Stages Of Bacterial Infection Research Articles

In-depth analysis of isochorismate synthase-derived metabolism in plant immunity: Identification of meta-substituted benzoates and salicyloyl-malate

Isochorismate-derived metabolism enables biosynthesis of the plant defence hormone salicylic acid (SA) and its derivatives. In Arabidopsis thaliana, the stress-induced accumulation of SA depends on ISOCHORISMATE SYNTHASE1 (ICS1), and also requires the presumed isochorismate transporter ENHANCED DISEASE SUSCEPTIBILITY5 (EDS5) and the GH3 enzyme avrPphB SUSCEPTIBLE3 (PBS3). By comparative metabolite and structural analyses, we identified several hitherto unreported ICS1- and EDS5-dependent, biotic stress-inducible Arabidopsis metabolites. These involve meta-substituted SA derivatives (5-formyl-SA, 5-carboxy-SA, 5-carboxymethyl-SA), their benzoic acid (BA) analogues (3-formyl-BA, 3-carboxy-BA, 3-carboxymethyl-BA) and, besides the previously detected salicyloyl-aspartate (SA-Asp), the ester conjugate salicyloyl-malate (SA-Mal). SA functions as a biosynthetic precursor for SA-Mal and SA-Asp, but not for the meta-substituted SA- and BA-derivatives, which accumulate to moderate levels at later stages of bacterial infection. Interestingly, Arabidopsis leaves possess oxidising activity to effectively convert meta-formyl- into meta-carboxy-SA/BAs. In contrast to SA, exogenously applied meta-substituted SA/BA-derivatives and SA-Mal exert moderate impact on plant immunity and defence-related gene expression. While the isochorismate-derived metabolites are negatively regulated by the SA receptor NON-EXPRESSOR OF PR GENES1, SA conjugates (SA-Mal, SA-Asp, SA-glucose conjugates) and meta-substituted SA/BA-derivatives are oppositely affected by PBS3. Notably, our data indicate a PBS3-independent path to isochorismate-derived SA at later stages of bacterial infection, which does not considerably impact immune-related characteristics. Moreover, our results argue against a previously proposed role of EDS5 in the biosynthesis of the immune signal N-hydroxypipecolic acid and associated transport processes. We propose a significantly extended biochemical scheme of plant isochorismate metabolism that involves an alternative generation mode for benzoate- and salicylate-derivatives.

Dynamic surface adapts to multiple service stages by orchestrating responsive polymers and functional peptides

Control over the implant surface functions is highly desirable to enhance tissue healing outcomes but has remained unexplored to adapt to the different service stages. In the present study, we develop a smart titanium surface by orchestrating thermoresponsive polymer and antimicrobial peptide to enable dynamic adaptation to the implantation stage, normal physiological stage and bacterial infection stage. The optimized surface inhibited bacterial adhesion and biofilm formation during surgical implantation, while promoted osteogenesis in the physiological stage. The further temperature increase driven by bacterial infection induced polymer chain collapse to expose antimicrobial peptides by rupturing bacterial membranes, as well as protect the adhered cells from the hostile environment of infection and abnormal temperature. The engineered surface could inhibit infection and promote tissue healing in rabbit subcutaneous and bone defect infection models. This strategy enables the possibility to create a versatile surface platform to balance bacteria/cell-biomaterial interactions at different service stages of implants that has not been achieved before.

Arabidopsis Topless-related 1 mitigates physiological damage and growth penalties of induced immunity.

Transcriptional corepressors of the Topless (TPL) family regulate plant hormone and immunity signaling. The lack of a genome-wide profile of their chromatin associations limits understanding of the TPL family roles in transcriptional regulation. Chromatin immunoprecipitation with sequencing (ChIP-Seq) was performed on Arabidopsis thaliana lines expressing GFP-tagged Topless-related 1 (TPR1-GFP) with and without constitutive immunity via Enhanced Disease Susceptibility 1 (EDS1). RNA-Seq profiling of the TPR1-GFP lines and pathogen-infected tpl/tpr mutants, combined with measuring immunity, growth, and physiological parameters was employed to investigate TPL/TPR roles in immunity and defense homeostasis. TPR1 was enriched at promoter regions of c. 1400 genes and c. 10% of the detected binding required EDS1 immunity signaling. In a tpr1 tpl tpr4 (t3) mutant, resistance to bacteria was slightly compromised, and defense-related transcriptional reprogramming was weakly reduced or enhanced, respectively, at early (< 1 h) and late 24 h stages of bacterial infection. The t3 plants challenged with bacteria or pathogen-associated molecular pattern nlp24 displayed photosystem II dysfunctions. Also, t3 plants were hypersensitive to phytocytokine pep1 at the level of root growth inhibition. Transgenic expression of TPR1 rescued these t3 physiological defects. We propose that TPR1 and TPL family proteins function in Arabidopsis to reduce detrimental effects associated with activated transcriptional immunity.

