A Novel cdsAB Operon Is Involved in the Uptake of l -Cysteine and Participates in the Pathogenesis of Yersinia ruckeri

Abstract

Application of in vivo expression technology (IVET) to Yersinia ruckeri, an important fish pathogen, allowed the identification of two adjacent genes that represent a novel bacterial system involved in the uptake and degradation of L-cysteine. Analysis of the translational products of both genes showed permease domains (open reading frame 1 [ORF1]) and amino acid position identities (ORF2) with the L-cysteine desulfidase from Methanocaldococcus jannaschii, a new type of enzyme involved in the breakdown of L-cysteine. The operon was named cdsAB (cysteine desulfidase) and is found widely in anaerobic and facultative bacteria. cdsAB promoter analysis using lacZY gene fusion showed highest induction in the presence of L-cysteine. Two cdsA and cdsB mutant strains were generated. The limited toxic effect and the low utilization of L-cysteine observed in the cdsA mutant, together with radiolabeled experiments, strongly suggested that CdsA is an L-cysteine permease. Fifty percent lethal dose (LD 50 ) and competence index experiments showed that both the cdsA and cdsB loci were involved in the pathogenesis of the bacteria. In conclusion, this study has shown for the first time in bacteria the existence of an L-cysteine uptake system that together with an additional L-cysteine desulfidase-encoding gene constitutes a novel operon involved in bacterial virulence.

TheyrpABoperon ofYersinia ruckeriencoding two putative U32 peptidases is involved in virulence and induced under microaerobic conditions

“…Interestingly, this operon is situated next to the cdsAB operon in the genome of Y. ruckeri, and this is also induced under oxygen limitation. 6 This low oxygen environment is a constant in the gut of many animals 22 and seems to be a trigger for the expression of some virulence genes in pathogenic bacteria colonizing the gut such as V. cholerae 23 and Shigella, 24 although the mechanisms involved in this regulation have not been defined yet. Taking into account that the gut of the rainbow trout is the main organ affected during the Y. ruckeri infection, 1 together with the presence of a microaerobic environment in this organ, it is more than likely that the peptidases YrpA and YrpB are induced specifically in this tissue.…”

“…The analysis of the sequence adjacent to the 3′ end of the gene iviX (cdsB), previously selected by in vivo expression technology, 6,17 allowed the identification of two ORFs, in the same orientation and separated by 12 bp. A putative promoter sequence was identified at the 5′ end of the first ORF and a rho-independent transcription terminator at the 3′ position of the second one (Fig.…”

“…To obtain the complete sequence of the yrpAB operon adjacent to the cdsB gene, 6 genomic DNA from the cdsB mutant was isolated and digested with KpnI. The restriction fragments were re-joined and used to transform cells of E. coli S17-1λpir 28 by electroporation.…”

“…The most noteworthy among these involve extracellular factors such as the Yrp1 protease 2 and the YhlA hemolysin, 3 a high-affinity zinc transporter, 4 a response regulator of a two-component system 5 and an operon involved in the uptake of cysteine. 6 The proteolytic enzymes in bacteria can play a variety of roles: they can provide a source of amino acids by degrading extracellular proteins, intervene in regulation functions and contribute to virulence in pathogenic bacteria. In particular, proteolytic enzymes of Aeromonas salmonicida 7 and Listonella anguillarum 8 cause alteration in fish tissues and can be considered as virulence factors.…”

An Overview of Virulence-Associated Factors of Gram-Negative Fish Pathogenic Bacteria

“…Finally, different uptake systems such as a cysteine transporter and a zinc transporter were shown to be involved in the ability of Y. ruckeri to infect fish (Dahiya & Stevenson, 2010a;Méndez et al, 2011).…”