Actinobacterial Isolates Research Articles

Pigment from Streptomyces bellus MSA1 isolated from marine sediments

The existing study is purposeful on the intracellular pigment extraction from actinomycetes isolated from Kovalam Beach regions of Chennai, Tamil Nadu, India. Only one actinobacterial isolate showed pigmented growth out of total 4 isolates. Ethyl acetate as the solvent was used in cell disruption technique for the extraction of intracellular pigments. UV-Visible spectrophotometry, FT-IR spectroscopy, HPLC and GC-MS were used for the partial characterization of the pigment. The extracted pigment was applied for the preparation of lip balm and assessing its textile dyeing property. In addition, the extracted pigment was analysed for antioxidant, antibacterial activity, MTT assay and haemolytic activity. On optimization, dextrose and maltose were the best carbon sources. The finest nitrogen sources were found to be casein and peptone. The optimum temperature range was 35°C -40°C and optimal pH was found to be between 6.0 and 8.0. The obtained results showed potent antioxidant activity and found to be non-toxic to human erythrocytes.

Purification, characterization, and statistical optimization of a thermostable α-amylase from desert actinobacterium Streptomyces fragilis DA7-7.

In this study, preliminary screening revealed that of 134 desert soil actinobacterial isolates, only 43 isolates produced amylase. Among these, an isolate DA7-7, which was identified as Streptomyces fragilis DA7-7, showed a prominent zone of clearance and significant amount of α-amylase production. The pre-optimization studies showed varying physicochemical and nutrients properties of the medium influenced the enzyme production significantly. Consequently, central composite design was employed with the selected variables (pH, temperature, dextrose, and peptone) for α-amylase production. The optimum fermentation conditions were 3.07% dextrose, 1.085% peptone, pH 6.0, and incubation temperature 27.27°C. The predicted optimum α-amylase activity was 991.82U/mL/min, which was similar to the experimental amylase activity of 973.5U/mL/min. The crude α-amylase produced by S. fragilis DA7-7 was purified with ammonium sulfate precipitation, followed by gel filtration chromatography, and the estimated molecular mass was 51kDa. The purified α-amylase was stable under the following conditions: pH (4-9), temperature (40-80°C), NaCl (1-4M), and detergents (1-10mM). The Km and Vmax values of enzyme were found to be 0.624mU/mg and 0.836mg/mL, respectively.

Sponge-Associated Actinobacteria: Morphological Character and Antibacterial Activity against Pathogenic Bacteria

Sponge-associated actinobacteria may diverse and have potency to produce bioactive compounds. Diversity and antimicrobial activity of indigenous sponge-associated actinobacteria isolated from the marine ecosystem in Indonesia have not much been explored. This work aimed to assess morphological and antibacterial activity of sponge-associated actinobacteria. The morphological characteristics were examined based on their color of aerial and substrate mycelia, and pigmentation, while antibacterial activities were assayed using the antagonist technique. The selected actinobacterial isolate was identified using 16S rRNA gene. Various sponge-associated actinobacteria were successfully isolated from Hyrtios sp., Callyspongia sp., and Neofibularia sp. sponges. A total of 62 actinobacterial isolates were obtained, and each isolate showed a variety of morphological characters, which could be seen in aerial mass color, substrate mass color, and pigmentation. Actinobacterial isolates were tested against human pathogenic bacteria, i.e. Staphylococcus aureus and Methicillin-Resistant S. aureus, representing Gram-positive, and Escherichia coli EPEC K1-1 and Shigella dysenteriae, representing Gram-negative. Most of actinobacterial isolates had antimicrobial activities at least against one of pathogenic bacteria. High activity was shown by NOHa.2, isolated from Neofibularia, and HRHa.5 isolated from Hyrtios. The NOHa.2 showed the highest antimicrobial activity against S. dysenteriae, meanwhile, HRHa.5 showed antimicrobial activity against 3 of 4 tested bacterial pathogens. These data showed diversity of sponge-asccociated actinobacteria from marine ecosystem in Indonesia, and several of them have potency as source of antibacterial compounds

