A Chromosomally Located<i>traHIJKCLMN</i>Operon Encoding a Putative Type IV Secretion System Is Involved in the Virulence of<i>Yersinia ruckeri</i>

Méndez, Jessica; Fernández, Lucía; Menéndez, Aurora; Reimundo, Pilar; Pérez-Pascual, David; Navais, Roberto; Guijarro, José A.

doi:10.1128/aem.01377-08

Cited by 28 publications

(35 citation statements)

References 52 publications

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“…Such effects have been recognized since the 1960s, but in most reported cases, polar effect mutations are detrimental, interfering in some way with proper transcription or translation of a downstream gene (46)(47)(48)(49)(50). The predominantly adverse effects of reported polar mutations may be due to previous selection for bases or codons that function well under typical growth conditions.…”

Section: Discussionmentioning

confidence: 99%

A Synonymous Mutation Upstream of the Gene Encoding a Weak-Link Enzyme Causes an Ultrasensitive Response in Growth Rate

et al. 2016

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When microbes are faced with an environmental challenge or opportunity, preexisting enzymes with promiscuous secondary activities can be recruited to provide newly important functions. Mutations that increase the efficiency of a new activity often compromise the original activity, resulting in an inefficient bifunctional enzyme. We have investigated the mechanisms by which growth of Escherichia coli can be improved when fitness is limited by such an enzyme, E383A ProA (ProA*). ProA* can serve the functions of both ProA (required for synthesis of proline) and ArgC (required for synthesis of arginine), albeit poorly. We identified four genetic changes that improve the growth rate by up to 6.2-fold. Two point mutations in the promoter of the proBA* operon increase expression of the entire operon. Massive amplification of a genomic segment around the proBA* operon also increases expression of the entire operon. Finally, a synonymous point mutation in the coding region of proB creates a new promoter for proA*. This synonymous mutation increases the level of ProA* by 2-fold but increases the growth rate by 5-fold, an ultrasensitive response likely arising from competition between two substrates for the active site of the inefficient bifunctional ProA*. IMPORTANCEThe high-impact synonymous mutation we discovered in proB is remarkable for two reasons. First, most polar effects documented in the literature are detrimental. This finding demonstrates that polar effect mutations can have strongly beneficial effects, especially when an organism is facing a difficult environmental challenge for which it is poorly adapted. Furthermore, the consequence of the synonymous mutation in proB is a 2-fold increase in the level of ProA* but a disproportionately large 5.1-fold increase in growth rate. While ultrasensitive responses are often found in signaling networks and genetic circuits, an ultrasensitive response to an adaptive mutation has not been previously reported. Metabolic enzymes, although prodigious catalysts, are not perfectly specific for their physiological substrates. They typically possess secondary activities as a consequence of the assemblage of highly reactive functional groups, metal ions, and cofactors in their active sites. Secondary activities that are physiologically irrelevant, either because they are too inefficient to contribute to fitness or because the enzyme never encounters the substrate, are termed promiscuous activities (1).Promiscuous activities are important from an evolutionary standpoint because they provide a reservoir of catalytic potential within a proteome that can be drawn upon when the environment changes. A promiscuous activity may become important for fitness when a new source of carbon, nitrogen, or phosphorous appears in the environment or when a previously available compound, such as an amino acid or cofactor, becomes unavailable. A promiscuous activity may also become critical when the organism is exposed to a novel toxin, such as an antibiotic or pesticide.A newly recruited pro...

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Section: Discussionmentioning

confidence: 99%

A Synonymous Mutation Upstream of the Gene Encoding a Weak-Link Enzyme Causes an Ultrasensitive Response in Growth Rate

et al. 2016

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“…The application to Y. ruckeri of in vivo expression technology (IVET) has allowed the identification of 14 genes specifically induced during the infection process in rainbow trout (11). Some of them have been proven to participate in virulence, such as the iron uptake mechanism via the catecholate siderophore ruckerbactin (11), the YhlA hemolysin (13), and the tra chromosomally located operon, a type IV secretion system (22).…”

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confidence: 99%

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

et al. 2011

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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.

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“…Proteins using this pathway can be secreted into the extracellular milieu or directly into a host cell. In Y. ruckeri, the traHIJKCLMN operon, which encodes a putative type IVb secretion system, is involved in the virulence of the bacterium (Méndez et al, 2009). LD 50 determinations with rainbow trout fry indicated that a mutation in the traI gene resulted in virulence attenuation.…”

Section: Protein Secretion Systemsmentioning

confidence: 99%

“…LD 50 determinations with rainbow trout fry indicated that a mutation in the traI gene resulted in virulence attenuation. It is suggested that this system contributes to bacterial pathogenicity through the secretion of some effector molecules into the host cells (Méndez et al, 2009). …”

Section: Protein Secretion Systemsmentioning

confidence: 99%

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

Méndez¹,

Reimundo²,

Pérez-Pascual³

et al. 2012

Health and Environment in Aquaculture

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A Chromosomally LocatedtraHIJKCLMNOperon Encoding a Putative Type IV Secretion System Is Involved in the Virulence ofYersinia ruckeri

Cited by 28 publications

References 52 publications

A Synonymous Mutation Upstream of the Gene Encoding a Weak-Link Enzyme Causes an Ultrasensitive Response in Growth Rate

A Synonymous Mutation Upstream of the Gene Encoding a Weak-Link Enzyme Causes an Ultrasensitive Response in Growth Rate

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

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

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