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3. Discussion

In the present study we isolated gut bacteria from water monitor lizard, identified and cultured it in a minimal media (RPMI) to prepare CM. The CM were examined against several Gram-positive and Gram-negative bacteria to determine their antibacterial activities. Finally, the CM were tested for their cytotoxicity against HaCaT cell lines. The CM from A. hydrophila (CM2) exhibited cytotoxicity against HaCaT cells. This is likely because this bacterium secretes cytotoxic enterotoxins that binds to human, yeast proteins and human intestinal epithelial cell line (HT-29) and induced apoptosis []. These findings are supported by Chopra et al. [] and Krzymińska et al. [], which showed Aeromonas species produce enterotoxins, cytotonic and cytotoxic toxins that cause HEp-2 cell death, lyse red blood cells and abolish tissue culture cell lines. The CM exhibited robust bactericidal activities against selected pathogenic bacteria. Most of the CM showed antibacterial effects even after heat inactivation of these CM at 95 °C for 10 min. This further suggests that the active molecules could be possibly small secondary metabolites. The results from LCMS showed several secondary metabolites with antibacterial properties including flavonoids, alkaloids, terpenes, oxygenated fatty acids, hydroxylated fatty acids and pyrazine derivatives. Similar compounds have been reported for example, 2,5-Dihydroxymethyl-3, 4-dihydroxypyr- rolidine (DMDP) exhibited antiparasitic activity against plant parasite nematode []. Here for the first time, we identified the same compound from WML gut bacteria which suggests that bacteria from gut have the capability to produce anti-nematodal molecules. Similarly, Dehydrocurdione is found in turmeric [], while the same compound has been isolated from gut bacteria with significant antibacterial activity against B. subtilis in the current study. Littlefield-Wyer et al. [] identified 10-Hydroxymyristic acid from aquatic microorganisms, while similar molecule is shown to be synthesized by gut bacteria in this study. Several identified molecules with no reported biological activities are S-Methyl-1-thio-D-glycerate, omega-Hydroxymoracin N, 1,3,8-Trihydroxy-4-methyl-2,7-diprenylxanthone, Desmethyl-maprotiline glucuronide, Desmethyl-nortriptyline glucuronide, (3b,21b)-12-Oleanene-3,21,28-triol 28-[arabinosyl-(1->3)-arabinosyl-(1->3)-arabinoside], Chondrilla-sterol 3-[glucosyl-(1->2)-glucosyl-(1->2)-glucoside], 4-Methyl-dibenzothiophene, 1,2-Epoxy-3,4-butanediol 4-methane-sulfonate and 1R,2R)-3-oxo-2-pentyl-cyclopentanehexanoic acid. Further identification, characterization and their functional studies could be a major breakthrough in development of novel drugs against multi-drug-resistant bacteria. In future studies, individual compound(s) will be isolated and screened against MDR bacteria and human cell lines to determine their translational value in therapy.