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Hui W, Zhang W, Li J, Kwok LY, Zhang H, Kong J, Sun T. Functional analysis of the second methyltransferase in the bacteriophage exclusion system of Lactobacillus casei Zhang. J Dairy Sci 2022; 105:2049-2057. [PMID: 34998557 DOI: 10.3168/jds.2021-21000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 10/13/2021] [Indexed: 01/21/2023]
Abstract
The antiphage ability is an important feature of fermentation strains in the dairy industry. Our previous work described the bacteriophage exclusion (BREX) system in the probiotic strain, Lactobacillus casei Zhang. The function of L. casei Zhang pglX gene in mediating 5'-ACRCm6AG-3' methylation was also confirmed. This study aimed to further dissect the function of the BREX system of L. casei Zhang by inactivating its second methyltransferase gene (LCAZH_2054). The methylome of the mutant, L. casei Zhang Δ2054, was profiled by single-molecule real-time sequencing. Then, the cell morphology, growth, plasmid transformation efficiency, and stability of the wildtype and mutant were compared. The mutant did not have an observable effect in microscopic and colony morphology, but it reached a higher cell density after entering the exponential phase without obvious increase in the cell viability. The mutant had fewer 5'-ACRCm6AG-3' methylation compared with the wildtype (1835 versus 1906). Interestingly, no significant difference was observed in the transformation efficiency between the 2 strains when plasmids without cognate recognition sequence (pSec:Leiss:Nuc and pG+host9) were transformed, contrasting to transforming cells with cognate recognition sequence-containing plasmids (pMSP3535 and pTRKH2). The efficiency of transforming pMSP3535 into the LCAZH_2054 mutant was significantly lower than the wildtype, whereas an opposite trend was seen in pTRKH2 transformation. Moreover, compared with the wildtype, the mutant strain had higher capacity in retaining pMSP3535 and lower capacity in retaining pTRKH2, suggesting an unequal tolerance level to different foreign DNA. In conclusion, LCAZH_2054 was not directly responsible for 5'-ACRCm6AG-3' methylation in L. casei Zhang, but it might help regulate the function and specificity of the BREX system.
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Affiliation(s)
- Wenyan Hui
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China; Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China
| | - Wenyi Zhang
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China; Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China
| | - Jing Li
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China; Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China
| | - Lai-Yu Kwok
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China; Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China
| | - Heping Zhang
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China; Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China
| | - Jian Kong
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, P. R. China.
| | - Tiansong Sun
- Key Laboratory of Dairy Biotechnology and Engineering, Ministry of Education, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China; Key Laboratory of Dairy Products Processing, Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot 010018, P. R. China.
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A Novel Bacteriophage Exclusion (BREX) System Encoded by the pglX Gene in Lactobacillus casei Zhang. Appl Environ Microbiol 2019; 85:AEM.01001-19. [PMID: 31399407 DOI: 10.1128/aem.01001-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 08/05/2019] [Indexed: 01/21/2023] Open
Abstract
The bacteriophage exclusion (BREX) system is a novel prokaryotic defense system against bacteriophages. To our knowledge, no study has systematically characterized the function of the BREX system in lactic acid bacteria. Lactobacillus casei Zhang is a probiotic bacterium originating from koumiss. By using single-molecule real-time sequencing, we previously identified N6-methyladenine (m6A) signatures in the genome of L. casei Zhang and a putative methyltransferase (MTase), namely, pglX This work further analyzed the genomic locus near the pglX gene and identified it as a component of the BREX system. To decipher the biological role of pglX, an L. casei Zhang pglX mutant (ΔpglX) was constructed. Interestingly, m6A methylation of the 5'-ACRCAG-3' motif was eliminated in the ΔpglX mutant. The wild-type and mutant strains exhibited no significant difference in morphology or growth performance in de Man-Rogosa-Sharpe (MRS) medium. A significantly higher plasmid acquisition capacity was observed for the ΔpglX mutant than for the wild type if the transformed plasmids contained pglX recognition sites (i.e., 5'-ACRCAG-3'). In contrast, no significant difference was observed in plasmid transformation efficiency between the two strains when plasmids lacking pglX recognition sites were tested. Moreover, the ΔpglX mutant had a lower capacity to retain the plasmids than the wild type, suggesting a decrease in genetic stability. Since the Rebase database predicted that the L. casei PglX protein was bifunctional, as both an MTase and a restriction endonuclease, the PglX protein was heterologously expressed and purified but failed to show restriction endonuclease activity. Taken together, the results show that the L. casei Zhang pglX gene is a functional adenine MTase that belongs to the BREX system.IMPORTANCE Lactobacillus casei Zhang is a probiotic that confers beneficial effects on the host, and it is thus increasingly used in the dairy industry. The possession of an effective bacterial immune system that can defend against invasion of phages and exogenous DNA is a desirable feature for industrial bacterial strains. The bacteriophage exclusion (BREX) system is a recently described phage resistance system in prokaryotes. This work confirmed the function of the BREX system in L. casei and that the methyltransferase (pglX) is an indispensable part of the system. Overall, our study characterizes a BREX system component gene in lactic acid bacteria.
