Biology subjects

Kaval, K. G.

Publications and source records attributed to Kaval, K. G..

4 recordsLinked to original sources

bioRxiv2023

Role of Ethanolamine Utilization and Bacterial Microcompartment Formation in Listeria monocytogenes Intracellular Infection

Ethanolamine (EA) affects the colonization and pathogenicity of certain human bacterial pathogens in the gastrointestinal tract. However, EA can also affect the intracellular survival and replication of host-cell invasive bacteria such as Listeria monocytogenes (LMO) and Salmonella enterica serovar Typhimurium (S. Typhimurium). The EA utilization (eut) genes can be categorized as regulatory, enzymatic, or structural, and previous work in LMO showed that loss of genes encoding functions for the enzymatic breakdown of EA inhibited LMO intracellular replication. In this work, we sought to further characterize the role of EA utilization during LMO infection of host cells. Unlike what was previously observed for S. Typhimurium, in LMO, an EA regulator mutant ({Delta}eutV) was equally deficient in intracellular replication compared to an EA metabolism mutant ({Delta}eutB), and this was consistent across Caco-2, RAW 264.7 and THP-1 cell lines. The structural genes encode proteins that self-assemble into bacterial microcompartments (BMCs) that encase the enzymes necessary for EA metabolism. For the first time, native EUT BMCs were fluorescently tagged, and EUT BMC formation was observed in vitro, and in vivo. Interestingly, BMC formation was observed in bacteria infecting Caco-2 cells, but not the macrophage cell lines. Finally, the cellular immune response of Caco-2 cells to infection with eut mutants was examined, and it was discovered that{Delta} eutB and{Delta} eutV mutants similarly elevated the expression of inflammatory cytokines. In conclusion, EA sensing and utilization during LMO intracellular infection are important for optimal LMO replication and immune evasion but are not always concomitant with BMC formation.

microbiology↗

bioRxiv2022

Enzymatic Specificity of Conserved Rho GTPase Deamidases Promotes Invasion of Vibrio parahaemolyticus at the Expense of Infection

Vibrio parahaemolyticus is among the leading causes of bacterial seafood-borne acute gastroenteritis. Like many intracellular pathogens, V. parahaemolyticus invades host cells during infection by deamidating host small Rho GTPases. The Rho GTPase deamidating activity of VopC, a type three secretion system (T3SS) translocated effector, drives V. parahaemolyticus invasion. The intracellular pathogen uropathogenic Escherichia coli (UPEC) invades host cells by secreting a VopC homolog, the secreted toxin cytotoxic necrotizing factor one (CNF1). Because of the homology between VopC and CNF1, we hypothesized topical application of CNF1 during V. parahaemolyticus infection could supplement VopC activity. Here, we demonstrate that CNF1 improves the efficiency of V. parahaemolyticus invasion, a bottleneck in V. parahaemolyticus infection, across a range of doses. CNF1 increases V. parahaemolyticus invasion independent of both VopC and the T3SS altogether, but leaves a disproportionate fraction of intracellular bacteria unable to escape the endosome and complete their infection cycle. This phenomenon holds true in the presence or absence of VopC, but is particularly pronounced in the absence of a T3SS. The native VopC, by contrast, promotes a far less efficient invasion, but permits the majority of internalized bacteria to escape the endosome and complete their infection cycle. These studies highlight the significance of enzymatic specificity during infection, as virulence factors (VopC and CNF1 in this instance) with similarities in function (bacterial uptake), catalytic activity (deamidation), and substrates (Rho GTPases) are not sufficiently interchangeable for mediating a successful invasion for neighboring bacterial pathogens. IMPORTANCEMany species of intracellular bacterial pathogens target host small Rho-GTPases to initiate invasion, including the human pathogens Vibrio parahaemolyticus and uropathogenic Eschericia coli (UPEC). The type three secretion system (T3SS) effector VopC of V. parahaemolyticus promotes invasion through the deamidation of Rac1 and CDC42 in the host, whereas the secreted toxin cytotoxic necrotizing factor one (CNF1) drives UPECs internalization through the deamidation of Rac1, CDC42, and RhoA. Despite these similarities in the catalytic activity of CNF1 and VopC, we observed the two enzymes were not interchangeable. Although CNF1 increased V. parahaemolyticus endosomal invasion, most intracellular V. parahaemolyticus aborted their infection cycle and remained trapped in endosomes. Our findings illuminate how the precise biochemical fine-tuning of T3SS effectors is essential for efficacious pathogenesis. They moreover pave the way for future investigations into the biochemical mechanisms underpinning V. parahaemolyticus endosomal escape, and more broadly, the regulation of successful pathogenesis.

microbiology↗

bioRxiv2022

Transertion is used for localized expression and assembly of Vibrio parahaemolyticus T3SS2

Using environmental cues, bacteria commit to the assembly of transmembrane complexes such as the type III secretion system 2 (T3SS2), a membrane-bound, syringe-like secretory apparatus used during infection to inject host cells with virulence factors. Here we report Vibrio parahaemolyticus uses transertion, localized transcription, translation, and membrane insertion, to assemble its T3SS2. Upon binding bile acids, the membrane bound receptor and transcription factor VtrA/VtrC captures the T3SS2 pathogenicity island at the inner membrane. Activated VtrA/VtrC induces production of VtrB, the membrane bound master T3SS2 transcriptional regulator. VtrB then induces the membrane-proximal T3SS2 genes to undergo transertion for assembly of the membrane inserted secretion machinery. Transertion is a process that can be used for the efficient assembly of membrane-bound molecular complexes in response to extracellular signals. One-Sentence SummaryLocalized transcription, translation, and membrane insertion of multi-protein complexes in bacteria in response to host cues.

microbiology↗

bioRxiv2020

Cardiac Microlesions Form During Severe Bacteremic Enterococcus faecalis Infection

Enterococcus faecalis is a significant cause of hospital-acquired bacteremia. Herein, the discovery is reported that cardiac microlesions form during severe bacteremic E. faecalis infection in mice. The cardiac microlesions were identical in appearance to those formed by Streptococcus pneumoniae during invasive pneumococcal disease (IPD). However, E. faecalis does not encode the virulence determinants implicated in pneumococcal microlesion formation. Rather, disulfide bond forming protein DsbA was found to be required for E. faecalis virulence in a C. elegans model and was necessary for efficient cardiac microlesion formation. Furthermore, E. faecalis promoted cardiomyocyte apoptotic and necroptotic cell death at sites of microlesion formation. Additionally, loss of DsbA caused an increase in pro-inflammatory cytokines unlike the wild-type strain, which suppressed the immune response. In conclusion, we establish that E. faecalis is capable of forming cardiac microlesions and identify features of both the bacterium and the host response that are mechanistically involved. SUMMARYThis work presents the observation of cardiac microlesion formation during severe blood stream infection with Enterococcus faecalis in mice. Moreover, we identify the contribution of a novel enterococcal virulence determinant in modulating microlesion formation and the host immune response.

microbiology↗