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

Abstract

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.

Lactobacillus , Bifidobacterium and Lactococcus response to environmental stress: Mechanisms and application of cross‐protection to improve resistance against freeze‐drying

“…Notably, intracellular pH can be significantly increased if potassium is added to the environment. Zhu et al (Zhu et al 2019a) showed that upregulation of ABC (ATP-binding cassette) transporters increases intracellular ATP concentration and protects cells from initial acid stress damage.…”

Differences in Acid Stress Response of Lacticaseibacillus paracasei Zhang Cultured from Solid-State Fermentation and Liquid-State Fermentation

“…The removal of protons from the cells requires the consumption of ATP, and some amino acid metabolic pathways produce ATP and ammonia, and the produced ammonia can further neutralize the protons in the cells to maintain the relative stability of intracellular pH [ 61 ]. Lactococcus Lactis NZ9000 has been reported to increase the intracellular ATP concentration in response to acid stress [ 62 ]. High H + -ATPase activity and sufficient energy guarantee the ability of cells to regulate intracellular pH homeostasis [ 63 ].…”

Transcriptomics and Proteomics Analyses of the Responses of Propionibacterium acidipropionici to Metabolic and Evolutionary Manipulation

“…To maintain the equilibrium conditions necessary for cell survival under stress, the transport of various substrates such as sugars, amino acids, peptides and ions is required, which is accomplished by ABC transporters present in the cell membrane ( Zhu et al, 2019 ). In this study, we paid particular attention to the differentially expressed genes related to the most enriched ABC transporters under multiple stress and genetic manipulation.…”