Intestinal Colonization Dynamics of Vibrio cholerae

To cause the diarrheal disease cholera, Vibrio cholerae must effectively colonize the small intestine. In order to do so, the bacterium needs to successfully travel through the stomach and withstand the presence of agents such as bile and antimicrobial peptides in the intestinal lumen and mucus. The bacterial cells penetrate the viscous mucus layer covering the epithelium and attach and proliferate on its surface. In this review, we discuss recent developments and known aspects of the early stages of V. cholerae intestinal colonization and highlight areas that remain to be fully understood. We propose mechanisms and postulate a model that covers some of the steps that are required in order for the bacterium to efficiently colonize the human host. A deeper understanding of the colonization dynamics of V. cholerae and other intestinal pathogens will provide us with a variety of novel targets and strategies to avoid the diseases caused by these organisms

Prevotella copri and microbiota members mediate the beneficial effects of a therapeutic food for malnutrition

Microbiota-directed complementary food (MDCF) formulations have been designed to repair the gut communities of malnourished children. A randomized controlled trial demonstrated that one formulation, MDCF-2, improved weight gain in malnourished Bangladeshi children compared to a more calorically dense standard nutritional intervention. Metagenome-assembled genomes from study participants revealed a correlation between ponderal growth and expression of MDCF-2 glycan utilization pathways by Prevotella copri strains. To test this correlation, here we use gnotobiotic mice colonized with defined consortia of age- and ponderal growth-associated gut bacterial strains, with or without P. copri isolates closely matching the metagenome-assembled genomes. Combining gut metagenomics and metatranscriptomics with host single-nucleus RNA sequencing and gut metabolomic analyses, we identify a key role of P. copri in metabolizing MDCF-2 glycans and uncover its interactions with other microbes including Bifidobacterium infantis. P. copri-containing consortia mediated weight gain and modulated energy metabolism within intestinal epithelial cells. Our results reveal structure-function relationships between MDCF-2 and members of the gut microbiota of malnourished children with potential implications for future therapies

Intestinal Colonization Dynamics of Vibrio cholerae.

To cause the diarrheal disease cholera, Vibrio cholerae must effectively colonize the small intestine. In order to do so, the bacterium needs to successfully travel through the stomach and withstand the presence of agents such as bile and antimicrobial peptides in the intestinal lumen and mucus. The bacterial cells penetrate the viscous mucus layer covering the epithelium and attach and proliferate on its surface. In this review, we discuss recent developments and known aspects of the early stages of V. cholerae intestinal colonization and highlight areas that remain to be fully understood. We propose mechanisms and postulate a model that covers some of the steps that are required in order for the bacterium to efficiently colonize the human host. A deeper understanding of the colonization dynamics of V. cholerae and other intestinal pathogens will provide us with a variety of novel targets and strategies to avoid the diseases caused by these organisms

Model for intestinal colonization dynamics of <i>V</i>. <i>cholerae</i>.

<p><i>V</i>. <i>cholerae</i> may be ingested as free-living cells (i), as forming microcolonies (ii), or as part of a biofilm (iii) (A). Cells in the lumen will first come in contact with the mucus layer (B). The bacterium must reach the intestinal epithelium by penetrating through the viscous mucus layer covering it (C). Once the bacterium reaches the intestinal epithelium, we hypothesize that noncommitted (reversible) attachment occurs, mediated by adhesins such as GbpA or Mam7 (D). Subsequently, specific attachment adhesins might be produced that would allow <i>V</i>. <i>cholerae</i> to bind in a committed fashion (E), the cells multiply (F), and, once a certain concentration of cells has been reached, the toxin coregulated pilus is produced, allowing for microcolony formation and toxin production (G).</p

Catabolism Of Mucus Components Influences Motility Of Vibrio Cholerae In The Presence Of Environmental Reservoirs

