ABSTRACT
INTRODUCTION: Shielding aimed to protect those predicted to be at highest risk from COVID-19 and was uniquely implemented in the UK during the first year of the pandemic from March 2020. As the first stage in the EVITE Immunity evaluation (Effects of shielding for vulnerable people during COVID-19 pandemic on health outcomes, costs and immunity, including those with cancer:quasi-experimental evaluation), we generated a logic model to describe the programme theory underlying the shielding intervention. DESIGN AND PARTICIPANTS: We reviewed published documentation on shielding to develop an initial draft of the logic model. We then discussed this draft during interviews with 13 key stakeholders involved in putting shielding into effect in Wales and England. Interviews were recorded, transcribed and analysed thematically to inform a final draft of the logic model. RESULTS: The shielding intervention was a complex one, introduced at pace by multiple agencies working together. We identified three core components: agreement on clinical criteria; development of the list of people appropriate for shielding; and communication of shielding advice. In addition, there was a support programme, available as required to shielding people, including food parcels, financial support and social support. The predicted mechanism of change was that people would isolate themselves and so avoid infection, with the primary intended outcome being reduction in mortality in the shielding group. Unintended impacts included negative impact on mental and physical health and well-being. Details of the intervention varied slightly across the home nations of the UK and were subject to minor revisions during the time the intervention was in place. CONCLUSIONS: Shielding was a largely untested strategy, aiming to mitigate risk by placing a responsibility on individuals to protect themselves. The model of its rationale, components and outcomes (intended and unintended) will inform evaluation of the impact of shielding and help us to understand its effect and limitations.
Subject(s)
COVID-19 , Humans , COVID-19/prevention & control , Pandemics/prevention & control , Qualitative Research , England , Social SupportABSTRACT
BACKGROUND: Policy throughout the United Kingdom promotes involvement of patients and public members in research to benefit patient care and health outcomes. PRIME Centre Wales is a national research centre, developing and coordinating research about primary and emergency care which forms 90% of health service encounters. In this paper, we describe our approach to public involvement and engagement in PRIME Centre Wales (hereafter called PRIME), in particular: how this approach has developed; ways in which public members contribute to PRIME activity; the strengths and limitations of our approach, challenges and future opportunities. PRIME ensures work is relevant to service users, carers, the public and policy makers by incorporating comprehensive patient and public involvement in every phase of our work. APPROACH: PRIME has policies and processes to enable and promote successful public involvement and engagement across research activities. This ensures public perspectives and patient experiences are integrated throughout research development, implementation and dissemination and in managing and delivering PRIME strategy over a 10 year timescale. A public/patient group called SUPER is a key resource providing wide-ranging perspectives via email and face-to-face discussion. We collect information on processes and experiences to assess value and impact, to guide ongoing involvement and engagement. A funded post provides leadership and support to staff and to public/patient contributors to facilitate collaborations. DISCUSSION: A stable, well-resourced structure has provided the timescales to build strong relationships and embed diverse approaches to public involvement and engagement within PRIME. Researchers and public contributors have committed to collaborations, developed knowledge and skills and sustained relationships. Effective approaches incorporate values and actions which, when operating together, strengthen processes and outcomes of public involvement and engagement. CONCLUSION: Supportive context, motivation and time are necessary to foster values and practices that enable effective public involvement and engagement. PRIME has embedded public involvement and engagement across research activities and structures. Central is the public/patient group SUPER offering experience-based expertise to add value to the research cycle. This innovative model, aligned with best practice, enhances relevance and quality of primary and emergency care research to benefit patients and the general population.
