Basic Study
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Infect Dis. May 15, 2020; 10(1): 14-23
Published online May 15, 2020. doi: 10.5495/wjcid.v10.i1.14
GadE regulates fliC gene transcription and motility in Escherichia coli
William R Schwan, Nicole L Flohr, Abigail R Multerer, Jordan C Starkey
William R Schwan, Nicole L Flohr, Abigail R Multerer, Jordan C Starkey, Department of Microbiology, University of Wisconsin-La Crosse, La Crosse, WI 54601, United States
Author contributions: Schwan WR, Flohr NL, Multerer AR, and Starkey JC designed the research, performed the research; Schwan WR, Flohr NL, and Multerer AR analyzed the data; Schwan WR wrote the paper.
Supported by the National Institutes of Health, No. 1R15AI-065432.
Institutional review board statement: No humans or samples from human were used in this study.
Institutional animal care and use committee statement: No animals were used in this study.
Conflict-of-interest statement: The authors report no conflict of interest.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: William R Schwan, PhD, Professor, Department of Microbiology, University of Wisconsin-La Crosse, 1725 State St, La Crosse, WI 54601, United States. wschwan@uwlax.edu
Received: February 7, 2020
Peer-review started: February 7, 2020
First decision: March 5, 2020
Revised: March 25, 2020
Accepted: May 5, 2020
Article in press: May 5, 2020
Published online: May 15, 2020
Processing time: 95 Days and 9.2 Hours
Abstract
BACKGROUND

Escherichia coli (E. coli) express flagella to ascend human urinary tracts. To survive in the acidic pH of human urine, E. coli uses the glutamate decarboxylase acid response system, which is regulated by the GadE protein.

AIM

To determine if growth in an acidic pH environment affected fliC transcription and whether GadE regulated that transcription.

METHODS

A fliC-lacZ reporter fusion was created on a single copy number plasmid to assess the effects of acidic pH on fliC transcription. Further, a ΔgadE mutant strain of a uropathogenic E. coli was created and tested for motility compared to the wild-type strain.

RESULTS

Escherichia coli cells carrying the fliC-lacZ fusion displayed significantly less fliC transcription when grown in an acidic pH medium compared to when grown in a neutral pH medium. Transcription of fliC fell further when the E. coli was grown in an acidic pH/high osmolarity environment. Since GadE is a critical regulator of one acid response system, fliC transcription was tested in a gadE mutant strain grown under acidic conditions. Expression of fliC was derepressed in the E. coli gadE mutant strain grown under acidic conditions compared to that in wild-type bacteria under the same conditions. Furthermore, a gadE mutation in a uropathogenic E. coli background exhibited significantly greater motility than the wild-type strain following growth in an acidic medium.

CONCLUSION

Together, our results suggest that GadE may down-regulate fliC transcription and motility in E. coli grown under acidic conditions.

Keywords: Escherichia coli, Flagella, GadE, Motility, Acid response, fliC

Core tip: Escherichia coli (E. coli) is the number one cause of urinary tract infections in women. The infections are the result of the E. coli cells ascending the urinary tract via flagella presented on the outside of the cells. In this study, we have shown that E. coli grown in a low pH/high-osmolarity environment display transcriptional repression of the fliC flagellin subunit gene. Furthermore, we demonstrate that GadE may regulate fliC transcription and subsequent motility of the E. coli cells.