Identification of a Novel Pyruvyltransferase Using 13 C Solid-State Nuclear Magnetic Resonance To Analyze Rhizobial Exopolysaccharides

The alphaproteobacterium Sinorhizobium meliloti secretes two acidic exopolysaccharides (EPSs), succinoglycan (EPSI) and galactoglucan (EPSII), which differentially enable it to adapt to a changing environment. Succinoglycan is essential for invasion of plant hosts and, thus, for the formation of nit...

Full description

Saved in:
Bibliographic Details
Published in:Journal of bacteriology 2021-11, Vol.203 (24), p.e0040321
Main Authors: Wells, Derek H, Goularte, Nicolette F, Barnett, Melanie J, Cegelski, Lynette, Long, Sharon R
Format: Article
Language:English
Subjects:
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Galactans - chemistry
Galactans - metabolism
Gene Expression Regulation, Bacterial - physiology
Gene Expression Regulation, Enzymologic - physiology
Glucans - chemistry
Glucans - metabolism
Humans
Magnetic Resonance Spectroscopy
Mutation
Polysaccharides, Bacterial - chemistry
Polysaccharides, Bacterial - genetics
Polysaccharides, Bacterial - metabolism
Sinorhizobium meliloti
Transferases - classification
Transferases - genetics
Transferases - metabolism
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The alphaproteobacterium Sinorhizobium meliloti secretes two acidic exopolysaccharides (EPSs), succinoglycan (EPSI) and galactoglucan (EPSII), which differentially enable it to adapt to a changing environment. Succinoglycan is essential for invasion of plant hosts and, thus, for the formation of nitrogen-fixing root nodules. Galactoglucan is critical for population-based behaviors such as swarming and biofilm formation and can facilitate invasion in the absence of succinoglycan on some host plants. The biosynthesis of galactoglucan is not as completely understood as that of succinoglycan. We devised a pipeline to identify putative pyruvyltransferase and acetyltransferase genes, construct genomic deletions in strains engineered to produce either succinoglycan or galactoglucan, and analyze EPS from mutant bacterial strains. EPS samples were examined by C cross-polarization magic-angle spinning (CPMAS) solid-state nuclear magnetic resonance (NMR). CPMAS NMR is uniquely suited to defining chemical composition in complex samples and enables the detection and quantification of distinct EPS functional groups. Galactoglucan was isolated from mutant strains with deletions in five candidate acyl/acetyltransferase genes ( , , , , and ) and a putative pyruvyltransferase ( or ). Most samples were similar in composition to wild-type EPSII by CPMAS NMR analysis. However, galactoglucan produced from a strain lacking exhibited a significant reduction in pyruvylation. Pyruvylation was restored through the ectopic expression of plasmid-borne . Our work has thus identified WgaE as a galactoglucan pyruvyltransferase. This exemplifies how the systematic combination of genetic analyses and solid-state NMR detection is a rapid means to identify genes responsible for modification of rhizobial exopolysaccharides. Nitrogen-fixing bacteria are crucial for geochemical cycles and global nitrogen nutrition. Symbioses between legumes and rhizobial bacteria establish root nodules, where bacteria convert dinitrogen to ammonia for plant utilization. Secreted exopolysaccharides (EPSs) produced by Sinorhizobium meliloti (succinoglycan and galactoglucan) play important roles in soil and plant environments. The biosynthesis of galactoglucan is not as well characterized as that of succinoglycan. We employed solid-state nuclear magnetic resonance (NMR) to examine intact EPS from wild-type and mutant S. meliloti strains. NMR analysis of EPS isolated from a gene mutant revealed a novel pyruvyltrans
ISSN:0021-9193
1098-5530
DOI:10.1128/JB.00403-21