ABSTRACT
BACKGROUND: The aim of this study was to determine whether volatile organic compounds (VOCs) present in the headspace of feces could be used to diagnose or distinguish between chronic diseases of the gastrointestinal tract and apparently healthy volunteers. METHODS: A total of 87 people were recruited, divided between 4 categories: healthy volunteers (n = 19), Crohn's disease (n = 22), ulcerative colitis (n = 20), and irritable bowel syndrome (n = 26). They each supplied fecal samples before, and except for the healthy volunteers, after treatment. Fecal samples were incubated in a sample bag with added purified air at 40°C and headspace samples were taken and concentrated on thermal sorption tubes. Gas chromatography-mass spectrometry then desorbed and analyzed these. The concentrations of a selection of high-abundance compounds were determined and assessed for differences in concentration between the groups. RESULTS: Crohn's disease samples showed significant elevations in the concentrations of ester and alcohol derivates of short-chain fatty acids and indole compared with the other groups; indole and phenol were elevated in ulcerative colitis and irritable bowel syndrome but not at a statistically significant level. After treatment, the levels of many of the VOCs were significantly reduced and were more similar to those concentrations in healthy controls. CONCLUSIONS: The abundance of a number of VOCs in feces differs markedly between Crohn's disease and other gastrointestinal conditions. Following treatment, the VOC profile is altered to more closely resemble that of healthy volunteers.
Subject(s)
Bacterial Infections/diagnosis , Colitis, Ulcerative/diagnosis , Crohn Disease/diagnosis , Feces/chemistry , Irritable Bowel Syndrome/diagnosis , Volatile Organic Compounds/analysis , Bacteria/isolation & purification , Bacterial Infections/microbiology , Case-Control Studies , Chronic Disease , Colitis, Ulcerative/microbiology , Crohn Disease/microbiology , Feces/microbiology , Female , Follow-Up Studies , Gas Chromatography-Mass Spectrometry , Healthy Volunteers , Humans , Irritable Bowel Syndrome/microbiology , Male , PrognosisABSTRACT
The relative abundance of different groups of sulphate-reducing bacteria (SRB) in faecal DNA collected before and after therapy from patients suffering from Crohn's disease (CD), irritable bowel syndrome (IBS) or ulcerative colitis (UC) has been compared with that from healthy controls. Growth tests revealed that SRB were not more abundant in samples from patients with CD before treatment than in the healthy control group. For most of the 128 samples available, these preliminary results were confirmed using degenerate PCR primers that amplify the dsrAB gene. However, some samples from patients with CD before treatment contained a growth inhibitor that was absent from IBS or UC samples. In-depth sequencing of PCR-generated dsrB fragments revealed that the diversity detected was surprisingly low, with only eight strains of SRB and the sulphite-reducing bacterium, Bilophila wadsworthia, detected above the 0.1% threshold. The proportion of the two major species detected, B. wadsworthia and Desulfovibrio piger, was as high as 93.5% of the total SRB population in the healthy control group and lower in all patient groups. Four previously undescribed species were found: it is impossible to predict whether they are sulphate or sulphite-reducing bacteria.
Subject(s)
Bacteria/classification , Bacteria/isolation & purification , Biota , Feces/microbiology , Inflammatory Bowel Diseases/microbiology , Metagenome , Sulfates/metabolism , Anti-Bacterial Agents/therapeutic use , Bacteria/genetics , Bacteria/metabolism , DNA Primers/genetics , DNA, Bacterial/genetics , High-Throughput Nucleotide Sequencing/methods , Human Experimentation , Humans , Inflammatory Bowel Diseases/drug therapy , Oxidation-Reduction , Polymerase Chain Reaction/methodsABSTRACT
High level expression of a recombinant gene results in growth arrest, followed by overgrowth by non-productive derivatives. Two methods are described for the isolation of E. coli BL21* strains that are improved hosts for recombinant protein production. Both are based upon the observations (i) that fluorescence of a C-terminal GFP tag is a reliable reporter of the production and correct folding of the N-terminal target domain; and (ii) rare mutants arise spontaneously that remain productive during long periods of high level recombinant protein production. The first method relies upon identifying these mutants amongst colonies on agar plates; the other exploits fluorescence activated cell sorting. Although identical mutations in the regulatory region of the T7 polymerase gene were found in all of the improved host strains isolated, they differed in their ability to accumulate the outer membrane protein, Ccp, or a cytoplasmic protein, CheY-GFP. Cytochrome c peroxidase activity of recombinant Ccp from one of these strains was demonstrated. Changes in levels of T7 polymerase expression are therefore insufficient to ensure increased accumulation of all recombinant proteins. We demonstrate that the methods described allow strains to be isolated that carry other, currently uncharacterised mutations that are required depending on the target protein.
