Another Brick in the Wall: a Rhamnan Polysaccharide Trapped inside Peptidoglycan of <italic toggle="yes">Lactococcus lactis</italic>

ABSTRACT Polysaccharides are ubiquitous components of the Gram-positive bacterial cell wall. In Lactococcus lactis, a polysaccharide pellicle (PSP) forms a layer at the cell surface. The PSP structure varies among lactococcal strains; in L. lactis MG1363, the PSP is composed of repeating hexasacchar...

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Autores principales:	Irina Sadovskaya, Evgeny Vinogradov, Pascal Courtin, Julija Armalyte, Mickael Meyrand, Efstathios Giaouris, Simon Palussière, Sylviane Furlan, Christine Péchoux, Stuart Ainsworth, Jennifer Mahony, Douwe van Sinderen, Saulius Kulakauskas, Yann Guérardel, Marie-Pierre Chapot-Chartier
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2017
Materias:	HR-MAS NMR Lactococcus cell wall polysaccharides rhamnan Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/4db1bb42c704414c96e182217ba8a2ad
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spelling	oai:doaj.org-article:4db1bb42c704414c96e182217ba8a2ad2021-11-15T15:51:51ZAnother Brick in the Wall: a Rhamnan Polysaccharide Trapped inside Peptidoglycan of <italic toggle="yes">Lactococcus lactis</italic>10.1128/mBio.01303-172150-7511https://doaj.org/article/4db1bb42c704414c96e182217ba8a2ad2017-11-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01303-17https://doaj.org/toc/2150-7511ABSTRACT Polysaccharides are ubiquitous components of the Gram-positive bacterial cell wall. In Lactococcus lactis, a polysaccharide pellicle (PSP) forms a layer at the cell surface. The PSP structure varies among lactococcal strains; in L. lactis MG1363, the PSP is composed of repeating hexasaccharide phosphate units. Here, we report the presence of an additional neutral polysaccharide in L. lactis MG1363 that is a rhamnan composed of α-l-Rha trisaccharide repeating units. This rhamnan is still present in mutants devoid of the PSP, indicating that its synthesis can occur independently of PSP synthesis. High-resolution magic-angle spinning nuclear magnetic resonance (HR-MAS NMR) analysis of whole bacterial cells identified a PSP at the surface of wild-type cells. In contrast, rhamnan was detected only at the surface of PSP-negative mutant cells, indicating that rhamnan is located underneath the surface-exposed PSP and is trapped inside peptidoglycan. The genetic determinants of rhamnan biosynthesis appear to be within the same genetic locus that encodes the PSP biosynthetic machinery, except the gene tagO encoding the initiating glycosyltransferase. We present a model of rhamnan biosynthesis based on an ABC transporter-dependent pathway. Conditional mutants producing reduced amounts of rhamnan exhibit strong morphological defects and impaired division, indicating that rhamnan is essential for normal growth and division. Finally, a mutation leading to reduced expression of lcpA, encoding a protein of the LytR-CpsA-Psr (LCP) family, was shown to severely affect cell wall structure. In lcpA mutant cells, in contrast to wild-type cells, rhamnan was detected by HR-MAS NMR, suggesting that LcpA participates in the attachment of rhamnan to peptidoglycan. IMPORTANCE In the cell wall of Gram-positive bacteria, the peptidoglycan sacculus is considered the major structural component, maintaining cell shape and integrity. It is decorated with other glycopolymers, including polysaccharides, the roles of which are not fully elucidated. In the ovococcus Lactococcus lactis, a polysaccharide with a different structure between strains forms a layer at the bacterial surface and acts as the receptor for various bacteriophages that typically exhibit a narrow host range. The present report describes the identification of a novel polysaccharide in the L. lactis cell wall, a rhamnan that is trapped inside the peptidoglycan and covalently bound to it. We propose a model of rhamnan synthesis based on an ABC transporter-dependent pathway. Rhamnan appears as a conserved component of the lactococcal cell wall playing an essential role in growth and division, thus highlighting the importance of polysaccharides in the cell wall integrity of Gram-positive ovococci.Irina SadovskayaEvgeny VinogradovPascal CourtinJulija ArmalyteMickael MeyrandEfstathios GiaourisSimon PalussièreSylviane FurlanChristine PéchouxStuart AinsworthJennifer MahonyDouwe van SinderenSaulius KulakauskasYann GuérardelMarie-Pierre Chapot-ChartierAmerican Society for MicrobiologyarticleHR-MAS NMRLactococcuscell wallpolysaccharidesrhamnanMicrobiologyQR1-502ENmBio, Vol 8, Iss 5 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	HR-MAS NMR Lactococcus cell wall polysaccharides rhamnan Microbiology QR1-502