The diversity and antibiotic properties of actinobacteria associated with endemic deepwater amphipods of Lake Baikal

The emergence of pathogenic bacteria resistant to antibiotics increases the need for discovery of new effective antimicrobials. Unique habitats such as marine deposits, wetlands and caves or unexplored biological communities are promising sources for the isolation of actinobacteria, which are among the major antibiotic producers. The present study aimed at examining cultivated actinobacteria strains associated with endemic Lake Baikal deepwater amphipods and estimating their antibiotic activity. We isolated 42 actinobacterial strains from crustaceans belonging to Ommatogammarus albinus and Ommatogammarus flavus. To our knowledge, this is the first report describing the isolation and initial characterization of representatives of Micromonospora and Pseudonocardia genera from Baikal deepwater invertebrates. Also, as expected, representatives of the genus Streptomyces were the dominant group among the isolated species. Some correlations could be observed between the number of actinobacterial isolates, the depth of sampling and the source of the strains. Nevertheless, >70% of isolated strains demonstrated antifungal activity. The dereplication analysis of extract of one of the isolated strains resulted in annotation of several known compounds that can help to explain the observed biological activities. The characteristics of ecological niche and lifestyle of deepwater amphipods suggests that the observed associations between crustaceans and isolated actinobacteria are not random and might represent long-term symbiotic interactions.

Bioconversion and bioethanol production from agro-residues through fermentation process using mangrove-associated actinobacterium Streptomyces olivaceus (MSU3)

ABSTRACTIn the present investigation, an actinobacterial strain of Streptomyces olivaceus (MSU3) was isolated from a rhizosphere sediment sample of a mangrove environment, and it was confirmed through 16S rRNA sequencing. The isolated strain saccharified various agro-residues such as vegetable, banana, mango peel, sugarcane bagasse and sugarcane juice, followed by bioethanol production. Among the tested residues, the actinobacterial strain exhibited the maximum percentage of saccharification and bioethanol production in sugarcane juice-substituted medium at the optimized culture conditions of pH 6, temperature 30°C, innoculum size 2.5% and incubation time 72 h, substituted with 2.5% dextrose and 2.0% urea, respectively, as carbon and nitrogen sources. The concentration of produced bioethanol was estimated through high-performance liquid chromatography (HPLC) and it was exhibited as 76% with the retention time of 2.055 min and percentage area of 135694.91μV/sec. In Fourier transmission infrared (FT-IR) analysis, six functional groups (O-H, C-O, C=O, C=C, -C=C and C-Br) from the produced bioethanol were denoted between the wavenumber of 3264.27 and 551.35 cm−1. Finally, the Gaschromatography-Massspectrphotometry (GC-MS) analysis confirmed that the functional group similar to bioethanol was detected in the chromatogram with a retention time of 2.50 as well as 13.87 min. Based on the results, it could be confirmed that the actinobacterial isolate is a potent strain and can also be used to hydrolyze agro-residues and to convert the agro-residues into economically important byproducts like bioethanol.

PRODUCTION OF KERATINASES FROM NOCARDIOPSIS SP. 28ROR AS A NOVEL IRAQI STRAIN

Objectives: isolate a novel feather- degrading actinobacterial species had the ability to produce wide pH activity keratinases.Methods: Of 23 actinobacterial isolates were recovered from farm soil, poultry farm soil and feather wastes, these isolates were screened for protease and keratinase production on skim milk agar, feather media, and antimicrobial production. One potential isolate was identified depending on phenotypical, physiological and molecular according to partial sequences of 16S r RNA gene analysis and optimized keratinase production. Results: 11 isolates out of 22 protease producer had the ability to degrade raw chicken feather and some of these isolates produced antifungal and antibacterial metabolites.The potential isolate, Nocardiopsis sp. 28ROR (GenBank: KC702802.1), produced two types of extracellular keratinases in feather meal medium at pH6 (acid type), 30-35°C for 7d and the alkaline keratinase at pH10, 40°C for 7d.Conclusion: The Nocardiopsis sp. 28ROR was a novel strain produced keratinases using feather meal degradation as a cheap waste medium. The wide tolerance of temperature and pH by keratinase makes it an ideal contender to be investigated further for potential application as a detergent additive.Keywords: Nocardiopsis, Keratinase, Optimization, Feather medium, Antibiotic.

