Genomewide transcriptional response of Escherichia coli O157:H7 to norepinephrine

Authors: Sharma, Vijay; Akavaram, Surya Tej; Bayles, Darrell

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2021
Publication Date: 2/8/2022
Citation: Sharma, V.K., Akavaram, S.N., Bayles, D.O. 2022. Genomewide transcriptional response of Escherichia coli O157:H7 to norepinephrine. BMC Genomics. 23. Article 107. https://doi.org/10.1186/s12864-021-08167-z.
DOI: https://doi.org/10.1186/s12864-021-08167-z

Interpretive Summary: Escherichia coli O157:H7 (O157) are serious foodborne bacteria capable of producing mild diarrheal illness to causing kidney failure and even death, especially in children and elderly patients. O157 bacteria colonize cattle intestines and are shed by colonized animal in their feces, which are a major risk factor in the contamination of meats produced from cattle. In addition cattle feces/manure are important source of contamination of other foods, especially ready to eat vegetable/greens. O157 bacteria can sense specific chemicals such as hormones that are released in cattle intestine when these animals experience a stress. O157 can perceive these stress hormones as signals to change their genetics/physiological properties to become better at colonizing and persisting in cattle intestines. By exposing O157 bacteria to one particular stress hormone (norepinephrine), we found that O157 bacteria underwent many genetic/physiological changes that could potentially enhance the ability of O157 to colonize cattle intestines and promote shedding of these bacteria in cattle feces. Having the knowledge of specific genetic/physiological changes promoting increased colonization/fecal shedding of O157 in cattle could enable development of interventions, such as better vaccines and/or probiotics, to block O157 colonization of cattle intestine.

Technical Abstract: Background: Chemical signaling between a mammalian host and its intestinal microbes is vital to the host animal health and maintenance of ‘healthy’ intestinal microbiota. Ability of foodborne human pathogen Escherichia coli O157:H7 to hijack both the host- and microbiota-produced chemical signals is advantageous for survival in the harsh and nutritionally competitive gastrointestinal environment and to colonize the terminal colon. The catecholamine, norepinephrine (NE), produced by the sympathetic neurons of the enteric nervous system has been shown in vitro to induce the expression of genes controlling E. coli O157:H7 swimming motility, acid resistance, and adherence to epithelial cells. Methods: An earlier study has used microarrays with a limited number of probes to identify differentially expressed genes in E. coli O157:H7 strain EDL933 in response to NE. To elucidate a comprehensive transcriptional response to NE, we performed RAN-Seq on rRNA-depleted RNA prepared from E. coli O157:H7 strain NADC 6564, a derivative of a foodbrone E. coli O157:H7 strain 86-24. We mapped the generated reads to the genome of strain NADC 6564 using HiSat2. The mapped reads were quantified by htseq-count and the reference GIF file (NADC 6564). Differentially expressed genes were identified by analyzing quantified reads by DESeq2. String-DB was used to determine networks of protein-protein interactions between the differentially expressed products. Results: Of the 1,918 differentially expressed genes (greater than/equal to 1.3 fold; adjusted p less than 0.05), many encoded pathways linked to virulence and ability of E. coli O157:H7 to colonize intestines of carrier animals and incidental human host. The specific virulence and colonization pathways induced in response to NE play important role in the ability of E. coli O157:H7 to adhere to epithelial cells, produce Shiga toxin 2, develop tolerance to extreme acidity, express specific transport systems for the influx/efflux of specific nutrients/metabolites, and modulate its tolerance to various stressors. A correlation was also observed in a direct regulatory role of EvgS/EvgA signal transduction system in the expression of acid resistance pathway 2 in response to NE. Many genes involved in nitrogen, sulfur, and amino acid metabolism were upregulated while genes linked to iron (Fe3 plus) acquisition via siderophore biosynthesis and transport were down-regulated. Conclusion: The availability of physiological levels of norepinephrine in gastrointestinal tract could serve as an important cue enabling E. coli O157:H7 to engineer its virulence, stress, and metabolic pathways for colonization and persistence in the asymptomatic carrier animal host, such as cattle, and for producing a disease in the incidental human host.