Fur in Magnetospirillum gryphiswaldense Influences Magnetosomes Formation and Directly Regulates the Genes Involved in Iron and Oxygen Metabolism

Magnetospirillum gryphiswaldense strain MSR-1 has the unique capability of taking up large amounts of iron and synthesizing magnetosomes (intracellular magnetic particles composed of Fe3O4). The unusual high iron content of MSR-1 makes it a useful model for studying biological mechanisms of iron uptake and homeostasis. The ferric uptake regulator (Fur) protein plays a key role in maintaining iron homeostasis in many bacteria. We identified and characterized a fur-homologous gene (MGR_1314) in MSR-1. MGR_1314 was able to complement a fur mutant of E. coli in iron-responsive manner in vivo. We constructed a fur mutant strain of MSR-1. In comparison to wild-type MSR-1, the mutant strain had lower magnetosome formation, and was more sensitive to hydrogen peroxide and streptonigrin, indicating higher intracellular free iron content. Quantitative real-time RT-PCR and chromatin immunoprecipitation analyses indicated that Fur protein directly regulates expression of several key genes involved in iron transport and oxygen metabolism, in addition it also functions in magnetosome formation in M. gryphiswaldense

Metabolic, Cardiovascular, and Cerebrovascular Outcomes in Growth Hormone-Deficient Subjects with Previous Cushing's Disease or Non-Functioning Pituitary Adenoma

Context: Previous exposure to hypercortisolism due to Cushing's disease ( CD) may adversely affect long-term metabolic and cardiovascular outcomes. In particular, metabolic and cardiovascular outcomes of patients with previous CD who require GH replacement have not been fully established. Objective: The aim of the study was to compare the prevalence and incidence of metabolic syndrome ( Adult Treatment Panel III criteria), diabetes mellitus, cardiovascular disease, and cerebrovascular disease in GH-treated subjects with previous CD with GH-treated subjects with previous nonfunctioning pituitary adenoma (NFPA). Design: We conducted post hoc analysis of the observational Hypopituitary Control and Complications Study conducted at 362 international centers (1995-2006). Subjects: We studied adult-onset GH-deficient subjects with previous CD (n = 160) or NFPA (n = 879). All subjects received GH replacement therapy and were GH naive at enrollment. Multiple pituitary deficits were prevalent in both groups. Main Outcome Measures: We measured the prevalence and incidence of metabolic syndrome, diabetes mellitus, cardiovascular disease, and cerebrovascular disease at baseline and at 3 yr, standardized for age and sex differences between groups. Results: Compared with subjects with previous NFPA, subjects with previous CD had a significantly greater 3-yr incidence of metabolic syndrome (CD, 23.4%; NFPA, 9.2%; P = 0.01), baseline ( CD, 6.3%; NFPA, 2.2%; P < 0.01) and 3-yr (CD, 7.6%; NFPA, 3.9%; P = 0.04) prevalence of cardiovascular disease, and baseline (CD, 6.4%; NFPA, 1.8%; P = 0.03) and 3-yr (CD, 10.2%; NFPA, 2.9%; P = 0.01) prevalence of cerebrovascular disease. Conclusions: Previous hypercortisolism may predispose GH-treated, GH-deficient subjects with prior CD to an increased risk of metabolic syndrome, cardiovascular disease, and cerebrovascular disease. ( J Clin Endocrinol Metab 95: 630-638, 2010

Two-pronged survival strategy for the major cystic fibrosis pathogen, Pseudomonas aeruginosa, lacking the capacity to degrade nitric oxide during anaerobic respiration

Protection from NO gas, a toxic byproduct of anaerobic respiration in Pseudomonas aeruginosa, is mediated by nitric oxide (NO) reductase (NOR), the norCB gene product. Nevertheless, a norCB mutant that accumulated ∼13.6 μM NO paradoxically survived anaerobic growth. Transcription of genes encoding nitrate and nitrite reductases, the enzymes responsible for NO production, was reduced >50- and 2.5-fold in the norCB mutant. This was due, in part, to a predicted compromise of the [4Fe–4S]2+ cluster in the anaerobic regulator ANR by physiological NO levels, resulting in an inability to bind to its cognate promoter DNA sequences. Remarkably, two O2-dependent dioxygenases, homogentisate-1,2-dioxygenase (HmgA) and 4-hydroxyphenylpyruvate dioxygenase (Hpd), were derepressed in the norCB mutant. Electron paramagnetic resonance studies showed that HmgA and Hpd bound NO avidly, and helped protect the norCB mutant in anaerobic biofilms. These data suggest that protection of a P. aeruginosa norCB mutant against anaerobic NO toxicity occurs by both control of NO supply and reassignment of metabolic enzymes to the task of NO sequestration

A kinetic approach to assess oxidative metabolism related features in the bivalve Mya arenaria

Electron paramagnetic resonance (EPR) uses the resonant microwave radiation absorption of paramagnetic substances to detect highly reactive and, therefore, short-lived oxygen and nitrogen centered radicals. Previously, steady state concentrations of nitric oxide, ascorbyl radical (A•) and the labile iron pool (LIP) were determined in digestive gland of freshly collected animals from the North Sea bivalve Mya arenaria. From these data by By the application of a simple kinetic analysis based on elemental reactions to these data allowed us to estimate the steady state concentrations of superoxide anion, the rate of A• disappearance and the content of unsaturated lipids. This analysis applied to a marine invertebrate opens the possibility of a mechanistic understanding of the complexity of free radical and LIP interactions in a metabolically slow, cold water organism under unstressed conditions. This data can be further used as a basis to assess the cellular response to stress in a simple system as the bivalve M. arenaria that can then be compared to cells of higher organisms