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Bicyclostreptins are radical SAM enzyme-modified peptides with unique cyclization motifs. Nat Chem Biol 2022; 18:1135-1143. [PMID: 35953547 DOI: 10.1038/s41589-022-01090-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 06/21/2022] [Indexed: 12/22/2022]
Abstract
Microbial natural products comprise diverse architectures that are generated by equally diverse biosynthetic strategies. In peptide natural products, amino acid sidechains are frequently used as sites of modification to generate macrocyclic motifs. Backbone amide groups, among the most stable of biological moieties, are rarely used for this purpose. Here we report the discovery and biosynthesis of bicyclostreptins-peptide natural products from Streptococcus spp. with an unprecedented structural motif consisting of a macrocyclic β-ether and a heterocyclic sp3-sp3 linkage between a backbone amide nitrogen and an adjacent α-carbon. Both reactions are installed, in that order, by two radical S-adenosylmethionine (RaS) metalloenzymes. Bicyclostreptins are produced at nM concentrations and are potent growth regulation agents in Streptococcus thermophilus. Our results add a distinct and unusual chemotype to the growing family of ribosomal peptide natural products, expand the already impressive catalytic scope of RaS enzymes, and provide avenues for further biological studies in human-associated streptococci.
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Zhang X, Garrett S, Graveley BR, Terns MP. Unique properties of spacer acquisition by the type III-A CRISPR-Cas system. Nucleic Acids Res 2021; 50:1562-1582. [PMID: 34893878 PMCID: PMC8860593 DOI: 10.1093/nar/gkab1193] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Revised: 11/12/2021] [Accepted: 11/19/2021] [Indexed: 12/11/2022] Open
Abstract
Type III CRISPR-Cas systems have a unique mode of interference, involving crRNA-guided recognition of nascent RNA and leading to DNA and RNA degradation. How type III systems acquire new CRISPR spacers is currently not well understood. Here, we characterize CRISPR spacer uptake by a type III-A system within its native host, Streptococcus thermophilus. Adaptation by the type II-A system in the same host provided a basis for comparison. Cas1 and Cas2 proteins were critical for type III adaptation but deletion of genes responsible for crRNA biogenesis or interference did not detectably change spacer uptake patterns, except those related to host counter-selection. Unlike the type II-A system, type III spacers are acquired in a PAM- and orientation-independent manner. Interestingly, certain regions of plasmids and the host genome were particularly well-sampled during type III-A, but not type II-A, spacer uptake. These regions included the single-stranded origins of rolling-circle replicating plasmids, rRNA and tRNA encoding gene clusters, promoter regions of expressed genes and 5′ UTR regions involved in transcription attenuation. These features share the potential to form DNA secondary structures, suggesting a preferred substrate for type III adaptation. Lastly, the type III-A system adapted to and protected host cells from lytic phage infection.
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Affiliation(s)
- Xinfu Zhang
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Sandra Garrett
- Department of Genetics and Genome Sciences, Institute for Systems Genomics, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Brenton R Graveley
- Department of Genetics and Genome Sciences, Institute for Systems Genomics, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Michael P Terns
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.,Department of Microbiology, University of Georgia, Athens, GA 30602, USA.,Department of Genetics, University of Georgia, Athens, GA 30602, USA
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3
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Bushin LB, Covington BC, Rued BE, Federle MJ, Seyedsayamdost MR. Discovery and Biosynthesis of Streptosactin, a Sactipeptide with an Alternative Topology Encoded by Commensal Bacteria in the Human Microbiome. J Am Chem Soc 2020; 142:16265-16275. [DOI: 10.1021/jacs.0c05546] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Leah B. Bushin
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Brett C. Covington
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Britta E. Rued
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois 60607, United States
| | - Michael J. Federle
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois 60607, United States
| | - Mohammad R. Seyedsayamdost
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, United States
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Hu T, Cui Y, Zhang Y, Qu X, Zhao C. Genome Analysis and Physiological Characterization of Four Streptococcus thermophilus Strains Isolated From Chinese Traditional Fermented Milk. Front Microbiol 2020; 11:184. [PMID: 32184766 PMCID: PMC7059025 DOI: 10.3389/fmicb.2020.00184] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 01/24/2020] [Indexed: 11/13/2022] Open
Abstract
Streptococcus thermophilus plays important roles in the dairy industry and is widely used as a dairy starter in the production of fermented dairy products. The genomes of S. thermophilus strains CS5, CS9, CS18, and CS20 from fermented milk in China were sequenced and used for biodiversity analysis. In the present study, the phylogenetic analysis of all 34 S. thermophilus genomes publicly available including these four strains reveals that the phylogenetic reconstruction does not match geographic distribution as strains isolated from the same continent are not even clustered on the nearby branches. The core and variable genes were also identified, which vary among strains from 0 to 202. CS9 strain contained 127 unique genes from a variety of distantly related species. It was speculated that CS9 had undergone horizontal gene transfer (HGT) during the long evolutionary process. The safety evaluation of these four strains indicated that none of them contains antibiotic resistance genes and that they are all sensitive to multiple antibiotics. In addition, the strains do not contain any pathogenic virulence factors or plasmids and thus can be considered safe. Furthermore, these strains were investigated in terms of their technological properties including milk acidification, exopolysaccharide (EPS) and γ-aminobutyric acid (GABA) production, and in vitro survival capacity in the gastrointestinal tract. CS9 possesses a special eps gene cluster containing significant traces of HGT, while the eps gene clusters of CS5, CS18, and CS20 are almost the same. The monosaccharide compositional analysis indicated that crude EPS-CS5, EPS-CS9, EPS-CS18, and EPS-CS20 contain similar monosaccharide compositions with different ratios. Furthermore, CS9 was one of a few GABA-producing strains that could ferment glutamate to produce GABA, which is beneficial for improving the acid tolerance of the strain. CS18 has the most potential for the production of fermented food among these four strains because of its fast growth rate, rapid acidifying capacity, and stronger acid and bile salt resistance capacity. This study focused on the genome analysis of the four new S. thermophilus strains to investigate the diversity of strains and provides a reference for selecting excellent strains by use of the genome data.
