Characterization of antibacterial compounds produced by psychrotrophic Alcaligenes faecalis HTP6 isolated from Passu glacier, Pakistan
By: Muhammad Rafiq, Muhammad Hayat, Noor Hassan, Muhammad Ibrar, Abdul Haleem, Maliha Rehman, Faisal Ahmad, Aamer Ali Shah, Fariha Hasan
Key Words: Psychrotrophic Alcaligenes faecalis HTP6, Passu glacier, Antimicrobial compound.
Int. J. Biosci. 8(5), 122-135, May 2016.
Low temperature microorganisms can produce secondary metabolites including anticancer, antiviral and antibacterial compounds. The purpose of the study was to evaluate the possibility of using cold adapted bacteria for production of antibiotics. In the present research work, bacteria were isolated from sediment sample, collected from Passu glacier, using R2A medium . These isolates were screened for their resistance towards various antibiotics, antimicrobial activity against P. aeruginosa, E. coli, S. aureus, E. faecalis, C. albicans and A. fumigatus and storage stability of crude extract along with cytotoxicity and haemolytic activity. The isolate HTP6 showed best inhibition using spot on lawn test and was selected for further study. The isolate HTP6 was Gram positive, non-pigmented rod, moderate halophilic, with optimum growth at mesophilic range and was identified as Alcaligenes faecalis HTP6 on the basis of 16S rRNA gene sequence analysis. The strain showed resistance to clindamycin, cefotaxime and sulfamethoxazole/trimethoprim and was able to inhibit P. aeruginosa, E. coli, S. aureus, E. faecalis, C. albicans and A. fumigatus. Maximum growth and inhibitory activity of Alcaligenes faecalis HTP6 was observed against selected ATCC strains [Staphylococcus aureus (ATCC 25923) and Pseudomonas aeruginosa (ATCC 27853)] and various clinical isolates (S. aureus, E. faecalis, Candida albicans and Aspergillus fumigatus) at pH 7 and 30°C, when LB (Luria Bertani) and LB1 (medium supplemented by FeSO4) broth media were used. The crude extract showed good storage and thermal stability at 55°C, and pH stability at 7 along with brine shrimp lethality up to 30%, however, there was no DNA binding and haemolytic activity observed. We can conclude from the study that Alcaligenes faecalis HTP6, isolated from Passu glacier, can be a good candidate for the production of wide spectrum potent thermostable antibiotic with less cytotoxicity.