Table of Contents

Volume 3, Issue 3

  May/June 2012

  Pages 173 - 276

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 Issue Catalogue (MARC XML)

THE INSIDE PASSAGE

Open Access Article

Naming names: Eponyms and biological history

Gayatri Vedantam and V.K. Viswanathan
Pages 173 - 175
http://dx.doi.org/10.4161/gmic.20454
Abstract | Full Text | PDF

The constraints imposed by available experimental data, and the need for precision, typically limits the eloquence of researchers. Scientists, however, indulge in their literary and poetic selves in the names that they bestow on genes and proteins, on organisms and diseases. We briefly review some familiar names in the Inside Passage, and explore their historical antecedents.




REVIEWS

Open Access Article

Microbes-induced EMT at the crossroad of inflammation and cancer

Paul Hofman and Valérie Vouret-Craviari
Pages 176 - 185
http://dx.doi.org/10.4161/gmic.20288
Abstract | Full Text | PDF

It is noteworthy that bacterial or viral infections, and the resulting chronic inflammation, have been shown to predispose individuals to certain types of cancer. Remarkably, these microbes upregulated some transcription factors involved in the regulation of the epithelial to mesenchymal transition, referred herein as EMT. EMT is a cellular process that consists in the conversion of epithelial cell phenotype to a mesenchymal phenotype. Under physiological conditions EMT is clearly important for embryogenesis, organ development, wound repair and tissue remodeling. However, EMT may also be activated under pathologic conditions, more particularly in carcinogenesis and metastatic progression. In this review, we make a parallel between microbes- and growth factors-induced transcription factors. A unifying EMT model then emerges that may help in understanding the development of microbial pathogenesis and in defining new potential future therapeutic strategy in treating diseases linked to infections.

Open Access Article

The gut microbiota and its relationship to diet and obesity: New insights

Siobhan F. Clarke, Eileen F. Murphy, Kanishka Nilaweera, Paul R. Ross, Fergus Shanahan, Paul W. O’Toole and Paul D. Cotter
Pages 186 - 202
http://dx.doi.org/10.4161/gmic.20168
Abstract | Full Text | PDF

Obesity develops from a prolonged imbalance of energy intake and energy expenditure. However, the relatively recent discovery that the composition and function of the gut microbiota impacts on obesity has lead to an explosion of interest in what is now a distinct research field. Here, research relating to the links between the gut microbiota, diet and obesity will be reviewed under five major headings: (1) the gut microbiota of lean and obese animals, (2) the composition of the gut microbiota of lean and obese humans, (3) the impact of diet on the gut microbiota, (4) manipulating the gut microbiota and (5) the mechanisms by which the gut microbiota can impact on weight gain.

Open Access Article

Composition of the early intestinal microbiota: Knowledge, knowledge gaps and the use of high-throughput sequencing to address these gaps

Fiona Fouhy, R. Paul Ross, Gerald F. Fitzgerald, Catherine Stanton and Paul D. Cotter
Pages 203 - 220
http://dx.doi.org/10.4161/gmic.20169
Abstract | Full Text | PDF

The colonization, development and maturation of the newborn gastrointestinal tract that begins immediately at birth and continues for two years, is modulated by numerous factors including mode of delivery, feeding regime, maternal diet/weight, probiotic and prebiotic use and antibiotic exposure pre-, peri- and post-natally. While in the past, culture-based approaches were used to assess the impact of these factors on the gut microbiota, these have now largely been replaced by culture-independent DNA-based approaches and most recently, high-throughput sequencing-based forms thereof. The aim of this review is to summarize recent research into the modulatory factors that impact on the acquisition and development of the infant gut microbiota, to outline the knowledge recently gained through the use of culture-independent techniques and, in particular, highlight advances in high-throughput sequencing and how these technologies have, and will continue to, fill gaps in our knowledge with respect to the human intestinal microbiota.




RESEARCH PAPERS

Open Access Article

Gut Balance, a synbiotic supplement, increases fecal Lactobacillus paracasei but has little effect on immunity in healthy physically active individuals

Nicholas P. West, David B. Pyne, Allan Cripps, Claus T. Christophersen, Michael A. Conlon and Peter A. Fricker
Pages 221 - 227
http://dx.doi.org/10.4161/gmic.19579
Abstract | Full Text | PDF