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Affiliation(s)
- Tong Hu
- Department of Food Science and Engineering, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, China
| | - Yanhua Cui
- Department of Food Science and Engineering, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, China
| | - Yishuang Zhang
- Department of Food Science and Engineering, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, China
| | - Xiaojun Qu
- Institute of Microbiology, Heilongjiang Academy of Sciences, Harbin, China
| | - Chunyu Zhao
- Department of Food Science and Engineering, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, China
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Chromosomal Conjugative and Mobilizable Elements in Streptococcus suis: Major Actors in the Spreading of Antimicrobial Resistance and Bacteriocin Synthesis Genes. Pathogens 2019; 9:pathogens9010022. [PMID: 31881744 PMCID: PMC7168690 DOI: 10.3390/pathogens9010022] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 12/10/2019] [Accepted: 12/20/2019] [Indexed: 12/30/2022] Open
Abstract
Streptococcus suis is a zoonotic pathogen suspected to be a reservoir of antimicrobial resistance (AMR) genes. The genomes of 214 strains of 27 serotypes were screened for AMR genes and chromosomal Mobile Genetic Elements (MGEs), in particular Integrative Conjugative Elements (ICEs) and Integrative Mobilizable Elements (IMEs). The functionality of two ICEs that host IMEs carrying AMR genes was investigated by excision tests and conjugation experiments. In silico search revealed 416 ICE-related and 457 IME-related elements. These MGEs exhibit an impressive diversity and plasticity with tandem accretions, integration of ICEs or IMEs inside ICEs and recombination between the elements. All of the detected 393 AMR genes are carried by MGEs. As previously described, ICEs are major vehicles of AMR genes in S. suis. Tn5252-related ICEs also appear to carry bacteriocin clusters. Furthermore, whereas the association of IME-AMR genes has never been described in S. suis, we found that most AMR genes are actually carried by IMEs. The autonomous transfer of an ICE to another bacterial species (Streptococcus thermophilus)-leading to the cis-mobilization of an IME carrying tet(O)-was obtained. These results show that besides ICEs, IMEs likely play a major role in the dissemination of AMR genes in S. suis.
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Alexandraki V, Kazou M, Blom J, Pot B, Papadimitriou K, Tsakalidou E. Comparative Genomics of Streptococcus thermophilus Support Important Traits Concerning the Evolution, Biology and Technological Properties of the Species. Front Microbiol 2019; 10:2916. [PMID: 31956321 PMCID: PMC6951406 DOI: 10.3389/fmicb.2019.02916] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 12/03/2019] [Indexed: 12/24/2022] Open
Abstract
Streptococcus thermophilus is a major starter for the dairy industry with great economic importance. In this study we analyzed 23 fully sequenced genomes of S. thermophilus to highlight novel aspects of the evolution, biology and technological properties of this species. Pan/core genome analysis revealed that the species has an important number of conserved genes and that the pan genome is probably going to be closed soon. According to whole genome phylogeny and average nucleotide identity (ANI) analysis, most S. thermophilus strains were grouped in two major clusters (i.e., clusters A and B). More specifically, cluster A includes strains with chromosomes above 1.83 Mbp, while cluster B includes chromosomes below this threshold. This observation suggests that strains belonging to the two clusters may be differentiated by gene gain or gene loss events. Furthermore, certain strains of cluster A could be further subdivided in subgroups, i.e., subgroup I (ASCC 1275, DGCC 7710, KLDS SM, MN-BM-A02, and ND07), II (MN-BM-A01 and MN-ZLW-002), III (LMD-9 and SMQ-301), and IV (APC151 and ND03). In cluster B certain strains formed one distinct subgroup, i.e., subgroup I (CNRZ1066, CS8, EPS, and S9). Clusters and subgroups observed for S. thermophilus indicate the existence of lineages within the species, an observation which was further supported to a variable degree by the distribution and/or the architecture of several genomic traits. These would include exopolysaccharide (EPS) gene clusters, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs)-CRISPR associated (Cas) systems, as well as restriction-modification (R-M) systems and genomic islands (GIs). Of note, the histidine biosynthetic cluster was found present in all cluster A strains (plus strain NCTC12958T) but was absent from all strains in cluster B. Other loci related to lactose/galactose catabolism and urea metabolism, aminopeptidases, the majority of amino acid and peptide transporters, as well as amino acid biosynthetic pathways were found to be conserved in all strains suggesting their central role for the species. Our study highlights the necessity of sequencing and analyzing more S. thermophilus complete genomes to further elucidate important aspects of strain diversity within this starter culture that may be related to its application in the dairy industry.