Marine Actinobacteria as a source of compounds for phytopathogen control: An integrative metabolic-profiling / bioactivity and taxonomical approach.

Marine bacteria are considered as promising sources for the discovery of novel biologically active compounds. In this study, samples of sediment, invertebrate and algae were collected from the Providencia and Santa Catalina coral reef (Colombian Caribbean Sea) with the aim of isolating Actinobateria-like strain able to produce antimicrobial and quorum quenching compounds against pathogens. Several approaches were used to select actinobacterial isolates, obtaining 203 strains from all samples. According to their 16S rRNA gene sequencing, a total of 24 strains was classified within Actinobacteria represented by three genera: Streptomyces, Micromonospora, and Gordonia. In order to assess their metabolic profiles, the actinobacterial strains were grown in liquid cultures, and LC-MS-based analyses from ethyl acetate fractions were performed. Based on taxonomical classification, screening information of activity against phytopathogenic strains and quorum quenching activity, as well as metabolic profiling, six out of the 24 isolates were selected for follow-up with chemical isolation and structure identification analyses of putative metabolites involved in antimicrobial activities.

Efficacy of protease inhibitor from marine Streptomyces sp. VITBVK2 against Leishmania donovani – An in vitro study

In the present study the leishmanicidal effect of potential protease inhibitor producing marine actinobacterial isolate has been investigated against Leishmania donovani, the causative agent of visceral leishmaniasis. Among 89 marine actinobacteria isolated from a salt pan in Kanyakumari, only one isolate (BVK2) showed 97% of protease inhibition activity against trypsin. Moderate to high protease inhibitor activity was shown by isolate BVK2 on proteinase (30%) and chymotrypsin (85%). In optimization study for protease inhibitor production glucose as carbon source and casein as nitrogen source showed the best activity. In the in-vitro Fluorescence-activated cell sorting (FACS) assay, 100 μg/ml of BVK2 extract was active against amastigotes in infected J774A.1 macrophages and showed 87% of parasitic inhibition. The isolate BVK2 showed significant anti-parasitic activity with an IC50 of 27.1 μg/ml after double doses were administered. The potential isolate was identified by molecular 16S rRNA gene sequencing as Streptomyces sp. VITBVK2. The results obtained suggest that the marine actinobacterial extract which have novel metabolites can be considered as a potential source for the development of drugs.

PRODUCTION OF ANTIMICROBIAL AND ANTICANCER FOM FEATHER-KERATINOLYTIC NOCARDIOPSIS SP. 28ROR AS A NOVEL STRAIN USING FEATHER MEAL MEDIUM