Subject(s)
Escherichia coli/isolation & purification , Green Fluorescent Proteins/metabolism , Recombinant Fusion Proteins/metabolism , Bacterial Proteins , Base Sequence , Cloning, Molecular , Colony Count, Microbial , Cytochrome-c Peroxidase/metabolism , Electrophoresis, Polyacrylamide Gel , Escherichia coli/genetics , Escherichia coli/metabolism , Escherichia coli Proteins , Flow Cytometry , Green Fluorescent Proteins/analysis , Green Fluorescent Proteins/genetics , Membrane Proteins , Methyl-Accepting Chemotaxis Proteins , Molecular Sequence Data , Mutation , Phenotype , Protein Engineering , Recombinant Fusion Proteins/analysis , Recombinant Fusion Proteins/genetics , Stress, Physiological/geneticsABSTRACT
Reports that bacteria within the Firmicutes phylum, especially the species Faecalibacterium prausnitzii, are less abundant in Crohn's disease (CD) patients and supernatants from cultures of this bacterium are anti-inflammatory prompted the investigation of the possible correlations between the abundance of F. prausnitzii and the response to treatment in patients with gut diseases and healthy controls. In a randomized, double-blind trial, faeces were collected from healthy volunteers, and from patients with active CD, ulcerative colitis (UC) and irritable bowel syndrome before and after treatment. The levels of F. prausnitzii DNA in faecal suspensions were determined by PCR. Treatment by an elemental diet was effective, resulting in decreases in both the Harvey and Bradshaw index (P<0.001) and the concentrations of serum C-reactive protein (P<0.05). The total levels of F. prausnitzii in faecal samples from CD patients at presentation were lower than those in the other groups both before and after the treatment. There was no correlation between F. prausnitzii abundance and the severity of CD before treatment. Clinical improvement unexpectedly correlated with a significant decrease in the abundance of F. prausnitzii, especially the A2-165 subgroup (P<0.05). Our data suggest that a paucity of F. prausnitzii in the gastrointestinal microbial communities is likely to be a minor aetiological factor in CD: recovery following elemental diet is attributed to lower levels of gut flora.
Subject(s)
Crohn Disease/diet therapy , Crohn Disease/microbiology , Food, Formulated , Gram-Positive Bacteria/physiology , Colitis, Ulcerative/microbiology , Feces/microbiology , Gram-Positive Bacteria/genetics , Irritable Bowel Syndrome/microbiology , Severity of Illness Index , Treatment OutcomeABSTRACT
Desulfovibrio desulfuricans strain 27774 is one of a relative small group of sulfate-reducing bacteria that can also grow with nitrate as an alternative electron acceptor, but how nitrate reduction is regulated in any sulfate-reducing bacterium is controversial. Strain 27774 grew more rapidly and to higher yields of biomass with nitrate than with sulfate or nitrite as the only electron acceptor. In the presence of both sulfate and nitrate, sulfate was used preferentially, even when cultures were continuously gassed with nitrogen and carbon dioxide to prevent sulfide inhibition of nitrate reduction. The napC transcription start site was identified 112 bases upstream of the first base of the translation start codon. Transcripts initiated at the napC promoter that were extended across the napM-napA boundary were detected by reverse transcription-PCR, confirming that the six nap genes can be cotranscribed as a single operon. Real-time PCR experiments confirmed that nap operon expression is regulated at the level of mRNA transcription by at least two mechanisms: nitrate induction and sulfate repression. We speculate that three almost perfect inverted-repeat sequences located upstream of the transcription start site might be binding sites for one or more proteins of the CRP/FNR family of transcription factors that mediate nitrate induction and sulfate repression of nitrate reduction by D. desulfuricans.
