Dataset Information

Differential roles for pathogenicity islands SPI-13 and SPI-8 in the interaction of Salmonella Enteritidis and Salmonella Typhi with murine and human macrophages.

ABSTRACT: Salmonella pathogenicity island (SPI)-13 is conserved in many serovars of S. enterica, including S. Enteritidis, S. Typhimurium and S. Gallinarum. However, it is absent in typhoid serovars such as S. Typhi and Paratyphi A, which carry SPI-8 at the same genomic location. Because the interaction with macrophages is a critical step in Salmonella pathogenicity, in this study we investigated the role played by SPI-13 and SPI-8 in the interaction of S. Enteritidis and S. Typhi with cultured murine (RAW264.7) and human (THP-1) macrophages.Our results showed that SPI-13 was required for internalization of S. Enteritidis in murine but not human macrophages. On the other hand, SPI-8 was not required for the interaction of S. Typhi with human or murine macrophages. Of note, the presence of an intact copy of SPI-13 in a S. Typhi mutant carrying a deletion of SPI-8 did not improve its ability to be internalized by, or survive in human or murine macrophages.Altogether, our results point out to different roles for SPI-13 and SPI-8 during Salmonella infection. While SPI-13 contributes to the interaction of S. Enteritidis with murine macrophages, SPI-8 is not required in the interaction of S. Typhi with murine or human macrophages. We hypothesized that typhoid serovars have lost SPI-13 and maintained SPI-8 to improve their fitness during another phase of human infection.

SUBMITTER: Espinoza RA

PROVIDER: S-EPMC5311848 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Differential roles for pathogenicity islands SPI-13 and SPI-8 in the interaction of Salmonella Enteritidis and Salmonella Typhi with murine and human macrophages.

Espinoza Rodrigo A RA Silva-Valenzuela Cecilia A CA Amaya Fernando A FA Urrutia Ítalo M ÍM Contreras Inés I Santiviago Carlos A CA

Biological research 20170215 1

<h4>Background</h4>Salmonella pathogenicity island (SPI)-13 is conserved in many serovars of S. enterica, including S. Enteritidis, S. Typhimurium and S. Gallinarum. However, it is absent in typhoid serovars such as S. Typhi and Paratyphi A, which carry SPI-8 at the same genomic location. Because the interaction with macrophages is a critical step in Salmonella pathogenicity, in this study we investigated the role played by SPI-13 and SPI-8 in the interaction of S. Enteritidis and S. Typhi with ...[more]

PMID: 28202086

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Project description:DNA topology has fundamental control over the ability of transcription factors to access their target DNA sites at gene promoters. However, the influence of DNA topology on protein-DNA and protein-protein interactions is poorly understood. For example, relaxation of DNA supercoiling strongly induces the well-studied pathogenicity gene ssrA (also called spiR) in Salmonella enterica, but neither the mechanism nor the proteins involved are known. We have found that relaxation of DNA supercoiling induces expression of the Salmonella pathogenicity island (SPI)-2 regulator ssrA as well as the SPI-1 regulator hilC through a mechanism that requires the two-component regulator OmpR-EnvZ. Additionally, the ompR promoter is autoregulated in the same fashion. Conversely, the SPI-1 regulator hilD is induced by DNA relaxation but is repressed by OmpR. Relaxation of DNA supercoiling caused an increase in OmpR binding to DNA and a concomitant decrease in binding by the nucleoid-associated protein FIS. The reciprocal occupancy of DNA by OmpR and FIS was not due to antagonism between these transcription factors, but was instead a more intrinsic response to altered DNA topology. Surprisingly, DNA relaxation had no detectable effect on the binding of the global repressor H-NS. These results reveal the underlying molecular mechanism that primes SPI genes for rapid induction at the onset of host invasion. Additionally, our results reveal novel features of the archetypal two-component regulator OmpR. OmpR binding to relaxed DNA appears to generate a locally supercoiled state, which may assist promoter activation by relocating supercoiling stress-induced destabilization of DNA strands. Much has been made of the mechanisms that have evolved to regulate horizontally-acquired genes such as SPIs, but parallels among the ssrA, hilC, and ompR promoters illustrate that a fundamental form of regulation based on DNA topology coordinates the expression of these genes regardless of their origins.

