Depletion of Glucose Activates Catabolite Repression during Pneumonic Plague

Abstract

Bacterial pathogenesis depends on changes in metabolic and virulence gene expression in response to changes within a pathogen's environment. The plague-causing pathogen, , requires expression of the gene encoding the Pla protease for progression of pneumonic plague. The catabolite repressor protein Crp, a global transcriptional regulator, may serve as the activator of in response to changes within the lungs as disease progresses. By using gene reporter fusions, the spatial and temporal activation of the and promoters was measured in a mouse model of pneumonic plague. In the lungs, was highly expressed in bacteria found within large aggregates resembling biofilms, while expression increased over time independent of the aggregated state. Increased expression of and correlated with a reduction in lung glucose levels. Deletion of the glucose-specific phosphotransferase system EIIBC (PtsG) of rescued glucose levels in the lungs, resulting in reduced expression of both and We propose that activation of expression during pneumonic plague is driven by an increase of both Crp and cAMP levels following consumption of available glucose in the lungs by Thus, Crp operates as a sensor linking the nutritional environment of the host to regulation of virulence gene expression. Using as a model for pneumonia, we discovered that glucose is rapidly consumed, leading to a catabolite-repressive environment in the lungs. As a result, expression of the gene encoding the plasminogen activator protease, a target of the catabolite repressor protein required for pathogenesis, is activated. Interestingly, expression of the catabolite repressor protein itself was also increased in the absence of glucose but only in biofilms. The data presented here demonstrate how a bacterial pathogen senses changes within its environment to coordinate metabolism and virulence gene expression.

The Cyclic AMP Receptor Protein Regulates Quorum Sensing and Global Gene Expression in Yersinia pestis During Planktonic Growth and Growth in Biofilms

“…Thus, we expect that variations in gene expression noted in this study will be linked specifically to Crp. This suggestion is consistent with our prior finding that regulation of pla (between planktonic and biofilm-grown cells) depends on differential expression of Crp as opposed to changes in cAMP (26).…”

“…This is not surprising giving the historical role of Crp in regulating the lac operon and genes for alternative sugar metabolisms (52). In our RNA-seq data, we found that Crp activated expression of ptsG, which is a gene required for acquiring glucose during pneumonia and is also important during bubonic plague (26). Crp was also found to increase expression of malT, the transcriptional activator of maltose metabolism (53).…”

“…Production of the main constituent of biofilms, poly-N-acetylglucosamine, is increased at 37°C in fully virulent strains of Y. pestis, suggesting additional roles for biofilm formation during mammalian infection (25). Further, we recently demonstrated increased expression of crp within biofilms in the lungs of Y. pestis-infected mice, revealing a link between in vivo biofilms, glucose availability, and essential virulence gene expression (26).…”

“…Y. pestis proliferates to ~10 9 colony forming units (CFUs), forms large biofilms in the lungs, and consumes all available glucose in the process. The declining concentration of glucose activates expression of crp within biofilms (26).…”

“…The significant increase in AHLs at 72 hpi correlates with the timeframe during pneumonia when Y. pestis depletes glucose from the lungs, forms large biofilms, and as a result, expresses crp to a high level ( Fig. 1A) (26). The formation of biofilms in the lungs may provide a favorable environment for amplification of quorum sensing-based gene regulation.…”