Investigating the Host Range Adaptability of Aeromonas veronii Using Comparative Genomics and Mutational Analysis

Aeromonas veronii is a bacterium capable of multi-host associations with varying outcomes. Abundant in the aquatic environment, A. veronii also forms beneficial or commensal digestive-tract symbioses with several organisms and is implicated in diseases that afflict humans and aquatic animals. The study of A. veronii provides a unique opportunity to investigate a group of bacteria that play disparate roles in a broad spectrum of host organisms. A key underlying question behind these multi-host associations asks what genetic attributes allow for this versatility and variable manipulation of hosts. Whole genome comparisons provide a comprehensive assessment of the presence of genes of interest among strains of a species that ostensibly occupy different niches. One important determinant in host colonization is symbiont nutrient utilization. This study investigated the importance of three metabolic pathways found to be upregulated by A. veronii in the leech gut: amino sugar catabolism, the glyoxylate cycle and the arginine deiminase pathway. We also find that the presence of a catabolic pathway for sialic acid is found predominantly in leech isolates. Another feature of interest in A. veronii is the type III secretion system (T3SS), which has been characterized in both pathogenic and beneficial associations. We show the distribution of T3SS genes among aeromonads and its significant role in virulence, particularly in fish. Genome comparisons provide a framework in which to investigate the physiological relevance of candidate genes. Combined with genetic tools and model hosts, we can further resolve the requirements for A. veronii to successfully proliferate in symbiotic associations

Tracing evolution in Aeromonas: the roles of shared ancestry and shared genes in niche adaptation.

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New Insights from Comparative Genomic Approaches about Aeromonas Infections, Evolution and Taxonomy.

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Exposure to pairs of Aeromonas strains enhances virulence in the Caenorhabditis elegans infection model

International audienceAeromonad virulence remains poorly understood, and is difficult to predict from strain characteristics. In addition, infections are often polymicrobial (i.e., are mixed infections), and 5-10% of such infections include two distinct aeromonads, which has an unknown impact on virulence. In this work, we studied the virulence of aeromonads recovered from human mixed infections. We tested them individually and in association with other strains with the aim of improving our understanding of aeromonosis. Twelve strains that were recovered in pairs from six mixed infections were tested in a virulence model of the worm Caenorhabditis elegans. Nine isolates were weak worm killers (median time to death, TD50, >=7 days) when administered alone. Two pairs showed enhanced virulence, as indicated by a significantly shortened TD50 after co-infection vs. infection with a single strain. Enhanced virulence was also observed for five of the 14 additional experimental pairs, and each of these pairs included one strain from a natural synergistic pair. These experiments indicated that synergistic effects were frequent and were limited to pairs that were composed of strains belonging to different species. The genome content of virulence-associated genes failed to explain virulence synergy, although some virulence-associated genes that were present in some strains were absent from their companion strain (e.g., T3SS). The synergy observed in virulence when two Aeromonas isolates were co-infected stresses the idea that consideration should be given to the fact that infection does not depend only on single strain virulence but is instead the result of a more complex interaction between the microbes involved, the host and the environment. These results are of interest for other diseases in which mixed infections are likely and in particular for water-borne diseases (e.g., legionellosis, vibriosis), in which pathogens may display enhanced virulence in the presence of the right partner. This study contributes to the current shift in infectiology paradigms from a premise that assumes a monomicrobial origin for infection to one more in line with the current pathobiome era

Mixed infection enhances the virulence of aeromonas in the Caenorhabditis elegans model

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Mixed infection enhances the virulence of aeromonas in the Caenorhabditis elegans model

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Approche intégrative pour la ré-évaluation taxonomique de l’espèce Aeromonas media et descriptio d’Aeromonas alphaquinta sp.

