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Background  Microbial cell factories are widely used in the production of acidic products such as organic acids and amino acids. However, the metabolic activity of microbial cells and their production efficiency are severely inhibited with the accumulation of intracellular acidic metabolites. Therefore, it remains a key issue to enhance the acid tolerance of microbial cells. In this study, we investigated the effects of four ATP-binding cassette (ABC) transporters on acid stress tolerance in  Lactococcus lactis .    Results  Overexpressing the  rbsA ,  rbsB ,  msmK , and  dppA  genes exhibited 5.8-, 12.2-, 213.7-, and 5.2-fold higher survival rates than the control strain, respectively, after acid shock for 3 h at pH 4.0. Subsequently, transcriptional profile alterations in recombinant strains were analyzed during acid stress. The differentially expressed genes associated with cold-shock proteins ( csp ), fatty acid biosynthesis ( fabH ), and coenzyme A biosynthesis ( coaD ) were up-regulated in the four recombinant strains during acid stress. Additionally, some genes were differentially expressed in specific recombinant strains. For example, in  L. lactis  (RbsB), genes involved in the pyrimidine biosynthetic pathway ( pyrCBDEK ) and glycine or betaine transport process ( busAA  and  busAB ) were up-regulated during acid stress, and the  argG  genes showed up-regulations in  L. lactis  (MsmK). Finally, we found that overexpression of the ABC transporters RbsB and MsmK increased intracellular ATP concentrations to protect cells against acidic damage in the initial stage of acid stress. Furthermore,  L. lactis  (MsmK) consistently maintained elevated ATP concentrations under acid stress.    Conclusions  This study elucidates the common and specific mechanisms underlying improved acid tolerance by manipulating ABC transporters and provides a further understanding of the role of ABC transporters in acid-stress tolerance.    Electronic supplementary material  The online version of this article (10.1186/s12934-019-1188-8) contains supplementary material, which is available to authorized users.

Enhanced acid-stress tolerance in Lactococcus lactis NZ9000 by overexpression of ABC transporters