LMOf2365_0442 encoding for a fructose specific PTS permease IIA may be required for virulence in L. monocytogenes Strain F2365

Authors: Liu, Yanhong; YOO, BRIAN BYONGKWON - Centers For Disease Control And Prevention (CDC) - United States; Hwang, Cheng An; SUO, YUJUAN - Shanghai Academy Of Agricultural Sciences; Sheen, Shiowshuh - Allen; Khosravi, Parvaneh; Huang, Lihan

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2017
Publication Date: 8/29/2017
Citation: Liu, Y., Yoo, B., Hwang, C., Suo, Y., Sheen, S., Khosravi, P., Huang, L. 2017. LMOf2365_0442 encoding for a fructose specific PTS permease IIA may be required for virulence in L. monocytogenes Strain F2365. Frontiers in Microbiology. 8:01611.

Interpretive Summary: The bacterium, Listeria monocytogenes, is an important food-borne pathogen that causes disease in humans and animals. Proteins that are known as the Phosphotransferase Transport System (PTS) are involved in sugar transport in L. monocytogenes. To understand how these transporters affect the disease causing ability (virulence) of L. monocytogenes, genes that encode for three PTS proteins were deleted from the bacterial genome forming what are referred to as mutant strains, and the characteristics of these strains were examined. The disease causing ability of these mutant strains was tested using a human cell line. Our results showed that one mutant strain was defective in virulence, and thus this gene may be important for L. monocytogenes to cause illness. Information from this study enhances the understanding of the role of PTS in L. monocytogenes virulence and provides information to help in the development new therapeutics and intervention strategies.

Technical Abstract: Listeria monocytogenes is a foodborne pathogen that causes listeriosis, which is a major public health concern due to the high fatality rate. The Phosphotransferase Transport System (PTS) is responsible for sugar transport. In previous studies, in-frame deletion mutants of a putative fructose-specific PTS permease (LMOf2365_0442, 0443, and 0444) were constructed and analyzed; however, the virulence potential of these deletion mutants has not been studied. In this study, two in vitro methods were used to analyze the virulence potential of these L. monocytogenes deletion mutants. First, invasion assays were used to measure the invasion efficiencies in host cells using the human HT-29 cell line. Second, plaque forming assays were used to measure cell-to-cell spread in host cells. Our results showed that the deletion mutant delta LMOf2365_0442 showed reduced invasion and cell-to-cell spread compared to the parental strain LMOf2365, indicating that LMOf2365_0442 may be required for virulence in L. monocytogenes. In addition, the gene expression levels of 15 virulence and stress-related genes were analyzed in stationary phase cells of the deletion mutants using RT-PCR assays. Virulence-related gene expression levels were elevated in the deletion mutants compared to the wild-type parental strain LMOf2365, indicating the down-regulation of virulence genes by this PTS permease in L. monocytogenes. Finally, the expression level of the stress-related gene clpC increased in all of the deletion mutants, suggesting the involvement of this PTS permease in stress response. Furthermore, these deletion mutants displayed the same high pressure tolerance and the same capacity for biofilm formation compared to the wild-type parental strain LMOf2365. In summary, our findings suggest that the LMOf2365_0442 gene can be used as a potential target to develop new therapeutic and pathogen control strategies for public health.