Environmental Acidification Drives S. pyogenes Pilus Expression and Microcolony Formation on Epithelial Cells in a FCT-Dependent Manner

Group A Streptococcus (GAS, Streptococcus pyogenes) is a Gram-positive human pathogen responsible for a diverse variety of diseases, including pharyngitis, skin infections, invasive necrotizing fasciitis and autoimmune sequelae. We have recently shown that GAS cell adhesion and biofilm formation is associated with the presence of pili on the surface of these bacteria. GAS pilus proteins are encoded in the FCT (Fibronectin- Collagen-T antigen) genomic region, of which nine different variants have been identified so far. In the present study we undertook a global analysis of GAS isolates representing the majority of FCT-variants to investigate the effect of environmental growth conditions on their capacity to form multicellular communities. For FCT-types 2, 3, 5 and 6 and a subset of FCT-4 strains, we observed that acidification resulting from fermentative sugar metabolism leads to an increased ability of the bacteria to form biofilm on abiotic surfaces and microcolonies on epithelial cells. The higher biofilm forming capacity at low environmental pH was directly associated with an enhanced expression of the genes encoding the pilus components and of their transcription regulators. The data indicate that environmental pH affects the expression of most pilus types and thereby the formation of multicellular cell-adhering communities that assist the initial steps of GAS infection

Impact of Orthologous Gene Replacement on the Circuitry Governing Pilus Gene Transcription in Streptococci

The evolutionary history of several genes of the bacterial pathogen Streptococcus pyogenes strongly suggests an origin in another species, acquired via replacement of the counterpart gene (ortholog) following a recombination event. An example of orthologous gene replacement is provided by the nra/rofA locus, which encodes a key regulator of pilus gene transcription. Of biological importance is the previous finding that the presence of the nra- and rofA-lineage alleles, which are approximately 35% divergent, correlates strongly with genetic markers for streptococcal infection at different tissue sites in the human host (skin, throat).In this report, the impact of orthologous gene replacement targeting the nra/rofA locus is experimentally addressed. Replacement of the native nra-lineage allele with a rofA-lineage allele, plus their respective upstream regions, preserved the polarity of Nra effects on pilus gene transcription (i.e., activation) in the skin strain Alab49. Increased pilus gene transcription in the rofA chimera correlated with a higher rate of bacterial growth at the skin. The transcriptional regulator MsmR, which represses nra and pilus gene transcription in the Alab49 parent strain, has a slight activating effect on pilus gene expression in the rofA chimera construct.Data show that exchange of orthologous forms of a regulatory gene is stable and robust, and pathogenicity is preserved. Yet, new phenotypes may also be introduced by altering the circuitry within a complex transcriptional regulatory network. It is proposed that orthologous gene replacement via interspecies exchange is an important mechanism in the evolution of highly recombining bacteria such as S. pyogenes

The Role of Galectin-1 and Galectin-3 in the Mucosal Immune Response to Citrobacter rodentium Infection

Despite their abundance at gastrointestinal sites, little is known about the role of galectins in gut immune responses. We have therefore investigated the Citrobacter rodentium model of colonic infection and inflammation in Galectin-1 or Galectin-3 null mice. Gal-3 null mice showed a slight delay in colonisation after inoculation with C. rodentium and a slight delay in resolution of infection, associated with delayed T cell, macrophage and dendritic cell infiltration into the gut mucosa. However, Gal-1 null mice also demonstrated reduced T cell and macrophage responses to infection. Despite the reduced T cell and macrophage response in Gal-1 null mice, there was no effect on C. rodentium infection kinetics and pathology. Overall, Gal-1 and Gal-3 play only a minor role in immunity to a gut bacterial pathogen

Bovine cryptosporidiosis: impact, host-parasite interaction and control strategies

International audienceAbstractGastrointestinal disease caused by the apicomplexan parasite Cryptosporidium parvum is one of the most important diseases of young ruminant livestock, particularly neonatal calves. Infected animals may suffer from profuse watery diarrhoea, dehydration and in severe cases death can occur. At present, effective therapeutic and preventative measures are not available and a better understanding of the host–pathogen interactions is required. Cryptosporidium parvum is also an important zoonotic pathogen causing severe disease in people, with young children being particularly vulnerable. Our knowledge of the immune responses induced by Cryptosporidium parasites in clinically relevant hosts is very limited. This review discusses the impact of bovine cryptosporidiosis and describes how a thorough understanding of the host–pathogen interactions may help to identify novel prevention and control strategies

Augmented and Virtual Reality in Mobile Fitness Applications: A Survey

Obesity is a major issue around the world. It is the main reason for several chronic diseases. Obesity can be stopped by encouraging people to do physical activities and making behaviour intervention regarding lifestyle. Mobile fitness apps are emerging because of the unique features that are provided. They are seen as a vital tool to motivate people suffering from obesity to perform physical activities and make behaviour intervention regarding health and fitness. Augmented reality (AR) and virtual reality (VR) technologies have been used successfully in different kinds of mobile apps. This paper presents a systematic review of some of the most recent AG and VR researches in mobile apps. It discusses the main findings of applying both technologies in different fields of mobile apps. Based on this systematic review, a fitness mobile app for obese individuals that consider both AR and VR technology will be developed