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A Novel Small RNA Regulates Tolerance and Virulence in Shigella flexneri by Responding to Acidic Environmental Changes.

ABSTRACT: Shigella flexneri is an important cause of bacillary dysentery in developing countries. Small regulatory RNAs (sRNAs) play essential roles in diverse cellular processes. We found a novel sRNA Ssr1 based on RT-PCR, northern blot, and 5'RACE in S. flexneri. Ssr1 responds to acidic environmental changes, as shown by a strong linear correlation between the pH value and Ssr1 expression (R = 0.785, P < 0.05) using the qRT-PCR method. Deletion of Ssr1 results in growth retardation at pH values ranging from 5.0 to 7.0 (P < 0.05), and the survival rate was reduced by 22% in acidic conditions (pH 3.0). Additionally, virulence was significantly increased in an Ssr1 mutant strain, as revealed in a murine lung invasion model and survival model assays. By using the sTarPicker method and proteomic analysis, we considered that DnaK, which is a major factor that confers acidic stress tolerance, may be a direct target of Ssr1. We also found that Ssr1 may enhance virulence by directly targeting OmpA; this leads to altered expression of genes in the type three secretion system (T3SS). This work provides new insight into the mechanism of adaptation to environmental stress and into the pathogenesis of Shigella.

SUBMITTER: Wang L

PROVIDER: S-EPMC4782007 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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A Novel Small RNA Regulates Tolerance and Virulence in Shigella flexneri by Responding to Acidic Environmental Changes.

Wang Ligui L Yang Guang G Qi Lihua L Li Xiang X Jia Leili L Xie Jing J Qiu Shaofu S Li Peng P Hao RongZhang R Wu Zhihao Z Du Xinying X Li Wuju W Song Hongbin H

Frontiers in cellular and infection microbiology 20160308

Shigella flexneri is an important cause of bacillary dysentery in developing countries. Small regulatory RNAs (sRNAs) play essential roles in diverse cellular processes. We found a novel sRNA Ssr1 based on RT-PCR, northern blot, and 5'RACE in S. flexneri. Ssr1 responds to acidic environmental changes, as shown by a strong linear correlation between the pH value and Ssr1 expression (R = 0.785, P < 0.05) using the qRT-PCR method. Deletion of Ssr1 results in growth retardation at pH values ranging ...[more]

PMID: 27014636

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Project description:The instability of Shigella genomes has been described, but how this instability causes phenotypic differences within the Shigella flexneri species is largely unknown and likely variable. We describe herein the genome of S. flexneri strain PE577, originally a clinical isolate, which exhibits several phenotypic differences compared to the model strain 2457T. Like many previously described strains of S. flexneri, PE577 lacks discernible, functional CRISPR and restriction-modification systems. Its phenotypic differences when compared to 2457T include lower transformation efficiency, higher oxygen sensitivity, altered carbon metabolism, and greater susceptibility to a wide variety of lytic bacteriophage isolates. Since relatively few Shigella phages have been isolated on 2457T or the previously characterized strain M90T, developing a more universal model strain for isolating and studying Shigella phages is critical to understanding both phages and phage-host interactions. In addition to phage biology, the genome sequence of PE577 was used to generate and test hypotheses of how pseudogenes in this strain-whether interrupted by degraded prophages, transposases, frameshifts, or point mutations-have led to metabolic rewiring compared to the model strain 2457T. Results indicate that PE577 can utilise the less-efficient pyruvate oxidase/acetyl-CoA synthetase (PoxB/Acs) pathway to produce acetyl-CoA, while strain 2457T cannot due to a nonsense mutation in acs, rendering it a pseudogene in this strain. Both strains also utilize pyruvate-formate lyase to oxidize formate but cannot survive with this pathway alone, possibly because a component of the formate-hydrogen lyase (fdhF) is a pseudogene in both strains.Importance Shigella causes millions of dysentery cases worldwide, primarily affecting children under five years old. Despite active research in developing vaccines and new antibiotics, relatively little is known about the variation of physiology or metabolism across multiple isolates. In this work, we investigate two strains of S. flexneri that share 98.9% genetic identity but exhibit drastic differences in metabolism, ultimately affecting the growth of the two strains. Results suggest additional strains within the S. flexneri species utilize different metabolic pathways to process pyruvate. Metabolic differences between these closely-related isolates suggest an even wider variety of differences in growth across S. flexneri and Shigella in general. Exploring this variation further may assist the development or application of vaccines and therapeutics to combat Shigella infections.

Dataset Information

A Novel Small RNA Regulates Tolerance and Virulence in Shigella flexneri by Responding to Acidic Environmental Changes.

Publications

A Novel Small RNA Regulates Tolerance and Virulence in Shigella flexneri by Responding to Acidic Environmental Changes.

Similar Datasets

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