Objective: Production of bioactive secondary metabolites from a feather-degrading actinobacterial species using feather meal medium. Methods: Protease producer actinobacterial isolates (22) recovered from farm soil, poultry farm soil and feather wastes were used to test the antagonistic effect on pathogenic bacteria and fungi, including Staphylococcus aureus, Escherichia coli, Microsporum canis and Trichophyton mentagrophyte using Mueller-Hinton agar and potato dextrose agar (PDA) media. The best isolate was used to produce the active metabolites in feather meal medium composed from (g/l) 10 feather meal, 5 sucrose and 0.3 l cement extract were dissolved in tap water, in addition to the standard medium composting of (g/l) glucose (1%), tryptone (1%), KH2PO4 (0.07%) and K2HPO4 (0.14%) were dissolved in distilled water, both of them at initial pH 9. The secondary metabolites were partially purified by Sephadex LH20 column and the antimicrobial activity and cytotoxic activity were assayed.Results: 31.82% of isolates inhibited the growth of both bacterial and fungal test organisms and the best one was Nocardiopsis sp. 28ROR (GenBank: KC702802.1) at a significant level P˂ 0.05. It produced bioactive metabolites in both feather meal broth and the standard media. The partially purified metabolites inhibit the breast cancer cell line MCF-7 (51%) and normal hepatic cell line WRL-68 (9%), in addition to inhibiting S. aureus andTrichophyton menta agrophyte growth.Conclusion: The actinobacteria has vast abilities to degrade very complex wastes and converted to simple constituents to reprocess in other industries. So the Nocardiopsis sp. 28ROR was a novel strain produced anticancer, antimicrobial substances using feather meal medium as a cheap waste medium.

Blastococcus colisei sp. nov, isolated from an archaeological amphitheatre.

The taxonomic position of an actinobacterial isolate, designated strain BMG 822T, isolated from limestone from the Amphitheater of El Jem (Coliseum Thysdrus), Tunisia, was established using a polyphasic approach. Strain BMG 822T was found to grow well at 30°C and pH 6.5-8.0, and to be coral-coloured, Gram-positive, catalase and oxidase negative. Whole cell hydrolysates contained meso-diaminopimelic acid as the diagnostic diamino acid, glucose, galactose and ribose. The phospholipids detected were diphosphatidylglycerol, phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine, hydroxy-phosphatidylethanolamine, an unidentified glycophospholipid and six unidentified phospholipids. MK-9(H4) was found to be the predominant menaquinone, followed by MK-9(H2) and MK-9. The major cellular fatty acids were identified as iso-C16:0, C18:1 ω9c, C17:1 ω8c and iso-H-C16:1. The G+C content of the DNA (73.2%) is typical of the genus. High degrees of 16S rRNA gene sequence similarity were found with the type strains of the genus Blastococcus (97.1-98.3%) followed by the type strains of Modestobacter (96.8-97.8%). Based on the above data and the phenotypic differences from the type strains ofBlastococcus species, it is proposed that the isolate BMG 822T (=DSM 46837T=CECT 8823T) should be classified as the type strain of a novel species,Blastococcus colisei sp. nov.

Potential for biocontrol of melanized fungi by actinobacteria isolated from intertidal region of Ilha Do Mel, Paraná, Brazil.

Actinobacteria occur in many environments and have the capacity to produce secondary metabolites with antibiotic potential. Identification and taxonomy of actinobacteria that produce antimicrobial substances is essential for the screening of new compounds, and sequencing of the 16S region of ribosomal DNA (rDNA), which is conserved and present in all bacteria, is an important method of identification. Melanized fungi are free-living organisms, which can also be pathogens of clinical importance. This work aimed to evaluate growth inhibition of melanized fungi by actinobacteria and to identify the latter to the species level. In this study, antimicrobial activity of 13 actinobacterial isolates from the genus Streptomyces was evaluated against seven melanized fungi of the genera Exophiala, Cladosporium, and Rhinocladiella. In all tests, all actinobacterial isolates showed inhibitory activity against all isolates of melanized fungi, and only one actinobacterial isolate had less efficient inhibitory activity. The 16S rDNA region of five previously unidentified actinobacterial isolates from Ilha do Mel, Paraná, Brazil, was sequenced; four of the isolates were identified as Streptomyces globisporus subsp. globisporus, and one isolate was identified as Streptomyces aureus. This work highlights the potential of actinobacteria with antifungal activity and their role in the pursuit of novel antimicrobial substances.

