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      The different ecological niches of enterotoxigenic E scherichia coli

      review-article
      1 , 2 ,
      Environmental Microbiology
      John Wiley and Sons Inc.

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          Summary

          Enterotoxigenic E scherichia coli ( ETEC) is a water and food‐borne pathogen that infects the small intestine of the human gut and causes diarrhoea. Enterotoxigenic E . coli adheres to the epithelium by means of colonization factors and secretes two enterotoxins, the heat labile toxin and/or the heat stable toxin that both deregulate ion channels and cause secretory diarrhoea. Enterotoxigenic E . coli as all E . coli, is a versatile organism able to survive and grow in different environments. During transmission and infection, ETEC is exposed to various environmental cues that have an impact on survivability and virulence. The ability to cope with exposure to different stressful habitats is probably shaping the pool of virulent ETEC strains that cause both endemic and epidemic infections. This review will focus on the ecology of ETEC in its different habitats and interactions with other organisms as well as abiotic factors.

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          Most cited references78

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          Escherichia coli acid resistance: tales of an amateur acidophile.

          Gastrointestinal pathogens are faced with an extremely acidic environment. Within moments, a pathogen such as Escherichia coli O157:H7 can move from the nurturing pH 7 environment of a hamburger to the harsh pH 2 milieu of the stomach. Surprisingly, certain microorganisms that grow at neutral pH have elegantly regulated systems that enable survival during excursions into acidic environments. The best-characterized acid-resistance system is found in E. coli.
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            Oligosaccharides in human milk: structural, functional, and metabolic aspects.

            Research on human milk oligosaccharides (HMOs) has received much attention in recent years. However, it started about a century ago with the observation that oligosaccharides might be growth factors for a so-called bifidus flora in breast-fed infants and extends to the recent finding of cell adhesion molecules in human milk. The latter are involved in inflammatory events recognizing carbohydrate sequences that also can be found in human milk. The similarities between epithelial cell surface carbohydrates and oligosaccharides in human milk strengthen the idea that specific interactions of those oligosaccharides with pathogenic microorganisms do occur preventing the attachment of microbes to epithelial cells. HMOs may act as soluble receptors for different pathogens, thus increasing the resistance of breast-fed infants. However, we need to know more about the metabolism of oligosaccharides in the gastrointestinal tract. How far are oligosaccharides degraded by intestinal enzymes and does oligosaccharide processing (e.g. degradation, synthesis, and elongation of core structures) occur in intestinal epithelial cells? Further research on HMOs is certainly needed to increase our knowledge of infant nutrition as it is affected by complex oligosaccharides.
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              Alkaline pH homeostasis in bacteria: new insights.

              The capacity of bacteria to survive and grow at alkaline pH values is of widespread importance in the epidemiology of pathogenic bacteria, in remediation and industrial settings, as well as in marine, plant-associated and extremely alkaline ecological niches. Alkali-tolerance and alkaliphily, in turn, strongly depend upon mechanisms for alkaline pH homeostasis, as shown in pH shift experiments and growth experiments in chemostats at different external pH values. Transcriptome and proteome analyses have recently complemented physiological and genetic studies, revealing numerous adaptations that contribute to alkaline pH homeostasis. These include elevated levels of transporters and enzymes that promote proton capture and retention (e.g., the ATP synthase and monovalent cation/proton antiporters), metabolic changes that lead to increased acid production, and changes in the cell surface layers that contribute to cytoplasmic proton retention. Targeted studies over the past decade have followed up the long-recognized importance of monovalent cations in active pH homeostasis. These studies show the centrality of monovalent cation/proton antiporters in this process while microbial genomics provides information about the constellation of such antiporters in individual strains. A comprehensive phylogenetic analysis of both eukaryotic and prokaryotic genome databases has identified orthologs from bacteria to humans that allow better understanding of the specific functions and physiological roles of the antiporters. Detailed information about the properties of multiple antiporters in individual strains is starting to explain how specific monovalent cation/proton antiporters play dominant roles in alkaline pH homeostasis in cells that have several additional antiporters catalyzing ostensibly similar reactions. New insights into the pH-dependent Na(+)/H(+) antiporter NhaA that plays an important role in Escherichia coli have recently emerged from the determination of the structure of NhaA. This review highlights the approaches, major findings and unresolved problems in alkaline pH homeostasis, focusing on the small number of well-characterized alkali-tolerant and extremely alkaliphilic bacteria.
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                Author and article information

                Journal
                Environ Microbiol
                Environ. Microbiol
                10.1111/(ISSN)1462-2920
                EMI
                Environmental Microbiology
                John Wiley and Sons Inc. (Hoboken )
                1462-2912
                1462-2920
                21 December 2015
                March 2016
                : 18
                : 3 , Special Issue on Pathogen Ecology ( doiID: 10.1111/emi.2016.18.issue-3 )
                : 741-751
                Affiliations
                [ 1 ] Department of Infectious Diseases Institute of Biomedicine Sahlgrenska AcademyUniversity of Gothenburg GothenburgSweden
                [ 2 ] Department of Microbiology, Tumor and Cell BiologyKarolinska Institutet StockholmSweden
                Author notes
                [*] [* ]For correspondence. E‐mail asa.sjoling@ 123456ki.se ; Tel. +46‐8‐52487504.
                Article
                EMI13106
                10.1111/1462-2920.13106
                4982042
                26522129
                750af5f2-f539-4974-bef0-1f801dff4291
                © 2015 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

                This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

                History
                : 06 July 2015
                : 30 September 2015
                : 26 October 2015
                Page count
                Pages: 11
                Funding
                Funded by: Swedish Research Council
                Funded by: Swedish International Development Cooperation Agency (Sida)
                Funded by: Swedish Foundation for Strategic Research (SSF)
                Categories
                Minireviews
                Minireview
                Custom metadata
                2.0
                emi13106
                March 2016
                Converter:WILEY_ML3GV2_TO_NLMPMC version:4.9.4 mode:remove_FC converted:16.08.2016

                Microbiology & Virology
                Microbiology & Virology

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