2), along with the known angucyclinone PD116740 (3) and oxachelin (4), was isolated from the EtOAc extract of the fermentation broth of the sea urchin (Anthocidaris crassispina)-derived actinobacterium, Streptomyces sp. HD01. The structures of these compounds were established on the basis of their HR-ESI-MS and NMR spectroscopic data. All of these compounds were assessed for their antibacterial activity.

A Flavor Lactone Mimicking AHL Quorum-Sensing Signals Exploits the Broad Affinity of the QsdR Regulator to Stimulate Transcription of the Rhodococcal qsd Operon Involved in Quorum-Quenching and Biocontrol Activities

In many Gram-negative bacteria, virulence, and social behavior are controlled by quorum-sensing (QS) systems based on the synthesis and perception of N-acyl homoserine lactones (AHLs). Quorum-quenching (QQ) is currently used to disrupt bacterial communication, as a biocontrol strategy for plant crop protection. In this context, the Gram-positive bacterium Rhodococcus erythropolis uses a catabolic pathway to control the virulence of soft-rot pathogens by degrading their AHL signals. This QS signal degradation pathway requires the expression of the qsd operon, encoding the key enzyme QsdA, an intracellular lactonase that can hydrolyze a wide range of substrates. QsdR, a TetR-like family regulator, represses the expression of the qsd operon. During AHL degradation, this repression is released by the binding of the γ-butyrolactone ring of the pathogen signaling molecules to QsdR. We show here that a lactone designed to mimic quorum signals, γ-caprolactone, can act as an effector ligand of QsdR, triggering the synthesis of qsd operon-encoded enzymes. Interaction between γ-caprolactone and QsdR was demonstrated indirectly, by quantitative RT-PCR, molecular docking and transcriptional fusion approaches, and directly, in an electrophoretic mobility shift assay. This broad-affinity regulatory system demonstrates that preventive or curative quenching therapies could be triggered artificially and/or managed in a sustainable way by the addition of γ-caprolactone, a compound better known as cheap food additive. The biostimulation of QQ activity could therefore be used to counteract the lack of consistency observed in some large-scale biocontrol assays.

Purification and characterization of actinomycins from Streptomyces strain M7 active against methicillin resistant Staphylococcus aureus and vancomycin resistant Enterococcus

Background

The increased rate of resistance among two highly concerned pathogens i.e. methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) necessitates the discovery of novel anti-MRSA and anti-VRE compounds. In microbial drug discovery, Streptomyces are well known source of two-thirds of natural antibiotics used clinically. Hence, screening of new strains of streptomycetes is the key step to get novel bioactive compounds with antimicrobial activity against drug resistant bacteria.

Results

In the present study, Streptomyces antibioticus strain M7, possessing potent antibacterial activity against different pathogenic bacteria, was isolated from rhizospheric soil of Stevia rebudiana. 16S rRNA sequence of M7 (1418 bp) showed 96.47–100% similarity with different Streptomyces spp. and the maximum similarity (100%) was observed with Streptomyces antibioticus NBRC 12838^T (AB184184). Phylogenetic analysis using neighbor joining method further validated its similarity with Streptomyces antibioticus NBRC 12838 T (AB184184) as it formed clade with the latter and showed high boot strap value (99%). Antibacterial metabolites isolated from the fermentation broth were characterized using NMR, FT-IR and LC-MS as actinomycins V, X₂ and D. The purified actinomycins exhibited potent antibacterial activities against test bacteria viz. B. subtilis, K. pneumoniae sub sp. pneumoniae, S. aureus, S. epidermidis, S. typhi, E. coli, MRSA and VRE. Among these actinomycins, actinomycin X₂ was more effective as compared to actinomycins D and V. The minimum inhibitory concentration values of purified compounds against a set of test bacterial organisms viz. VRE, MRSA, E. coli (S1-LF), K. pneumoniae sub sp. pneumoniae and B. subtilis ranged between 1.95 and 31.25 μg/ml.

Conclusions

This study demonstrates that actinomycins V, X₂ and D produced by S. antibioticus strain M7 hold the potential to be used against multidrug resistant bacteria, particularly VRE and MRSA.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1405-y) contains supplementary material, which is available to authorized users.