LACCASE PRODUCING STREPTOMYCES BIKINIENSIS CSC12 ISOLATED FROM COMPOST

Lignin degradation by actinobacteria is more attractive than well known white rot fungal system by the fact of their higher survival rate, sporulating ability, economic production of useful chemicals rather than evolution of CO2 as in white-rot fungi. One of the important enzymes in ligninolysis is laccase, which oxidize a broad range of substrates, preferably phenolic and non-phenolic compounds. Among the laccase producing microbes in nature, white rot fungi have been characterized much, very little is known about the laccase producing actinobacteria. The present investigation aims to isolate and screen active laccase producing actinobacteria from diverse environments. Fifteen isolates of actinobacteria were isolated from various organic substrates viz., coir compost, groundnut shell compost, fully and partially decomposed municipal solid waste and identified based on molecular characterization. With initial screening using ρ-anisidin and Poly-R 478, seven actinobacterial isolates had more efficient ligninolytic activity than others. Of which, isolate CSC12 secreted highest laccase and was identified as Streptomyces bikiniensis CSC12. Laccase from S.bikiniensis CSC12 was partially purified as monomer having molecular mass ~69 kDa based on SDS-PAGE and had pH and temperature optima of 6 to 7 and 50 to 60 °C respectively.

Diversity, Biogeography, and Biodegradation Potential of Actinobacteria in the Deep-Sea Sediments along the Southwest Indian Ridge.

The phylum Actinobacteria has been reported to be common or even abundant in deep marine sediments, however, knowledge about the diversity, distribution, and function of actinobacteria is limited. In this study, actinobacterial diversity in the deep sea along the Southwest Indian Ridge (SWIR) was investigated using both 16S rRNA gene pyrosequencing and culture-based methods. The samples were collected at depths of 1662–4000 m below water surface. Actinobacterial sequences represented 1.2–9.1% of all microbial 16S rRNA gene amplicon sequences in each sample. A total of 5 actinobacterial classes, 17 orders, 28 families, and 52 genera were detected by pyrosequencing, dominated by the classes Acidimicrobiia and Actinobacteria. Differences in actinobacterial community compositions were found among the samples. The community structure showed significant correlations to geochemical factors, notably pH, calcium, total organic carbon, total phosphorus, and total nitrogen, rather than to spatial distance at the scale of the investigation. In addition, 176 strains of the Actinobacteria class, belonging to 9 known orders, 18 families, and 29 genera, were isolated. Among these cultivated taxa, 8 orders, 13 families, and 15 genera were also recovered by pyrosequencing. At a 97% 16S rRNA gene sequence similarity, the pyrosequencing data encompassed 77.3% of the isolates but the isolates represented only 10.3% of the actinobacterial reads. Phylogenetic analysis of all the representative actinobacterial sequences and isolates indicated that at least four new orders within the phylum Actinobacteria were detected by pyrosequencing. More than half of the isolates spanning 23 genera and all samples demonstrated activity in the degradation of refractory organics, including polycyclic aromatic hydrocarbons and polysaccharides, suggesting their potential ecological functions and biotechnological applications for carbon recycling.

Detection of biosynthetic gene and phytohormone production by endophytic actinobacteria associated with Solanum lycopersicum and their plant-growth-promoting effect

In the present study, fifteen endophytic actinobacterial isolates recovered from Solanum lycopersicum were studied for their antagonistic potential and plant-growth-promoting (PGP) traits. Among them, eight isolates showed significant antagonistic and PGP traits, identified by amplification of the 16S rRNA gene. Isolate number DBT204, identified as Streptomyces sp., showed multiple PGP traits tested in planta and improved a range of growth parameters in seedlings of chili (Capsicum annuum L.) and tomato (S. lycopersicum L.). Further, genes of indole acetic acid (iaaM) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase (acdS) were successively amplified from five strains. Six antibiotics (trimethoprim, fluconazole, chloramphenicol, nalidixic acid, rifampicin and streptomycin) and two phytohormones [indole acetic acid (IAA) and kinetin (KI)] were detected and quantified in Streptomyces sp. strain DBT204 using UPLC-ESI-MS/MS. The study indicates the potential of these PGP strains for production of phytohormones and shows the presence of biosynthetic genes responsible for production of secondary metabolites. It is the first report showing production of phytohormones (IAA and KI) by endophytic actinobacteria having PGP and biosynthetic potential. We propose Streptomyces sp. strain DBT204 for inoculums production and development of biofertilizers for enhancing growth of chili and tomato seedlings.

