Bacterial Physiology, R&D Microbial Platform, Chr. Hansen A/S, Hørsholm, Denmark.
Department of Food Science, University of Copenhagen, Frederiksberg, Denmark.
Appl Environ Microbiol. 2018 Nov 15;84(23). doi: 10.1128/AEM.01847-18. Print 2018 Dec 1.
Receptors on the cell surfaces of bacterial hosts are essential during the infection cycle of bacteriophages. To date, the phage receptors of the industrial relevant dairy starter bacterium remain elusive. Thus, we set out to identify cell surface structures that are involved in host recognition by dairy streptococcal phages. Five industrial strains sensitive to different phages ( type, type, and the new type 987), were selected to generate spontaneous bacteriophage-insensitive mutants (BIMs). Of these, approximately 50% were deselected as clustered regularly interspaced short palindromic repeat (CRISPR) mutants, while the other pool was further characterized to identify receptor mutants. On the basis of genome sequencing data, phage resistance in putative receptor mutants was attributed to nucleotide changes in genes encoding glycan biosynthetic pathways. Superresolution structured illumination microscopy was used to visualize the interactions between and its phages. The phages were either regularly distributed along the cells or located at division sites of the cells. The cell wall structures mediating the latter type of phage adherence were further analyzed via phenotypic and biochemical assays. Altogether, our data suggested that phage adsorption to is mediated by glycans associated with the bacterial cell surface. Specifically, the -type phage CHPC951 adsorbed to polysaccharides anchored to peptidoglycan, while the 987-type phage CHPC926 recognized exocellular polysaccharides associated with the cell surface. is widely used in starter cultures for cheese and yoghurt production. During dairy fermentations, infections of bacteria with bacteriophages result in acidification failures and a lower quality of the final products. An understanding of the molecular factors involved in phage-host interactions, in particular, the phage receptors in dairy bacteria, is a crucial step for developing better strategies to prevent phage infections in dairy plants.
细菌宿主细胞表面的受体在噬菌体的感染周期中是必不可少的。迄今为止，工业相关的乳制品起始细菌的噬菌体受体仍然难以捉摸。因此，我们着手确定参与乳链球菌噬菌体宿主识别的细胞表面结构。选择了 5 株对不同噬菌体（类型、类型和新型 987）敏感的工业菌株，以产生自发的噬菌体不敏感突变体（BIMs）。其中，约 50%被选为成簇规则间隔短回文重复序列（CRISPR）突变体，而其他突变体则进一步进行特征分析以鉴定受体突变体。基于基因组测序数据，推测受体突变体中的噬菌体抗性归因于编码聚糖生物合成途径的基因中的核苷酸变化。超分辨率结构照明显微镜用于可视化噬菌体和其噬菌体之间的相互作用。噬菌体要么沿细胞规则分布，要么位于细胞分裂部位。通过表型和生化分析进一步研究介导后一种类型噬菌体附着的细胞壁结构。总的来说，我们的数据表明，噬菌体吸附到是由与细菌细胞表面相关的聚糖介导的。具体来说，CHPC951 型噬菌体吸附到锚定在肽聚糖上的多糖，而 987 型噬菌体 CHPC926 识别与细胞表面相关的细胞外多糖。广泛用于奶酪和酸奶生产的起始培养物。在乳制品发酵过程中，噬菌体感染细菌会导致酸化失败和最终产品质量下降。了解噬菌体-宿主相互作用中涉及的分子因素，特别是乳制品细菌中的噬菌体受体，是开发更好的策略来防止乳制品工厂中噬菌体感染的关键步骤。
