data of figure 6

The data used to produce the figure 6 are presented in this tabl

Animal and human pathogenic Escherichia coli strains share common genetic backgrounds

Escherichia coli is a versatile species encompassing both commensals of the digestive tracts of many vertebrates, including humans, and pathogenic strains causing various intra- and extraintestinal infections. Despite extensive gene flow between strains, the E. coli species has a globally clonal population structure, consisting of distinct phylogenetic groups. Little is known about the relationships between phylogenetic groups and host specificity. We therefore used multilocus sequence typing (MLST) to investigate phylogenetic relationships and evaluated the virulence gene content of 35 E. coli strains representative of the diverse diseases encountered in domestic animals. We compared these strains with a panel of 101 human pathogenic and 98 non-human and human commensal strains representative of the phylogenetic and pathovar diversity of this species. A global factorial analysis of correspondence indicated that extraintestinal infections were caused mostly by phylogenetic group B2 strains, whereas intraintestinal infections were caused mostly by phylogenetic group A/B1/E strains, with strains responsible from extraintestinal or intraintestinal infections having specific virulence factors. It was not possible to distinguish between strains of human and animal origin. A detailed phylogenetic analysis of the MLST data showed that numerous pathogenic animal and human strains are very closely related, and had a number of virulence genes in common. However, a set of specific adhesins was identified in animal non-B2 group strains of all pathotypes. In conclusion, human and animal pathogenic strains share common genetic backgrounds, but non-B2 strains of different origins seem to have different sets of adhesins that could be involved in host specificity

Using long-term experimental evolution to uncover the patterns and determinants of molecular evolution of an Escherichia coli natural isolate in the streptomycin-treated mouse gut.

International audienceAlthough microbial ecology of the gut is now a major focus of interest, little is known about the molecular determinants of microbial adaptation in the gut. Experimental evolution coupled with whole-genome sequencing can provide insights of the adaptive process. In vitro experiments have revealed some conserved patterns: intermediate convergence, and epistatic interactions between beneficial mutations and mutations in global regulators. To test the relevance of these patterns and to identify the selective pressures acting in vivo, we have performed a long-term adaptation of an E. coli natural isolate, the streptomycin-resistant strain 536, in the digestive tract of streptomycin-treated mice. After a year of evolution, a clone from 15 replicates was sequenced. Consistently with in vitro observations, the identified mutations revealed a strong pattern of convergence at the mutation, gene, operon and functional levels. Yet, the rate of molecular evolution was lower than in in vitro, and no mutations in global regulators were recovered. More specific targets were observed: the dgo operon, involved in the galactonate pathway that improved growth on D-galactonate, and rluD and gidB, implicated in the maturation of the ribosomes, which mutations improved growth only in the presence of streptomycin. As in vitro, the nonrandom associations of mutations within the same pathways suggested a role of epistasis in shaping the adaptive landscape. Overall, we show that 'evolve and sequence' approach coupled with an analysis of convergence, when applied to a natural isolate, can be used to study adaptation in vivo and uncover the specific selective pressures of that environment

Capturing the mutational landscape of the beta-lactamase TEM-1

International audienceAdaptation proceeds through the selection of mutations. The distribution of mutant fitness effect and the forces shaping this distribution are therefore keys to predict the evolutionary fate of organisms and their constituents such as enzymes. Here, by producing and sequencing a comprehensive collection of 10,000 mutants, we explore the mutational landscape of one enzyme involved in the spread of antibiotic resistance, the beta-lactamase TEM-1. We measured mutation impact on the enzyme activity through the estimation of amoxicillin minimum inhibitory concentration on a subset of 990 mutants carrying a unique missense mutation, representing 64% of possible amino acid changes in that protein reachable by point mutation. We established that mutation type, solvent accessibility of residues, and the predicted effect of mutations on protein stability primarily determined alone or in combination changes in minimum inhibitory concentration of mutants. Moreover, we were able to capture the drastic modification of the mutational landscape induced by a single stabilizing point mutation (M182T) by a simple model of protein stability. This work thereby provides an integrated framework to study mutation effects and a tool to understand/define better the epistatic interactions

data of figure 1

Quantification of E. coli 536 in the feces in each mouse along the experimen

data of figure 5

The data used to produce the box plots of the figure 5 are presented in this tabl

data of figure 4

The results of flux cytometry are presented in this tabl

Interactions between genotype and environment drive the metabolic phenotype within Escherichia coli isolates