Vibrio cholerae O1, the etiological agent of cholera, is a natural inhabitant of aquatic ecosystems. Motility is a critical element for the colonization of both the human host and its environmental reservoirs. In this study, we investigated the molecular mechanisms underlying the chemotactic response of V. cholerae in the presence of some of its environmental reservoirs. We found that, from the several oligosaccharides found in mucin, two specifically triggered motility of V. cholerae O1: N-acetylneuraminic acid (Neu5Ac) and N-acetylglucosamine (GlcNAc). We determined that the compounds need to be internally catabolized in order to trigger motility of V. cholerae. Interestingly, the catabolism of Neu5Ac and GlcNAc converges and the production of one molecule common to both pathways, glucosamine-6-phosphate (GlcN-6P), is essential to induce motility in the presence of both compounds. Mutants unable to produce GlcN-6P show greatly reduced motility towards mucin. Furthermore, we determined that the production of GlcN-6P is necessary to induce motility of V. cholerae in the presence of some of its environmental reservoirs such as crustaceans or cyanobacteria, revealing a molecular link between the two distinct modes of the complex life cycle of V. cholerae. Finally, cross-species comparisons revealed varied chemotactic responses towards mucin, GlcNAc, and Neu5Ac for environmental (non-pathogenic) strains of V. cholerae, clinical and environmental isolates of the human pathogens Vibrio vulnificus and Vibrio parahaemolyticus, and fish and squid isolates of the symbiotic bacterium Vibrio fischeri. The data presented here suggest nuance in convergent strategies across species of the same bacterial family for motility towards suitable substrates for colonization

Catabolism of mucus components influences motility of <i>Vibrio cholerae</i> in the presence of environmental reservoirs

<div><p><i>Vibrio cholerae</i> O1, the etiological agent of cholera, is a natural inhabitant of aquatic ecosystems. Motility is a critical element for the colonization of both the human host and its environmental reservoirs. In this study, we investigated the molecular mechanisms underlying the chemotactic response of <i>V</i>. <i>cholerae</i> in the presence of some of its environmental reservoirs. We found that, from the several oligosaccharides found in mucin, two specifically triggered motility of <i>V</i>. <i>cholerae</i> O1: <i>N</i>-acetylneuraminic acid (Neu5Ac) and <i>N</i>-acetylglucosamine (GlcNAc). We determined that the compounds need to be internally catabolized in order to trigger motility of <i>V</i>. <i>cholerae</i>. Interestingly, the catabolism of Neu5Ac and GlcNAc converges and the production of one molecule common to both pathways, glucosamine-6-phosphate (GlcN-6P), is essential to induce motility in the presence of both compounds. Mutants unable to produce GlcN-6P show greatly reduced motility towards mucin. Furthermore, we determined that the production of GlcN-6P is necessary to induce motility of <i>V</i>. <i>cholerae</i> in the presence of some of its environmental reservoirs such as crustaceans or cyanobacteria, revealing a molecular link between the two distinct modes of the complex life cycle of <i>V</i>. <i>cholerae</i>. Finally, cross-species comparisons revealed varied chemotactic responses towards mucin, GlcNAc, and Neu5Ac for environmental (non-pathogenic) strains of <i>V</i>. <i>cholerae</i>, clinical and environmental isolates of the human pathogens <i>Vibrio vulnificus</i> and <i>Vibrio parahaemolyticus</i>, and fish and squid isolates of the symbiotic bacterium <i>Vibrio fischeri</i>. The data presented here suggest nuance in convergent strategies across species of the same bacterial family for motility towards suitable substrates for colonization.</p></div

Motility of <i>V</i>. <i>cholerae</i> mutants in the presence of Neu5Ac and GlcNAc.

<p>The motility responses of different mutants involved in the catabolism of Neu5Ac and GlcNAc were tested on soft agar plates containing A) 0.1% glycerol or 0.1% glycerol supplemented with B) Neu5Ac and C) GlcNAc. Columns represent the mean of four independent experiments and error bars the standard deviation. Wild-type N16961 (WT), Δ<i>motAB</i> (non-motile), Δ<i>nanA</i> and Δ<i>nanEK</i> (cannot use Neu5Ac as a carbon source), Δ<i>nagE</i> and Δ<i>nagK</i> (cannot use exogenous or endogenous GlcNAc as a carbon source respectively), Δ<i>nagA1-A2</i> and Δ<i>nagB</i> (cannot use Neu5Ac or GlcNAc as carbon sources). Statistical comparisons were made using one-way ANOVA and comparing diameters of the mutants relative to wild-type using Tukey’s HSD test; bars within a panel with the same letter are not significantly different at alpha = 0.05. In A bars with the letter a are not significantly different at alpha = 0.05 from one another but are different from b at P < 0.0001. In B bars with the letter a are not significantly different at alpha = 0.05 from one another but are different from b and c at P < 0.0001. Furthermore, b and c are also significantly different from each other with a P < 0.0001. In C bars with the letter a are not significantly different at alpha = 0.05 from one another but are different from b, c and d at P < 0.0001. Furthermore, b and c are also significantly different from each other with a P < 0.0001.</p

Motility of <i>V</i>. <i>cholerae</i> in the presence of mucus components.

