Systemic understanding of Lactococcus lactis response to acid stress using transcriptomics approaches
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During fermentation, acid stress caused by the accumulation of acidic metabolites seriously affects the metabolic activity and production capacity of microbial cells. To elucidate the acid stress-tolerance mechanisms of microbial cells, we performed genome mutagenesis combined with high-throughput technologies to screen acid stress-tolerant strains. Mutant strain Lactococcus lactis WH101 showed a 16,000-fold higher survival rate than that of the parent strain after 5 h of acid shock at pH 4.0 and maintained higher ATP, NH4+, and intracellular pH (pHi) levels during acid stress. Additionally, comparative transcriptomics analysis revealed enhanced regulation of carbohydrate metabolism and sugar transport to provide additional energy, amino acid metabolism and transport to maintain pHi homeostasis and ATP generation, and fatty acid metabolism to enhance cellular acid tolerance. Moreover, overexpression of identified components resulted in 12.6- and 12.9-fold higher survival rates after acid shock for 3 h at pH 4.0 in L. lactis (ArcB) and L. lactis (MalQ) compared to the control strain, respectively. These findings provide valuable insight into the acid stress-response mechanisms of L. lactis and promote the further development of robust industrial strains.
KeywordsLactococcus lactis High-throughput screening Acid stress Transcriptomics Metabolic engineering
This work was supported by the National Key Research and Development Program of China (2017YFB0308401), the Program of Introducing Talents of Discipline to Universities (No. 111-2-06), the Grant from Pioneer Innovative Research Team of Dezhou, the Open Project of Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University (KLIB-KF201706), and the National First-class Discipline Program of Light Industry Technology and Engineering (LITE2018-08).
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Conflict of interest
The authors declare that they have no conflict of interest.
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