BIOPHYSICAL AND MOLECULAR BASIS OF Listeria monocytogenes RESISTANCE TOWARDS ENTEROCIN CRL35

MASÍAS EMILSE; FERNANDO G. DUPUY; JUAN V. FARIZANO; LUCILA SAAVEDRA; CARLOS J. MINAHK

CABA

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

SOCIEDADES DE BIOCIENCIAS

Enterocin CRL35 is a pediocin-like bacteriocin active against thefoodborne pathogen Listeria monocytogenes. Resistance to thesepeptides can be associated with either downregulation of the receptorMan-PTS, a glucose transporter, or changes in the bacterial cellenvelope. The aim of this work was to analyze resistant strains ofL. monocytogenes INS7 by means of biochemical and biophysicalstudies of the cells and their cytoplasmic membranes. Two resistantclones to enterocin CRL35, L. monocytogenes INS7 R2 andR3, which were characterized by 16S RNA gene sequencing andrep-PCR, had been isolated in our laboratory. Bacterial growth wasstudied in different culture media. Plasma membranes of sensitiveand resistant bacteria were obtained and characterized by infraredspectroscopy and Langmuir monolayer techniques. The results indicatethat the growth rate of resistant strains in TSB medium is slowerthan sensitive ones. On the other hand, resistant cells were not ableto grow in minimal defined medium with glucose as the sole energysource, suggesting that Listeria resistant isolates have an alterationin the glucose transporter Man-PTS complex, which is the receptorof the IIa peptides in L. monocytogenes. The assessment of the bacterialcells membranes demonstrated difference in the membranelipids composition. Moreover, the interaction of enterocin CRL35with the three Listeria lipid samples displayed that this peptide couldnot get inserted into the hydrophobic core of resistant bacteria.These results indicate that both bacteriocin receptor downregulationand membrane structural modifications as well are involved in enterocinCRL35-resistance of L. monocytogenes strains.