Biology subjects

Hendrixson, D. R.

Publications and source records attributed to Hendrixson, D. R..

6 recordsLinked to original sources

bioRxiv2025

FliO is an evolutionarily conserved yet diversified core component of the bacterial flagellar type III secretion system

The bacterial flagellum is a complex nanomachine essential for motility, environmental sensing, and host colonization. While many of its core components have been well characterized, the relevance of proteins such as FliO, which are inconsistently annotated and poorly conserved at the sequence level, has remained ambiguous in their evolutionary and functional status. Here, we present a comprehensive phylogenomic and structural analysis of FliO across >30,000 representative genomes spanning >100 bacterial phyla. Additionally, during this analysis, we found that approximately 40% of bacterial genomes contain flagellar genes - significantly fewer than previously reported. Using a custom pipeline combining low-threshold HMM searches, operon context analysis, and structural information, we demonstrate that FliO is present in [~]95% of genomes encoding the core flagellar components FliP, FliQ, and FliR. This suggests that FliO is a nearly ubiquitous and ancestral core component of the flagellar type III secretion system (fT3SS). FliO exhibits considerable structural diversity, including lineage-specific acquisitions of LysM and AMIN domains. We identify FliO homologs not only in canonical flagellar systems but also in some virulence-associated T3SS and even some non-flagellated organisms, suggesting functional repurposing and highlighting its functional plasticity. Functional studies in Campylobacter jejuni reveal that FliO and its AMIN domain are critical for efficient bipolar flagellation, membrane stability of the export gate component FlhB, and colonization of the host. These findings establish FliO as a core, yet evolutionarily dynamic, component of flagella and provide new insights into the evolution and diversification of bacterial secretion systems.

microbiology↗

bioRxiv2025

Functional genomics of Campylobacter-host interactions in an intestinal tissue model reveals a small lipoprotein essential for flagellar assembly

Campylobacter jejuni is the leading cause of bacterial food-poisoning, with motility being an essential virulence factor. While many aspects of flagella biogenesis have been studied, a complete picture of the components and regulators of these multi-protein machines is still missing. To identify genes crucial for C. jejuni pathogenesis and motility, we applied transposon sequencing in a humanized tissue model. This revealed three largely uncharacterized genes (pflC , pflD , pflE ) as essential for motility. While PflC/D turned out to be components of the flagellar motor disk structures, PflE is a small protein of only 57 aa. PflE strikingly affects motor biogenesis, with complete loss of motor structures upon its deletion. We demonstrate PflE is a lipoprotein and supports outer-membrane localization of the main basal-disk protein FlgP. With motility as a critical Campylobacter virulence factor, our work demonstrates that deletion of a small protein can bring a bacterial pathogen to a halt.

microbiology↗

bioRxiv2024

Gene regulation of infection-associated L-tartrate metabolism in Salmonella enterica serovar Typhimurium

Enteric pathogens such as Salmonella enterica serovar Typhimurium experience spatial and temporal changes to the metabolic landscape throughout infection. Host reactive oxygen and nitrogen species non-enzymatically convert monosaccharides to alpha hydroxy acids, including L-tartrate. Salmonella utilizes L-tartrate early during infection to support fumarate respiration, while L-tartrate utilization ceases at later time points due to the increased availability of exogenous electron acceptors such as tetrathionate, nitrate, and oxygen. It remains unknown how Salmonella regulates its gene expression to metabolically adapt to changing nutritional environments. Here, we investigated how the transcriptional regulation for L-tartrate metabolism in Salmonella is influenced by infection-relevant cues. L-tartrate induces the transcription of ttdBAU, genes involved in L-tartrate utilization. L-tartrate metabolism is negatively regulated by two previously uncharacterized transcriptional regulators TtdV (STM3357) and TtdW (STM3358), and both TtdV and TtdW are required for sensing of L-tartrate. The electron acceptors nitrate, tetrathionate, and oxygen repress ttdBAU transcription via the two-component system ArcAB. Furthermore, regulation of L-tartrate metabolism is required for optimal fitness in a mouse model of Salmonella-induced colitis. TtdV, TtdW, and ArcAB allow for the integration of two cues, substrate availability and availability of exogenous electron acceptors, to control L-tartrate metabolism. Our findings provide novel insights into how Salmonella prioritizes utilization of different electron acceptors for respiration as it experiences transitional nutrient availability throughout infection. IMPORTANCEBacterial pathogens must adapt their gene expression profiles to cope with diverse environments encountered during infection. This coordinated process is carried out by the integration of cues that the pathogen senses to fine-tune gene expression in a spatiotemporal manner. Many studies have elucidated the regulatory mechanisms on how Salmonella sense metabolites in the gut to activate or repress its virulence program, however our understanding of how Salmonella coordinates its gene expression to maximize the utilization of carbon and energy sources found in transitional nutrient niches is not well understood. In this study, we discovered how Salmonella integrates two infection-relevant cues, substrate availability and exogenous electron acceptors, to control L-tartrate metabolism. From our experiments, we propose a model for how L-tartrate metabolism is regulated in response to different metabolic cues in addition to characterizing two previously unknown transcriptional regulators. This study expands our understanding of how microbes combine metabolic cues to enhance fitness during infection.