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Chen P, Jeannotte R, Weimer BC. Exploring bacterial epigenomics in the next-generation sequencing era: a new approach for an emerging frontier. Trends Microbiol 2014; 22:292-300. [PMID: 24725482 DOI: 10.1016/j.tim.2014.03.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 03/13/2014] [Accepted: 03/13/2014] [Indexed: 02/08/2023]
Abstract
Epigenetics has an important role for the success of foodborne pathogen persistence in diverse host niches. Substantial challenges exist in determining DNA methylation to situation-specific phenotypic traits. DNA modification, mediated by restriction-modification systems, functions as an immune response against antagonistic external DNA, and bacteriophage-acquired methyltransferases (MTase) and orphan MTases - those lacking the cognate restriction endonuclease - facilitate evolution of new phenotypes via gene expression modulation via DNA and RNA modifications, including methylation and phosphorothioation. Recent establishment of large-scale genome sequencing projects will result in a significant increase in genome availability that will lead to new demands for data analysis including new predictive bioinformatics approaches that can be verified with traditional scientific rigor. Sequencing technologies that detect modification coupled with mass spectrometry to discover new adducts is a powerful tactic to study bacterial epigenetics, which is poised to make novel and far-reaching discoveries that link biological significance and the bacterial epigenome.
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Affiliation(s)
- Poyin Chen
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, USA; Universidad de Tarapacá, Avenida General Velásquez N°1775, Arica, Chile
| | - Richard Jeannotte
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, USA; Universidad de Tarapacá, Avenida General Velásquez N°1775, Arica, Chile; Facultad de Ciencias, Universidad de Tarapacá, Arica, Chile
| | - Bart C Weimer
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, USA; Universidad de Tarapacá, Avenida General Velásquez N°1775, Arica, Chile.
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Dineen DG, Schröder M, Higgins DG, Cunningham P. Ensemble approach combining multiple methods improves human transcription start site prediction. BMC Genomics 2010; 11:677. [PMID: 21118509 PMCID: PMC3053590 DOI: 10.1186/1471-2164-11-677] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 11/30/2010] [Indexed: 11/20/2022] Open
Abstract
Background The computational prediction of transcription start sites is an important unsolved problem. Some recent progress has been made, but many promoters, particularly those not associated with CpG islands, are still difficult to locate using current methods. These methods use different features and training sets, along with a variety of machine learning techniques and result in different prediction sets. Results We demonstrate the heterogeneity of current prediction sets, and take advantage of this heterogeneity to construct a two-level classifier ('Profisi Ensemble') using predictions from 7 programs, along with 2 other data sources. Support vector machines using 'full' and 'reduced' data sets are combined in an either/or approach. We achieve a 14% increase in performance over the current state-of-the-art, as benchmarked by a third-party tool. Conclusions Supervised learning methods are a useful way to combine predictions from diverse sources.
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Affiliation(s)
- David G Dineen
- Complex and Adaptive Systems Laboratory (CASL), University College Dublin, Belfield, Dublin 4, Ireland.
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Dineen DG, Wilm A, Cunningham P, Higgins DG. High DNA melting temperature predicts transcription start site location in human and mouse. Nucleic Acids Res 2010; 37:7360-7. [PMID: 19820114 PMCID: PMC2794178 DOI: 10.1093/nar/gkp821] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
The accurate computational prediction of transcription start sites (TSS) in vertebrate genomes is a difficult problem. The physicochemical properties of DNA can be computed in various ways and a many combinations of DNA features have been tested in the past for use as predictors of transcription. We looked in detail at melting temperature, which measures the temperature, at which two strands of DNA separate, considering the cooperative nature of this process. We find that peaks in melting temperature correspond closely to experimentally determined transcription start sites in human and mouse chromosomes. Using melting temperature alone, and with simple thresholding, we can predict TSS with accuracy that is competitive with the most accurate state-of-the-art TSS prediction methods. Accuracy is measured using both experimentally and manually determined TSS. The method works especially well with CpG island containing promoters, but also works when CpG islands are absent. This result is clear evidence of the important role of the physical properties of DNA in the process of transcription. It also points to the importance for TSS prediction methods to include melting temperature as prior information.
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Affiliation(s)
- David G Dineen
- Complex and Adaptive Systems Laboratory (CASL), University College Dublin, Belfield, Dublin 4, Ireland.
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