Abstract
The virulence factor database (VFDB, http://www.mgc.ac.cn/VFs/) is dedicated to presenting a comprehensive knowledge base and a versatile analysis platform for bacterial virulence factors ...(VFs). Recent developments in sequencing technologies have led to increasing demands to analyze potential VFs within microbiome data that always consist of many different bacteria. Nevertheless, the current classification of VFs from various pathogens is based on different schemes, which create a chaotic situation and form a barrier for the easy application of the VFDB dataset for future panbacterial metagenomic analyses. Therefore, based on extensive literature mining, we recently proposed a general category of bacterial VFs in the database and reorganized the VFDB dataset accordingly. Thus, all known bacterial VFs from 32 genera of common bacterial pathogens collected in the VFDB are well grouped into 14 basal categories along with over 100 subcategories in a hierarchical architecture. The new coherent and well-defined VFDB dataset will be feasible and applicable for future panbacterial analysis in terms of virulence factors. In addition, we introduced a redesigned JavaScript-independent web interface for the VFDB website to make the database readily accessible to all users with various client settings worldwide.
The virulence factor database (VFDB, http://www.mgc.ac.cn/VFs/) is dedicated to providing up-to-date knowledge of virulence factors (VFs) of various bacterial pathogens. Since its inception the VFDB ...has served as a comprehensive repository of bacterial VFs for over a decade. The exponential growth in the amount of biological data is challenging to the current database in regard to big data analysis. We recently improved two aspects of the infrastructural dataset of VFDB: (i) removed the redundancy introduced by previous releases and generated two hierarchical datasets--one core dataset of experimentally verified VFs only and another full dataset including all known and predicted VFs and (ii) refined the gene annotation of the core dataset with controlled vocabularies. Our efforts enhanced the data quality of the VFDB and promoted the usability of the database in the big data era for the bioinformatic mining of the explosively growing data regarding bacterial VFs.
The virulence factor database (VFDB, http://www.mgc.ac.cn/VFs/) has served as a comprehensive repository of bacterial virulence factors (VFs) for >7 years. Bacterial virulence is an exciting and ...dynamic field, due to the availability of complete sequences of bacterial genomes and increasing sophisticated technologies for manipulating bacteria and bacterial genomes. The intricacy of virulence mechanisms offers a challenge, and there exists a clear need to decipher the 'language' used by VFs more effectively. In this article, we present the recent major updates of VFDB in an attempt to summarize some of the most important virulence mechanisms by comparing different compositions and organizations of VFs from various bacterial pathogens, identifying core components and phylogenetic clades and shedding new light on the forces that shape the evolutionary history of bacterial pathogenesis. In addition, the 2012 release of VFDB provides an improved user interface.
Dental plaque biofilms are responsible for numerous chronic oral infections and cause a severe health burden. Many of these infections cannot be eliminated, as the bacteria in the biofilms are ...resistant to the host's immune defenses and antibiotics. There is a critical need to develop new strategies to control biofilm-based infections. Biofilm formation in Streptococcus mutans is promoted by major virulence factors known as glucosyltransferases (Gtfs), which synthesize adhesive extracellular polysaccharides (EPS). The current study was designed to identify novel molecules that target Gtfs, thereby inhibiting S. mutans biofilm formation and having the potential to prevent dental caries. Structure-based virtual screening of approximately 150,000 commercially available compounds against the crystal structure of the glucosyltransferase domain of the GtfC protein from S. mutans resulted in the identification of a quinoxaline derivative, 2-(4-methoxyphenyl)-N-(3-{2-(4-methoxyphenyl)ethylimino}-1,4-dihydro-2-quinoxalinylidene)ethanamine, as a potential Gtf inhibitor. In vitro assays showed that the compound was capable of inhibiting EPS synthesis and biofilm formation in S. mutans by selectively antagonizing Gtfs instead of by killing the bacteria directly. Moreover, the in vivo anti-caries efficacy of the compound was evaluated in a rat model. We found that the compound significantly reduced the incidence and severity of smooth and sulcal-surface caries in vivo with a concomitant reduction in the percentage of S. mutans in the animals' dental plaque (P < 0.05). Taken together, these results represent the first description of a compound that targets Gtfs and that has the capacity to inhibit biofilm formation and the cariogenicity of S. mutans.
Bordetella pertussis persists inside host cells, and virulence factors are crucial for intracellular adaptation. The regulation of B. pertussis virulence factor transcription primarily occurs through ...the modulation of the two-component system (TCS) known as BvgAS. However, additional regulatory systems have emerged as potential contributors to virulence regulation. Here, we investigate the impact of BP1092, a putative TCS histidine kinase that shows increased levels after bacterial internalization by macrophages, on B. pertussis proteome adaptation under nonmodulating (Bvg+) and modulating (Bvg−) conditions. Using mass spectrometry, we compare B. pertussis wild-type (wt), a BP1092-deficient mutant (ΔBP1092), and a ΔBP1092 trans-complemented strain under both conditions. We find an altered abundance of 10 proteins, including five virulence factors. Specifically, under nonmodulating conditions, the mutant strain showed decreased levels of FhaB, FhaS, and Cya compared to the wt. Conversely, under modulating conditions, the mutant strain exhibited reduced levels of BvgA and BvgS compared to those of the wt. Functional assays further revealed that the deletion of BP1092 gene impaired B. pertussis ability to survive within human macrophage THP-1 cells. Taken together, our findings allow us to propose BP1092 as a novel player involved in the intricate regulation of B. pertussis virulence factors and thus in adaptation to the intracellular environment. The data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the data set identifier PXD041940.