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Affiliation(s)
- Voula Alexandraki
- Laboratory of Dairy Research, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
| | - Maria Kazou
- Laboratory of Dairy Research, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
| | - Jochen Blom
- Bioinformatics and Systems Biology, Justus Liebig University Giessen, Giessen, Germany
| | - Bruno Pot
- Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Department of Bioengineering Sciences (DBIT), Vrije Universiteit Brussel, Brussels, Belgium
| | - Konstantinos Papadimitriou
- Laboratory of Dairy Research, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
| | - Effie Tsakalidou
- Laboratory of Dairy Research, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
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Gaudu P, Yamamoto Y, Jensen PR, Hammer K, Lechardeur D, Gruss A. Genetics of Lactococci. Microbiol Spectr 2019; 7:10.1128/microbiolspec.gpp3-0035-2018. [PMID: 31298208 PMCID: PMC10957224 DOI: 10.1128/microbiolspec.gpp3-0035-2018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Indexed: 11/20/2022] Open
Abstract
Lactococcus lactis is the best characterized species among the lactococci, and among the most consumed food-fermenting bacteria worldwide. Thanks to their importance in industrialized food production, lactococci are among the lead bacteria understood for fundamental metabolic pathways that dictate growth and survival properties. Interestingly, lactococci belong to the Streptococcaceae family, which includes food, commensal and virulent species. As basic metabolic pathways (e.g., respiration, metal homeostasis, nucleotide metabolism) are now understood to underlie virulence, processes elucidated in lactococci could be important for understanding pathogen fitness and synergy between bacteria. This chapter highlights major findings in lactococci and related bacteria, and covers five themes: distinguishing features of lactococci, metabolic capacities including the less known respiration metabolism in Streptococcaceae, factors and pathways modulating stress response and fitness, interbacterial dialogue via metabolites, and novel applications in health and biotechnology.
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Affiliation(s)
| | - Yuji Yamamoto
- Laboratory of Cellular Microbiology, School of Veterinary Medicine, Kitasato University, Towada, 034-8628, Aomori Japan
| | - Peter Ruhdal Jensen
- National Food Institute, Technical University of Denmark, DK-2800 Lyngby, Denmark
| | - Karin Hammer
- DTU Bioengineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
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Gut Symbionts Lactobacillus reuteri R2lc and 2010 Encode a Polyketide Synthase Cluster That Activates the Mammalian Aryl Hydrocarbon Receptor. Appl Environ Microbiol 2019; 85:AEM.01661-18. [PMID: 30389766 PMCID: PMC6498181 DOI: 10.1128/aem.01661-18] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 10/24/2018] [Indexed: 12/20/2022] Open
Abstract
Temporary changes in the composition of the microbiota, for example, by oral administration of probiotics, can modulate the host immune system. However, the underlying mechanisms by which probiotics interact with the host are often unknown. Here, we show that Lactobacillus reuteri R2lc and 2010 harbor an orthologous PKS gene cluster that activates the aryl hydrocarbon receptor (AhR). AhR is a ligand-activated transcription factor that plays a key role in a variety of diseases, including amelioration of intestinal inflammation. Understanding the mechanism by which a bacterium modulates the immune system is critical for applying rational selection strategies for probiotic supplementation. Finally, heterologous and/or optimized expression of PKS is a logical next step toward the development of next-generation probiotics to prevent and treat disease. A mechanistic understanding of microbe-host interactions is critical to developing therapeutic strategies for targeted modulation of the host immune system. Different members of the gut symbiont species Lactobacillus reuteri modulate host health by, for example, reduction of intestinal inflammation. Previously, it was shown that L. reuteri activates the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that plays an important role in the mucosal immune system, by the production of tryptophan catabolites. Here, we identified a novel pathway by which L. reuteri activates AhR, which is independent of tryptophan metabolism. We screened a library of 36 L. reuteri strains and determined that R2lc and 2010, strains with a pigmented phenotype, are potent AhR activators. By whole-genome sequencing and comparative genomics, we identified genes unique to R2lc and 2010. Our analyses demonstrated that R2lc harbors two genetically distinct polyketide synthase (PKS) clusters, functionally unknown (fun) and pks, each carried by a multicopy plasmid. Inactivation of pks, but not fun, abolished the ability of R2lc to activate AhR. L. reuteri 2010 has a gene cluster homologous to the pks cluster in R2lc with an identical gene organization, which is also responsible for AhR activation. In conclusion, we identified a novel PKS pathway in L. reuteri R2lc and 2010 that is responsible for AhR activation. IMPORTANCE Temporary changes in the composition of the microbiota, for example, by oral administration of probiotics, can modulate the host immune system. However, the underlying mechanisms by which probiotics interact with the host are often unknown. Here, we show that Lactobacillus reuteri R2lc and 2010 harbor an orthologous PKS gene cluster that activates the aryl hydrocarbon receptor (AhR). AhR is a ligand-activated transcription factor that plays a key role in a variety of diseases, including amelioration of intestinal inflammation. Understanding the mechanism by which a bacterium modulates the immune system is critical for applying rational selection strategies for probiotic supplementation. Finally, heterologous and/or optimized expression of PKS is a logical next step toward the development of next-generation probiotics to prevent and treat disease.
