Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.770950
Title: Molecular-genetic analysis of iron transport and bacterial pathogenicity: role and mechanism of the EfeUOB system of Escherichia coli O157:H7
Author: Salunkhe, Arvindkumar
ISNI:       0000 0004 7655 4894
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2016
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Abstract:
Iron acquisition is important for pathogens since iron withdrawal is key for innate immune defence. Escherichia coli 0157 is a potentially lethal intestinal pathogen. It possesses a ferrous transporter, EfeUOB, that functions at low pH aerobically; this system is cryptic in some E. coli strains (e.g. K-12). EfeUOB of E. coli 0157 represents the ideal target for further investigation of the role of this type of iron transport system in bacterial pathogenicity. efeUOB and feoABC (anaerobic ferrous-iron uptake) single and double mutants of E. coli 0157 were constructed. Growth studies showed that iron restriction reduces growth of the feo mutant under anaerobic and aerobic conditions. At low pH, with competing divalent metals and reducing agents, Mn2+ markedly inhibited growth of the efe mutant, although other metals failed to do so. Reductant was not required for this effect in liquid medium using a Bioscreen format for growth, although was required on agar plates. However, although the feo mutant was unaffected by Mn2+, the efe feo double mutant exhibited an enhanced iron-limited growth defect with respect to the efe mutant. In addition, Ni2+, Zn2+, Co2+and Mo inhibited growth of the feo mutant under iron restriction but not the efe mutant. The poor growth of the efe mutant under low iron, reducing and acidic conditions with Mn2+ was found to be dependent on the presence of hydrogen peroxide; various catalases caused reversal of the low iron growth advantage provided by the EfeUOB system. The effect on the FeoABC system was opposite, with catalase enhancing the ability of the Feo system to improve growth under aerobic iron restriction conditions. Thus, the results provided suggest a clear rationale for the presence of two dedicated ferrous iron uptake systems in E. coli 0157, with EfeUOB operational when peroxide is available (i.e. aerobically) at low pH (favouring ferrous iron stability) and FeoABC operational under low oxygen conditions when peroxide is not likely to be generated (again favouring ferrous iron stability). Colonisation studies, with Galleria mellonella as a model, suggested reduced pathogenicity for the feo mutant. In macrophage infection studies, the feo and efe feo double mutant showed statistically significant reductions in survival; survival was reduced for the efe mutant but this was not significant. A human in vitro gut model was used to study the gut colonisation and infection capacity of the efe and Teo mutants, as well as the
Supervisor: Andrews, Simon Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.770950  DOI: Not available
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