Campylobacter jejuni genes Cj1492c and Cj1507c are involved in host cell adhesion and invasion

Molecular structures mediating adhesion of Campylobacter jejuni to abiotic and biotic surfaces

Microaerophilic, Gram-negative Campylobacter jejuni is the causative agent of campylobacteriosis, the most common bacterial gastrointestinal infection worldwide. Adhesion is the crucial first step in both infection or interaction with the host and biofilm formation, and is a critical factor for bacterial persistence. Here we describe the proteins and other surface structures that promote adhesion to various surfaces, including abiotic surfaces, microorganisms, and animal and human hosts. In addition, we provide insight into the distribution of adhesion proteins among strains from different ecological niches and highlight unexplored proteins involved in C. jejuni adhesion. Protein-protein, protein-glycan, and glycan-glycan interactions are involved in C. jejuni adhesion, with different factors contributing to adhesion to varying degrees under different circumstances. As adhesion is essential for survival and persistence, it represents an interesting target for C. jejuni control. Knowledge of the adhesion process is incomplete, as different molecular and functional aspects have been studied for different structures involved in adhesion. Therefore, it is important to strive for an integration of different approaches to obtain a clearer picture of the adhesion process on different surfaces and to consider the involvement of proteins, glycoconjugates, and polysaccharides and their cooperation.

Natural Antimicrobial Mixtures Disrupt Attachment and Survival of E. coli and C. jejuni to Non-Organic and Organic Surfaces

The contact and adherence of bacteria to various surfaces has significant consequences on biofilm formation through changes in bacterial surface structures or gene expression with potential ramifications on plant and animal health. Therefore, this study aimed to investigate the effect of organic acid-based mixtures (Ac) on the ability Campylobacter jejuni and Escherichia coli to attach and form biofilm on various surfaces, including plastic, chicken carcass skins, straw bedding, and eggshells. Moreover, we aimed to explore the effect of Ac on the expression of E. coli (luxS, fimC, csgD) and C. jejuni (luxS, flaA, flaB) bacterial genes involved in the attachment and biofilm formation via changes in bacterial surface polysaccharidic structures. Our results show that Ac had a significant effect on the expression of these genes in bacteria either attached to these surfaces or in planktonic cells. Moreover, the significant decrease in bacterial adhesion was coupled with structural changes in bacterial surface polysaccharide profiles, impacting their adhesion and biofilm-forming ability. Essentially, our findings accentuate the potential of natural antimicrobials, such as Ac, in reducing bacterial attachment and biofilm formation across various environments, suggesting promising potential applications in sectors like poultry production and healthcare.

miR-125a-5p regulates the sialyltransferase ST3GAL1 in murine model of human intestinal campylobacteriosis

BACKGROUND

Zoonotic microorganisms are increasingly impacting human health worldwide. Due to the development of the global population, humans and animals live in shared and progressively crowded ecosystems, which enhances the risk of zoonoses. Although Campylobacter species are among the most important bacterial zoonotic agents worldwide, the molecular mechanisms of many host and pathogen factors involved in colonisation and infection are poorly understood. Campylobacter jejuni colonises the crypts of the human colon and causes acute inflammatory processes. The mucus and associated proteins play a central host-protective role in this process. The aim of this study was to explore the regulation of specific glycosyltransferase genes relevant to differential mucin-type O-glycosylation that could influence host colonisation and infection by C. jejuni.

RESULTS

Since microRNAs are known to be important regulators of the mammalian host cell response to bacterial infections, we focussed on the role of miR-125a-5p in C. jejuni infection. Combining in vitro and in vivo approaches, we show that miR-125a-5p regulates the expression of the sialyltransferase ST3GAL1 in an infection-dependent manner. The protein ST3GAL1 shows markedly increased intestinal levels in infected mice, with enhanced distribution in the mucosal epithelial layer in contrast to naïve mice.

CONCLUSION

From our previous studies and the data presented here, we conclude that miR-125a-5p and the previously reported miR-615-3p are involved in regulating the glycosylation patterns of relevant host cell response proteins during C. jejuni infection. The miRNA-dependent modulation of mucin-type O-glycosylation could be part of the mucosal immune response, but also a pathogen-driven modification that allows colonisation and infection of the mammalian host.

Butyrate decreases Campylobacter jejuni motility and biofilm partially through influence on LysR expression

The food pathogen Campylobacter jejuni both colonizes the lower intestines of poultry and infects the lower intestines of humans. The lower intestines of both poultry and humans are also home to a wide range of commensal organisms which compete with an organism like C. jejuni for space and resources. The commensal organisms are believed to protect humans against infection by pathogens of the digestive tract like C. jejuni. The short chain fatty acid (SCFA) butyrate is a metabolite commonly produced by commensal organisms within both the poultry and human digestive tract. We investigated the effect that physiologically relevant concentrations of butyrate have on C. jejuni under in vitro conditions. Butyrate at concentrations of 5 and 20 mM negatively impacted C. jejuni motility and biofilm formation. These two traits are believed important for C. jejuni's ability to infect the lower intestines of humans. Additionally, 20 mM butyrate concentrations were observed to influence the expression of a range of different Campylobacter proteins. Constitutive expression of one of these proteins, LysR, within a C. jejuni strain partially lessened the negative influence butyrate had on the bacteria's motility.

