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Wu H, Zhang Y, Li L, Li Y, Yuan L, E Y, Qiao J. Positive regulation of the DLT operon by TCSR7 enhances acid tolerance of Lactococcus lactis F44. J Dairy Sci 2022; 105:7940-7950. [PMID: 36028342 DOI: 10.3168/jds.2022-21898] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Accepted: 05/14/2022] [Indexed: 11/19/2022]
Abstract
Lactococcus lactis, a lactic acid bacterium, has been widely used in the fermented dairy products. The acid tolerance of L. lactis is of great importance to food fermentation and probiotic applications. As the first barrier of bacteria, the cell wall has a protective effect on strains under many stress conditions, whereas the regulatory mechanism has rarely been reported. Here, based on the transcription analysis of 9 cell wall or membrane-related genes of L. lactis F44 under acid stress, the transcription levels of DACB, DLTD, YLBA, HRTA, WP_080613266.1 (1610), and ERFK genes were significantly increased. We constructed 9 overexpressing strains with the cell wall or membrane-related genes, respectively. It was demonstrated that the survival rates under acid stress of DACB, DLTD, and ERFK were significantly higher than that of wild-type F44. To investigate the regulatory mechanism, a DNA pull-down assay was used to identify the transcriptional regulators of these 3 genes. It was discovered that the 2-component system (TCS) transcriptional regulator TCSR7 bound to the upstream region of DLTD involved in the teichoic acid (TA) alanylation. The combination was confirmed through an electrophoretic mobility shift assay in vitro. Reverse-transcription quantitative PCR results indicated that TCSR7 upregulated the expression of DLTD gene. In addition, the transcription level of TCSR7 increased approximately 1.8-fold (log2 fold change) under acidic conditions. In summary, this study found that TCSR7 was induced by acid stress to upregulate the transcription level of the DLT operon genes, which might increase the positive charge on the cell membrane surface to increase the acid tolerance of the strain. This study lays the foundation for the regulatory mechanism of TA alanylation under acid stress.
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Affiliation(s)
- Hao Wu
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China; Zhejiang Shaoxing Research Institute of Tianjin University, Shaoxing 312300, P. R. China
| | - Yangling Zhang
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China
| | - Li Li
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China; Zhejiang Shaoxing Research Institute of Tianjin University, Shaoxing 312300, P. R. China; Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, P. R. China; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, P. R. China
| | - Yanni Li
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China
| | - Lin Yuan
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China; Department of Bioengineering, School of Food Science and Bioengineering, Tianjin Agricultural University, Tianjin 300072, P. R. China
| | - Yue E
- Zhejiang Shaoxing Research Institute of Tianjin University, Shaoxing 312300, P. R. China
| | - Jianjun Qiao
- Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China; Zhejiang Shaoxing Research Institute of Tianjin University, Shaoxing 312300, P. R. China; Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, P. R. China; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, P. R. China.
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