Sinorhizobium Meliloti Chemotaxis to Multiple Amino Acids is Mediated by the Chemoreceptor Mcp U

Abstract

The legume symbiont Sinorhizobium meliloti is chemoattracted to compounds exuded by germinating seeds of its host alfalfa. This response is mainly mediated by the S. meliloti chemoreceptor McpU. McpU also has a prominent contribution in sensing a synthetic amino acid (aa) mixture mimicking the amounts and composition observed in seed exudate. Here, we used the hydrogel capillary assay to quantify chemotactic responses of S. meliloti to individual aa exuded by germinating alfalfa seeds and to define the role of McpU in this behavior. S. meliloti exhibited positive chemotaxis responses to all proteinogenic aa, except for aspartate, and to citrulline, cystine, gamma-aminobutyric acid, and ornithine. Wild-type responses were diverse in intensity, while a strain lacking mcpU displayed strongly diminished responses. Differential scanning fluorimetry demonstrated interaction of the purified periplasmic region of McpU (McpU-PR) with the aa, except glutamate and aspartate. We additionally tested organic acids and sugars, but there were no significant interactions with the McpU ligand-binding domain, except for citrate. Using ligand displacement, we confirmed the interaction of McpU-PR with aa representing strong and weak attractants. Our results show that S. meliloti McpU is a broad-range aa receptor mediating differential responses to individual attractants, which does not bind negatively charged aa.

Department(s)

Chemistry

Publication Status

Open Access

Comments

National Science Foundation, Grant MCB-1253234

International Standard Serial Number (ISSN)

0894-0282

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2024 Learned Society, All rights reserved.

Publication Date

01 Oct 2017

PubMed ID

28745538

Link to Full Text

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