Venugopal, M.N.Krishna Moorthy, M.Indrani KarunasagarKarunasagar, IMaragal, M.M.Udupa, K.S.Suresh, T.2016-07-042016-07-042009-11-19http://krishikosh.egranth.ac.in/handle/1/68411Ph.D. ThesisMicroorganisms have been recognized as an important resource for bioactive compounds. Majority of such compounds that are widely used are isolated from terrestrial sources. However, microorganisms isolated from marine sources are known to synthesize metabolites that are unique from the terrestrial counterparts. In recent years marine bacteria are becoming a major source for several novel bioactive compounds. In the present study a total of 1,11, 277 isolates were screened and about 176 bacteria with antimicrobial property were isolated. Among them 64% were identified as Bacillus spp and 36% as Pseudomonas spp. Further screening of these 176 isolates based on zone of inhibition against two indicator bacteria (Staphylococcus aureus as a representative of gram positive bacteria and Vibrio harveyi as representative of gram negative bacteria) led to selection of 28 that showed significant activity. The antimicrobial compounds produced by the strains SM 5 (Bacillus spp) and SK 9 (Pseudomonas spp) inhibited many pathogenic bacteria and the activity was maximum against L. monocytogens, V. fisheri and V.parahemolyticus. Ammonium sulphate fractionation of culture supernatant revealed maximum activity in the 30% fraction. The dialyzed protein fraction extracted from the strain SM 5 also showed promising inhibitory activity against HeLa cell line. As the development of resistance to drugs by pathogenic bacteria is a major concern in the medical science in recent days, isolation of such antimicrobial compounds are very much essential. However the compound isolated in this study needs further study to characterize its unique chemical and antimicrobial properties.enThesis