<p>Motility assays of <i>V</i>. <i>cholerae</i> N16961 in glycerol supplemented with mucin and oligosaccharides found in mucin. The <i>y</i> axis denotes the diameter of the motility zone in cm and the <i>x</i> axis indicates the carbon source added to the motility plates. Columns represent the mean of four independent experiments and error bars the standard deviation. Statistical comparisons used one-way ANOVA followed by Tukey’s HSD test; bars with the letter a are not significantly different at alpha = 0.05 from one another but are different from b and c at P < 0.0001. Furthermore, b and c are also significantly different from each other with a P < 0.0001.</p

Motility of <i>V</i>. <i>cholerae</i> mutants in the presence of environmental reservoirs.

<p>The motility responses of different mutants involved in the catabolism of Neu5Ac and GlcNAc were tested on soft agar plates containing 0.1% Glycerol supplemented with 0.01% A) hexaacetyl-chitohexaose B) <i>Microcystis aeruginosa</i> C) oyster gill lysate. Columns represent the mean of four independent experiments and error bars the standard deviation. Wild-type N16961 (WT), Δ<i>motAB</i> (non-motile), Δ<i>nanA</i> and Δ<i>nanEK</i> (cannot use Neu5Ac as a carbon source), Δ<i>nagE</i> and Δ<i>nagK</i> (cannot use exogenous or endogenous GlcNAc as a carbon source respectively), Δ<i>nagA1-A2</i> (cannot use Neu5Ac or GlcNAc as carbon sources and is non-motile on mucin plates) and Δ<i>nagB</i> (cannot use Neu5Ac or GlcNAc as carbon sources). Statistical comparisons were made using one-way ANOVA and comparing diameters of the mutants relative to wild-type using Tukey’s HSD test; bars within a panel with the same letter are not significantly different at alpha = 0.05. In A bars with the same letter are not significantly different at alpha = 0.05 from one another. c and d are significantly different from a and b at P < 0.0001. In B and C bars with the letter a are not significantly different at alpha = 0.05 from one another but are different from b at P < 0.0001.</p

Schematic of Neu5Ac and GlcNAc catabolic pathways.

<p>A) The catabolic pathway of <i>N</i>-acetylneuraminic acid (Neu5Ac, red circle) converges with the catabolic pathway of <i>N</i>-acetylglucosamine (GlcNAc, blue circle) through the production of three common catabolites: <i>N</i>-acetylglucosamine-6-phosphate (GlcNAc-6P), glucosamine-6-phosphate (GlcN-6P) and fructose-6-phosphate (Fru-6P). Abbreviations are as follows; <i>N</i>-acetylmannosamine (ManNAc), <i>N</i>-acetylmannosamine-6-phosphate (ManNAc-6P), <i>N</i>-acetylglucosamine-6-phosphate (GlcNAc-6P). Names of enzymes and the locus tags of the genes that encode them are shown in orange and are abbreviated as follows; <i>N</i>-acetylglucosamine-specific IIA component (NagE), <i>N</i>-acetylglucosamine kinase, (NagK), <i>N</i>-acetylneuraminate lyase, (NanA), <i>N</i>-acetylmannosamine kinase (NanK), <i>N</i>-acetylmannosamine-6-phosphate epimerase (NanE), <i>N</i>-acetylglucosamine-6-phosphate deacetylase 1 (NagA-1) and 2 (NagA-2), glucosamine-6-phosphate deaminase (NagB). B) Arrow diagrams of Neu5Ac and GlcNAc catabolic clusters. Red and blue arrows represent genes encoding enzymes involved in the catabolism of Neu5Ac and GlcNAc. Grey arrows represent genes encoding genes with other functions such as Neu5Ac scavenging (<i>nanH</i>) and transport (<i>dctQ</i>, <i>dctP</i>, and <i>dctM</i>) or regulators (<i>nagC</i> and <i>rpiR</i>). Genes without a label underneath encode hypothetical proteins.</p