Synbiotic supplements, which contain multiple functional ingredients, may enhance the immune system more than the use of individual ingredients alone. A double blind active controlled parallel trial over a 21 day exercise training period was conducted to evaluate the effect of Gut Balance^TM, which contains Lactobacillus paracasei subsp paracasei (L. casei 431^®), Bifidobacterium animalis ssp lactis (BB-12^®), Lactobacillus acidophilus (LA-5^®), Lactobacillus rhamnosus (LGG^®), two prebiotics (raftiline and raftilose) and bovine whey derived lactoferrin and immunoglobulins with acacia gum on fecal microbiota, short chain fatty acids (SCFA), gut permeability, salivary lactoferrin and serum cytokines. All subjects randomized were included in the analysis. There was a 9-fold (1.2-fold to 64-fold; 95% confidence intervals p = 0.03) greater increase in fecal L. paracasei numbers with Gut Balance^TM compared with acacia gum supplementation. Gut Balance^TM was associated with a 50% (-12% to 72%; p = 0.02) smaller increase in the concentration of serum IL-16 in comparison to acacia gum from pre- to post-study. No substantial effects of either supplement were evident in fecal SCFA concentrations, measures of mucosal immunity or GI permeability. Clinical studies are now required to determine whether Gut Balance^TM may exert beneficial GI health effects by increasing the recovery of fecal L. paracasei. Both supplements had little effect on immunity. Twenty-two healthy physically active male subjects (mean age = 33.9 ± 6.5 y) were randomly allocated to either daily prebiotic or synbiotic supplementation for 21 day. Saliva, blood, urine and fecal samples were collected pre-, mid- and post-intervention. Participants recorded patterns of physical activity on a self-reported questionnaire.

Open Access Article

Study on the association of helicobacter species with viral hepatitis-induced hepatocellular carcinoma

Alexander Krüttgen, Hans-Peter Horz, Josefine Weber-Heynemann, Mihael Vucur, Christian Trautwein, Gerhard Haase, Tom Luedde and Christoph Roderburg
Pages 228 - 233
http://dx.doi.org/10.4161/gmic.19922
Abstract | Full Text | PDF

Helicobacter species are important pathogens and previous studies in mice suggested a link between colonization by Helicobacter hepaticus (H. hepaticus) and hepatocellular carcinoma (HCC). This study aimed at corroborating this potential link in human patients. We used a sensitive and specific Helicobacter ssp PCR assay to screen stool samples from a collective of patients with viral-induced HCC (hepatitis B or hepatitis C) and a control group for presence of Helicobacter ssp DNA. Although retrieving DNA of H. pylori and H. canadensis from stool samples of non-HCC patients, we found no evidence indicating the presence of H. hepaticus in HCC-patients with chronic hepatitis B or hepatitis C. Interestingly we found H. canadensis in a stool sample of a patient presenting with diarrhea. Taken together, our data argue against a pathogenic role of H. hepaticus in viral-induced HCC. Yet, our results do not exclude a role of H. hepaticus in those HCC cases caused by other carcinogens, such as aflatoxin. Moreover, we speculate that H. canadensis might be a novel gastrointestinal pathogen.

Open Access Article

Comparative evaluation of establishing a human gut microbial community within rodent models

Melissa L. Wos-Oxley, André Bleich, Andrew P.A. Oxley, Silke Kahl, Lydia M. Janus, Anna Smoczek, Hannes Nahrstedt, Marina C. Pils, Stefan Taudien, Matthias Platzer, Hans-Jürgen Hedrich, Eva Medina and Dietmar H. Pieper
Pages 234 - 249
http://dx.doi.org/10.4161/gmic.19934
Abstract | Full Text | PDF

The structure of the human gut microbial community is determined by host genetics and environmental factors, where alterations in its structure have been associated with the onset of different diseases. Establishing a defined human gut microbial community within inbred rodent models provides a means to study microbial-related pathologies, however, an in-depth comparison of the established human gut microbiota in the different models is lacking. We compared the efficiency of establishing the bacterial component of a defined human microbial community within germ-free (GF) rats, GF mice and antibiotic-treated specific pathogen-free mice. Remarkable differences were observed between the different rodent models. While the majority of abundant human-donor bacterial phylotypes were established in the GF rats, only a subset was present in the GF mice. Despite the fact that members of the phylum Bacteriodetes were well established in all rodent models, mice enriched for phylotypes related to species of Bacteroides. In contrary to the efficiency of Clostridiales to populate the GF rat in relative proportions to that of the human-donor, members of Clostridia cluster IV only poorly colonize the mouse gut. Thus, the genetic background of the different recipient rodent systems (that is, rats and mice) strongly influences the nature of the populating human gut microbiota, determining each model’s biological suitability.

