Copper efflux is induced during anaerobic amino acid limitation in Escherichia coli to protect iron-sulfur cluster enzymes and biogenesis.

Adaptation to changing environments is essential to bacterial physiology. Here we report a unique role of the copper homeostasis system in adapting Escherichia coli to its host-relevant environment of anaerobiosis coupled with amino acid limitation. We found that expression of the copper/silver efflux pump CusCFBA was significantly upregulated during anaerobic amino acid limitation in E. coli without the supplement of exogenous copper. Inductively coupled plasma mass spectrometry analysis of the total intracellular copper content combined with transcriptional assay of the P(cusC)-lacZ reporter in the presence of specific Cu(I) chelators indicated that anaerobic amino acid limitation led to the accumulation of free Cu(I) in the periplasmic space of E. coli, resulting in Cu(I) toxicity. Cells lacking cusCFBA and another copper transporter, copA, under this condition displayed growth defects and reduced ATP production during fumarate respiration. Ectopic expression of the Fe-S cluster enzyme fumarate reductase (Frd), or supplementation with amino acids whose biosynthesis involves Fe-S cluster enzymes, rescued the poor growth of ΔcusC cells. Yet, Cu(I) treatment did not impair the Frd activity in vitro. Further studies revealed that the alternative Fe-S cluster biogenesis system Suf was induced during the anaerobic amino acid limitation, and ΔcusC enhanced this upregulation, indicating the impairment of the Fe-S cluster assembly machinery and the increased Fe-S cluster demands under this condition. Taken together, we conclude that the copper efflux system CusCFBA is induced during anaerobic amino acid limitation to protect Fe-S cluster enzymes and biogenesis from the endogenously originated Cu(I) toxicity, thus facilitating the physiological adaptation of E. coli.

Institutionalized elders with dementia: collaboration between family caregivers and nursing home staff in Taiwan.

AIMS AND OBJECTIVES: To explore the process of development of collaborative relationship between family caregivers of institutionalized elders with dementia and nursing home staff in Taiwan. BACKGROUND: Evidence suggests that family members are continuously involved in the lives of loved ones and have not given up their roles as caregivers after the institutionalization of a family member. Little is known, however, about how family caregivers develop a collaborative relationship with nursing home staff, particularly in Asian countries. DESIGN AND METHODS: Grounded theory methodology was used. Data were collected via interviews and observations from 11 family caregivers of patients who were suffering from dementia and living in an institution for persons with dementia in northern Taiwan. Data were analysed by constant comparative analysis. RESULTS: Findings revealed that 'institutional social penetration' was the process most used by family caregivers to achieve an harmonious collaborative relationship with the nursing home staff. Institutional social penetration is a dynamic process, which includes three components: self-disclosure, evaluation of care and penetration strategies. Family caregivers, who had developed a 'socially penetrating' relationship with the nursing home staff, were more likely to disclose information in more breadth and depth, to receive positive care evaluations and to adopt multiple effective penetration strategies. CONCLUSIONS: Institutional social penetration between family caregivers and nursing home staff can sensitize healthcare providers to meet the family's needs during the placement of their loved one and provide a basis for developing intervention strategies. RELEVANCE TO CLINICAL PRACTICE: Findings of this study may help healthcare providers to understand the ways in which collaborative relationships develop between the families of elders with dementia and nursing home staff. Interventions can be developed to facilitate self-disclosure of both the family members and nursing home staff through timely feedback and familiarising family caregivers with different penetration strategies.