Abstract
Both low temperatures and encounters with host phagocytes are two stresses that have been relatively well studied in many species of bacteria. Previous work has shown that the exoribonuclease polynucleotide phosphorylase (PNPase) is required for Yersiniae to grow at low temperatures. Here, we show that PNPase also enhances the ability of Yersinia pseudotuberculosis and Yersinia pestis to withstand the killing activities of murine macrophages. PNPase is required for the optimal functioning of the Yersinia type three secretion system (TTSS), an organelle that injects effector proteins directly into host cells. Unexpectedly, the effect of PNPase on the TTSS is independent of its ribonuclease activity and instead requires its S1 RNA binding domain. In contrast, catalytically inactive enzyme does not enhance the low temperature growth effect of PNPase. Surprisingly, wild-type-like TTSS functioning was restored to the pnp mutant strain by expressing just the approximately 70 amino acid S1 domains from either PNPase, RNase R, RNase II, or RpsA. Our findings suggest that PNPase plays multifaceted roles in enhancing Yersinia survival in response to stressful conditions.
Highlights
Bacteria can rapidly modulate their metabolism to enhance their survival during periods of environmental change
Viability of polynucleotide phosphorylase (PNPase) and Various Ribonuclease-deficient Strains in an Infection Assay—The viability of a Y. pseudotuberculosis (YPT) PNPasedeficient mutant strain was tested in a cell infection assay
There was a decrease in the number of cfu of the YPT three secretion system (TTSS)-deficient yopB strain during the 6-h infection period
Summary
Bacteria can rapidly modulate their metabolism to enhance their survival during periods of environmental change. Differential expression of TTSS and fimbriae-encoding genes may account for the differences observed between the wild-type and pnp strains in cell culture and animal infection assays [12]. Transforming the YP and YPT pnp strains with a plasmid encoding E. coli PNPase restored the HeLa cell cytotoxicity to levels observed in wild-type-infected cells (Fig. 2).
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