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Front. Microbiol. | doi: 10.3389/fmicb.2018.00315

Serine Hydroxymethyltransferase ShrA (PA2444) Controls Rugose Small-Colony Variant Formation in Pseudomonas aeruginosa

  • 1Pennsylvania State University, United States

Pseudomonas aeruginosa causes many biofilm infections, and the rugose small-colony variants (RSCVs) of this bacterium are important for infection. We found here that inactivation of PA2444, which we determined to be a serine hydroxymethyltransferase (SHMT), leads to the RSCV phenotype of P. aeruginosa PA14. In addition, loss of PA2444 increases biofilm formation by two orders of magnitude, increases exopolysaccharide by 45-fold, and abolishes swarming. The RSCV phenotype is related to higher cyclic diguanylate concentrations due to increased activity of the Wsp chemosensory system, including diguanylate cyclase WspR. By characterizing the PA2444 enzyme in vitro, we determined the physiological function of PA2444 protein by relating it to S-adenosylmethionine (SAM) concentrations and methylation of a membrane bound methyl-accepting chemotaxis protein WspA. A transcriptome analysis also revealed PA2444 is related to the redox state of the cells, and the altered redox state was demonstrated by an increase in the intracellular NADH/NAD+ ratio. Hence, we provide a mechanism for how an enzyme of central metabolism controls the community behavior of the bacterium, and suggest PA2444 protein should be named ShrA for serine hydroxymethyltransferase related to rugose colony formation.

Keywords: Rugose, small colony variants, serine hydromethyltransferase, Pseudomonas aeruginosa, Biofilm formation

Received: 11 Dec 2017; Accepted: 09 Feb 2018.

Edited by:

Inês A C. Pereira, Instituto de Tecnologia Química e Biológica (ITQB-NOVA), Portugal

Reviewed by:

Franz Narberhaus, Ruhr University Bochum, Germany
Yosuke Tashiro, Shizuoka University, Japan  

Copyright: © 2018 Pu, Sheng, Song, Gong and Wood. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Thomas K. Wood, Pennsylvania State University, University Park, United States, twood@engr.psu.edu