Isolation, Identification and Bioproprospecting theAntibacterial Activity of Actinobacteria Associated with Chamomile sp.

Background and Aim : Antibiotic resistance is rising dramatically worldwide. Thus, theproduction of new antibiotics is indispensable. Recent scientific efforts have been aimed at thebioprospecting of microorganisms' secondary metabolites, with special emphasis on the search forantimicrobial natural products derived from endophytes. Endophytes are microorganisms thatinhabit the internal tissues of plants without causing apparent harm to their host. Currently, it isstrongly believed that all types of plant species do anchorage endophytic bacteria (EB). The naturaltherapeutic compounds produced by EB do have several potential applications in medicine,agriculture and pharmaceutical industry. To investigate antibacterial properties, in this study,Actinobacteria were isolated from Chamomile sp., identified and bioprospected by morphologicaland molecular methods.Methods : Samples were collected from Ilam and then divided into roots, leaves, stems andflowers. After disinfection, they were cut into ۲ mm pieces and cultured on casein agar culturemedium and incubated at ۲۸ ºC for up to four weeks. Using PCR method targeting ۱۶S rRNAgene, identification of Actinobacteria was carried out. To evaluate the antibacterial properties ofthe isolated Actinobacteria, the agar diffusion method was used. In parallel, frequencies for thepresence of biosynthetic gene clusters, polyketide synthase- (PKS-) I, PKS-II, and nonribosomalpeptide synthetase (NRPS) among isolated Actinobacteria were determined.Results : Ninety bacteria were isolated from different parts of chamomile flowers. It wasdetermined that ۴۷ bacteria (۵۲.۲۲%) of these bacteria belong to the phylum Actinobacteria. andout of ۴۷ bacteria, ۱۵ isolates (۳۱.۹۱%) had antibacterial properties. Of these, ۱۲ isolates (۸۰%)exhibited antibacterial effects against Staphylococcus aureus, ۲ isolates (۱۳.۳۳%) againstPseudomonas aeruginosa, ۳ isolates (۲۰%) against Escherichia coli and ۲ isolates (۱۳.۳۳%) againstSalmonella typhi. The results of molecular analysis of NRPS, PKS-I and PKS-II genes showedthat out of ۴۷ isolated Actinobacteria strains, ۲۰ isolates (۴۲.۵۵%) had NRPS gene, ۶ isolates(۱۲.۷۶%) had PKS-I gene and ۲۳ isolates (۴۸.۹۳%) had PKS-II gene.Conclusion : This study indicates that Chamomile sp. has a number of active Actinobacteria thatproduce secondary metabolites with antibacterial properties. Hence, this medicinal plant can be avaluable source for the isolation of Actinobacteria with the potential of producing new antibiotics.

کلیدواژه ها:

Bioprospecting ، Identification ، Actinobacteria ، Chamomile sp.