Virginia Research Day 2022

Graduate Student Research Biomedical

06 A Chromosomally Encoded Homoserine Lactone Reporter System For Brucella Abortus

Mitchell T. Caudill; Clayton C. Caswell Corresponding author: mtcau@vt.edu

Virginia Maryland College of Veterinary Medicine

Brucella species are the causative agent of brucellosis, a worldwide zoonosis that debilitates millions and severely impacts agriculture production. Brucella uses a repertoire of virulence factors, including the tightly regulated Type IV secretion system, to establish a replicative niche within macrophages and evade immune-mediated destruction. One of the regulatory components of the Type IV secretion system are the homoserine lactone responsive transcriptional regulators, VjbR and BabR. While it is known that Brucella synthesizes C12 homoserine lactone at low levels, the mechanisms of this synthesis and the manner by which Brucella alters homoserine lactone concentration during the macrophage infection have remained obscure. Due to this gap in knowledge, the environmental stimuli altering confirmation of VjbR and BabR, and ultimately expression levels of the Type IV secretion system, are unknown. To identify the mechanism of homoserine lactone synthesis within Brucella , we have constructed a chromosomally encoded homoserine lactone reporter system. In this system, the lux operon of Photorhabdus luminescens is placed under the control of the traI promotor of Agrobacterium tumefaciens. Additionally, the homoserine lactone responsive TraR of Agrobacterium tumefaciens is constitutively expressed, resulting in TraR binding of the traI promotor in the presence of homoserine lactone. This system will be used to detect alterations of homoserine lactone production by Brucella , and may aid in identifying the mechanisms of Brucella’s homoserine lactone synthesis.

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