Antimicrobial activities of actinomycetes isolated from unexplored regions of Sundarbans mangrove ecosystem

Abstract

BackgroundNew broad spectrum antimicrobial agents are urgently needed to combat frequently emerging multi drug resistant pathogens. Actinomycetes, the most talented group of microorganisms isolated from unexplored regions of the world may be the ultimate solution to this problem. Thus the aim of this study was to isolate several bioactive actinomycetes strains capable of producing antimicrobial secondary metabolite from Sundarbans, the only mangrove tiger land of the world.ResultsFifty four actinomycetes were isolated and analyzed for antimicrobial activity against fifteen test organisms including three phytopathogens. Nine morphologically distinct and biologically active isolates were subjected to polyphasic identification study.16 s rDNA sequencing indicated eight isolates to reveal maximum similarity to the genus streptomyces, whereas one isolate presented only 93.57 % similarity with Streptomyces albogriseolus NRRL B-1305T. Seventy-one carbon sources and twenty-three chemical sources utilization assay revealed their metabolic relatedness. Among these nine isolates three specific strains were found to have notably higher degree of antimicrobial potential effective in a broader range including phyto-pathogenic fungus. Finally the strain SMS_SU21, which showed antimicrobial activity with MIC value of 0.05 mg ml−1 and antioxidant activity with IC50 value of 0.242 ± 0.33 mg ml−1 was detected to be the most potential one. True prospective of this strain was evaluated utilizing GC-MS and the bioactive compound responsible for antimicrobial activity was purified.ConclusionRare bioactive actinomycetes were isolated from unexplored heritage site. Antimicrobial compound has also been identified and purified which is active against a broad range of pathogens.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-015-0495-4) contains supplementary material, which is available to authorized users.

Methods of Isolating Actinomycetes from the Soils of Menengai Crater in Kenya.

“…In isolating actinomycetes, soil samples are collected from the study area [16][17][18][19][20]. To kill most of the Gram negative bacteria, the soil is dried on the bench inside the laboratory for a period of one week [17].…”

“…To kill most of the Gram negative bacteria, the soil is dried on the bench inside the laboratory for a period of one week [17]. The soil is further held in a water bath at 50°C to further destroy other vegetative microorganisms [13].…”

Endophytic Nocardiopsis sp. from Zingiber officinale with both antiphytopathogenic mechanisms and antibiofilm activity against clinical isolates

“…Optimization of the media plays a significant role in the expression of genes of the metabolic pathways, and thereby production of maximum antimicrobial compounds (Sengupta et al 2015). In the current study, crude extract prepared from King's B media was found to exhibit highest inhibition against the selected test organisms (Table 3).…”

Production of novel antifungal compounds from actinomycetes isolated from waste dump soil in Western Uganda

“…100 L from 10 -2 dilution was spread on starch casein nitrate agar (composition in media g/L: starch 10, casein 0.3, KNO3 5, NaCl2 2, K2HPO4 2, MgSO4.7H2O 0.5, CaCO3 0.02, FeSO4.7H2O 0.01 and agar 18; pH was adjusted to 7 ± 0.2) (Sengupta et al, 2015), glycerol casein agar (Kuster agar) (composition in media g/L: glycerol 10, casein 0.3, KNO3 2, K2HPO4 2, MgSO4 0.05, CaCO3 0.02, Fe2 (SO4)3.6H2O 0.01, Agar 15 and pH was adjusted to 7 ± 0.2 ) (Lakshmanaperumalsamy et al, 1984) and yeast extract starch casein agar (YSCA) (composition in media g/L: yeast extract 3, peptone 3, casein 3, starch 8, K2HPO4 0.5, MgSO4.7H2O 0.5, NaCl 2, agar 15 and pH 7.0 to 7.6 ) (Mincer et al, 2002). The inoculated plates were incubated at 28°C for 7 to 14 days.…”