CHANDRASHEKARA, K.GUNDAPPA, S.2017-03-222017-03-222009-08-25Th-9151http://krishikosh.egranth.ac.in/handle/1/5810005715Dung beetles which inhibit the microbially challenging environment of the dung were screened for antimicrobial peptides. The extracts from 16 species were obtained both from ‘unchallenged’ and ‘challenged’ individuals; each extract was tested against Eschericia coli, Staphylococcus aureus and Candida albicans. Protocols were developed for collection and processing of dung beetles for preparation of extracts to assess antimicrobial activity. The antimicrobial activity against E. coli was particularly important since the strain of E. coli used in the study was resistant to all antibiotics, including Methicillin. There were significant differences among the extracts from different species with respect to antimicrobial activity. The extract from Copris repertus showed the highest level of antimicrobial activity at 10 h and 20 h after treatment. The antimicrobial activity of the ‘challenged’ extracts was significantly greater than the ‘unchallenged’ extracts in bioassay against all the three test microbes. Further, positive correlation in antimicrobial activity of ‘challenged’ and ‘unchallenged’ extracts was also observed. The significant increase in the antimicrobial activity of the challenged extracts is indicative of the evolution of inducible defenses which respond quickly to produce nonspecific antimicrobial compounds as the first line of defense against invading pathogens. The results of the bioassay showed that extracts from all the species were significantly more active against S. aureus; as reflected by a significant larger zone of inhibition. The results showed that dung beetles belonging to the guild of ‘breeders’ had a stronger immune response, in the sense that the extracts from such species showed a high level of antimicrobial activity at least at 10 h post-treatment as opposed to ‘rollers’ and ‘tunnelers’.en---Thesis