Biology subjects

Lancaster, R.

Publications and source records attributed to Lancaster, R..

5 recordsLinked to original sources

bioRxiv2025

Klebsiella pneumoniae remodels its Kdo2-lipid A in a TLR4-dependent manner to adapt to the macrophage intracellular environment

Pathogen adaptations to the intracellular macrophage environment remain poorly understood. We performed a high-resolution structural analysis of the lipid A purified from intracellular Klebsiella pneumoniae (KP). In both mouse and human macrophages, KP produces hexa- and hepta-acylated lipid A species modified with palmitate and 2-hydroxylated. LpxL1, PagP, and LpxO enzymes govern the intracellular lipid A in a PhoPQ-dependent manner triggered by the acidic pH of the KP-containing vacuole (KCV). Absence of LpxO and PagP lipid A modifications impairs intracellular survival and heightens NF-{kappa}B and IRF3-mediated inflammation, though KCV maturation remains unaffected. Instead, these modifications fortify the bacterial membrane. Absence of TLR4-TRAM-TRIF signalling increases KCV pH, impairing the production of the intracellular lipid A. KP intracellular survival is reduced in tlr4-/- macrophages, highlighting the critical role of this signalling pathway in KP immune evasion and how the pathogen has evolved to rely on innate immune system cues for virulence.

microbiology↗

bioRxiv2025

Interrogating the genus Yersinia to define the rules of lipopolysaccharide lipid A structure associated with pathogenicity.

Pathogen recognition by the immune system relies on germline-encoded pathogen recognition receptors which identify conserved pathogen-associated molecular patterns (PAMPs) such as the lipid A section of the lipopolysaccharide (LPS). The assumption that pathogens and mammalian-associated bacteria remodel their lipid A PAMP because of host-microbe co-evolution is a long held-belief of microbial pathogenesis. We set out to test this fundamental principle by interrogating a Gram-negative genus presenting evidence of evolutionary events linked to the acquisition of essential virulence traits, resulting in pathogenic and non-pathogenic species. The genus Yersinia fulfil these requirements; the acquisition of the pYV virulence plasmid is one of the evolutionary events associated with virulence. At 37{degrees}C, only pathogenic Yersinia switch to deacylated lipid A, a modification that diminishes TLR4/MD-2 recognition and reduces inflammation. An engineered chimeric pathogenic Yersinia strain expressing the non-pathogenic lipid A profile efficiently engages with TLR4, demonstrating it is sufficient to switch the acylation pattern to modify the recognition by TLR4 and subsequent activation of inflammation. The lipid As of pathogenic and non-pathogenic species are modified with aminoarabinose and palmitate; therefore, only the reduced acylation of the lipid A PAMP is a trait associated with virulence. The decorations of lipid A do not alter TLR4 engagement but confer resistance to antimicrobial peptides. The chimeric pathogenic Yersinia strain expressing the non-pathogenic lipid A profile allows to ascertain whether the switch in the lipid A PAMP affects virulence. This strain showed enhanced motility due to an upregulation of the flhDC master regulator, and impaired cellular invasion through downregulation of rovA, a key invasion regulator. The expression and function of pYV-encoded virulence factors Yops and YadA were not affected. Nonetheless, the chimeric strain was attenuated in vivo, demonstrating that virulence factors cannot overcome a switch in the lipid A PAMP associated with pathogenicity.

microbiology↗

bioRxiv2025

Klebsiella pneumoniae disrupts vasodilation by targeting eNOS post translational modifications via the type VI secretion system and the capsule polysaccharide

Vasodilation is a crucial protective response to inflammation and infection. Endothelial cells control vasodilation through the bioavailability of eNOS-produced nitric oxide (NO), and the generation of endothelium-dependent hyperpolarization (EDH). Here, we demonstrate that Klebsiella pneumoniae, one of the most prevalent blood stream infection pathogens, inhibits agonist-induced vasodilation by blunting the NO-dependent pathway and attenuating the EDH pathway. The type VI secretion system (T6SS) effector VgrG4 licences the kinase PKC{beta} in an NLRX1-controlled mitochondria reactive oxygen species (mtROS)-dependent manner to phosphorylate the eNOS inhibitory site Thr495, effectively dampening eNOS activity. The capsule polysaccharide, on the other hand, limits the phosphorylation of the eNOS activation site Ser1177 by inducing the phosphatase PP2Ac upon activation of an EGF receptor-dependent pathway. VgrG4-induced mtROS attenuates the EDH pathway. Overall, this work reveals a new anti-host activity of the T6SS and illustrates how pathogens can control vascular biology by targeting eNOS post translational modifications.

microbiology↗

bioRxiv2021

In vivo single cell transcriptomics reveals Klebsiella pneumoniae rewiring of lung macrophages to promote infection

The strategies deployed by antibiotic resistant bacteria to counteract host defences are poorly understood. Here, we elucidate a novel host-pathogen interaction that results in the control of lung macrophage polarisation by the human pathogen Klebsiella pneumoniae. We identify interstitial macrophages (IMs) as the main population of lung macrophages associated with Klebsiella. Single cell transcriptomics and trajectory analysis of cells uncover that type I IFN and IL10 signalling, and macrophage polarization are characteristic of infected IMs, whereas Toll-like receptor (TLR) and Nod-like receptor signalling are features of infected alveolar macrophages. Klebsiella-induced macrophage polarization is a singular M2-type we termed M(Kp). To rewire macrophages towards M(Kp), K. pneumoniae hijacks a hitherto unknown TLR-type I IFN-IL10-STAT6 innate axis. Absence of STAT6 limits the intracellular survival of Klebsiella whereas the inhibition of STAT6 facilitates the clearance of the pathogen in vivo. Glycolysis characterises M(Kp) metabolism, and inhibition of glycolysis results in clearance of intracellular Klebsiella. We demonstrate the capsule polysaccharide is the Klebsiella factor governing M(Kp). Klebsiella also skews human macrophage polarization towards M(Kp) in a type I IFN-IL10-STAT6-dependent manner. Altogether, our work demonstrates that Klebsiella induction of M(Kp) represents a hitherto unknown strategy to overcome host restriction during pneumonia.

microbiology↗

bioRxiv2021

Post-Insemination Selection Dominates Pre-Insemination Selection in Driving Rapid Evolution of Male Competitive Ability

Sexual reproduction is a complex process that contributes to differences between the sexes and divergence between species. From a males perspective, sexual selection can optimize reproductive success by acting on the variance in mating success (pre-insemination selection) as well as the variance in fertilization success (post-insemination selection). The balance between pre- and post-insemination selection has not yet been investigated using a strong hypothesis-testing framework that directly quantifies the effects of post-insemination selection on the evolution of reproductive success. Here we use experimental evolution of a uniquely engineered genetic system that allows sperm production to be turned off and on in obligate male-female populations of Caenorhabditis elegans. We show that enhanced post-insemination competition increases the efficacy of selection and surpasses pre-insemination sexual selection in driving a polygenic response in male reproductive success. We find that after 30 generations post-insemination selection increased male reproductive success by an average of 5- to 7-fold. Contrary to expectation, enhanced pre-insemination competition hindered selection and slowed the rate of evolution. Furthermore, we found that post-insemination selection resulted in a strong polygenic response at the whole-genome level. Our results demonstrate that post-insemination sexual selection plays a critical role in the rapid optimization of male reproductive fitness. Therefore, explicit consideration should be given to post-insemination dynamics when considering the population effects of sexual selection.

evolutionary biology↗