Subject(s)
Bacterial Proteins/metabolism , Desulfovibrio desulfuricans/metabolism , Nitrates/metabolism , Sulfates/metabolism , Bacterial Proteins/genetics , Binding Sites , Blotting, Western , Desulfovibrio desulfuricans/genetics , Electrophoresis, Polyacrylamide Gel , Nitrites/metabolism , Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , Transcription Initiation SiteABSTRACT
AIM: This paper is a report of a study to understand the impact of telenursing from the perspective of nurses involved in its provision, and in more traditional roles. BACKGROUND: Nurse-led telephone helplines have recently been introduced across the United Kingdom, a major step in the development of nursing practice. METHOD: A structured questionnaire was sent to all nurses working in the NHS Direct (National Health Service Direct) Wales telephone service (n = 111). Ninety-two completed questionnaires were returned (response rate 83 per cent). Two focus groups were conducted: one with telephone service nurses (n = 8) and one with other nurses (n = 5). The data were collected in 2002. FINDINGS: Respondents represented a highly educated workforce from a range of healthcare specialties. They reported that they joined the telephone service for improved salary and flexible working. Two-thirds reported improved job satisfaction. All focus group participants reported that the development of nursing skills was affected by the use of decision support software and the remote nature of the consultation. Participants reported opportunities for skill development, although the role could be stressful. All agreed that the service was popular with callers, but the nurses from outside raised concerns about whether telenursing was 'real' nursing and about the evidence base for the service and access by disadvantaged groups. CONCLUSION: Differences between the groups reflect policy tensions between the need to develop new nursing skills, including the use of technology, to improve efficiency and recognition of the worth of hands-on nursing. These tensions must be addressed for the telephone service to function as part of an integrated healthcare system.
Subject(s)
Delivery of Health Care, Integrated/organization & administration , Nursing Care/organization & administration , State Medicine/organization & administration , Telemedicine/organization & administration , Adult , Aged , Female , Focus Groups , Humans , Job Satisfaction , Male , Middle Aged , Nurse's Role , Professional-Patient Relations , Surveys and Questionnaires , United KingdomABSTRACT
AIM: This paper is a report of a study to map school nursing provision across the health and education sectors in Wales to identify the number, age, qualifications, terms of employment, location, functions and access to continuing professional development and clinical supervision of school nurses. BACKGROUND: School nurses are important in promoting the health of school-aged children. Increased demands have arisen from changes in patterns of health, illness and lifestyles. METHODS: An interview survey was conducted with a purposive sample of school nursing/health visiting managers from 13 healthcare sector providers, senior personnel officers from 22 Local Education Authorities and 45 head teachers/school nurses from independent schools. Data were collected between March and June 2004 and the overall response rate exceeded 80%. RESULTS: A total of 249 school nurses were identified: 90% employed by the healthcare sector and 10% by the education sector. An ageing, under-developed and under-resourced service was identified. Disparity in practice within and across the sectors was evident, resulting from lack of policy direction regarding the scope and content of school nursing services. Workforce size, age and educational profile pose challenges for service delivery. CONCLUSION: Investment in recruitment and education is required if school nurses are to meet increasing demands and fulfil their public health role. The low percentage of school nurses aged under 30 years may reflect lack of a career pathway and understanding of school nursing. The findings enable national and international comparisons in terms of numbers, size of caseload, age, qualifications, terms of employment and activities and functions.
