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Autumn Meeting 6–9 September 2010 University of Nottingham – www.sgmnottingham2010.org.uk SESSION ABSTRACTS ↑CONTENTS NT01 CONT. opened up exciting possibilities for understanding and exploiting its biological consequences. Microbiological interests in CO have been mostly restricted to CO oxidation, CO sensing mechanisms, and the use of CO as a haem ligand in microbial biochemistry but, more recently, CO toxicity and the microbial stress responses. An important advance in recent years has been the development of COreleasing molecules (CORMs) for experimental administration of CO as an alternative to the use of CO gas. CORMs have therapeutic potential in vascular disease, anti-inflammatory effects, CO-mediated cell signalling in apoptosis, applications in organ preservation, and as antimicrobial agents, particularly in the control of bacterial infections. Many CORMs are metal carbonyl compounds, including CORM-3 [Ru(CO) 3 Cl(glycinate)]. Here, recent experimental data on the antimicrobial activities of CORM-3 are presented. CORM-3 is a potent inhibitor of bacterial growth and respiration; the compound penetrates bacterial cells and delivers CO to biological targets. The effects include not only the binding to ferrous respiratory oxidases, but global changes in the transcriptome affecting genes for respiration, metal homeostasis and other functions. Future prospects are suggested and unanswered questions posed. Metal-induced oxidative stress and iron–sulfur proteins in yeast Simon Avery School of Biology, University of Nottingham, Nottingham NG7 2RD (Email simon.avery@nottingham.ac.uk) The molecular targets of metal toxicity are generally not well characterized. Oxidative stress is a commonly cited cause of metal action. Therefore, it might be anticipated that metals and oxidants share common toxicity mechanisms. The redox activity of metals like Cu, Cr and Fe can account for their catalysis of oxidative stress. Other metals like Cd may perturb antioxidant defence systems, lowering the cell’s capacity to deal with reactive oxygen species. The reversal of methionine oxidation by methionine sulfoxide reductases (MSRs) is a well conserved antioxidant defence mechanism. MSRs protect cells from oxidative stress and, we show in the yeast model, Cu toxicity. This action of yeast MSRs centres on a novel role in helping to preserve the integrity of Fe–S clusters, major targets of oxidative stress. Thus, Cu toxicity in yeast can involve an action on Fe–S proteins. Furthermore, this action centres on an extra-mitochondrial Fe–S protein that is also susceptible to stress associated with other metals and pro-oxidants. The work highlights novel and common mechanisms involved in the toxic action of diverse pro-oxidants. Oxidative stress and metalloenzymes Jim Imlay Dept of <strong>Microbiology</strong>, University of Illinois at Urbana–Champaign, B103 CLSL, 601 S Goodwin Avenue, Urbana IL 61801, USA The adventitious autoxidation of redox enzymes ensures that aerobic organisms continuously form intracellular superoxide and hydrogen peroxide. The endogenous superoxide is constrained to non-toxic levels by the actions of superoxide dismutases and reductases, while hydrogen peroxide is scavenged by peroxidases and catalases. However, when hydrogen peroxide is present in microbial environments, it flows across membranes and into the cell, where it may accumulate to concentrations that exceed the capacity of basal defenses. When E. coli encounters this situation, the OxyR stress response activates several strategies that protect the organism. Hydrogen peroxide is especially hazardous for iron-containing enzymes, and a key element of the OxyR response is the Suf system, which takes over the synthesis and repair of iron-sulfur enzymes. Peroxide also threatens mononuclear iron enzymes. They are protected by the concerted import of manganese and sequestration of iron, which together ensure that the vulnerable iron atoms in these enzymes are replaced with non-reactive manganese. Iron and copper acquisition in the fungal pathogen Candida albicans: an intimate partnership Annette Cashmore Dept of Genetics, University of Leicester, Leicester LE1 7RH (Email amc19@le.ac.uk) Candida albicans is an opportunistic pathogen of humans, existing in yeast and hyphal forms. Both copper and iron are essential for Candida to grow, but levels of these metals are tightly regulated in order to avoid toxic effects to the cell. We have identified surface reductase genes, CaFRE7 and CaFRE10, both of which code for iron and copper reductase activities. There is a copper transporter, encoded by CaCTR1 and an iron transporter, enoded by CaFTR1. The FTR1 transporter is complexed with multi-copper oxidase proteins, with copper being essential for iron uptake. Therefore the processes of iron and copper acquisition are inextricably linked. We have also identified a gene CaMAC1 , that encodes a transcription factor, and demonstrated that this transcription factor regulates several genes in response to copper levels. The CAMAC1 regulon includes genes involved in both iron and copper uptake (eg. CaFRE7, CaFRE10, CaCTR1); it also regulates itself. This emphasizes the intimate relationship between the processes involved in the acquisition of these two metals. In order to elucidate CaMAC1-mediated regulation we are investigating the protein/DNA and protein/protein interactions involved. Please note: Abstracts are published as received from the authors and are not subject to editing. society for general microbiology 5 sgmconferences
