Differential Gene Expression Patterns of Yersinia pestis and Yersinia pseudotuberculosis during Infection and Biofilm Formation in the Flea Digestive Tract

Abstract

Yersinia pestis, the etiologic agent of plague, emerged as a fleaborne pathogen only within the last 6,000 years. Just five simple genetic changes in the Yersinia pseudotuberculosis progenitor, which served to eliminate toxicity to fleas and to enhance survival and biofilm formation in the flea digestive tract, were key to the transition to the arthropodborne transmission route. To gain a deeper understanding of the genetic basis for the development of a transmissible biofilm infection in the flea foregut, we evaluated additional gene differences and performed in vivo transcriptional profiling of Y. pestis, a Y. pseudotuberculosis wild-type strain (unable to form biofilm in the flea foregut), and a Y. pseudotuberculosis mutant strain (able to produce foregut-blocking biofilm in fleas) recovered from fleas 1 day and 14 days after an infectious blood meal. Surprisingly, the Y. pseudotuberculosis mutations that increased c-di-GMP levels and enabled biofilm development in the flea did not change the expression levels of the hms genes responsible for the synthesis and export of the extracellular polysaccharide matrix required for mature biofilm formation. The Y. pseudotuberculosis mutant uniquely expressed much higher levels of Yersinia type VI secretion system 4 (T6SS-4) in the flea, and this locus was required for flea blockage by Y. pseudotuberculosis but not for blockage by Y. pestis. Significant differences between the two species in expression of several metabolism genes, the Psa fimbrial genes, quorum sensing-related genes, transcription regulation genes, and stress response genes were evident during flea infection. IMPORTANCE Y. pestis emerged as a highly virulent, arthropod-transmitted pathogen on the basis of relatively few and discrete genetic changes from Y. pseudotuberculosis. Parallel comparisons of the in vitro and in vivo transcriptomes of Y. pestis and two Y. pseudotuberculosis variants that produce a nontransmissible infection and a transmissible infection of the flea vector, respectively, provided insights into how Y. pestis has adapted to life in its flea vector and point to evolutionary changes in the regulation of metabolic and biofilm development pathways in these two closely related species.

Transcriptomic profiling of the digestive tract of the rat flea, Xenopsylla cheopis, following blood feeding and infection with Yersinia pestis

“…Fleas are blood-feeding arthropods that are vectors of several Gram-negative bacterial pathogens including Bartonella spp., Rickettsia felis, Rickettsia typhi, and Yersinia pestis [1]. Once ingested by a flea, the bacteria must overcome insect immunity, establish a replicative niche in the gut, and alter their gene expression to promote survival and transmission [2][3][4][5][6][7][8]. For Y. pestis, infection is initiated when fleas ingest blood from a highly bacteremic animal, typically a rodent.…”

RovC - a novel type of hexameric transcriptional activator promoting type VI secretion gene expression

“…pseudotuberculosis during infection in the flea digestive tract revealed that the expression of the Y . pseudotuberculosis T6SS4 system, including the rovC homologous gene is strongly upregulated during flea infection compared to in vitro growth [ 66 ]. It is still unclear how the different regulators and regulatory circuits are integrated and coordinated to produce active T6SS4 when needed.…”

“…fleas, flies) and RovC homologues are found in several insect and plant pathogens (S4A Fig), it is likely that the Yersinia T6SS4 system, besides its described role during infection of mammals [21], is important in the species' native environment. In fact, a recent study comparing gene expression patterns of Y. pestis and Y. pseudotuberculosis during infection in the flea digestive tract revealed that the expression of the Y. pseudotuberculosis T6SS4 system, including the rovC homologous gene is strongly upregulated during flea infection compared to in vitro growth [66]. It is still unclear how the different regulators and regulatory circuits are integrated and coordinated to produce active T6SS4 when needed.…”

Antioxidant Function and Metabolomics Study in Mice after Dietary Supplementation with Methionine

“…Primer 5.0 was used to design the primer ( Table 1 ). RT-PCR was performed according to previous studies [ 14 – 18 ].…”