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Douillard FP, Mora D, Eijlander RT, Wels M, de Vos WM. Comparative genomic analysis of the multispecies probiotic-marketed product VSL#3. PLoS One 2018; 13:e0192452. [PMID: 29451876 PMCID: PMC5815585 DOI: 10.1371/journal.pone.0192452] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 01/23/2018] [Indexed: 02/07/2023] Open
Abstract
Several probiotic-marketed formulations available for the consumers contain live lactic acid bacteria and/or bifidobacteria. The multispecies product commercialized as VSL#3 has been used for treating various gastro-intestinal disorders. However, like many other products, the bacterial strains present in VSL#3 have only been characterized to a limited extent and their efficacy as well as their predicted mode of action remain unclear, preventing further applications or comparative studies. In this work, the genomes of all eight bacterial strains present in VSL#3 were sequenced and characterized, to advance insights into the possible mode of action of this product and also to serve as a basis for future work and trials. Phylogenetic and genomic data analysis allowed us to identify the 7 species present in the VSL#3 product as specified by the manufacturer. The 8 strains present belong to the species Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus plantarum, Lactobacillus helveticus, Bifidobacterium breve and B. animalis subsp. lactis (two distinct strains). Comparative genomics revealed that the draft genomes of the S. thermophilus and L. helveticus strains were predicted to encode most of the defence systems such as restriction modification and CRISPR-Cas systems. Genes associated with a variety of potential probiotic functions were also identified. Thus, in the three Bifidobacterium spp., gene clusters were predicted to encode tight adherence pili, known to promote bacteria-host interaction and intestinal barrier integrity, and to impact host cell development. Various repertoires of putative signalling proteins were predicted to be encoded by the genomes of the Lactobacillus spp., i.e. surface layer proteins, LPXTG-containing proteins, or sortase-dependent pili that may interact with the intestinal mucosa and dendritic cells. Taken altogether, the individual genomic characterization of the strains present in the VSL#3 product confirmed the product specifications, determined its coding capacity as well as identified potential probiotic functions.
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Affiliation(s)
- François P. Douillard
- Research Program Unit Immunobiology, Medicum, University of Helsinki, Helsinki, Finland
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Diego Mora
- Department of Food, Environmental, and Nutritional Sciences (DeFENS), University of Milan, Milan, Italy
| | | | | | - Willem M. de Vos
- Research Program Unit Immunobiology, Medicum, University of Helsinki, Helsinki, Finland
- Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands
- * E-mail:
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Technological properties assessment and two component systems distribution of Streptococcus thermophilus strains isolated from fermented milk. Arch Microbiol 2017; 200:567-580. [PMID: 29236144 DOI: 10.1007/s00203-017-1468-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 11/25/2017] [Accepted: 12/06/2017] [Indexed: 10/18/2022]
Abstract
Streptococcus thermophilus is one of the economically most representatives of lactic acid bacteria, which is widely used as a starter to produce fermented milk products. In this study, 22 S. thermophilus strains were isolated from 26 fermented milk samples. Most isolates showed the ability to ferment a broad range of carbohydrates. Interestingly, eight strains are galactose positive, which is a desirable property in various industrial dairy fermentations. Four different nucleotide sequences were found in the galR-galK intergenic regions. The 16S-23S intergenic spacer region sequences of most isolates were determined as ITS-St-II type, which are related with protease positive and fast acidification. CS18 presented excellent technological performances, and showed potential as a promising starter candidate. To gain a comprehensive view of stress response mechanisms of strains, the distribution of all the two-component systems (TCSs) in strains were investigated. TCS analysis indicated that the nucleotide sequence of TCSs have obvious differences in different strains. And the strains with the special nucleotide sequences of TCS have distinctive traits. Therefore, it was speculated that there is a certain connection between the traits' difference and the TCS difference of strains.
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Genome comparison and physiological characterization of eight Streptococcus thermophilus strains isolated from Italian dairy products. Food Microbiol 2017; 63:47-57. [DOI: 10.1016/j.fm.2016.11.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 09/27/2016] [Accepted: 11/01/2016] [Indexed: 12/20/2022]
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New advances in exopolysaccharides production of Streptococcus thermophilus. Arch Microbiol 2017; 199:799-809. [PMID: 28357474 DOI: 10.1007/s00203-017-1366-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Revised: 03/12/2017] [Accepted: 03/15/2017] [Indexed: 10/19/2022]
Abstract
Streptococcus thermophilus is the most important thermophilic dairy starter, and is widely used in the dairy industry. Streptococcus thermophilus exopolysaccharides received wide attention over recent decades, because they can improve the properties of the dairy product and confer beneficial health effects. The understanding of the regulatory and biosynthetic mechanisms of EPS will improve the EPS biosynthesis, increase the productivity of EPSs, and develop EPSs with desirable properties. The structure of EPSs is the focus of this study. Revealing the structure-function relationship can lead to increase the knowledge base and from there to increased research of EPS. The EPS yield is a key limiting factor in the research and utilization of EPS. In the present review, biosynthetic pathways and genetics of S. thermophilus EPSs were described and reviewed. At the same time, functional properties and applications of EPS, and strategies for enhancement of EPS production are discussed.