microbiology↗

bioRxiv2023

Evolution of a large periplasmic disk in Campylobacterota flagella facilitated efficient motility alongside autoagglutination

Although the bacterial flagella of Escherichia coli and Salmonella enterica are distributed around the cell body, many bacteria instead place their flagella at their poles. This widespread form of flagellar motility is relatively poorly understood, but these polar flagellar motors invariably feature periplasmic disk structures of unknown function. The flagellar motor of Campylobacter jejuni features a 100 nm-wide periplasmic disk associated with scaffolding a wider ring of motor proteins to increase torque, but the size of this disk is excessive for a role solely in scaffolding motor proteins. Here we show that the basal disk in C. jejuni is a flange that braces the motor during disentanglement of the flagellar filament from interactions with the cell body and other filaments, interactions that are otherwise important for host colonization. Our results reveal an entanglement of co-dependencies in the evolution of flagellar motor structure and cell plan in the Campylobacterota (previously epsilonproteobacteria). Note that this manuscript has a sibling manuscript titled Molecular model of a bacterial flagellar motor in situ reveals a "parts-list" of protein adaptations to increase torque that describes a molecular model of the Campylobacter jejuni flagellar motor discussed here.

microbiology↗

bioRxiv2023

Molecular model of a bacterial flagellar motor in situ reveals a "parts-list" of protein adaptations to increase torque

One hurdle to understanding how molecular machines work, and how they evolve, is our inability to see their structures in situ. Here we describe a minicell system that enables in situ cryogenic electron microscopy imaging and single particle analysis to investigate the structure of an iconic molecular machine, the bacterial flagellar motor, which spins a helical propeller for propulsion. We determine the structure of the high-torque Campylobacter jejuni motor in situ, including the subnanometre-resolution structure of the periplasmic scaffold, an adaptation essential to high torque. Our structure enables identification of new proteins, and interpretation with molecular models highlights origins of new components, reveals modifications of the conserved motor core, and explain how these structures both template a wider ring of motor proteins, and buttress the motor during swimming reversals. We also acquire insights into universal principles of flagellar torque generation. This approach is broadly applicable to other membrane-residing bacterial molecular machines complexes.

molecular biology↗

bioRxiv2019

Campylobacter jejuni motility integrates specialized cell shape, flagellar filament, and motor, to coordinate action of its opposed flagella in viscous media

Campylobacter jejuni rotates a flagellum at each pole to swim through the viscous mucosa of its hosts gastrointestinal tracts. Despite their importance for host colonization, however, how C. jejuni coordinates rotation of these two opposing flagella is unclear. As well as their polar placement, C. jejunis flagella deviate from the Enterobacteriaceael norm in other ways: their flagellar motors produce much higher torque and their flagellar filament is made of two different zones of two different flagellins. To understand how C. jejunis opposed motors coordinate, and what contribution these factors play in C. jejuni motility, we developed strains with flagella that could be fluorescently labeled, and observed them by high-speed video microscopy. We found that C. jejuni coordinates its dual flagella by wrapping the leading filament around the cell body during swimming in high-viscosity media and that its differentiated flagellar filament has evolved to facilitate this wrapped-mode swimming. Unexpectedly, C. jejunis helical body is important for facile unwrapping of the flagellar filament from the cell body during switching of swimming trajectory. Our findings demonstrate how multiple facets of C. jejunis flagella and cell plan have co-evolved for optimal motility in high-viscosity environments.

microbiology↗