PBP2b mutations improve the growth of phage-resistant Lactococcus cremoris lacking polysaccharide pellicle

Guérin, Hugo; Quénée, Pascal; Palussière, Simon; Courtin, Pascal; André, Gwenaëlle; Péchoux, Christine; Costache, Vlad; Mahony, Jennifer; van Sinderen, Douwe; Kulakauskas, Saulius; Chapot-Chartier, Marie-Pierre

PBP2b mutations improve the growth of phage-resistant Lactococcus cremoris lacking polysaccharide pellicle

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aem.02103-22.pdf(2.46 MB)

Published Version

Date

2023-05-24

Authors

Guérin, Hugo

Quénée, Pascal

Palussière, Simon

Courtin, Pascal

André, Gwenaëlle

Péchoux, Christine

Costache, Vlad

Mahony, Jennifer

van Sinderen, Douwe

Kulakauskas, Saulius

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Publisher

American Society for Microbiology

Published Version

10.1128/aem.02103-22

Abstract

Lactococcus lactis and Lactococcus cremoris are Gram-positive lactic acid bacteria widely used as starter in milk fermentations. Lactococcal cells are covered with a polysaccharide pellicle (PSP) that was previously shown to act as the receptor for numerous bacteriophages of the Caudoviricetes class. Thus, mutant strains lacking PSP are phage resistant. However, because PSP is a key cell wall component, PSP-negative mutants exhibit dramatic alterations of cell shape and severe growth defects, which limit their technological value. In the present study, we isolated spontaneous mutants with improved growth, from L. cremoris PSP-negative mutants. These mutants grow at rates similar to the wild-type strain, and based on transmission electron microscopy analysis, they exhibit improved cell morphology compared to their parental PSP-negative mutants. In addition, the selected mutants maintain their phage resistance. Whole-genome sequencing of several such mutants showed that they carried a mutation in pbp2b, a gene encoding a penicillin-binding protein involved in peptidoglycan biosynthesis. Our results indicate that lowering or turning off PBP2b activity suppresses the requirement for PSP and ameliorates substantially bacterial fitness and morphology.

Keywords

Lactococcus , Bacteriophage resistance , Cell wall , Lactic acid bacteria , Penicillin-binding proteins , Polysaccharide pellicle

Citation

Guérin, H., Quénée, P., Palussière, S., Courtin, P., André, G., Péchoux, C., Costache, V., Mahony, J., van Sinderen, D., Kulakauskas, S. and Chapot-Chartier, M. P. (2023) 'PBP2b mutations improve the growth of phage-resistant Lactococcus cremoris lacking polysaccharide pellicle', Applied and Environmental Microbiology, 89(6), e02103-22 (14pp). doi: 10.1128/aem.02103-22