Absence of a putative mannose-specific phosphotransferase system enzyme IIAB component in a leucocin A-resistant strain of Listeria monocytogenes, asshown by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis
M. Ramnath et al., Absence of a putative mannose-specific phosphotransferase system enzyme IIAB component in a leucocin A-resistant strain of Listeria monocytogenes, asshown by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis, APPL ENVIR, 66(7), 2000, pp. 3098-3101
Leucocin A is a class IIa bacteriocin produced by Leuconostoc spp. that has
preciously been shown to inhibit the growth of Listeria monocytogenes. A s
pontaneous resistant mutant of L. monocytogenes was isolated and found to b
e resistant to leucocin A at levels in excess of 2 mg/ml. The mutant showed
no significant cross-resistance to nontype IIa bacteriocins including nisa
plin and ESF1-7GR. However, there were no inhibition zones found on a lawn
of the mutant when challenged with an extract containing 51,200 AU of pedio
cin PA-2 per ml as determined by a simultaneous assay on the sensitive wild
-type strain. DNA and protein analysis of the resistant and susceptible str
ains were carried out using silver-stained amplified fragment length polymo
rphism (ssAFLP) and one- and two-dimensional sodium dodecyl sulfate-polyacr
ylamide gel electrophoresis (SDS-PAGE), respectively. Two-dimensional SDS-P
AGE clearly showed a 35-kDa protein which was present in the sensitive but
absent from the resistant strain. The N-terminal end of the 35-kDa protein
was sequenced and found to have an 83% homology to the mannose-specific pho
sphotransferase system enzyme IIAB of Streptococcus salivarius.