International audienceAeromonas media groups bacteria mainly found in aquatic habitats that can act occasionally as opportunistic pathogens in human and animals. The aim of this study is to explore the diversity of the bacteria currently affiliated to the species A. media. Forty strains were included in a population study integrating, multilocus genetics, genomics, phylogenetics as well as lifestyle and evolutionary features. Sixteen gene-based multilocus phylogeny delineated three clades. The emergence of clades was mainly due to mutations even if horizontal gene transfers occurred within and between clades. Data from 14 whole genome sequences showed that clades corresponded to different groups defined by both average nucleotide identity and in silico DNA-DNA Hybridization, i.e. to different genomospecies. DL-lactate utilization, cefoxitin susceptibility and several signatures clearly distinguished two clades/genomospecies, which were proposed as two species: emended A. media and Aeromonas alphaquinta sp. nov. (type strain LMG 13459T = ATCC 51107T = CIP 74.32T). The third clade was proposed as Aeromonas sp. genomospecies Paramedia (reference strain 1086C = CECT 8838 = LMG 28708) awaiting larger number of strains for a robust species description. Data used for polyphasic barcoding that support the description A. alphaquinta sp. nov. and the emendation A. media were further analyzed in an integrative approach giving a more comprehensive knowledge of the two species among aeromonads

Exposure to pairs of Aeromonas strains enhances virulence in the Caenorhabditis elegans infection model

Aeromonad virulence remains poorly understood, and is difficult to predict from strain characteristics. In addition, infections are often polymicrobial (i.e., are mixed infections), and 5-10% of such infections include two distinct aeromonads, which has an unknown impact on virulence. In this work, we studied the virulence of aeromonads recovered from human mixed infections. We tested them individually and in association with other strains with the aim of improving our understanding of aeromonosis. Twelve strains that were recovered in pairs from six mixed infections were tested in a virulence model of the worm Caenorhabditis elegans. Nine isolates were weak worm killers (median time to death, TD50, ≥7 days) when administered alone. Two pairs showed enhanced virulence, as indicated by a significantly shortened TD50 after co-infection versus infection with a single strain. Enhanced virulence was also observed for five of the 14 additional experimental pairs, and each of these pairs included one strain from a natural synergistic pair. These experiments indicated that synergistic effects were frequent and were limited to pairs that were composed of strains belonging to different species. The genome content of virulence-associated genes failed to explain virulence synergy, although some virulence-associated genes that were present in some strains were absent from their companion strain (e.g., T3SS). The synergy observed in virulence when 2 Aeromonas isolates were co-infected stresses the idea that consideration should be given to the fact that infection does not depend only on single strain virulence but is instead the result of a more complex interaction between the microbes involved, the host and the environment. These results are of interest for other diseases in which mixed infections are likely and in particular for water-borne diseases (e.g., legionellosis, vibriosis), in which pathogens may display enhanced virulence in the presence of the right partner. This study contributes to the current shift in infectiology paradigms from a premise that assumes a monomicrobial origin for infection to one more in line with the current pathobiome era

Vibrio natriegens genome‐scale modeling reveals insights into halophilic adaptations and resource allocation

Abstract Vibrio natriegens is a Gram‐negative bacterium with an exceptional growth rate that has the potential to become a standard biotechnological host for laboratory and industrial bioproduction. Despite this burgeoning interest, the current lack of organism‐specific qualitative and quantitative computational tools has hampered the community's ability to rationally engineer this bacterium. In this study, we present the first genome‐scale metabolic model (GSMM) of V. natriegens. The GSMM (iLC858) was developed using an automated draft assembly and extensive manual curation and was validated by comparing predicted yields, central metabolic fluxes, viable carbon substrates, and essential genes with empirical data. Mass spectrometry‐based proteomics data confirmed the translation of at least 76% of the enzyme‐encoding genes predicted to be expressed by the model during aerobic growth in a minimal medium. iLC858 was subsequently used to carry out a metabolic comparison between the model organism Escherichia coli and V. natriegens, leading to an analysis of the model architecture of V. natriegens' respiratory and ATP‐generating system and the discovery of a role for a sodium‐dependent oxaloacetate decarboxylase pump. The proteomics data were further used to investigate additional halophilic adaptations of V. natriegens. Finally, iLC858 was utilized to create a Resource Balance Analysis model to study the allocation of carbon resources. Taken together, the models presented provide useful computational tools to guide metabolic engineering efforts in V. natriegens