A Specific Sugar Moiety in the Lactococcus lactis Cell Wall Pellicle Is Required for Infection by CHPC971, a Member of the Rare 1706 Phage Species

Abstract

Lactococcus lactis is a Gram-positive bacterium widely used as a starter culture for the production of different dairy products, especially a large variety of cheeses. Infection of lactococcal starter cultures by bacteriophages is one of the major causes of fermentation failure and often leads to production halt. Lactococcal bacteriophages belonging to the c2, 936, and P335 species are the most commonly isolated in dairy plants and have been extensively investigated in the past three decades. Information regarding bacteriophages belonging to less commonly isolated species is, on the other hand, less extensive, although these phages can also contribute to starter culture infection. Here, we report the nucleotide sequence of the newly isolated L. lactis phage CHPC971, belonging to the rare 1706 species of lactococcal phages. We investigated the nature of the host receptor recognized by the phage and collected evidence that strongly suggests that it binds to a specific sugar moiety in the cell wall pellicle of its host. An in silico analysis of the genome of phage CHPC971 identified the hypothetical genes involved in receptor binding. IMPORTANCE Gathering information on how lactococcal bacteriophages recognize their host and proliferate in the dairy environment is of vital importance for the establishment of proper starter culture rotation plans and to avoid fermentation failure and consequent great economic losses for dairy industries. We provide strong evidence on the type of receptor recognized by a newly isolated 1706-type lactococcal bacteriophage, increasing knowledge of phage-host interactions relevant to dairying. This information can help to prevent phage infection events that, so far, are hard to predict and avoid.

Bacteriophage-host interactions as a platform to establish the role of phages in modulating the microbial composition of fermented foods

“…The cwps gene cluster is responsible for the biosynthesis of two CWPS elements: the peptidoglycan-embedded rhamnan (whose biosynthetic machinery is encoded by the 5' portion of the cwps cluster) and surface-exposed polysaccharide pellicle (PSP; the biosynthesis of which is performed by enzymes that are encoded by the 3' portion of the cwps cluster). Of the 11 distinct groups of lactococcal phages, Skunavirus, P335, 1358, 949, P087, and 1706 phages have been demonstrated to utilise saccharidic host receptors [44][45][46][47][48][49]63,66] . These lactococcal phages specifically bind to the PSP component of the CWPS on the host cell surface, mediated by the phage RBP.…”

L. lactis Bacteriophages and Methods of Their Elimination from Dairy Products

“…In the study of the authors Marcelli et al (2019) showed that the resistance mechanism of four bacteriophage-insensitive mutants of L. lactis involves changes in the phage receptor. For example, phage CHPC971 shows a low or very low adsorption rate for all four bacteriophage-insensitive mutant L. lactis strains compared to its sensitive strains CH LC01 and CH LC02.…”

Host genetic requirements for DNA release of lactococcal phage TP901‐1

“…The initial and specific interaction between a tailed phage and its cognate host is typically achieved through a phage‐encoded receptor binding protein (RBP) and a surface‐exposed receptor moiety. The majority of studied lactococcal phages recognise (part of) a particular cell wall polysaccharide (CWPS) present on the bacterial cell surface (Ainsworth et al, 2014 ; Dupont et al, 2004 ; Mahony et al, 2017 ; Marcelli et al, 2019 ).…”