# Sulfur Starvation, Sulfide Supplementation, and cysM Transcription in Campylobacter jejuni Strains with a Single Nucleotide Polymorphism

## TL;DR

This study explores how a single nucleotide polymorphism affects the survival and gene activity of Campylobacter jejuni under sulfur starvation and sulfide conditions.

## Contribution

The study identifies a gene regulatory element linked to a SNP in the cysM gene's untranslated region.

## Key findings

- Strains with different SNP forms showed survival differences under low sulfide conditions.
- cysM transcription profiles varied with sulfide concentration and SNP form.
- The SNP is part of a gene regulatory element in the untranslated region.

## Abstract

The amino acid cysteine is essential to Campylobacter jejuni survival, providing the bacterial cells with the element sulfur. When cysteine is not available for uptake, C. jejuni can synthesize cysteine from serine and sulfide or thiosulfate. The cysM gene produces a cysteine synthase protein required for this process. Transcriptional control for cysM has been shown to reside within an untranslated sequence directly upstream of the gene. The untranslated sequence contains a conserved single-nucleotide polymorphism that was previously shown to influence gene transcription. Identification of the 5′ end of the cysM mRNA transcript confirmed that the SNP is present within full-length gene transcripts. A new sulfur starvation medium was deployed to study the survival and cysM transcription of C. jejuni strains with different SNP forms in the presence or absence of sulfide. Differences in survival between the SNP forms were observed during supplementation with low concentrations of sulfide. Additionally, differences in the cysM transcription profiles between the same strains with different SNP forms were observed when supplemented with a range of sulfide concentrations. The results support the hypothesis that a gene regulatory element is localized to the area around the SNP in the untranslated region upstream of cysM.