Fungi have the capability to produce a tremendous number of so-called secondary metabolites, which possess a multitude of functions, e.g., communication signals during coexistence with other ...microorganisms, virulence factors during pathogenic interactions with plants and animals, and in medical applications. Therefore, research on this topic has intensified significantly during the past 10 years and thus knowledge of regulatory mechanisms and the understanding of the role of secondary metabolites have drastically increased. This review aims to depict the complexity of all the regulatory elements involved in controlling the expression of secondary metabolite gene clusters, ranging from epigenetic control and signal transduction pathways to global and specific transcriptional regulators. Furthermore, we give a short overview on the role of secondary metabolites, focusing on the interaction with other microorganisms in the environment as well as on pathogenic relationships.
Cytolytic proteins and peptide toxins are classical virulence factors of several bacterial pathogens which disrupt epithelial barrier function, damage cells and activate or modulate host immune ...responses. Such toxins have not been identified previously in human pathogenic fungi. Here we identify the first, to our knowledge, fungal cytolytic peptide toxin in the opportunistic pathogen Candida albicans. This secreted toxin directly damages epithelial membranes, triggers a danger response signalling pathway and activates epithelial immunity. Membrane permeabilization is enhanced by a positive charge at the carboxy terminus of the peptide, which triggers an inward current concomitant with calcium influx. C. albicans strains lacking this toxin do not activate or damage epithelial cells and are avirulent in animal models of mucosal infection. We propose the name 'Candidalysin' for this cytolytic peptide toxin; a newly identified, critical molecular determinant of epithelial damage and host recognition of the clinically important fungus, C. albicans.
Fungal diseases are severe and have very high morbidity as well as up to 60% mortality for patients diagnosed with invasive fungal infection. In this review, in vitro and in vivo studies provided us ...with the insight into the role of Candida virulence factors that mediate their success as pathogens, such as: membrane and cell wall (CW) barriers, dimorphism, biofilm formation, signal transduction pathway, proteins related to stress tolerance, hydrolytic enzymes (e.g. proteases, lipases, haemolysins), and toxin production. The review characterized the virulence of clinically important C. albicans, C. parapsilosis, C. tropicalis, C. glabrata and C. krusei. Due to the white-opaque transition in the mating-type locus MTL-homozygous cells, C. albicans demonstrates an advantage over other less related species of Candida as a human commensal and pathogen. It was reviewed that Candida ergosterol biosynthesis genes play a role in cellular stress and are essential for Candida pathogenesis both in invasive and superficial infections. Hydrolases associated with CW are involved in the host-pathogen interactions. Adhesins are crucial in colonization and biofilm formation, an important virulence factor for candidiasis. Calcineurin is involved in membrane and CW stress as well as virulence. The hyphae-specific toxin, named candidalysin, invades mucosal cells facilitating fungal invasion into deeper tissues. Expression of this protein promotes resistance to neutrophil killing in candidiasis. The virulence factors provide immunostimulatory factors, activating dendric cells and promoting T cell infiltration and activation. Targeting virulence factors, can reduce the risk of resistance development in Candida infections.
Severe liver abscess infections caused by hypervirulent clonal-group CG23 Klebsiella pneumoniae have been increasingly reported since the mid-1980s. Strains typically possess several virulence ...factors including an integrative, conjugative element ICEKp encoding the siderophore yersiniabactin and genotoxin colibactin. Here we investigate CG23's evolutionary history, showing several deep-branching sublineages associated with distinct ICEKp acquisitions. Over 80% of liver abscess isolates belong to sublineage CG23-I, which emerged in ~1928 following acquisition of ICEKp10 (encoding yersiniabactin and colibactin), and then disseminated globally within the human population. CG23-I's distinguishing feature is the colibactin synthesis locus, which reportedly promotes gut colonisation and metastatic infection in murine models. These data show circulation of CG23 K. pneumoniae decades before the liver abscess epidemic was first recognised, and provide a framework for future epidemiological and experimental studies of hypervirulent K. pneumoniae. To support such studies we present an open access, completely sequenced CG23-I human liver abscess isolate, SGH10.
The nematicidal activity of the common plant-pathogenic bacterium
against certain nematodes has been recently identified, but little is known about its virulence factors. In the current study, ...predictive analysis of nematode-virulent factors in the genome of a
wild-type strain MB03 revealed a variety of factors with the potential to be pathogenic against nematodes. One of these virulence factors that was predicted with a high score, namely, YqfO03, was a protein with structural domains that are similar to the Nif3 superfamily. This protein was expressed and purified in
, and was investigated for nematicidal properties against the model nematode
and an agriculturally important pest
. Our results showed that YqfO03 exhibits lethal activity toward
and
worms, and it also caused detrimental effects on the growth, brood size, and motility of
worms. However,
worms were able to defend themselves against YqfO03 via a physical defense response by avoiding contact with the protein. Discovery of the diverse nematicidal activities of YqfO03 provides new knowledge on the biological function of a bacterial Nif3-family protein and insight into the potential of this protein as a specific means of controlling agricultural nematode pests.
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