Subject(s)
School Nursing , Adult , Education, Nursing, Continuing , Health Care Surveys , Health Services Needs and Demand , Humans , Interviews as Topic , Middle Aged , School Nursing/education , School Nursing/organization & administration , Task Performance and Analysis , Wales , Workforce , WorkloadABSTRACT
The transcription factor FNR, the regulator of fumarate and nitrate reduction, regulates major changes as Escherichia coli adapts from aerobic to anaerobic growth. In an anaerobic glycerol/trimethylamine N-oxide/fumarate medium, the fnr mutant grew as well as the parental strain, E. coli K12 MG1655, enabling us to reveal the response to oxygen, nitrate, and nitrite in the absence of glucose repression or artifacts because of variations in growth rate. Hence, many of the discrepancies between previous microarray studies of the E. coli FNR regulon were resolved. The current microarray data confirmed 31 of the previously characterized FNR-regulated operons. Forty four operons not previously known to be included in the FNR regulon were activated by FNR, and a further 28 operons appeared to be repressed. For each of these operons, a match to the consensus FNR-binding site sequence was identified. The FNR regulon therefore minimally includes at least 103, and possibly as many as 115, operons. Comparison of transcripts in the parental strain and a narXL deletion mutant revealed that transcription of 51 operons is activated, directly or indirectly, by NarL, and a further 41 operons are repressed. The narP gene was also deleted from the narXL mutant to reveal the extent of regulation by phosphorylated NarP. Fourteen promoters were more active in the narP+ strain than in the mutant, and a further 37 were strongly repressed. This is the first report that NarP might function as a global repressor as well as a transcription activator. The data also revealed possible new defense mechanisms against reactive nitrogen species.
Subject(s)
DNA-Binding Proteins/chemistry , Escherichia coli Proteins/chemistry , Escherichia coli Proteins/physiology , Escherichia coli/physiology , Iron-Sulfur Proteins/physiology , Membrane Proteins/chemistry , Nitrates/chemistry , Nitrites/chemistry , Oxygen/metabolism , Phosphoproteins/chemistry , Protein Kinases/chemistry , Binding Sites , Chromatin Immunoprecipitation , DNA Primers/chemistry , Escherichia coli/metabolism , Escherichia coli Proteins/metabolism , Gene Deletion , Genome, Bacterial , Glucose/metabolism , Iron-Sulfur Proteins/metabolism , Models, Biological , Mutation , Nucleic Acid Hybridization , Oligonucleotide Array Sequence Analysis , Promoter Regions, Genetic , Time Factors , Transcriptional ActivationABSTRACT
Neisseria gonorrhoeae is a prolific source of c-type cytochromes. Five of the constitutively expressed cytochromes are predicted, based on in silico analysis of the N. gonorrhoeae genome, to be components of the cytochrome bc1 complex, cytochrome c oxidase cbb3 or periplasmic cytochromes involved in electron transfer reactions typical of a bacterium with a microaerobic physiology. Cytochrome c peroxidase was previously shown to be a lipoprotein expressed only during oxygen-limited growth. The final c-type cytochrome, cytochrome c', similar to cytochrome c peroxidase, includes a lipobox required for targeting to the outer membrane. Maturation of cytochrome c' was partially inhibited by globomycin, an antibiotic that specifically inhibits signal peptidase II, resulting in the accumulation of the prolipoprotein in the cytoplasmic membrane. Disruption of the gonococcal cycP gene resulted in an extended lag phase during microaerobic growth in the presence but not in the absence of nitrite, suggesting that cytochrome c' protects the bacteria from NO generated by nitrite reduction during adaptation to oxygen-limited growth. The cytochrome c' gene was overexpressed in Escherichia coli and recombinant cytochrome c' was shown to be targeted to the outer membrane. Spectroscopic evidence is presented showing that gonococcal cytochrome c' is similar to previously characterized cytochrome c' proteins and that it binds NO in vitro. The demonstration that two of the seven gonococcal c-type cytochromes fulfil specialized functions and are outer membrane lipoproteins suggests that the localization of these lipoproteins close to the bacterial surface provides effective protection against external assaults from reactive oxygen and reactive nitrogen species.
