BarA-UvrY Two-Component System Regulates Virulence of Uropathogenic E. coli CFT073

Uropathogenic Escherichia coli (UPEC), a member of extraintestinal pathogenic E. coli, cause ∼80% of community-acquired urinary tract infections (UTI) in humans. UPEC initiates its colonization in epithelial cells lining the urinary tract with a complicated life cycle, replicating and persisting in intracellular and extracellular niches. Consequently, UPEC causes cystitis and more severe form of pyelonephritis. To further understand the virulence characteristics of UPEC, we investigated the roles of BarA-UvrY two-component system (TCS) in regulating UPEC virulence. Our results showed that mutation of BarA-UvrY TCS significantly decreased the virulence of UPEC CFT073, as assessed by mouse urinary tract infection, chicken embryo killing assay, and cytotoxicity assay on human kidney and uroepithelial cell lines. Furthermore, mutation of either barA or uvrY gene reduced the production of hemolysin, lipopolysaccharide (LPS), proinflammatory cytokines (TNF-α and IL-6) and chemokine (IL-8). The virulence phenotype was restored similar to that of wild-type by complementation of either barA or uvrY gene in trans. In addition, we discussed a possible link between the BarA-UvrY TCS and CsrA in positively and negatively controlling virulence in UPEC. Overall, this study provides the evidences for BarA-UvrY TCS regulates the virulence of UPEC CFT073 and may point to mechanisms by which virulence regulations are observed in different ways may control the long-term survival of UPEC in the urinary tract

Uropathogenic Escherichia coli P and Type 1 Fimbriae Act in Synergy in a Living Host to Facilitate Renal Colonization Leading to Nephron Obstruction

The progression of a natural bacterial infection is a dynamic process influenced by the physiological characteristics of the target organ. Recent developments in live animal imaging allow for the study of the dynamic microbe-host interplay in real-time as the infection progresses within an organ of a live host. Here we used multiphoton microscopy-based live animal imaging, combined with advanced surgical procedures, to investigate the role of uropathogenic Escherichia coli (UPEC) attachment organelles P and Type 1 fimbriae in renal bacterial infection. A GFP+ expressing variant of UPEC strain CFT073 and genetically well-defined isogenic mutants were microinfused into rat glomerulus or proximal tubules. Within 2 h bacteria colonized along the flat squamous epithelium of the Bowman's capsule despite being exposed to the primary filtrate. When facing the challenge of the filtrate flow in the proximal tubule, the P and Type 1 fimbriae appeared to act in synergy to promote colonization. P fimbriae enhanced early colonization of the tubular epithelium, while Type 1 fimbriae mediated colonization of the center of the tubule via a mechanism believed to involve inter-bacterial binding and biofilm formation. The heterogeneous bacterial community within the tubule subsequently affected renal filtration leading to total obstruction of the nephron within 8 h. Our results reveal the importance of physiological factors such as filtration in determining bacterial colonization patterns, and demonstrate that the spatial resolution of an infectious niche can be as small as the center, or periphery, of a tubule lumen. Furthermore, our data show how secondary physiological injuries such as obstruction contribute to the full pathophysiology of pyelonephritis

Mise en place d'un élevage de Chironomus riparius Meigen (Diptera, Chironomidae) à l'aval d'une station d'épuration par lagunage

Un système d'élevage de Chironomus riparius Meigen a été mis en place sur le chenal d'amenée du rejet du 3e bassin de la station d'épuration par lagunage de Baraqueville dans le département de l'Aveyron. Un suivi hebdomadaire des principaux facteurs physico-chimiques, sur une période d'un an, a permis de définir les caractéristiques et le fonctionnement de ce système d'élevage. 51 kg de PF de larves ont été récoltés durant 183 jours d'exploitation (mai à octobre) soit 1,77 kg de PS ha-1 an-1. La température, la teneur en O2 dissous et le taux de sédimentation sont les principaux facteurs susceptibles d'influencer la production

Deux nouvelles espèces d'Enchytraeus (Oligochaeta, Enchytraeidae) et redescription d'E. bigeminus Niel. & Chr. Remarques sur le genre Enchytraeus

Ce travail comprend la description de 2 nouvelles espèces d'Enchytraeus : E. varithecatus n. sp. et E. variatus n. sp. et la redescription d'E. bigeminus Niel. & Chr. Ces 3 espèces ont été obtenues à partir de cultures. Les auteurs font ensuite des remarques sur la biologie, la morphologie et surtout la taxinomie des espèces européennes du genre Enchytraeus