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Connections between exoproteome heterogeneity and virulence in the oral pathogen Aggregatibacter actinomycetemcomitans

ABSTRACT: Aggregatibacter actinomycetemcomitans (Aa) is a Gram-negative bacterial pathogen associated with severe periodontitis and non-oral diseases. Clinical isolates of Aa display a rough (R) colony phenotype with strong adherent properties. Upon prolonged culturing, non-adherent strains with a smooth (S) colony phenotype emerge. To date, most virulence studies on Aa have been performed with S strains of Aa, whereas the virulence of clinical R isolates received relatively little attention. Since the extracellular proteome is the main bacterial reservoir of virulence factors, the present study was aimed at a comparative analysis of this sub-proteome fraction for a collection of R isolates and derivative S strains, in order to link particular proteins to the virulence of Aa with serotype b. To assess the bacterial virulence, we applied different infection models based on larvae of the greater wax moth Galleria mellonella, a human salivary gland-derived epithelial cell line, and freshly isolated neutrophils from healthy human volunteers. A total number of 351 extracellular Aa proteins was identified by mass spectrometry, with the S strains consistently showing more extracellular proteins than their parental R isolates. A total of 50 known extracellular virulence factors was identified, of which 15 were expressed by all investigated bacteria. Importantly, the comparison of differences in exoproteome composition and virulence highlights critical roles of 10 extracellular proteins in the different infection models. Altogether, our present study provides novel cues for understanding the virulence of Aa, and for development of potential preventive or therapeutic avenues to neutralize this important oral pathogen.

INSTRUMENT(S): LTQ Orbitrap

ORGANISM(S): Aggregatibacter Actinomycetemcomitans (actinobacillus Actinomycetemcomitans) (haemophilus Actinomycetemcomitans)

SUBMITTER: Sandra Maass

LAB HEAD: Dörte Becher

PROVIDER: PXD028940 | Pride | 2022-06-01

REPOSITORIES: Pride

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Project description:Livestock-associated (LA) methicillin-resistant Staphylococcus aureus (MRSA) and strains of sequence type 398 (ST398), which first became known for its widespread colonization of pigs but are now also rapidly emerging in the number of human colonization and infections. The ability of broad host adaption in combination with a consciously evolves by acquisition of virulence gene or mobile genetic elements (MGE) have been increasingly addressed ST398 lineage a serious threat to public health. The present study was aimed to track out how the diverse ST398 lineage, which colonized or infected in a broad range of reservoirs and various geographic regions, is actually reflected in the course of virulence evolution. We therefore profiled the extracellular proteome, representing the main reservoir of virulence factors, of 30 representative clinical isolates using label-free quantitative mass spectrometry. The results show that these isolates can be divided into five distinct clusters based on their exoproteome identities and abundance signatures. The majority of proteins identified were predicted as cytoplasmic proteins showing substantial heterogeneity among our 30 investigated isolates. Only 50% of isolates their exoproteome clustering of isolates can be correlated the clustering based on genome sequences suggested that the large-scale extend of genotype changes over time. To assess the virulence and cytotoxicity of the 30 investigated isolates, we employed infection models based on Galleria mellonella and HeLa cells. The results uncovered the grouping of clinical isolates based on their virulence or cytotoxicity have apparently distinctive exoproteome signatures and particular exoproteins could play decisive roles in pathogenicity of this specific S. aureus lineage. Altogether, the combination of exoproteome and virulence analysis contribute to the comprehensive insights for the impact of genome diversity on the global production of virulence factors of this zoonotic lineage, and more importantly, our outcomes as well as our approach provided an effective pipeline to define proteomic signatures of S. aureus virulence.

Project description:An array analysis of C. gattii (C. bacillosporus), intended to identify loci associated with the hypervirulence of the Vancouver Island Outbreak (VIO). 23 C. gattii isolates, representing both VIO strains and control strains, were grown for 24 hours in mammalian macrophages. RNA was isolated and gene expression for each strain quantified relative to pooled RNA from all 23 samples. Linear regression was used to identify loci showing positive or negative correlation with "intracellular proliferation rate", a proxy measure for virulence. Data from this analysis is included in Ma et al, 2009, PNAS 106(31) 12980-12985. The abstract is included below. In 1999, the population of Vancouver Island, Canada, began to experience an outbreak of a fatal fungal disease caused by a highly virulent lineage of Cryptococcus gattii. This organism has recently spread to the Canadian mainland and Pacific Northwest, but the molecular cause of the outbreak remains unknown. Here we show that the Vancouver Island outbreak (VIO) isolates have dramatically increased their ability to replicate within macrophages of the mammalian immune system in comparison with other C. gattii strains. We further demonstrate that such enhanced intracellular parasitism is directly linked to virulence in a murine model of cryptococcosis, suggesting that this phenotype may be the cause of the outbreak. Finally, microarray studies on 24 C. gattii strains reveals that the hypervirulence of the VIO isolates is characterized by the up-regulation of a large group of genes, many of which are encoded by mitochondrial genome or associated with mitochondrial activities. This expression profile correlates with an unusual mitochondrial morphology exhibited by the VIO strains after phagocytosis. Our data thus demonstrate that the intracellular parasitism of macrophages is a key driver of a human disease outbreak, a finding that has significant implications for a wide range of other human pathogens. Dual-colour hybridization (each sample was hybridized against pooled RNA), one array per isolate, 23 biological samples, no technical replicates.

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Connections between exoproteome heterogeneity and virulence in the oral pathogen Aggregatibacter actinomycetemcomitans

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