Subject(s)
Cytochromes c'/metabolism , Neisseria gonorrhoeae/enzymology , Oxygen/physiology , Adaptation, Physiological , Cytochromes c'/chemistry , Escherichia coli/genetics , Gene Expression Regulation, Bacterial , Gene Expression Regulation, Enzymologic , Lipoproteins/chemistry , Mutagenesis, Site-Directed , Neisseria gonorrhoeae/genetics , Neisseria gonorrhoeae/growth & development , Nitric Oxide/metabolism , Nitrites/metabolism , Phenotype , Protein Binding , Protein Processing, Post-TranslationalABSTRACT
Abstract Ensuring collaboration between health and social care providers is a well-established policy concern in most developed countries. Thus far, however, this has proved to be a frustratingly elusive goal. Despite the growing body of empirical work devoted to this issue, social scientific theorising on the management of complex caring trajectories remains under-developed. This paper is an attempt to begin to address this gap in the literature. Drawing on Strauss et al.'s (1985) writings on illness trajectories and Elias's (1978) game model, we offer a framework - centred on the notion of a caring trajectory game - that can assist understanding of the linkages between individual trajectories of care and broader health and social care systems. It is only when we have developed a more theoretically sophisticated understanding of this relationship that we can begin to explain why trajectories of care take the course that they do. The framework arises from our analysis of eight ethnographic case studies of adults undergoing rehabilitation from a first acute stroke. In this paper we illustrate its utility by reference to one specific case: Edward.
Subject(s)
Interinstitutional Relations , Patient Care Team/organization & administration , Social Work/organization & administration , State Medicine/organization & administration , Stroke Rehabilitation , Anthropology, Cultural , Attitude of Health Personnel , Continuity of Patient Care/organization & administration , Humans , Needs Assessment , Nursing Methodology Research , Surveys and Questionnaires , WalesABSTRACT
This paper explores routine resource allocation processes in health and social care. While there has been a small body of work which has drawn on Lipsky's (1980) insights into street level bureaucracy, few have taken seriously the opportunity offered by ethnography to explore in detail the work of front-line staff as a way of observing policy processes in action. Utilising ethnographic data from research into the continuing care of adults who had suffered a first acute stroke, we analyse how staff accommodated patient need and consider the implications that this had for the quality, equality and equity of service provision.
Subject(s)
Health Care Rationing/economics , Health Care Rationing/methods , Stroke Rehabilitation , Stroke/economics , Aged , Aged, 80 and over , Continuity of Patient Care , Female , Health Services Accessibility/economics , Health Services Needs and Demand/economics , Humans , MaleABSTRACT
This paper explores the questions: What has work published in Sociology of Health and Illness contributed to our understanding of 'healthcare organisation'? What are the key research issues for the future? The paper reviews past articles with these questions in mind and uses the first issue of the Journal as a starting point for identifying themes and issues which have remained relevant throughout the first 25 years of its history. I argue that, though the disparate contributions in this area sometimes fail to build on earlier research, when read together they offer a valuable picture of a complex range of healthcare settings and their social organisation. The importance of insights gained from other areas of sociological work is emphasised and some significant examples are identified. The willingness to cross boundaries into other disciplines is also recognised as a strength and this is seen as an important issue for future research, as is increased attention to international comparative research. In similar vein the author argues that the multiplicity of methodological approaches allows the reader to weigh the value of different kinds of data and to look for common underlying patterns of action. It is suggested that future work could usefully revisit past studies, so that we consolidate and accumulate knowledge of the field and avoid a cycle where we continually retread old ground.