spellingShingle	HR-MAS NMR Lactococcus cell wall polysaccharides rhamnan Microbiology QR1-502 Irina Sadovskaya Evgeny Vinogradov Pascal Courtin Julija Armalyte Mickael Meyrand Efstathios Giaouris Simon Palussière Sylviane Furlan Christine Péchoux Stuart Ainsworth Jennifer Mahony Douwe van Sinderen Saulius Kulakauskas Yann Guérardel Marie-Pierre Chapot-Chartier Another Brick in the Wall: a Rhamnan Polysaccharide Trapped inside Peptidoglycan of <italic toggle="yes">Lactococcus lactis</italic>
description	ABSTRACT Polysaccharides are ubiquitous components of the Gram-positive bacterial cell wall. In Lactococcus lactis, a polysaccharide pellicle (PSP) forms a layer at the cell surface. The PSP structure varies among lactococcal strains; in L. lactis MG1363, the PSP is composed of repeating hexasaccharide phosphate units. Here, we report the presence of an additional neutral polysaccharide in L. lactis MG1363 that is a rhamnan composed of α-l-Rha trisaccharide repeating units. This rhamnan is still present in mutants devoid of the PSP, indicating that its synthesis can occur independently of PSP synthesis. High-resolution magic-angle spinning nuclear magnetic resonance (HR-MAS NMR) analysis of whole bacterial cells identified a PSP at the surface of wild-type cells. In contrast, rhamnan was detected only at the surface of PSP-negative mutant cells, indicating that rhamnan is located underneath the surface-exposed PSP and is trapped inside peptidoglycan. The genetic determinants of rhamnan biosynthesis appear to be within the same genetic locus that encodes the PSP biosynthetic machinery, except the gene tagO encoding the initiating glycosyltransferase. We present a model of rhamnan biosynthesis based on an ABC transporter-dependent pathway. Conditional mutants producing reduced amounts of rhamnan exhibit strong morphological defects and impaired division, indicating that rhamnan is essential for normal growth and division. Finally, a mutation leading to reduced expression of lcpA, encoding a protein of the LytR-CpsA-Psr (LCP) family, was shown to severely affect cell wall structure. In lcpA mutant cells, in contrast to wild-type cells, rhamnan was detected by HR-MAS NMR, suggesting that LcpA participates in the attachment of rhamnan to peptidoglycan. IMPORTANCE In the cell wall of Gram-positive bacteria, the peptidoglycan sacculus is considered the major structural component, maintaining cell shape and integrity. It is decorated with other glycopolymers, including polysaccharides, the roles of which are not fully elucidated. In the ovococcus Lactococcus lactis, a polysaccharide with a different structure between strains forms a layer at the bacterial surface and acts as the receptor for various bacteriophages that typically exhibit a narrow host range. The present report describes the identification of a novel polysaccharide in the L. lactis cell wall, a rhamnan that is trapped inside the peptidoglycan and covalently bound to it. We propose a model of rhamnan synthesis based on an ABC transporter-dependent pathway. Rhamnan appears as a conserved component of the lactococcal cell wall playing an essential role in growth and division, thus highlighting the importance of polysaccharides in the cell wall integrity of Gram-positive ovococci.
format	article
author	Irina Sadovskaya Evgeny Vinogradov Pascal Courtin Julija Armalyte Mickael Meyrand Efstathios Giaouris Simon Palussière Sylviane Furlan Christine Péchoux Stuart Ainsworth Jennifer Mahony Douwe van Sinderen Saulius Kulakauskas Yann Guérardel Marie-Pierre Chapot-Chartier
author_facet	Irina Sadovskaya Evgeny Vinogradov Pascal Courtin Julija Armalyte Mickael Meyrand Efstathios Giaouris Simon Palussière Sylviane Furlan Christine Péchoux Stuart Ainsworth Jennifer Mahony Douwe van Sinderen Saulius Kulakauskas Yann Guérardel Marie-Pierre Chapot-Chartier
author_sort	Irina Sadovskaya
title	Another Brick in the Wall: a Rhamnan Polysaccharide Trapped inside Peptidoglycan of <italic toggle="yes">Lactococcus lactis</italic>
title_short	Another Brick in the Wall: a Rhamnan Polysaccharide Trapped inside Peptidoglycan of <italic toggle="yes">Lactococcus lactis</italic>
title_full	Another Brick in the Wall: a Rhamnan Polysaccharide Trapped inside Peptidoglycan of <italic toggle="yes">Lactococcus lactis</italic>
title_fullStr	Another Brick in the Wall: a Rhamnan Polysaccharide Trapped inside Peptidoglycan of <italic toggle="yes">Lactococcus lactis</italic>
title_full_unstemmed	Another Brick in the Wall: a Rhamnan Polysaccharide Trapped inside Peptidoglycan of <italic toggle="yes">Lactococcus lactis</italic>
title_sort	another brick in the wall: a rhamnan polysaccharide trapped inside peptidoglycan of <italic toggle="yes">lactococcus lactis</italic>
publisher	American Society for Microbiology
publishDate	2017
url	https://doaj.org/article/4db1bb42c704414c96e182217ba8a2ad
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Another Brick in the Wall: a Rhamnan Polysaccharide Trapped inside Peptidoglycan of <italic toggle="yes">Lactococcus lactis</italic>

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