Autumn Meeting 6–9 September 2010 University of Nottingham – www.sgmnottingham2010.org.uk SESSION ABSTRACTS ↑CONTENTS NT01 CONT. Nickel, iron and urease: the acid-resistance triangle of pathogenic Helicobacter species ARNOUD H.M. VAN VLIET 1 & Jeroen Stoof 2 1 Institute of Food Research, Norwich; 2 University of Nottingham, Nottingham The acidic gastric environment of mammals can be chronically colonized by pathogenic Helicobacter species (with Helicobacter pylori as the best known example). Nickel plays a key role in gastric colonization by Helicobacter species, as nickel cofactors the urease and hydrogenase enzymes. Both enzymes are essential colonization factors, with urease conferring acid resistance by urea hydrolysis, and hydrogenase allowing usage of microflora-produced hydrogen for energy production. Iron is also an essential metal for Helicobacter species, both for metabolism and for systems protecting against oxidative damage. Hence it is no surprise that Helicobacter species have intricate systems to both acquire sufficient nickel and iron to allow growth, while simultaneously preventing toxicity by uncontrolled nickel- and iron-acquisition. One interesting aspect is that nickel availability in the GI-tract is low, being mostly restricted to vegetarian dietary sources, and while this is no problem for Helicobacter species colonizing omnivores, it does present a challenge for Helicobacter species colonizing obligate carnivores. We have recently shown that these carnivore-colonizing Helicobacter species have adapted by expressing a second urease enzyme lacking nickel, demonstrating the intricate link between host, diet and pathogen evolution. In this overview the recent developments in Helicobacter urease, nickel- and iron-metabolism will be discussed. Interplay between manganese and iron during pneumococcal pathogenesis ALASTAIR G. MCEWAN 1 , Cheryl-Lyn Ong 1 Christopher A. McDevitt 2 , Adam J. Potter 2 , Abiodun D. Ogunniyi 2 & James C. Paton 2 1 School of Chemistry & Molecular Biosciences, The University of Queensland, St Lucia 4072, Australia; 2 Research Centre for Infectious Diseases; School of Molecular & Biomedical Science, University of Adelaide SA 5005, Australia (Email mcewan@uqedu.au; Tel. +61 7 3365 4622) Variation in transition metal ion concentrations may strongly influence pneumococcal virulence. The nasopharynx has a high level of available manganese, relative to iron, while in blood the opposite is the case. The response regulator RitR appears to be central to the response to iron in S. pneumoniae. A ritR mutant was defective in growth in medium with a high Fe/Mn ratio but was not affected when the ratio of Mn/Fe was increased. In a mouse model system the ritR mutant was able to colonize the nasopharynx but was unable to survive in lung or blood. Our results show that RitR is essential for the adaptation of pneumococcus to a high Fe/low Mn environment found in the lung and blood. Antimicrobial metals – back to the future? Jon L. Hobman School of Biosciences, The University of Nottingham, Sutton Bonington Campus, Sutton Bonington, Leicestershire LE12 5RD (Email jon.hobman@nottingham.ac.uk) Metals such as mercury, arsenic, copper and silver have been used in various forms as antimicrobials for certainly hundreds – if not thousands – of years. The discovery of antibiotics and new organic antimicrobial compounds during the twentieth century saw a general decline in the clinical use of antimicrobial metal compounds, possibly with the exception of silver for burns treatments. These ‘new’ antibiotics and antimicrobials were regarded as generally being safer to the patient and more effective antimicrobials than the metalbased compounds they supplanted. However, increasing concerns about antibiotic and multidrug resistance (MDR) in emerging and re-emerging pathogens, and new, and rediscovered uses for antimicrobial metals have promoted a recent upsurge in interest in their use in both clinical and non-clinical products. Metal ion resistance mechanisms have already been characterized in a wide range of bacteria, but how widespread are these resistances in emerging and re-emerging pathogens? This talk will examine the evidence for antimicrobial metal ion resistances in recent genome sequence data from emerging pathogens – suggesting that the resistance genes are already present in some of these organisms – and will address some of the possible consequences of resistance to antimicrobial metals in these bacteria. Structure and function of Fur proteins from Mycobacterium tuberculosis Ehmke Pohl School of Biological & Biomedical Sciences, University of Durham, Durham University, South Road DH1 3LE The ferric uptake regulator (Fur) proteins form a diverse family of metal-dependent transcriptional regulator. Fur was originally identified in E. coli but homologues have been found in many Gram-positive and negative bacteria. Members of the Fur family control a wide Please note: Abstracts are published as received from the authors and are not subject to editing. society for general microbiology 6 sgmconferences
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Microbiology

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