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New Insights into Various Production Characteristics of Streptococcus thermophilus Strains. Int J Mol Sci 2016; 17:ijms17101701. [PMID: 27754312 PMCID: PMC5085733 DOI: 10.3390/ijms17101701] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 09/19/2016] [Accepted: 09/23/2016] [Indexed: 01/01/2023] Open
Abstract
Streptococcus thermophilus is one of the most valuable homo-fermentative lactic acid bacteria, which, for a long time, has been widely used as a starter for the production of fermented dairy products. The key production characteristics of S. thermophilus, for example the production of extracellular polysaccharide, proteolytic enzymes and flavor substances as well as acidifying capacity etc., have an important effect on the quality of dairy products. The acidification capacity of the strains determines the manufacturing time and quality of dairy products. It depends on the sugar utilization ability of strains. The production of extracellular polysaccharide is beneficial for improving the texture of dairy products. Flavor substances increase the acceptability of dairy products. The proteolytic activity of the strain influences not only the absorption of the nitrogen source, but also the formation of flavor substances. Different strains have obvious differences in production characteristics via long-time evolution and adaptation to environment. Gaining new strains with novel and desirable characteristics is an important long-term goal for researchers and the fermenting industry. The understanding of the potential molecular mechanisms behind important characteristics of different strains will promote the screening and breeding of excellent strains. In this paper, key technological and functional properties of different S. thermophilus strains are discussed, including sugar metabolism, proteolytic system and amino acid metabolism, and polysaccharide and flavor substance biosynthesis. At the same time, diversity of genomes and plasmids of S. thermophilus are presented. Advances in research on key production characteristics and molecular levels of S. thermophilus will increase understanding of molecular mechanisms of different strains with different important characteristics, and improve the industrialization control level for fermented foods.
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Huang J, Liang Y, Guo D, Shang K, Ge L, Kashif J, Wang L. Comparative Genomic Analysis of the ICESa2603 Family ICEs and Spread of erm(B)- and tet(O)-Carrying Transferable 89K-Subtype ICEs in Swine and Bovine Isolates in China. Front Microbiol 2016; 7:55. [PMID: 26870017 PMCID: PMC4735348 DOI: 10.3389/fmicb.2016.00055] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 01/13/2016] [Indexed: 11/13/2022] Open
Abstract
Integrative and conjugative elements (ICEs) of the ICESa2603 family have been isolated from several species of Streptococcus spp.; however, the comparative genomic and evolutionary analyses of these particular ICEs are currently only at their initial stages. By investigating 13 ICEs of the ICESa2603 family and two ICESa2603 family-like ICEs derived from diverse hosts and locations, we have determined that ICEs comprised a backbone of 30 identical syntenic core genes and accessory genes that were restricted to the intergenic sites or the 3′-end of the non-conserved domain of core genes to maintain its function. ICESa2603 family integrase IntICESa2603 specifically recognized a 15-bp att sequence (TTATTTAAGAGTAAC) at the 3′-end of rplL, which was highly conserved in genus Streptococcus. Phylogenetic analyses suggest that extensive recombination/insertion and the occurrence of a hybrid/mosaic in the ICESa2603 family were responsible for the significant increase in ICE diversity, thereby broadening its host range. Approximately 42.5 and 38.1% of the tested Streptococcus suis and Streptococcus agalactiae clinical isolates respectively contained ICESa2603 family Type IV secretion system (T4SS) genes, and 80.5 and 62.5% of which also respectively carried intICESa2603, indicating that ICESa2603 family is widely distributed across these bacteria. Sequencing and conjugation transfer of a novel sequence type ST303 clinical S. suis isolate HB1011 demonstrated that the 89K-subtype ICESsuHB1011 retained its transferrable function, thereby conferring tetracycline and macrolide resistance.
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Affiliation(s)
- Jinhu Huang
- College of Veterinary Medicine, Nanjing Agricultural University Nanjing, China
| | - Yuan Liang
- College of Veterinary Medicine, Nanjing Agricultural University Nanjing, China
| | - Dawei Guo
- College of Veterinary Medicine, Nanjing Agricultural University Nanjing, China
| | - Kexin Shang
- College of Veterinary Medicine, Nanjing Agricultural University Nanjing, China
| | - Lin Ge
- College of Veterinary Medicine, Nanjing Agricultural University Nanjing, China
| | - Jam Kashif
- Department of Veterinary Pharmacology, Sindh Agricultural University Tandojam, Pakistan
| | - Liping Wang
- College of Veterinary Medicine, Nanjing Agricultural University Nanjing, China
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Couvigny B, Thérial C, Gautier C, Renault P, Briandet R, Guédon E. Streptococcus thermophilus Biofilm Formation: A Remnant Trait of Ancestral Commensal Life? PLoS One 2015; 10:e0128099. [PMID: 26035177 PMCID: PMC4452758 DOI: 10.1371/journal.pone.0128099] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 04/23/2015] [Indexed: 12/27/2022] Open
Abstract
Microorganisms have a long history of use in food production and preservation. Their adaptation to food environments has profoundly modified their features, mainly through genomic flux. Streptococcus thermophilus, one of the most frequent starter culture organisms consumed daily by humans emerged recently from a commensal ancestor. As such, it is a useful model for genomic studies of bacterial domestication processes. Many streptococcal species form biofilms, a key feature of the major lifestyle of these bacteria in nature. However, few descriptions of S. thermophilus biofilms have been reported. An analysis of the ability of a representative collection of natural isolates to form biofilms revealed that S. thermophilus was a poor biofilm producer and that this characteristic was associated with an inability to attach firmly to surfaces. The identification of three biofilm-associated genes in the strain producing the most biofilms shed light on the reasons for the rarity of this trait in this species. These genes encode proteins involved in crucial stages of biofilm formation and are heterogeneously distributed between strains. One of the biofilm genes appears to have been acquired by horizontal transfer. The other two are located in loci presenting features of reductive evolution, and are absent from most of the strains analyzed. Their orthologs in commensal bacteria are involved in adhesion to host cells, suggesting that they are remnants of ancestral functions. The biofilm phenotype appears to be a commensal trait that has been lost during the genetic domestication of S. thermophilus, consistent with its adaptation to the milk environment and the selection of starter strains for dairy fermentations.