Preliminary screening of Ni(II) metal tolerance and dye-decolorizing by Nocardiopsis sp. SD8

Objective: To reveal the screening of metal tolerance and dye-decolorizing of Nocardiopsis sp. Methods: NiSO4 and Congo red dye were used for evaluating the metal tolerance and dyedecolorizing of the randomly selected actinobacterial isolates. Results: Nocardiopsis sp. SD8 showed a better efficiency in Ni(II) tolerance, though a longer lag phase was observed for this microorganism grown for 7 days in integrated mismatch negativity. Interestingly, we also found that Nocardiopsis sp. SD8 had dye-decolorizing, hemolytic, lipase and protease activity. Conclusions: The present results revealed the bioremediation of metal resistant and diverse properties of Nocardiopsis sp. SD8 and further investigations are needed to extract and identify the potent molecule.

Coral-Associated Actinobacteria: Diversity, Abundance, and Biotechnological Potentials.

Marine Actinobacteria, particularly coral-associated Actinobacteria, have attracted attention recently. In this study, the abundance and diversity of Actinobacteria associated with three types of coral thriving in a thermally stressed coral reef system north of the Arabian Gulf were investigated. Coscinaraea columna, Platygyra daedalea and Porites harrisoni have been found to harbor equivalent numbers of culturable Actinobacteria in their tissues but not in their mucus. However, different culturable actinobacterial communities have been found to be associated with different coral hosts. Differences in the abundance and diversity of Actinobacteria were detected between the mucus and tissue of the same coral host. In addition, temporal and spatial variations in the abundance and diversity of the cultivable actinobacterial communities were detected. In total, 19 different actinobacterial genera, namely Micrococcus, Brachybacterium, Brevibacterium, Streptomyces, Micromonospora, Renibacterium, Nocardia, Microbacterium, Dietzia, Cellulomonas, Ornithinimicrobium, Rhodococcus, Agrococcus, Kineococcus, Dermacoccus, Devriesea, Kocuria, Marmoricola, and Arthrobacter, were isolated from the coral tissue and mucus samples. Furthermore, 82 isolates related to Micromonospora, Brachybacterium, Nocardia, Micrococcus, Arthrobacter, Rhodococcus, and Streptomyces showed antimicrobial activities against representative Gram-positive and/or Gram-negative bacteria. Even though Brevibacterium and Kocuria were the most dominant actinobacterial isolates, they failed to show any antimicrobial activity, whereas less dominant genera, such as Streptomyces, did show antimicrobial activity. Focusing on the diversity of coral-associated Actinobacteria may help to understand how corals thrive under harsh environmental conditions and may lead to the discovery of novel antimicrobial metabolites with potential biotechnological applications.

The cell aggregating propensity of probiotic actinobacterial isolates: isolation and characterization of the aggregation inducing peptide pheromone

The auto-aggregating ability of a probiotic is a prerequisite for colonization and protection of the gastrointestinal tract, whereas co-aggregation provides a close interaction with pathogenic bacteria. Peptide pheromone mediated signaling has been studied in several systems. However, it has not yet been explored in prokaryotes, especially actinobacteria. Hence, in the present study, the diffusible aggregation promoting factor was purified from the culture supernatant of a potent actinobacterial probiont and characterized using 20 different actinobacterial cultures isolated from the gut region of chicken and goat. The results showed that the pheromone-like compound induces the aggregation propensity of treated isolates. The factor was found to be a heat stable, acidic pH resistant, low molecular weight peptide which enhances the biofilm forming ability of other actinobacterial isolates. The aggregation promoting factor represents a bacterial sex factor (pheromone) and its characterization confirms its usage in the probiotic formulation

Cultural, Transcriptomic, and Proteomic Analyses of Water-Stressed Cells of Actinobacterial Strains Isolated from Compost: Ecological Implications in the Fed-Batch Composting Process.

