Analysis of the role of the Listeria monocytogenes F0F1-ATPase operon in the acid tolerance response

As little is known about the genes involved in the induction of an acid tol erance response in Listeria monocytogenes, the role of the F0F1-ATPase was analyzed as a consequence of its role in the acid tolerance of a number of other bacteria and its conserved nature. It was found that acid adapted cel ls treated with N,N'-dicyclohexylcarbodiimide (DCCD) exhibited greatly enha nced sensitivity to low pH stress. Degenerate primers were designed to ampl ify and sequence a portion of the atpD gene. Subsequently, a PCR product fr om atpA to atpD was identified. While we were unable to create a deletion i n the atpA gene, the plasmid pORI19 was inserted in a region between atpA a nd atpG to reduce, rather than eliminate, expression of the downstream gene s. As expected this mutant displayed enhanced resistance to neomycin and ex hibited slower growth than the wild type strain. This mutant could still in duce an acid tolerance response and remained susceptible to DCCD treatment, but its relative acid sensitivity was difficult to assess as a consequence of its slow growth. (C) 2000 Elsevier Science B.V. All rights reserved.