Virginia Research Day 2021

Graduate Student Research Biomedical

04 A New Regulatory Small RNA, VcrS, is Crucial for Virulence of Brucella abortus

Kellie A King; Angela H Benton; Kevin K Lahmers; Pawel Michalak; Clayton C Caswell Corresponding author: Kellieking@vt.edu

Virginia-Maryland College of Veterinary Medicine Via College of Osteopathic Medicine-Virginia Campus

Brucellosis is a zoonotic disease caused by Brucella spp . infecting goats ( B. melitensis ), pigs ( B. suis ), and cattle ( B. abortus ). Brucellosis leads to major reproductive pathologies such as spontaneous abortions and sterility in livestock. Transmission to humans most commonly occurs through ingestion of contaminated animal products, such as unpasteurized milk. Human brucellosis results in undulant fever. Brucella abortus is a facultative, intracellular, zoonotic pathogen that resides inside macrophages during infection. This is a specialized niche where B. abortus encounters various stresses, such as acidic conditions and reactive oxygen species, as it navigates through the macrophage. In order to survive this harsh environment, B. abortus must sense its environment and adapt its genetic composition

to overcome these stressors. B. abortus utilizes post-transcriptional regulation through the use of small regulatory RNAs (sRNAs). sRNAs bind to messenger RNA (mRNA) targets via complementary base pairing; however, this is usually imperfect and requires a chaperone called Hfq. sRNAs can bind to mRNA and lead to rapid changes in gene expression by influencing translation initiation through the availability of the ribosomal binding site or affecting RNA stability through degradation with RNases. B. abortus encodes various sRNA molecules. While some have been linked to virulence, few have been characterized. In this study, a new sRNA, VcrS has been identified, and following genetic manipulation, a vcrS knockout strain was created. This mutant strain was used to infect both naïve murine macrophages,

as well as BALB/c mice. Both virulence studies exhibited significantly decreased bacterial recovery of the sRNA mutant strain compared to the wildtype strain. Quantitative proteomics revealed that one protein, BAB1_1454 is 30-fold over-produced when vcrS is knocked out compared to wildtype. This protein encodes MurF, which is directly involved in peptidoglycan synthesis. Ongoing work is focusing on evaluating cell wall composition in the vcrS knockout strain and assessing the regulatory mechanism of VcrS.

This study was funded in part by the VCOM One Health Seed Grant.

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