Open Access Article

Activated fluid transport regulates bacterial-epithelial interactions and significantly shifts the murine colonic microbiome

Simon Keely, Caleb J. Kelly, Thomas Weissmueller, Adrianne Burgess, Brandie D. Wagner, Charles E. Robertson, J. Kirk Harris and Sean P. Colgan
Pages 250 - 260
http://dx.doi.org/10.4161/gmic.20529
Abstract | Full Text | PDF

Within the intestinal mucosa, epithelial cells serve multiple functions to partition the lumen from the lamina propria. As part of their natural function, intestinal epithelial cells actively transport electrolytes with passive water movement as a mechanism for mucosal hydration. Here, we hypothesized that electrogenic Cl^- secretion, and associated mucosal hydration, influences bacterial-epithelial interactions and significantly influences the composition of the intestinal microbiota. An initial screen of different epithelial secretagogues identified lubiprostone as the most potent agonist for which to define these principles. In in vitro studies using cultured T84 cells, lubiprostone decreased E. coli translocation in a concentration-dependent manner (p < 0.001) and decreased S. typhimurium internalization and translocation by as much as 71 ± 6% (p < 0.01). Such decreases in bacterial translocation were abolished by inhibition of electrogenic Cl^- secretion and water transport using the Na-K-Cl^- antagonist bumetanide (p < 0.01). Extensions of these findings to microbiome analysis in vivo revealed that lubiprostone delivered orally to mice fundamentally shifted the intestinal microbiota, with notable changes within the Firmicutes and Bacteroidetes phyla of resident colonic bacteria. Such findings document a previously unappreciated role for epithelial Cl^- secretion and water transport in influencing bacterial-epithelial interactions and suggest that active mucosal hydration functions as a primitive innate epithelial defense mechanism.




ARTICLE ADDENDA

Open Access Article

Portrait of an immunoregulatory bifidobacterium

Patrycja Konieczna, Cezmi A. Akdis, Eamonn M.M. Quigley, Fergus Shanahan and Liam O'Mahony
Pages 261 - 266
http://dx.doi.org/10.4161/gmic.20358
Abstract | Full Text | PDF

There is increasing interest in the administration of microbes or microbial metabolites for the prevention and treatment of aberrant inflammatory activity. The protective effects associated with these microbes are mediated by multiple mechanisms involving epithelial cells, DCs and T cells, but most data are derived from animal models. In this addendum, we summarize our recent data, showing that oral consumption of Bifidobacterium infantis 35624 is associated with enhanced IL-10 secretion and Foxp3 expression in human peripheral blood. In addition, we discuss the potential DC subset-specific mechanisms, which could contribute to DC_REG and T_REG programming by specific gut microbes.

Open Access Article

Retraction of enteropathogenic E. coli type IV pili promotes efficient host cell colonization, effector translocation and tight junction disruption

Benjamin Aroeti, Gil Friedman, Efrat Zlotkin-Rivkin and Michael S. Donnenberg
Pages 267 - 271
http://dx.doi.org/10.4161/gmic.19814
Abstract | Full Text | PDF

Type IV pili (Tfp) play a primary role in mediating the adherence of pathogenic bacteria to their hosts. The pilus filament can retract with an immense force. However, the role of this activity in microbial pathogenesis has not been rigorously explored. Experiments performed on volunteers suggested that the retraction capacity of enteropathogenic Escherichia coli (EPEC) Tfp is required for full virulence. Here we review our recent study¹ in which we showed that the retraction capacity of the EPEC Tfp facilitates tight-junction disruption and actin-rich pedestal formation by promoting efficient bacterial protein effector translocation into epithelial host cells. We also present new data using live imaging confocal microscopy suggesting that EPEC adheres to monolayers in microcolonies and that Tfp retraction facilitates significant changes in the microcolony shape, which may be critical for efficient effector delivery. Our studies hence suggest novel insights into the role of pili retraction in EPEC pathogenesis.

Open Access Article

Fimbriation and curliation in Escherichia coli O157:H7: A paradigm of intestinal and environmental colonization

Sonja J. Lloyd, Jennifer M. Ritchie and Alfredo G. Torres
Pages 272 - 276
http://dx.doi.org/10.4161/gmic.20661
Abstract | Full Text | PDF

Shiga toxin-producing Escherichia coli (STEC) serotypes, particularly E. coli O157:H7, possess a variety of fimbrial and afimbrial adhesins which have emerged as important contributors to intestinal colonization. E. coli O157:H7 possesses two chromosomal operons encoding long polar fimbriae (Lpf), which have been found to influence adherence in vitro and colonization in vivo. In a recent Infection and Immunity paper, we further explored the role of Lpf in E. coli O157:H7 intestinal colonization by using the infant rabbit model of STEC infection. We found that an E. coli O157:H7 Lpf-deficient mutant was outcompeted in the rabbit intestine by its parental strain, which may suggest that Lpf contributes to colonization. In contrast, the Lpf-deficient mutant showed an increased adherence to cultured intestinal epithelial cells, and we discovered that this strain overexpressed curli fibers. In this addendum article, we provide a continued perspective on the predicted roles of Lpf and curli, both in vivo and in vitro.