Physiological implications of class IIa bacteriocin resistance in Listeria monocytogenes strains.
High-level resistance to class IIa bacteriocins has been directly associated with the absent EIIAB(Man) (MptA) subunit of the mannose-specific phosphoenolpyruvate-dependent phosphotransferase system (PTS) (EIIt(MAN)) in Listeria monocytogenes strains. Class IIa bacteriocin-resistant strains used in this study were a spontaneous resistant, L. monocytogenes B73-MR1, and a defined mutant, L. monocytogenes EGDe-mptA. Both strains were previously reported to have the EIIAB(Man) PTS component missing. This study shows that these class IIa bacteriocin-resistant strains have significantly decreased specific growth and glucose consumption rates, but they also have a significantly higher growth yield than their corresponding wild-type strains, L. monocytogenes B73 and L. monocytogenes EGDe, respectively. In the presence of glucose, the strains showed a shift from a predominantly lactic-acid to a mixed-acid fermentation. It is here proposed that elimination of the EIIAB(Man) in the resistant strains has caused a reduced glucose consumption rate and a reduced specific growth rate. The lower glucose consumption rate can be correlated to a shift in metabolism to a more efficient pathway with respect to ATP production per glucose, leading to a higher biomass yield. Thus, the cost involved in obtaining bacteriocin resistance, i.e. losing substrate transport capacity leading to a lower growth rate, is compensated for by a higher biomass yield.
Vadyvaloo
Viveka
V
Department of Biochemistry, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa.
Snoep
Jacky L
JL
Department of Biochemistry, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa.
Hastings
John W
JW
Department of Biochemistry, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa.
Rautenbach
Marina
M
Department of Biochemistry, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa.
D001430:Bacteriocins / Q000494:pharmacology*; D003470:Culture Media; D024881:Drug Resistance, Bacterial / Q000502:physiology*; D005285:Fermentation; D005947:Glucose / Q000494:pharmacology; D008089:Listeria monocytogenes / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D013696:Temperature
D001430:Bacteriocins; D003470:Culture Media; D005947:Glucose