To gain insights into the adaptation of the Escherichia coli species to different environments, we monitored protein abundances using quantitative proteomics and measurements of enzymatic activities of central metabolism in a set of five representative strains grown in four contrasted culture media including human urine. Two hundred and thirty seven proteins representative of the genome-scale metabolic network were identified and classified into pathway categories. We found that nutrient resources shape the general orientation of metabolism through coordinated changes in the average abundances of proteins and in enzymatic activities that all belong to the same pathway category. For example, each culture medium induces a specific oxidative response whatever the strain. On the contrary, differences between strains concern isolated proteins and enzymes within pathway categories in single environments. Our study confirms the predominance of genotype by environment interactions at the proteomic and enzyme activity levels. The buffering of genetic variation when considering life-history traits suggests a multiplicity of evolutionary strategies. For instance, the uropathogenic isolate CFT073 shows a deregulation of iron demand and increased oxidative stress response

Commensal Escherichia coli strains in Guiana reveal a high genetic diversity with host-dependant population structure

International audienceWe undertook a large-scale epidemiological survey of commensal Escherichia coli in Trois-Sauts, an isolated village located in the south of French Guiana where human population exchanges are restricted and source of antibiotics controlled. Stools from 162 Wayampi Amerindians and rectal swabs from 33 human associated and 198 wild animals were collected in the close proximity of the village. The prevalence of E. coli was decreasing from humans (100%) to human associated (64%) and wild (45%) animals. A clear genetic structure between these three E. coli populations was observed with human strains belonging very rarely to B2 phylogroup (3.7%), exhibiting few virulence genes and bacteriocins but being antibiotic resistant whereas wild animal strains were characterized by 46.1% of B2 phylogroup belonging, with very unique and infrequent sequence types, numerous extraintestinal genes and bacteriocins but no antibiotic resistance; the human-associated animal strains being intermediate. Furthermore, an unexpected genetic diversity was observed among the strains, as the housekeeping gene nucleotide diversity per site of the Trois-Sauts's strains was higher than the one of reference strains representative of the known species diversity. The existence of such E. coli structured phylogenetic diversity within various hosts of a single localization has never been reporte

Enterobacteriaceae are essential for the modulation of colitis severity by fungi

Abstract Background Host-microbe balance maintains intestinal homeostasis and strongly influences inflammatory conditions such as inflammatory bowel diseases (IBD). Here we focused on bacteria-fungi interactions and their implications on intestinal inflammation, a poorly understood area. Methods Dextran sodium sulfate (DSS)-induced colitis was assessed in mice treated with vancomycin (targeting gram-positive bacteria) or colistin (targeting Enterobacteriaceae) and supplemented with either Saccharomyces boulardii CNCM I-745 or Candida albicans. Inflammation severity as well as bacterial and fungal microbiota compositions was monitored. Results While S. boulardii improved DSS-induced colitis and C. albicans worsened it in untreated settings, antibiotic treatment strongly modified DSS susceptibility and effects of fungi on colitis. Vancomycin-treated mice were fully protected from colitis, while colistin-treated mice retained colitis phenotype but were not affected anymore by administration of fungi. Antibacterial treatments not only influenced bacterial populations but also had indirect effects on fungal microbiota. Correlations between bacterial and fungal relative abundance were dramatically decreased in colistin-treated mice compared to vancomycin-treated and control mice, suggesting that colistin-sensitive bacteria are involved in interactions with fungi. Restoration of the Enterobacteriaceae population by administrating colistin-resistant Escherichia coli reestablished both beneficial effects of S. boulardii and pathogenic effects of C. albicans on colitis severity. This effect was at least partly mediated by an improved gut colonization by fungi. Conclusions Fungal colonization of the gut is affected by the Enterobacteriaceae population, indirectly modifying effects of mycobiome on the host. This finding provides new insights into the role of inter-kingdom functional interactions in intestinal physiopathology and potentially in IBD