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Affiliation(s)
- Benoit Couvigny
- INRA, UMR 1319 Micalis, Domaine de Vilvert, F-78352 Jouy-en-Josas, France
- AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| | - Claire Thérial
- INRA, UMR 1319 Micalis, Domaine de Vilvert, F-78352 Jouy-en-Josas, France
- AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| | - Céline Gautier
- INRA, UMR 1319 Micalis, Domaine de Vilvert, F-78352 Jouy-en-Josas, France
- AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| | - Pierre Renault
- INRA, UMR 1319 Micalis, Domaine de Vilvert, F-78352 Jouy-en-Josas, France
- AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| | - Romain Briandet
- INRA, UMR 1319 Micalis, Domaine de Vilvert, F-78352 Jouy-en-Josas, France
- AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
| | - Eric Guédon
- INRA, UMR 1319 Micalis, Domaine de Vilvert, F-78352 Jouy-en-Josas, France
- AgroParisTech, UMR MICALIS, Jouy-en-Josas, France
- * E-mail:
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17
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Kelleher P, Murphy J, Mahony J, van Sinderen D. Next-generation sequencing as an approach to dairy starter selection. DAIRY SCIENCE & TECHNOLOGY 2015; 95:545-568. [PMID: 26798445 PMCID: PMC4712225 DOI: 10.1007/s13594-015-0227-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 03/25/2015] [Accepted: 04/02/2015] [Indexed: 02/06/2023]
Abstract
Lactococcal and streptococcal starter strains are crucial ingredients to manufacture fermented dairy products. As commercial starter culture suppliers and dairy producers attempt to overcome issues of phage sensitivity and develop new product ranges, there is an ever increasing need to improve technologies for the rational selection of novel starter culture blends. Whole genome sequencing, spurred on by recent advances in next-generation sequencing platforms, is a promising approach to facilitate rapid identification and selection of such strains based on gene-trait matching. This review provides a comprehensive overview of the available methodologies to analyse the technological potential of candidate starter strains and highlights recent advances in the area of dairy starter genomics.
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Affiliation(s)
- Philip Kelleher
- School of Microbiology, University College Cork, Cork, Ireland
| | - James Murphy
- School of Microbiology, University College Cork, Cork, Ireland
| | - Jennifer Mahony
- School of Microbiology, University College Cork, Cork, Ireland
| | - Douwe van Sinderen
- School of Microbiology, University College Cork, Cork, Ireland
- Alimentary Pharmabiotic Centre, Biosciences Institute, University College Cork, Cork, Ireland
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18
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Gezginc Y, Topcal F, Comertpay S, Akyol I. Quantitative analysis of the lactic acid and acetaldehyde produced by Streptococcus thermophilus and Lactobacillus bulgaricus strains isolated from traditional Turkish yogurts using HPLC. J Dairy Sci 2014; 98:1426-34. [PMID: 25547312 DOI: 10.3168/jds.2014-8447] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 09/30/2014] [Indexed: 11/19/2022]
Abstract
The present study was conducted to evaluate the lactic acid- and acetaldehyde-producing abilities of lactic acid bacterial species isolated from traditionally manufactured Turkish yogurts using HPLC. The lactic acid bacterial species purified from the yogurts were the 2 most widely used species in industrial yogurt production: Streptococcus thermophilus and Lactobacillus bulgaricus. These bacteria have the ability to ferment hexose sugars homofermentatively to generate lactic acid and some carbonyl compounds, such as acetaldehyde through pyruvate metabolism. The levels of the compounds produced during fermentation influence the texture and the flavor of the yogurt and are themselves influenced by the chemical composition of the milk, processing conditions, and the metabolic activity of the starter culture. In the study, morphological, biochemical, and molecular characteristics were employed to identify the bacteria obtained from homemade yogurts produced in different regions of Turkey. A collection of 91 Strep. thermophilus and 35 L. bulgaricus strains were investigated for their lactic acid- and acetaldehyde-formation capabilities in various media such as cow milk, LM17 agar, and aerobic-anaerobic SM17 agar or de Man, Rogosa, and Sharpe agar. The amounts of the metabolites generated by each strain in all conditions were quantified by HPLC. The levels were found to vary depending on the species, the strain, and the growth conditions used. Whereas lactic acid production ranged between 0 and 77.9 mg/kg for Strep. thermophilus strains, it ranged from 0 to 103.5 mg/kg for L. bulgaricus. Correspondingly, the ability to generate acetaldehyde ranged from 0 to 105.9 mg/kg in Strep. thermophilus and from 0 to 126.9 mg/kg in L. bulgaricus. Our study constitutes the first attempt to determine characteristics of the wild strains isolated from traditional Turkish yogurts, and the approach presented here, which reveals the differences in metabolite production abilities of the wild lactic acid bacteria strains, holds the potential for the selection of the most desirable strains to be used as starters in commercial yogurt manufacture in the future.