Subject(s)
Bibliometrics , Health Services Administration , Periodicals as Topic , Sociology, Medical , Health Services Research , HumansABSTRACT
This paper considers how middle-level managers in British Health Authorities and hospital Trusts orient to media reportage in the process of negotiating and monitoring contracts for clinical services. Although they sometimes produce media representations aimed at influencing the general public, local policy actors on both sides of the purchaser/provider split also use media messages as part of their negotiations with each other. We examine how they seek to manage negative publicity, and what happens when one side threatens to 'go public'. Managers must strike a balance between negotiating advantage and maintaining organisational relationships. Thus the powerful, but potentially double-edged, weapon of public disclosure was usually broached in indirect terms, and approached with some ambivalence. In rare cases, parties resorted to hostile press releases as relationships deteriorated. Arguably, these interactions reflect more general tensions that arise when managerial discourses, emphasising concepts such as adversarial contracting, markets and competition, are imported into professional organisations with a public service mission.
Subject(s)
Contract Services/organization & administration , Mass Media , State Medicine/organization & administration , Attitude to Health , Community-Institutional Relations , Humans , Negotiating , Persuasive Communication , Private Sector , Public Sector , United KingdomSubject(s)
Family Practice/education , Internship and Residency , Rural Health Services , Humans , OntarioABSTRACT
Ensuring "seamless" health and social services provision has been a concern of policy makers for many years but our understanding of this complex system of work remains underdeveloped. This article reports selected findings from a series of ethnographic case studies of health and social services provision to adults recovering from a first acute stroke. Flexible working, the need for a lead professional and the transition from hospital to home are themes considered. The need for high quality data in order to develop our existing understanding of complex caring interfaces is underlined.
Subject(s)
Interinstitutional Relations , Patient Care Team/organization & administration , Social Work/organization & administration , State Medicine/organization & administration , Stroke Rehabilitation , Anthropology, Cultural , Attitude of Health Personnel , Continuity of Patient Care/organization & administration , Humans , Needs Assessment , Nursing Methodology Research , Surveys and Questionnaires , WalesABSTRACT
Two polytopic membrane proteins, NarK and NarU, are assumed to transport nitrite out of the Escherichia coli cytoplasm, but how nitrate enters enteric bacteria is unknown. We report the construction and use of four isogenic strains that lack nitrate reductase Z and the periplasmic nitrate reductase, but express all combinations of narK and narU. The active site of the only functional nitrate reductase, nitrate reductase A, is located in the cytoplasm, so nitrate reduction by these four strains is totally dependent upon a mechanism for importing nitrate. These strains were exploited to determine the roles of NarK and NarU in both nitrate and nitrite transport. Single mutants that lack either NarK or NarU were competent for nitrate-dependent anaerobic growth on a non-fermentable carbon source, glycerol. They transported and reduced nitrate almost as rapidly as the parental strain. In contrast, the narK-narU double mutant was defective in nitrate-dependent growth unless nitrate transport was facilitated by the nitrate ionophore, reduced benzyl viologen (BV). It was also unable to catalyse nitrate reduction in the presence of physiological electron donors. Synthesis of active nitrate reductase A and the cytoplasmic, NADH-dependent nitrite reductase were unaffected by the narK and narU mutations. The rate of nitrite reduction catalysed by the cytoplasmic, NADH-dependent nitrite reductase by the double mutant was almost as rapid as that of the NarK+-NarU+ strain, indicating that there is a mechanism for nitrite uptake by E. coli that is in-dependent of either NarK or NarU. The nir operon encodes a soluble, cytoplasmic nitrite reductase that catalyses NADH-dependent reduction of nitrite to ammonia. One additional component that contributes to nitrite uptake was shown to be NirC, the hydrophobic product of the third gene of the nir operon, which is predicted to be a polytopic membrane protein with six membrane-spanning helices. Deletion of both NarK and NirC decreased nitrite uptake and reduction to a basal rate that was fully restored by a single chromosomal copy of either narK or nirC. A multicopy plasmid encoding NarU complemented a narK mutation for nitrite excretion, but not for nitrite uptake. We conclude that, in contrast to NirC, which transports only nitrite, NarK and NarU provide alternative mechanisms for both nitrate and nitrite transport. However, NarU might selectively promote nitrite ex-cretion, not nitrite uptake.