SCREENING OF GIANT LINEAR PLASMIDS IN ANTIBIOTIC RESISTANT RARE ACTINOBACTERIA ISOLATED FROM ARGENTINEAN HIGH ALTITUDE WETLANDS

JULIÁN R. DIB; MARÍA E. FARIAS; RUSSELL T. HILL

Cairns, Australia

Simposio; 12th International Symposium on Microbial Ecology; 2008

Argentinean high altitude Andean wetlands (HAW) represent pristine environments with extreme conditions and are interesting sources for microorganisms with exceptional phenotypic and genotypic characteristics. Rare actinobacteria with high UV-B resistance, arsenate tolerance and antibiotic resistance were previously isolated from these wetlands (4000 to 4500 m above sea level). The aim of this work was to screen for giant linear plasmids in antibiotic resistant rare actinobacteria and to study the horizontal transfer of the isolated plasmids in order to obtain the expression of antibiotic resistance in the antibiotic-sensitive recipient strain, Streptomyces lividans TK24. Quadrisphaera, Cellulomonas, Rhodococcus, Braquibacterium, Micrococcus, Microbacterium Nocardia, Brevibacterium, Dietzia, Agrococcus and Kocuria strains, isolated from HAW at Northwest of Argentina and with multiple antibiotic-resistant profiles and elevated minimal inhibitory concentrations for macrolides were used in this study. Large plasmids in these actinobacteria were screened using Pulse Field Gel Electrophoresis. Conjugation assays were done by spreading donor strains and recipient TK24 on agar plates and selecting for appropriate selective markers. 53 % of the strains harboured giant plasmids with estimated sizes between 80 and 244 kb. Most of the strains had one plasmid while three strains showed the presence of two plasmids. Large plasmids from strains Micrococcus A1 and H5 showed similar restriction profiles. Putative TK24 transconjugants were obtained from strains Brevibacterium Ap13, Micrococcus A7 and Agrococcus Ch9. These results demonstrated high frequencies and biodiversity of giant plasmids in the studied actinobacteria. Molecular analysis of these plasmids could reveal mechanisms of resistance to antibiotics and adaptations to the extreme conditions in HAW.