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Affiliation(s)
- Y Gezginc
- Faculty of Agriculture, Department of Food Engineering, Kahramanmaraş Sutcu İmam University, 46060/Avsar, Kahramanmaras, Turkey
| | - F Topcal
- Research and Development Center for University-Industry Public Relations (USKIM), Microbiology and Microbial Genetics Laboratory, and Kahramanmaraş Sutcu İmam University, 46060/Avsar, Kahramanmaras, Turkey
| | - S Comertpay
- Faculty of Agriculture, Department of Agricultural Biotechnology, Kahramanmaraş Sutcu İmam University, 46060/Avsar, Kahramanmaras, Turkey.
| | - I Akyol
- Research and Development Center for University-Industry Public Relations (USKIM), Microbiology and Microbial Genetics Laboratory, and Kahramanmaraş Sutcu İmam University, 46060/Avsar, Kahramanmaras, Turkey; Faculty of Agriculture, Department of Agricultural Biotechnology, Kahramanmaraş Sutcu İmam University, 46060/Avsar, Kahramanmaras, Turkey
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19
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Genomic insights into high exopolysaccharide-producing dairy starter bacterium Streptococcus thermophilus ASCC 1275. Sci Rep 2014; 4:4974. [PMID: 24827399 PMCID: PMC4021336 DOI: 10.1038/srep04974] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 04/22/2014] [Indexed: 01/20/2023] Open
Abstract
Streptococcus thermophilus ASCC 1275 (ST 1275), a typical dairy starter bacterium, yields the highest known amount (~1,000 mg/L) of exopolysaccharide (EPS) in milk among the species of S. thermophilus. The addition of this starter in milk fermentation exhibited texture modifying properties for fermented dairy foods such as yogurt and cheese in the presence of EPS as its important metabolite. In this genomic study, a novel eps gene cluster for EPS assembly of repeating unit has been reported. It contains two-pair epsC-epsD genes which are assigned to determine the chain length of EPS. This also suggests this organism produces two types of EPSs – capsular and ropy EPS, as observed in our previous studies. Additionally, ST 1275 appears to exhibit effective proteolysis system and sophisticated stress response systems to stressful conditions, and has the highest number of four separate CRISPR/Cas loci. These features may be conducive to milk adaptation of this starter and against undesirable bacteriophage infections which leads to failure of milk fermentation. Insights into the genome of ST 1275 suggest that this strain may be a model high EPS-producing dairy starter.
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SASAKI Y, HORIUCHI H, KAWASHIMA H, MUKAI T, YAMAMOTO Y. NADH Oxidase of Streptococcus thermophilus 1131 is Required for the Effective Yogurt Fermentation with Lactobacillus delbrueckii subsp. bulgaricus 2038. BIOSCIENCE OF MICROBIOTA, FOOD AND HEALTH 2014; 33:31-40. [PMID: 24936380 PMCID: PMC4034325 DOI: 10.12938/bmfh.33.31] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 09/09/2013] [Indexed: 11/23/2022]
Abstract
We previously reported that dissolved oxygen (DO) suppresses yogurt fermentation with an industrial starter culture composed of Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus) 2038 and Streptococcus thermophilus 1131, and also found that reducing the DO in the medium prior to fermentation (deoxygenated fermentation) shortens the fermentation time. In this study, we found that deoxygenated fermentation primarily increased the cell number of S. thermophilus 1131 rather than that of L. bulgaricus 2038, resulting in earlier l-lactate and formate accumulation. Measurement of the DO concentration and hydrogen peroxide generation in the milk medium suggested that DO is mainly removed by S. thermophilus 1131. The results using an H2O-forming NADH oxidase (Nox)-defective mutant of S. thermophilus 1131 revealed that Nox is the major oxygen-consuming enzyme of the bacterium. Yogurt fermentation with the S. thermophilus Δnox mutant and L. bulgaricus 2038 was significantly slower than with S. thermophilus 1131 and L. bulgaricus 2038, and the DO concentrations of the mixed culture did not decrease to less than 2 mg/kg within 3 hr. These observations suggest that Nox of S. thermophilus 1131 contributes greatly to yogurt fermentation, presumably by removing the DO in milk.
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Affiliation(s)
- Yasuko SASAKI
- School of Agriculture, Meiji University, 1-1-1 Higashimita,
Tama-ku, Kawasaki, Kanagawa 214-8571, Japan
| | - Hiroshi HORIUCHI
- Food Science Institute, Meiji Co., Ltd., 540 Naruda, Odawara,
Kanagawa 250-0862, Japan
| | - Hiroko KAWASHIMA
- Food Science Institute, Meiji Co., Ltd., 540 Naruda, Odawara,
Kanagawa 250-0862, Japan
| | - Takao MUKAI
- School of Veterinary Medicine, Kitasato University, 35-1
Higashi 23, Towada, Aomori, 034-8628, Japan
| | - Yuji YAMAMOTO
- School of Veterinary Medicine, Kitasato University, 35-1
Higashi 23, Towada, Aomori, 034-8628, Japan
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Whole-Genome Sequences of Streptococcus thermophilus Strains TH1435 and TH1436, Isolated from Raw Goat Milk. GENOME ANNOUNCEMENTS 2014; 2:2/1/e01129-13. [PMID: 24435859 PMCID: PMC3894273 DOI: 10.1128/genomea.01129-13] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report the genome sequences of two Streptococcus thermophilus strains, TH1435 and TH1436, isolated from raw goat milk devoted to the production of artisanal cheese in the Friuli-Venezia Giulia region in Italy. The genome sequences of these two quickly acidifying strains are the first available genome sequences of S. thermophilus strains isolated in Italy.
