Screening of marine seaweeds for bioactive compound against fish pathogenic bacteria and active fraction analysed by gas chromatography-mass spectrometry

Objective:To isolate bioactive molecules from marine seaweeds and check the antimicrobial activity against the fish pathogenic bacteria.Methods:Fresh marine seaweeds Gracilaria edulis,Kappaphycus spicifera,Sargassum wightii(S.wightii)were collected.Each seaweed was extracted with different solvents.In the study,test pathogens were collected from microbial type culture collection.Antibacterial activity was carried out by using disc diffusion method and minimum inhibition concentration(MIC)was calculated.Best seaweed was analysed by fourier transform infrared spectroscopy.The cured extract was separated by thin layer chromatography(TLC).Fraction was collected from TLC to check the antimicrobial activity.Best fraction was analysed by gas chromatography mass spectrometer(GCMS).Results:Based on the disc diffusion method,S.wightii showed a better antimicrobial activity than other seaweed extracts.Based on the MIC,methanol extract of S.wightii showed lower MIC than other solvents.S.wightii were separated by TLC.In this TLC,plate showed a two fraction.These two fractions were separated in preparative TLC and checked for their antimicrobial activity.Fraction 2 showed best MIC value against the tested pathogen.Fraction 2 was analysed by GCMS.Based on the GCMS,fraction 2 contains n-hexadecanoic acid(59.44%).Conclusions:From this present study,it can be concluded that S.wightii was potential sources of bioactive compounds.

An in vivo efficacy validation and immune-modulatory potential of Streptomyces sp.

Objective:To investigate the in vivo efficacy and immune-modulatory potential of antagonistic strain,Streptomyces sp.MAPS15 isolated from marine sponge in Penaeus monodon(P.monodon).Methods:In this study,culture of Streptomyces sp.was incorporated into a commercial feed.P.monodon was orally administered with MAPS15 diet for a period of 21 days followed by a challenge experiment and survival rate was calculated.In addition,the effect of MAPS15 diet on immunological parameters of the haemolymph of P.monodon was also assessed.Results:The overall results of the study showed that survival performance was prominent in MAPS15 treated group when compared with un-treated control groups.That could pertain to the ability of MAPS15 to produce antibiotic compounds to suppress the growth of invading pathogens and thereby increase the disease resistance potency and survival rate.From the results of the immunological studies,it can be envisaged that the immune responses were generally more pronounced with MAPS15 diet treated group.Conclusions:Based on the overall findings,it could be inferred that the health of P.monodon is improved when they are fed with MAPS15 diet for a period of 21 days.