A survey of Fusobacterium nucleatum genes modulated by host cell infection.

Here, we report comprehensive transcriptomic profiles from Fusobacterium nucleatum under conditions that mimic the first stages of bacterial infection in a highly differentiated adenocarcinoma epithelial cell line. Our transcriptomic in vitro adenocarcinoma approach allows us to measure the expression dynamics and regulation of bacterial virulence and response factors in real time, and is a novel strategy for clarifying the role of F. nucleatum infection in colorectal cancer (CRC) progression. Our data show that: (i) infection alters metabolic and functional pathways in F. nucleatum , allowing the bacterium to adapt to the host-imposed milieu; (ii) infection also stimulates the expression of genes required to help induce and promote a hypoxic and inflammatory microenvironment in the host; and (iii) F. nucleatum invasion occurs by a haematogenous route of infection. Our study identifies novel gene targets from F. nucleatum that are activated during invasion and which may aid in determining how this species invades and promotes disease within the human gastrointestinal tract. These invasion-specific genes may be useful as biomarkers for CRC progression in a host and could also assist in the development of new diagnostic tools and treatments (such as vaccines or small molecule drug targets), which will be able to combat infection and inflammation in the host while circumventing the potential problem of F. nucleatum tolerization.

How Shigella Utilizes Ca(2+) Jagged Edge Signals during Invasion of Epithelial Cells.

Shigella, the causative agent of bacillary dysentery invades intestinal epithelial cells using a type III secretion system (T3SS). Through the injection of type III effectors, Shigella manipulates the actin cytoskeleton to induce its internalization in epithelial cells. At early invasion stages, Shigella induces atypical Ca2+ responses confined at entry sites allowing local cytoskeletal remodeling for bacteria engulfment. Global Ca2+ increase in the cell triggers the opening of connexin hemichannels at the plasma membrane that releases ATP in the extracellular milieu, favoring Shigella invasion and spreading through purinergic receptor signaling. During intracellular replication, Shigella regulates inflammatory and death pathways to disseminate within the epithelium. At later stages of infection, Shigella downregulates hemichannel opening and the release of extracellular ATP to dampen inflammatory signals. To avoid premature cell death, Shigella activates cell survival by upregulating the PI3K/Akt pathway and downregulating the levels of p53. Furthermore, Shigella interferes with pro-apoptotic caspases, and orients infected cells toward a slow necrotic cell death linked to mitochondrial Ca2+ overload. In this review, we will focus on the role of Ca2+ responses and their regulation by Shigella during the different stages of bacterial infection.

Procalcitonin as a Biomarker of the Early Stage of Bacterial Infections in HIV/AIDS Patients

We observed that low concentrations of procalcitonin (PCT) in the early stages of bacterial infection among HIV/AIDS patients are not always associated with a good prognosis. Many of our patients developed sepsis despite a PCT level of &lt;0.5 ng/ml on the first days of infection. The aim of our study was to assess whether laboratory standards for PCT in patients with HIV/AIDS correlate with their clinical condition. We analyzed the concentration of PCT and other inflammatory markers in the early stages of bacterial infection among 40 HIV-infected patients and 52 AIDS patients enrolled for the study. The control group consisted of 37 healthy individuals. In comparison with PCT and WBC, PCT proved to be the most reliable in the early stages of bacterial infection. To conclude, we suggest new PCT cut-off ranges for HIV/AIDS patients with bacterial infection.

Disentangling the influence of parasite genotype, host genotype and maternal environment on different stages of bacterial infection in Daphnia magna

Individuals naturally vary in the severity of infectious disease when exposed to a parasite. Dissecting this variation into genetic and environmental components can reveal whether or not this variation depends on the host genotype, parasite genotype or a range of environmental conditions. Complicating this task, however, is that the symptoms of disease result from the combined effect of a series of events, from the initial encounter between a host and parasite, through to the activation of the host immune system and the exploitation of host resources. Here, we use the crustacean Daphnia magna and its parasite Pasteuria ramosa to show how disentangling genetic and environmental factors at different stages of infection improves our understanding of the processes shaping infectious disease. Using compatible host-parasite combinations, we experimentally exclude variation in the ability of a parasite to penetrate the host, from measures of parasite clearance, the reduction in host fecundity and the proliferation of the parasite. We show how parasite resistance consists of two components that vary in environmental sensitivity, how the maternal environment influences all measured aspects of the within-host infection process and how host-parasite interactions following the penetration of the parasite into the host have a distinct temporal component.

