Improved acid tolerance of a recombinant strain of Escherichia coli expressing genes from the acidophilic bacterium Oenococcus oeni

Aims: Oenococcus oeni is a lactic acid bacterium used in wine fermentation. Two open reading frames (orfB and orfC) were identified in the upstream region of the hsp18 gene, encoding the small heat-shock protein Lo18. Expression of these genes in conditions of acid stress was studied in Escherichia coli. Methods and Results: Sequence analysis showed that orfB encodes a putative transcriptional regulator of the LysR family. The protein encoded by orfC shares homologies with multi-drug resistance systems. Heterologous expression of orfB, orfC and hsp18 genes in Escherichia coli significantly enhanced the viability of the host strain under acidic conditions. Conclusions: It was demonstrated that the three genes were needed for acquisition of this acid tolerance phenotype. Significance and Impact of the Study: Heterologous expression of Oenococcus genes could be used to confer acidophilic behaviour on strains of biotechnological interest.