The effet of wall lipopolysaccharidde defects upon the antibiotic activity of microcinJ25

LATINA CF, DUPUY F, VINCENT PA, MORERO RD

Mar del Plata, Argentina

Congreso; XLIII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2007

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

The most significant components of the outer cell envelope in Gram (-) bacteria are the lipopolysaccharide (LPS).  LPS are composed by a hydrophobic lipid A, a short non-repeating oligosaccharide core and a distal polysaccharide named O-antigen. S. typhimurium mutant strains which produce a LPS which either does not contain heptose or contains heptose residues but no glucose belong to the rfa class. These mutants become much more sensitive to a variety of hydrophobic dyes, antibiotics, and detergents. In this communication we have examined the microcin J25 (MccJ25) sensitivity of a series of well-characterized rfa mutants through determination of the minimal inhibitory concentration (MIC) in liquid media. The results indicate that mutants rfaH, rfaD, rfaI and rfaE, just like the wild type strain, were resistant to MccJ25. On the other hand, rfaG, rfaL-rfaE, rfaF and rfaC were sensitive with a MIC of 62,5; 125; 250 and 500 µg/ml, respectively. Just in opposite to the resistant strains, the sensitive mutants showed a notable uptake of a fluorescent microcine derivative. Some sensible bacteria showed filament formation uncorrelated with their degree of sensitivity. The results provide evidence on the importance of non specific interaction of MccJ25 with the cell outer membrane in order to confirm its antibiotic activity.