Early responses of rice (Oryza sativa L.) seedlings to inoculation with beneficial diazotrophic bacteria are dependent on plant and bacterial genotypes

Rice cultivars, in combination with diazotrophic bacteria, can obtain variable contributions from Biological Nitrogen Fixation (BNF). Plant genetic controls and the genotype of the bacterial strains might regulate in particular ways the plant responses during these associations. Some of this regulation is likely to occur during the first stages of bacterial infection and plant colonization, and some of the early plant responses might involve ethylene signaling, as previously reported for sugarcane. The aim of this work was to investigate whether rice early responses to inoculation with beneficial diazotrophic bacteria and the expression of ethylene receptors (ERs) by the host are dependent on plant and bacterial genotypes. Bacterial colonization, lateral root development and expression of ERs were measured in seedlings of two rice cultivars, IR42 and IAC4440, which, respectively, are known to have higher and lower BNF capabilities. Inoculation experiments were performed with two strains of bacteria: Azospirillum brasilense sp245 and Burkholderia kururiensis M130. Cultivar IR42, which has a relatively high BNF capability, was more colonized by the bacteria early after inoculation in comparison with cv. IAC 4440, which has a lower BNF capability. However, although both cultivars showed a significant increase in lateral root numbers 10 days after inoculation with A. brasilense sp245, plants inoculated with B. kururiensis M130 did not. In addition, a differential ER expression pattern was observed between IR42 and IAC4440 in response to inoculation with the two strains. The expression of ERs was higher in the more BNF-effective cultivar IR42, than in the less BNF-effective cv. IAC4440, especially when cv. IR42 was inoculated with A. brasilense sp245. Moreover, plants associated with B. kururiensis M130 showed a different ER expression profile compared to those inoculated with A. brasilense sp245, with the latter exhibiting greater increases of ER mRNA levels three days after bacterial inoculation. We have shown that two rice genotypes contrasting in their BNF capability responded differentially to early inoculation with different strains of diazotrophic bacteria. The two rice genotypes were colonized with different bacterial numbers during their early association with two strains of diazotrophic bacteria, and the two strains had different effects on the promotion of lateral root development early after inoculation. They also triggered distinct ER expression patterns in the two rice cultivars. These data thus suggest that rice ethylene responses to beneficial diazotrophic bacteria are controlled by both plant and bacterial genotypes.

In vivo natural killer and natural killer T-cell depletion affects mortality in a murine pneumococcal pneumonia sepsis model

Apart from macrophages and neutrophils, natural killer (NK) and natural killer T (NKT) cells have been found to play a role in the early stages of bacterial infection. In this study, we investigated the role of NK and NKT cells in host defense against Streptococcus pneumoniae, using a murine pneumococcal pneumonia sepsis model. Our hypothesis was that NK and NKT cells play an immune-regulatory role during sepsis and thus in vivo depletion of those cell populations may affect mortality.

The sweet connection: Solving the riddle of multiple sugar‐binding fimbrial adhesins in Escherichia coli

Proteinaceous stalks produced by Gram-negative bacteria are often used to adhere to environmental surfaces. Among them, chaperone-usher (CU) fimbriae adhesins, related to prototypical type 1 fimbriae, interact in highly specific ways with different ligands at different stages of bacterial infection or surface colonisation. Recent analyses revealed a large number of potential and often "cryptic" CU fimbriae homologues in the genome of commensal and pathogenic Escherichia coli and closely related bacteria. We propose that CU fimbriae form a yet unexplored arsenal of lectins, carbohydrate-binding proteins involved in various aspects of bacterial surface adhesion and tissue tropism. Combined efforts of molecular and structural biologists will be required to unravel the biological contribution of the bacterial lectome, however, current progress has already opened up new perspectives in the design of novel anti-infective strategies.

Effect of bacterial infection on the lipid composition of carp blood lymphocytes

The initial stage of bacterial infection is characterized by an increase in the level of total lipids and polyenoic fatty acids in membrane phospholipids of blood lymphocytes of carp (Cyprinus carpio L.). In the fish infected with aeromonads, changes in the ratios of fatty acids in phospholipids are similar for either lymphocytes, liver, or whole blood. The extent to which these changes are pronounced depends on the original physiological status of the fish.