Isolation and screening of antibacterial and enzyme producing marine actinobacteria to approach probiotics against some pathogenic vibrios in shrimp Litopenaeus vannamei

The application of new probiotics is a good strategy in the biological control of infectious diseases in aquaculture. Approximately 100 marine actinobacteria isolates were obtained from 10 sediment samples of shrimp farms. Heat treatment of sediment samples resulted in a selective reduction of the non actinobacterial heterotrophic microflora. Starch nitrate agar medium exhibited more efficacy than glycerol arginine agar medium for isolation. Twenty seven percent of actinobacterial isolates showed antagonistic activities against pathogenic Vibrio spp. All the antagonistic isolates showed the typical morphology of genus Streptomyces. Exoenzymatic activity screening showed that 44%, 26%, 37% of antagonistic isolates represented amylase, lipase and protease activities, respectively. MNM-1400 strain exhibited highest antagonistic and exoenzymatic activity. The pathogenicity experiment revealed that MNM-1400 strain did not cause disease in Litopenaeus vannamei larvae. Extraction of produced antibacterial compounds by MNM-1400 strain showed that the active constituent didn’t have non polar property. Morphological, physiological and biochemical identification confirmed that MNM-1400 strain belonged to the genus Streptomyces. Phylogenetic analysis by 16S rRNA gene sequencing showed a high similarity between MNM-1400 strain and Streptomyces californicus (similarity: 99%). These results suggest that the MNM-1400 strain can be considered as a potential probiotic in aquaculture

Isolation, identification and evaluation of antimicrobial activity of Actinomycetes from marine sediments of Persian Gulf (Hormozgan Province)

Actinomycetes are gram positive and filamentous bacteria and produce a major portion of bioactive compounds. The aim of this study was to isolate and identify antibiotic-producing actinomycetes from Persian Gulf marine sediments within Hormozgan province territory. Among 3 selected isolation media the M1 medium showed highest efficacy by isolation of 32 colonies. Heat treatment of 100 ºC for 60 min isolated 26 colonies and showed the best result. Approximately 60 Actinomycete isolates were obtained from 10 sediment samples. Evaluation of antimicrobial activity showed that 33, 20 and 30 % of isolates exhibited antimicrobial activity against S.aureus, E.coli and C.albicans respectively.Morphologic, physiologic and chemotaxonomic studies showed that selected potent isolates consist of Ifro12, Ifro 33 and Ifro 47 belonged to Streptomyces genus. Molecular genetic studies based on 16s rRNA gene analysis revealed that Ifro12, Ifro 33 and Ifro 47 exhibited 99 % similarity to S.olivaceus, S.cacaoi and S.variabilis respectively. Phylogenetic analysis showed that Ifro12 and Ifro 47 derived from a common ancestor. The results of the present research indicated that these three isolates could be considered as promising candidates for antibiotic discovery researches

Antimicrobial activities of semi polar-nonpolar and polar secondary metabolites of sponge Dysidea pallescens from Hengam Island, Persian Gulf

Sponges are the simplest multicellular animals that lack defense mechanisms and rely on chemical defense that have been used by mankind to develop antimicrobial drugs against diseases. The present study was designed to demonstrate the antibacterial and antifungal activities of marine sponge Dysidea pallescens semipolar and nonpolar extracts. In this study, D. pallescens were collected from Hengam Island in the Persian Gulf. The extracts were produced by Bligh and Dyer method. Broth Dilution Methods were used to check the antimicrobial activity of D. pallescens extracts against Escherichia coli (ATCC 15224), Pseudomonas aeruginosa (ATCC 25619), Staphylococcus aureus aureus (ATCC 1764), Bacillus subtilis pizizenii (ATCC 6633), Candida albicans (ATCC 10231) and Aspergillus fumigates (PTCC 5009). The results showed diethyl ether extract has bactericidal activity against S. aureus aureus (MBC=10mg/mL) and B. subtilis spizizenii (MBC=20mg/mL). D. pallescens diethyl ether extract showed a very weak antifungal activity but methanol extract showed fungicidal activity against A. fumigates (MFC=5mg/mL) and C. albicans (MFC=1.5 mg/mL). Therefore nonpolar-semipolar secondary metabolites of D. pallescens solutions in diethyl ether have shown significant antibacterial activity and polar-secondary metabolites solutions in methanol have shown significant antifungal activity

Isolation, identification and antimicrobial evaluation of marine actinomycetes from Oman sea sediments

Actinomycetes are gram positive and filamentous bacteria and produce major portion of the bioactive compounds hence play an integral role in the novel drugs development. Recent studies demonstrated that marine habitats inhabiting actinomycetes have unique biodiversity and metabolic activity. For the first time Oman Sea sediments were investigated as a source of antibiotic producing marine actinomycetes in this project. Approximately 84 isolates were obtained from 14 collected sediment samples. Among four culture media and two treatments, Glucose asparagine agar and heat treatment isolated 32 and 47 isolates respectively and exhibited highest efficiency. Evaluation of antimicrobial activity of the isolated actinomycetes by top layer agar revealed that 24, 12, 23 percent of isolates showed antimicrobial activity against S.aureus, E.coli and C.albicans respectively. Determination of Minimum inhibitory concentrations of extracted antibiotics were recorded as 128256, 128-512 and 62-128 µg/ml against S.aureus, E.coli and C.albicans respectively. Preliminary identification studies showed that the potent isolates exhibited typical morphology of Streptomyces genus predominantly. Result of Morphological, biochemical and chemotaxonomical identification revealed that IFSIRI 70 ، IFSIRI 137 ، IFSIRI 145، IFSIRI 193،IFSIRI 214 belonged to Streptomyces genus. Molecular identification by 16s rRNA gene analysis showed high similarity (99%) between IFSIRI 70 ، IFSIRI 137 ، IFSIRI 145، IFSIRI 193،IFSIRI 214 strains with S. chartreusis، S. qinglanensis، S. Cacaoi، S. violaceoruber and S. diastaticus respectively. Phylogenetic analysis showed that isolated producer strains and some commercial antibiotic strains located in a common cluster. These results exhibited high antimicrobial potential of the potent actinomycetes isolates for new antibiotic discovery