Anticancer and antibacterial activities of secondary bioactive compounds from endosymbiotic bacteria of aphid and their surrounding organisms (predator and protector)

Secondary metabolites of bacterial origin are a valuable source of diverse molecules with antibacterial and anticancer activities. In the current study, 10 endosymbiotic bacteria were isolated from aphids, aphid predators and ants. Bacterial strains were identified based on the 16S rRNA gene. Crude extracts were prepared from each isolated bacteria and tested for their antibacterial activities using the disk diffusion method. The extracts of three bacterial species; Planococcus sp, Klebsiella aerogenes, Enterococcus avium from Aphis punicae, Chrysoperia carnea and Tapinoma magnum, respectively were found to have strong antibacterial activities against one or more of the five pathogenic bacteria tested. The inhibition zones ranged from 10.00{+/-} 0.13 to 20.00{+/-} 1.11mm with minimum inhibitory concentration (MIC) values ranged from 0.156 mg/mL to 1.25 mg/mL. The notable antibacterial activity was for the crude extract of K. aerogenes against Klebsiella pneumonia and Escherichia coli at MIC value of 0.156 mg/mL. The cytotoxic activity of the crude extracts varied according to the tested cell line. The most cytotoxic effect was for the extracts of K. aerogenes and E. avium at a concentration of 0.16 mg/mL against lung carcinoma epithelial cells (A549) with cell reduction of 79.4% and 67.2%, respectively. Crude extracts of K. aerogenes and Pantoea agglomerans at a concentration of 0.16 mg/mL showed 69.4% and 67.8% cell reduction against human colon cancer (Hct116), respectively. Gas chromatography-mass spectrometry (GC-MS) analysis of three crude extracts revealed the presence of several bioactive secondary metabolites that have been reported previously to possess antibacterial and anticancer properties. To the best of our knowledge, this is the first study to report the biological activities of endosymbiotic bacteria from aphids, aphid predators and ants. The promising data presented in this study opens a new avenue for alternative drugs to overcome the continuous emergence of multidrug-resistant bacteria and to find alternative drugs for traditional cancer therapies.