Plasmids profiles, antibiotic and heavy metal resistance incidence of endophytic bacteria isolated from grapevine (<i>Vitis vinifera</i> L.)

Abstract

Little is known about the bacterial communities associated with the plant inhabiting desert ecosystem. In this study, the bacterial population associated with grapevine (Vitis vinifera L.) plant, growing desert
soil was analyzed using the culture dependent approach. A total of 111 bacterial isolates were isolated from stems and leaves samples, collected from different locations and subjected to further analyses. Based on the identification methods, the bacterial isolates were grouped into 14 genera. The main genera are Acetobacter, Acinetobacter, Citrobacter, Enterobacter, Erwinia, Escherichia, Methylococcus, Xanthomonas, Vibrio, Bacillus, Micrococcus, Planococcus, Staphylococcus and Streptomyces.
Significant differences in the endophytic communities were observed between plants collected from different sites and also between plant stems and leaves. All the isolates were examined for plasmid DNA content and resistance to antibiotics (Ampicillin, Kanamycin, Tetracyclin) and heavy metals. Minimum inhibitory concentrations (MICs) of Cu, Cd, Hg, Mn, Ni and Zn for isolates were also determined. Resistance was most frequent to Ampicillin (57%), followed by Kanamycin (53%) and Tetracycline (26%). The highest MICs observed were 10 ìg/ml for mercury, 50 ìg/ml for Cu and Cd and 200 ìg/ml for other metals. On a percentage basis, 18.48% of total strains from leaves were found to harbour plasmids, whereas, 11.83% of the roots isolates contained plasmids.