A Rhodococcal Transcriptional Regulatory Mechanism Detects the Common Lactone Ring of AHL Quorum-Sensing Signals and Triggers the Quorum-Quenching Response

The biocontrol agent Rhodococcus erythropolis disrupts virulence of plant and human Gram-negative pathogens by catabolizing their N-acyl-homoserine lactones. This quorum-quenching activity requires the expression of the qsd (quorum-sensing signal degradation) operon, which encodes the lactonase QsdA and the fatty acyl-CoA ligase QsdC, involved in the catabolism of lactone ring and acyl chain moieties of signaling molecules, respectively. Here, we demonstrate the regulation of qsd operon expression by a TetR-like family repressor, QsdR. This repression was lifted by adding the pathogen quorum signal or by deleting the qsdR gene, resulting in enhanced lactone degrading activity. Using interactomic approaches and transcriptional fusion strategy, the qsd operon derepression was elucidated: it is operated by the binding of the common part of signaling molecules, the homoserine lactone ring, to the effector-receiving domain of QsdR, preventing a physical binding of QsdR to the qsd promoter region. To our knowledge, this is the first evidence revealing quorum signals as inducers of the suitable quorum-quenching pathway, confirming this TetR-like protein as a lactone sensor. This regulatory mechanism designates the qsd operon as encoding a global disrupting pathway for degrading a wide range of signal substrates, allowing a broad spectrum anti-virulence activity mediated by the rhodococcal biocontrol agent. Understanding the regulation mechanisms of qsd operon expression led also to the development of biosensors useful to monitor in situ the presence of exogenous signals and quorum-quenching activity.

The Complete Structure of the Mycobacterium smegmatis 70S Ribosome

The ribosome carries out the synthesis of proteins in every living cell. It consequently represents a frontline target in anti-microbial therapy. Tuberculosis ranks among the leading causes of death worldwide, due in large part to the combination of difficult-to-treat latency and antibiotic resistance. Here, we present the 3.3-Å cryo-EM structure of the 70S ribosome of Mycobacterium smegmatis, a close relative to the human pathogen Mycobacterium tuberculosis. The structure reveals two additional ribosomal proteins and localizes them to the vicinity of drug-target sites in both the catalytic center and the decoding site of the ribosome. Furthermore, we visualized actinobacterium-specific rRNA and protein expansions that extensively remodel the ribosomal surface with implications for polysome organization. Our results provide a foundation for understanding the idiosyncrasies of mycobacterial translation and reveal atomic details of the structure that will facilitate the design of anti-tubercular therapeutics.

Isolation, identification, optimization, and metabolite profiling of Streptomyces sparsus VSM-30

Deep sea sediment samples of Bay of Bengal (Visakhapatnam) have been analyzed for actinomycetes as an elite source to screen for the production of bioactive metabolites. The actinomycetes strain VSM-30 has an exciting bioactivity profile and was isolated during our systemic screening of marine actinomycetes. It was identified as Streptomyces sparsus based on morphological, physiological, biochemical, and molecular approaches. Response surface methodology regression analysis was carried out to fit the experimental data of each response by the second-order polynomial. The results have proven right interaction among process variables at optimized values of incubation time at 12 days, pH at 8, temperature at 30 °C, concentrations of starch at 1%, and tryptone at 1% and the data have been adequately fitted into the second-order polynomial models. Under these conditions, the responses (zones of inhibition) of plant pathogenic fungi Aspergillus niger, Aspergillus flavus, Fusarium oxysporum, Fusarium solani, and Penicillium citrinum were also matched with experimental and predicted results. Chemotypic analysis of ethyl acetate extract of the strain was done using LC-Q-TOF-MS revealed the presence of bioactive compounds including tryptophan dehydrobutyrine diketopiperazine, maculosin, 7-o-demethyl albocycline, albocycline M-2, and 7-o-demethoxy-7-oxo albocycline in a negative ion mode. The ethyl acetate extract of actinobacterium has been subjected to gas chromatography and mass spectroscopy (GC-MS) revealed the presence of diverse compounds such as dotriacontane, tetracosane 11-decyl-, diheptyl phthalate, 1-hexadecanesulfonyl chloride, L-alanyl-L-tryptophan, phthalic acid ethyl pentyl ester, 4-trifluoroacetoxyhexadecane, and 1H-imidazole 4,5-dihydro-2,4-dimethyl. Hence, the ethyl acetate extract of Streptomyces sparsus VSM-30 may have antibacterial, antifungal, and antioxidant activities due to the presence of secondary metabolites in ethyl acetate extract. The study also supports marine sediment samples of Bay of Bengal, a promising marine ecosystem remained to be explored for new bioactive compounds.