LysR-type transcriptional regulators: state of the art

The LysR-type transcriptional regulators (LTTRs) are DNA-binding proteins present in bacteria, archaea, and in algae. Knowledge about their distribution, abundance, evolution, structural organization, transcriptional regulation, fundamental roles in free life, pathogenesis, and bacteria-plant interaction has been generated. This review focuses on these aspects and provides a current picture of LTTR biology.

The glycosyltransferase ST3GAL2 is regulated by miR-615-3p in the intestinal tract of Campylobacter jejuni infected mice

Background

Campylobacter jejuni (C. jejuni) infections are of increasing importance worldwide. As a typical mucosal pathogen, the interaction of C. jejuni with mucins is a prominent step in the colonisation of mucosal surfaces. Despite recent advances in understanding the interaction between bacterial pathogens and host mucins, the mechanisms of mucin glycosylation during intestinal C. jejuni infection remain largely unclear. This prompted us to identify relevant regulatory networks that are concerted by miRNAs and could play a role in the mucin modification and interaction.

Results

We firstly used a human intestinal in vitro model, in which we observed altered transcription of MUC2 and TFF3 upon C. jejuni NCTC 11168 infection. Using a combined approach consisting of in silico analysis together with in vitro expression analysis, we identified the conserved miRNAs miR-125a-5p and miR-615-3p associated with MUC2 and TFF3. Further pathway analyses showed that both miRNAs appear to regulate glycosyltransferases, which are related to the KEGG pathway ‘Mucin type O-glycan biosynthesis’. To validate the proposed interactions, we applied an in vivo approach utilising a well-established secondary abiotic IL-10^−/− mouse model for infection with C. jejuni 81-176. In colonic tissue samples, we confirmed infection-dependent aberrant transcription of MUC2 and TFF3. Moreover, two predicted glycosyltransferases, the sialyltransferases ST3GAL1 and ST3GAL2, exhibited inversely correlated transcriptional levels compared to the expression of the identified miRNAs miR-125a-5p and miR-615-3p, respectively. In this study, we mainly focused on the interaction between miR-615-3p and ST3GAL2 and were able to demonstrate their molecular interaction using luciferase reporter assays and RNAi. Detection of ST3GAL2 in murine colonic tissue by immunofluorescence demonstrated reduced intensity after C. jejuni 81-176 infection and was thus consistent with the observations made above.

Conclusions

We report here for the first time the regulation of glycosyltransferases by miRNAs during murine infection with C. jejuni 81-176. Our data suggest that mucin type O-glycan biosynthesis is concerted by the interplay of miRNAs and glycosyltransferases, which could determine the shape of intestinal glycosylated proteins during infection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00437-1.

Campylobacter Virulence Factors and Molecular Host-Pathogen Interactions

Campylobacter jejuni and Campylobacter coli can be frequently isolated from poultry and poultry-derived products, and in combination these two species cause a large portion of human bacterial gastroenteritis cases. While birds are typically colonized by these Campylobacter species without clinical symptoms, in humans they cause (foodborne) infections at high frequencies, estimated to cost billions of dollars worldwide every year. The clinical outcome of Campylobacter infections comprises malaise, diarrhea, abdominal pain and fever. Symptoms may continue for up to two weeks and are generally self-limiting, though occasionally the disease can be more severe or result in post-infection sequelae. The virulence properties of these pathogens have been best-characterized for C. jejuni, and their actions are reviewed here. Various virulence-associated bacterial determinants include the flagellum, numerous flagellar secreted factors, protein adhesins, cytolethal distending toxin (CDT), lipooligosaccharide (LOS), serine protease HtrA and others. These factors are involved in several pathogenicity-linked properties that can be divided into bacterial chemotaxis, motility, attachment, invasion, survival, cellular transmigration and spread to deeper tissue. All of these steps require intimate interactions between bacteria and host cells (including immune cells), enabled by the collection of bacterial and host factors that have already been identified. The assortment of pathogenicity-associated factors now recognized for C. jejuni, their function and the proposed host cell factors that are involved in crucial steps leading to disease are discussed in detail.

Metal homeostasis in pathogenic Epsilonproteobacteria: mechanisms of acquisition, efflux, and regulation

Epsilonproteobacteria are a diverse class of eubacteria within the Proteobacteria phylum that includes environmental sulfur-reducing bacteria and the human pathogens, Campylobacter jejuni and Helicobacter pylori. These pathogens infect and proliferate within the gastrointestinal tracts of multiple animal hosts, including humans, and cause a variety of disease outcomes. While infection of these hosts provides nutrients for the pathogenic Epsilonproteobacteria, many hosts have evolved a variety of strategies to either sequester metals from the invading pathogen or exploit the toxicity of metals and drive their accumulation as an antimicrobial strategy. As a result, C. jejuni and H. pylori have developed mechanisms to sense changes in metal availability and regulate their physiology in order to respond to either metal limitation or accumulation. In this review, we will discuss the challenges of metal availability at the host-pathogen interface during infection with C. jejuni and H. pylori and describe what is currently known about how these organisms alter their gene expression and/or deploy bacterial virulence factors in response to these environments.