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22
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Salzano AM, Novi G, Arioli S, Corona S, Mora D, Scaloni A. Mono-dimensional blue native-PAGE and bi-dimensional blue native/urea-PAGE or/SDS-PAGE combined with nLC–ESI-LIT-MS/MS unveil membrane protein heteromeric and homomeric complexes in Streptococcus thermophilus. J Proteomics 2013; 94:240-61. [DOI: 10.1016/j.jprot.2013.09.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 09/04/2013] [Accepted: 09/14/2013] [Indexed: 02/06/2023]
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Abstract
CRISPR (clustered regularly interspaced short palindromic repeats) together with cas (CRISPR-associated) genes form the CRISPR–Cas immune system, which provides sequence-specific adaptive immunity against foreign genetic elements in bacteria and archaea. Immunity is acquired by the integration of short stretches of invasive DNA as novel ‘spacers’ into CRISPR loci. Subsequently, these immune markers are transcribed and generate small non-coding interfering RNAs that specifically guide nucleases for sequence-specific cleavage of complementary sequences. Among the four CRISPR–Cas systems present in Streptococcus thermophilus, CRISPR1 and CRISPR3 have the ability to readily acquire new spacers following bacteriophage or plasmid exposure. In order to investigate the impact of building CRISPR-encoded immunity on the host chromosome, we determined the genome sequence of a BIM (bacteriophage-insensitive mutant) derived from the DGCC7710 model organism, after four consecutive rounds of bacteriophage challenge. As expected, active CRISPR loci evolved via polarized addition of several novel spacers following exposure to bacteriophages. Although analysis of the draft genome sequence revealed a variety of SNPs (single nucleotide polymorphisms) and INDELs (insertions/deletions), most of the in silico differences were not validated by Sanger re-sequencing. In addition, two SNPs and two small INDELs were identified and tracked in the intermediate variants. Overall, building CRISPR-encoded immunity does not significantly affect the genome, which allows the maintenance of important functional properties in isogenic CRISPR mutants. This is critical for the development and formulation of sustainable and robust next-generation starter cultures with increased industrial lifespans.
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24
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Magadán AH, Dupuis MÈ, Villion M, Moineau S. Cleavage of phage DNA by the Streptococcus thermophilus CRISPR3-Cas system. PLoS One 2012; 7:e40913. [PMID: 22911717 PMCID: PMC3401199 DOI: 10.1371/journal.pone.0040913] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 06/15/2012] [Indexed: 12/26/2022] Open
Abstract
Streptococcus thermophilus, similar to other Bacteria and Archaea, has developed defense mechanisms to protect cells against invasion by foreign nucleic acids, such as virus infections and plasmid transformations. One defense system recently described in these organisms is the CRISPR-Cas system (Clustered Regularly Interspaced Short Palindromic Repeats loci coupled to CRISPR-associated genes). Two S. thermophilus CRISPR-Cas systems, CRISPR1-Cas and CRISPR3-Cas, have been shown to actively block phage infection. The CRISPR1-Cas system interferes by cleaving foreign dsDNA entering the cell in a length-specific and orientation-dependant manner. Here, we show that the S. thermophilus CRISPR3-Cas system acts by cleaving phage dsDNA genomes at the same specific position inside the targeted protospacer as observed with the CRISPR1-Cas system. Only one cleavage site was observed in all tested strains. Moreover, we observed that the CRISPR1-Cas and CRISPR3-Cas systems are compatible and, when both systems are present within the same cell, provide increased resistance against phage infection by both cleaving the invading dsDNA. We also determined that overall phage resistance efficiency is correlated to the total number of newly acquired spacers in both CRISPR loci.
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Affiliation(s)
- Alfonso H. Magadán
- Département de Biochimie, de Microbiologie et Bio-Informatiques, Faculté des Sciences et de Génie, Groupe de Recherche en Ecologie Buccale, Université Laval, Québec, Canada
| | - Marie-Ève Dupuis
- Département de Biochimie, de Microbiologie et Bio-Informatiques, Faculté des Sciences et de Génie, Groupe de Recherche en Ecologie Buccale, Université Laval, Québec, Canada
| | - Manuela Villion
- Département de Biochimie, de Microbiologie et Bio-Informatiques, Faculté des Sciences et de Génie, Groupe de Recherche en Ecologie Buccale, Université Laval, Québec, Canada
| | - Sylvain Moineau
- Département de Biochimie, de Microbiologie et Bio-Informatiques, Faculté des Sciences et de Génie, Groupe de Recherche en Ecologie Buccale, Université Laval, Québec, Canada
- Félix d’Hérelle Reference Center for Bacterial Viruses, Université Laval, Québec, Canada
- * E-mail:
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25
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Nelson OW, Garrity GM. Genome sequences of Bacteria and Archaea published outside of Standards in Genomic Sciences, June – September 2011. Stand Genomic Sci 2011. [DOI: 10.4056/sigs.2324675] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Oranmiyan W. Nelson
- 1Editorial Office, Standards in Genomic Sciences and Department of Microbiology, Michigan State University, East Lansing, MI, USA
| | - George M. Garrity
- 1Editorial Office, Standards in Genomic Sciences and Department of Microbiology, Michigan State University, East Lansing, MI, USA
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