, 2007). Antimicrobial activity was assayed by the disc diffusion susceptibility test, according to the recommendations of the National Committee for Clinical Laboratory Standards (NCCLS, 2000). The disk diffusion test was performed on Muller–Hinton agar (Himedia Laboratories) for the bacterial pathogens. The culturable actinomycetes count Navitoclax datasheet in the mucus were 7.0 × 104±3 × 102 CFU cm−2. In comparison, numbers of culturable actinomycetes in seawater and sediment adjacent to the corals were 2.0 × 102±1.3 × 103 CFU mL−1 and 3.7
× 102±2 × 103 CFU g−1. A total of 15 actinomycetes strains were isolated from the coral mucus. Amplified products of about 870 bp were generated. ARDRA showed the presence of different polymorphic group of actinomycetes in coral mucus. ARDRA revealed five polymorphic patterns for HinfI, 10 polymorphic patterns for RsaI followed by 11 polymorphic patterns for MspI (Fig. 1). All the strains were identified by 16S rRNA gene sequencing. Phylogenetic analysis of actinomycetes associated with the mucus of the coral A. digitifera showed that Streptomyces sp. were the predominant actinomycetes members. CA3 had 99.8% similarity to Streptomyces akiyoshiensis (FJ486367.1) isolated from China. Strains CA4 and CA18 had 96.7% homology Ivacaftor nmr with Streptomyces sp.
(EU523135.1) a species having antimicrobial activity. Strain CA7 had only 96.7% similarity with Propionibacterium sp. (AM410900.1) a deep sea bacterium screened to produce antitumour compounds (Fig. 2). The actinomycetes strains isolated in this study had different biochemical profiles and exhibited variable sensitivity to six different commercial antibiotics (Supporting Information, Table S1). Isolates that are close relatives according to the phylogenetic tree exhibited different biochemical profiles and antibiotic sensitivity, indicating phenotypic diversity in strains that were very closely related on the basis of 16S rRNA gene sequence analysis.
For example, CA14 and CA15 fall closely together but their biochemical profiles and antibiotic sensitivities show that they are different bacterial strains (Table S1). In primary screening, actinomycetes strains Glycogen branching enzyme were screened for their antibacterial activity against test pathogens through the cross-streak method. All the 15 actinomycetes strains showed antibacterial activity against various bacterial pathogens. Five strains namely CA5, CA7, CA10, CA15 and CA18 showed antibacterial activity towards all the tested pathogens (Table 1). Secondary screening results showed that supernatants of 12 strains namely CA1, CA2, CA3, CA4, CA5, CA6, CA7, CA8, CA9, CA10, CA12 and CA14 showed antibacterial activity against the pathogens. Each actinomycete was grown in ISP2 medium culture and then the filtered culture fluid was extracted with one of three solvents.