This study was undertaken to examine the effects of water activity (aw) on the viability of actinobacterial isolates from a fed-batch composting (FBC) process by comparing culturability and stainability with 5-cyano-2,3-ditoryl tetrazolium chloride (CTC). The FBC reactor as the source of these bacteria was operated with the daily loading of household biowaste for 70 d. During this period of composting, aw in the reactor decreased linearly with time and reached approximately 0.95 at the end of operation. The plate counts of aerobic chemoorganotrophic bacteria were 3.2-fold higher than CTC-positive (CTC+) counts on average at the fully acclimated stage (after 7 weeks of operation), in which Actinobacteria predominated, as shown by lipoquinone profiling and cultivation methods. When the actinobacterial isolates from the FBC process were grown under aw stress, no significant differences were observed in culturability among the cultures, whereas CTC stainability decreased with reductions in aw levels. A cDNA microarray-based transcriptomic analysis of a representative isolate showed that many of the genes involved in cellular metabolism and genetic information processing were down-regulated by aw stress. This result was fully supported by a proteomic analysis. The results of the present study suggest that, in low aw mature compost, the metabolic activity of the community with Actinobacteria predominating is temporarily reduced to a level that hardly reacts with CTC; however, these bacteria are easily recoverable by exposure to a high aw culture medium. This may be a plausible reason why acclimated FBC reactors in which Actinobacteria predominate yields higher plate counts than CTC+ counts.

Screening of Antifouling Compound Producing Marine Actinobacteria against Biofouling Bacteria Isolated from Poultries of Namakkal District, South India

Growth of biofouling microorganisms in surfaces of poultry, marine and other ecosystems is one of the major issues. Thus it is essential to control the growth of biofouling bacterial growth in surface of biological ecosystem. The present study has aimed to isolate novel antifouling compound from marine actinobacterial isolates. A total of 55 actinobacteria were isolated from Palk Strait coastal region (Bay of Bengal), Tamilnadu, India. All of them were preliminarily screened for their antifouling activity against six different biofouling bacterial (BFB) species isolated from poultry farms by cross streak plate method. Among them, 20 isolates possessed antibacterial activity against biofouling bacteria. From the 20 antifouling compound producers, 10 actinobacterial isolates were selected for further confirmation of antifouling compound production and their antifouling efficacies by shake flask culture method. Of them, one potential strain VS6 was found to be more active against all the six BFB. Thus, the result of the present study represents that the coastal areas of Tamil Nadu are rich in antifouling compound producing actinobacteria.

In vitro biocontrol activity of halotolerant Streptomyces aureofaciens K20: A potent antagonist against Macrophomina phaseolina (Tassi) Goid.

A halotolerant actinobacterial strain isolated from salinity affected soil of Eastern Indo-Gangetic plains (IGP), Uttar Pradesh, India, was characterised for its antagonistic potential against Macrophomina phaseolina by dual-culture assay. It was shown to effectively inhibit the growth of M. phaseolina with an inhibition zone of 27 ± 1.33 mm. Further the actinobacterial strain was evaluated for its plant growth promoting (PGP) properties and its ability to produce biocontrol related extracellular enzymes viz. amylase, protease, cellulase, chitinase, gelatinase and urease. The results revealed that the actinobacterial strain had PGP potential along with positive assay for amylase, chitinase and urease. The interaction study between antagonist strain and fungal pathogen, performed by scanning electron microscopy technique revealed that the actinobacterium was able to damage fungal mycelia may be due to chitinase, establishing its role as a potential antagonist against M. phaseolina. The actinobacterial isolate was characterised by 16S rDNA gene sequencing, and was identified as Streptomyces genera. The identified gene sequence was deposited to NCBI GenBank with an accession number KP331758.