Project description:Although four of the five Salmonella pathogenicity islands (SPIs) have been characterized in detail for Salmonella enterica serovar Typhimurium, and the fifth has been characterized for Salmonella enterica serovar Dublin, there have been limited studies to examine them in detail in a range of pathogenic serovars of S. enterica. The aim of this study was to examine these regions, shown to be crucial in virulence, in pathogenic serovars to identify any major deletions or insertions that may explain variation in virulence and provide further understanding of the elements involved in the evolution of these regions. Multiple strains of each of the 13 serovars were compared by Southern blot hybridization using a series of probes that together encompassed the full length of all five SPIs. With the exception of serovar Typhimurium, all strains of the same serovar were identical in all five SPIs. Those serovars that differed from serovar Typhimurium in SPI-1 to SPI-4 and from serovar Dublin in SPI-5 were examined in more detail in the variant regions by PCR, and restriction endonuclease digestion and/or DNA sequencing. While most variation in hybridization patterns was attributable to loss or gain of single restriction endonuclease cleavage sites, three regions, in SPI-1, SPI-3, and SPI-5, had differences due to major insertions or deletions. In SPI-1 the avrA gene was replaced by a 200-base fragment in three serovars, as reported previously. In SPI-5, two serovars had acquired an insertion with similarity to the pagJ and pagK genes between pipC and pipD. In SPI-3 the genes sugR and rhuM were deleted in most serovars and in some were replaced by sequences that were very similar to either the Escherichia coli fimbrial operon, flanked by two distinct insertion sequence elements, or to the E. coli retron phage PhiR73. The distribution of these differences suggests that there have been a number of relatively recent horizontal transfers of genes into S. enterica and that in some cases the same event has occurred in multiple lineages of S. enterica. Thus, it seems that insertion sequences and retron phages are likely to be involved in continuing evolution of the pathogenicity islands of pathogenic Salmonella serovars.

Project description:The pathogenesis of Salmonella enterica serovar Typhi (S. Typhi), the cause of typhoid fever in humans, is mainly attributed to the acquisition of horizontally acquired DNA elements. Salmonella pathogenicity islands (SPIs) are indubitably the most important form of horizontally acquired DNA with respect to pathogenesis of this bacterium. The insertion or deletion of any of these transferrable SPIs may have impact on the virulence potential of S. Typhi. In this study, the virulence potential and genetic relatedness of 35 S. Typhi isolates, collected from 2004 to 2013 was determined by identification of SPI and non-SPI virulence factors through a combination of techniques including virulotyping, Whole Genome Sequencing (WGS), and Variable Number of Tandem Repeats (VNTR) profiling. In order to determine the virulence potential of local S. Typhi isolates, 56 virulence related genes were studied by PCR. These genes are located in the core as well as accessory genome (SPIs and plasmid). Major variations among studied virulence determinants were found in case of SPI-7 and SPI-10 associated genes. On the basis of presence of virulence related genes, the studied S. Typhi isolates from Pakistan were clustered into two virulotypes Vi-positive and Vi-negative. Interestingly, SPI-7 and SPI-10 were collectively absent or present in Vi-negative and Vi-positive strains, respectively. Two Vi-negative and 11 Vi-positive S. Typhi strains were also analyzed by whole genome sequencing (WGS) and their results supported the PCR results. Genetic diversity was tested by VNTR-based molecular typing. All 35 isolates were clustered into five groups. Overall, all Vi-negative isolates were placed in a single group (T5) whereas Vi-positive isolates were grouped into four types. Vi-negative and Vi-positive isolates were mutually exclusive. This is the first report on the comparative distribution of SPI and non-SPI related virulence genes in Vi-negative and Vi-positive S. Typhi isolates with an important finding that SPI-10 is absent in all Vi-negative isolates.

Dataset Information

Differential roles for pathogenicity islands SPI-13 and SPI-8 in the interaction of Salmonella Enteritidis and Salmonella Typhi with murine and human macrophages.

Publications

Differential roles for pathogenicity islands SPI-13 and SPI-8 in the interaction of Salmonella Enteritidis and Salmonella Typhi with murine and human macrophages.

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