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Streptococcus gordonii Challisin protease is required for sensing cell-cell contact with Actinomyces oris

Lookup NU author(s): Waleed Mohammed, Professor Natalio KrasnogorORCiD, Professor Nicholas JakubovicsORCiD



This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).


The ability of microorganisms to regulate gene expression is thought to be critical for survival and growth during the development of polymicrobial biofilms such as dental plaque. The commensal dental plaque colonizer, Streptococcus gordonii, responds to cell-cell contact (coaggregation) with Actinomyces oris by regulating >20 genes, including those involved in arginine biosynthesis. We hypothesized that an S. gordonii extracellular protease is critical for sensing by providing amino acids that modulate gene expression. S. gordonii coaggregated strongly with A. oris in buffer, saliva or chemically defined medium (CDM). In wild-type S. gordonii, expression of arginine biosynthesis genes argC and argG increased within two hours’ growth in CDM in monocultures, but not following coaggregation with A. oris. By contrast, coaggregation of A. oris with an S. gordonii mutant lacking sgc, encoding the extracellular protease Challisin, resulted in increases in argC and argG gene expression that were similar to monocultures. Genetic complementation of sgc restored the ability of S. gordonii to sense coaggregation with A. oris. Coaggregation enabled growth of S. gordonii in low/no arginine and disruption of sgc did not affect this ability. We propose that extracellular bacterial proteases may be key mediators of cell-cell contact sensing by diverse microbial species.

Publication metadata

Author(s): Mohammed WK, Krasnogor N, Jakubovics NS

Publication type: Article

Publication status: Published

Journal: FEMS Microbiology Ecology

Year: 2018

Volume: 94

Issue: 5

Print publication date: 01/05/2018

Online publication date: 14/03/2018

Acceptance date: 13/03/2018

Date deposited: 15/03/2018

ISSN (print): 0168-6496

ISSN (electronic): 1574-6941

Publisher: Oxford University Press


DOI: 10.1093/femsec/fiy043


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