nov., an actinobacterium isolated from Saharan soil

During our investigations of new actinobacterial taxa, a novel actinobacterial strain, designated MB20^T, was isolated from a Saharan soil sample, collected in the Mzab region (Ghardaïa province, southern Algeria). In order to reveal its taxonomic position, the novel strain was characterized following a polyphasic taxonomic approach. It was noticed that strain MB20^T produced white, branched and fragmented substrate mycelium with no aerial mycelium on most of the media tested. Chemotaxonomic and phylogenetic studies clearly demonstrated that strain MB20^T belonged to the family Pseudonocardiaceae and was closely related to the genus Actinophytocola. Cell-wall hydrolysates contained meso-diaminopimelic acid but not glycine, and whole-cell hydrolysates contained galactose, glucose and ribose. The diagnostic phospholipid was phosphatidylethanolamine. Mycolic acids were not detected while the predominant fatty acid was found to be iso-branched hexadecanoate (iso-C16 : 0). The major menaquinone was MK-9(H4). Results of the 16S rRNA gene sequence comparison revealed that strain MB20^T shared the highest degree of similarity with Actinophytocola gilvus DSM 45828^T (98.5 %), Actinophytocola corallina DSM 45659^T (98.0 %) and Actinophytocola timorensis DSM 45660^T (97.5 %). However, DNA-DNA hybridization studies showed only 32.9 % similarity with A. timorensis, 23.7 % similarity with A. gilvus and 17.9 % similarity with A. corallina. On the basis of phenotypic characteristics, 16S rRNA gene sequence comparisons and DNA-DNA hybridization, strain MB20^T was revealed to be a representative of a novel species of the genus Actinophytocola, for which the name Actinophytocola algeriensis sp. nov. (type strain MB20^T =DSM 46746^T =CECT 8960^T) is proposed.

Electron Microscopy and X-ray Analysis of Cr-Containing Precipitates Synthesized by Newly Isolated Actinobacterium, Flexivirga alba ST13(T.)

Chromium(Cr) precipitate synthesized by Cr(VI)-reducing bacterium Flexivirga alba ST13(T) was examined using transmission electron microscopy (TEM) and the energy dispersive X-ray (EDX). The strain showed altered-morphology after exposing to Cr(VI) in minimal medium. The resultant precipitate included bacterial pellet and needle-like structure which was similar to the structure made from Cr(OH)3 precipitate. Cr was observed in bacterial cells using TEM-EDX. Bacteria with high electron density showed the precipitation of Ca in addition to Cr. The isolated strain would be useful to precipitate Cr from Cr(VI)-containing environment.

Production of bioemulsifiers by Amycolatopsis tucumanensis DSM 45259 and their potential application in remediation technologies for soils contaminated with hexavalent chromium

In recent years, increasing interest has been shown in the use of bioemulsifiers as washing agents that can enhance desorption of soil-bound metals. However, high production costs derived from the use of expensive substrates for formulation of the fermentation media represent the main challenge for full, large-scale implementation of bioemulsifiers. This work reports on a first study of bioemulsifier production by the actinobacterium Amycolatopsis tucumanensis DSM 45259 using different carbon and nitrogen sources. Preliminary results on the potential use of these compounds as washing agents for soils contaminated with Cu(II) and Cr(VI) are also presented. The best specific production was detected using glycerol and urea as carbon and nitrogen substrates, respectively. However, with all of the substrates used during the batch assay, the bioemulsifiers showed high levels of stability at extreme conditions of pH, temperature, and salt concentration. Under the current assay conditions, the bioemulsifiers were not effective in removing Cu(II) from soil. However, they were able to mediate Cr(VI) recovery, with the removal percentage doubled compared to that seen when using deionized water. These findings appear promising for the development of remediation technologies for hexavalent chromium compounds based upon direct use of these microbial emulsifiers.

Antibacterial activity of some actinomycetes from Tamil Nadu, India

OBJECTIVE

To isolate novel actinomycetes and to evaluate their antibacterial activity.

METHODS

Three soil samples were collected from Vengodu (village) in Kanchipuram district, Tamil Nadu, India. Actinomycetes were isolated using serial dilution and plating method on actinomycetes isolation agar.

RESULTS

Totally 35 isolates were obtained on the basis of colony characteristics on actinomycetes isolation agar. All the isolates were screened for antibacterial activity by cross streak method. Medium and optimization of day were done for the potent strains using Nathan's agar well diffusion method. Isolation of bioactive compounds from significant active isolates was done by using different media. The most active isolate VAS 10 was identified as Actinobacterium Loyola PBT VAS 10 (accession No. JF501398) using 16s rRNA sequence method. The hexane, ethyl acetate, dichloromethane and butanol extracts of VAS 10 were tested against bacteria. The maximum antibacterial activity was observed in dichloromethane and ethyl acetate; maximum zones of inhibition were observed against Enterococcus durans. The rRNA secondary structure and the restriction sites of Actinobacterium Loyola VAS 10 were predicted using Genebee and NEBCutter online tools respectively.

CONCLUSIONS

The present study showed that among the isolated actinomycetes, Actinobacterium Loyola PBT VAS 10 (accession No. JF501398) showed good antibacterial activity against the tested bacteria.