Influence of Nutrient Concentrations on MPN Quantification and Enrichment of Nitrate-Reducing Fe(II)-Oxidizing and Fe(III)-Reducing Bacteria from Littoral Freshwater Lake Sediments

The application of culture-dependent studies to quantify Fe-metabolizing microorganisms from the environment is a necessity, as there are so far no universal functional marker genes for application in culture-independent studies. Media composition can vary between studies, therefore, we determined the effects of three different growth media on the quantification (MPNs) and identity (via cloning and sequencing of dominant DGGE bands) of nitrate-reducing Fe(II)-oxidizers and lactate- or acetate-oxidizing Fe(III)-reducers from a lacustrine sediment: low sulphate freshwater medium (FWM), sterile filtered bicarbonate-buffered lake water (BLW) and a mixture of both (MIX). We consistently found fewer cells in the BLW than in the FWM and the MIX. The DGGE banding patterns of the microbial communities enriched in different media types clustered together according to the e^? donor and acceptor couples and not according to the medium used. Thus, although the medium composition significantly influenced the quantification and thereby conclusions on the abundance and potential significance of the targeted group within the ecosystem, biodiversity assessments through enrichment cultures were less influenced by the medium, but instead were affected by the type and concentration of the e^? donor/acceptor.     

Removal of Cr6+ from groundwater using zero-valence iron in the laboratory

Abstract

In this paper, we describe a series of laboratory experiments which quantify the rate of Cr⁶⁺ reduction by Fe⁰. The main goal of these experiments was to determine the removal efficiency of Cr⁶⁺ by iron. The results indicate that Fe⁰ reduces Cr⁶⁺ to Cr³⁺ under alkaline and slightly acidic conditions. The removal efficiency rises with an increase of the initial concentration of Cr⁶⁺ (1 mg/L to 10 mg/L) when the quantity of Fe⁰ is stable. The removal efficiency increases as the quantity of Fe⁰ is raised when other conditions are constant. The removal efficiency would not be affected by other inorganic ions unless they were present at very high concentrations. When the initial concentration Cr⁶⁺ is 10mg/L and pH is 6.5–7.7, the final concentration of Cr⁶⁺ in effluent is less than 0.05 mg/L and the total Fe is less than 0.3 mg/L in effluent.     

The Amino Acid Content in Gamma-irradiated Rice†

High phosphate accumulating bacteria were isolated by autoradiography. One isoate, Arthrobacter globiformis PAB-6 accumulated phosphate intracellularly at 20% of dry cell mass in a simple synthetic medium. This amount was 3~7 times higher than type cultures examined. Almost no phosphate was released into the medium after cessation of growth. Fifty percent of total intracellular phosphate was fractionated as nucleic acids, while 20% each was recovered from cold PCA soluble fractions and polyphosphate fractions. The large content of nucleic acids in this bacterium appeared due to increased RNA content, specifically 4 S RNA fraction.     

Introduction: Metals in Biology: α-Ketoglutarate/Iron-Dependent Dioxygenases

Four minireviews deal with aspects of the α-ketoglutarate/iron-dependent dioxygenases in this eighth Thematic Series on Metals in Biology. The minireviews cover a general introduction and synopsis of the current understanding of mechanisms of catalysis, the roles of these dioxygenases in post-translational protein modification and de-modification, the roles of the ten-eleven translocation (Tet) dioxygenases in the modification of methylated bases (5mC, T) in DNA relevant to epigenetic mechanisms, and the roles of the AlkB-related dioxygenases in the repair of damaged DNA and RNA. The use of α-ketoglutarate (alternatively termed 2-oxoglutarate) as a co-substrate in so many oxidation reactions throughout much of nature is notable and has surprisingly emerged from biochemical and genomic analysis. About 60 of these enzymes are now recognized in humans, and a number have been identified as having critical functions.     

Conflicting effects of BMI and waist circumference on iron status

The association between obesity and iron status has a long history and is still receiving attention. However comparative analysis of the association between general obesity (BMI) and visceral obesity (waist circumference) with iron status has not been extensively researched. The aim of the present study is thus to determine if body mass index and waist circumference have the same correlation with iron status. One thousand one hundred and thirty people (225 men and 905 women) aged 30 years and above participated in this study. Anthropometric parameters, haemoglobin, iron and total iron binding capacity concentrations were measured using standard methods. Percentage transferrin saturation was calculated and ferritin concentrations were measured using an enzyme linked immunosorbent assay. Obese or overweight women had significantly lower iron and transferrin saturation concentration when compared to non-obese women. In contrast, women with high waist circumference had comparable plasma iron and transferrin saturation to women with normal waist circumference. Partial correlation analysis and linear regression analysis showed that BMI is negatively and significantly associated with plasma iron, transferrin saturation, Hb and ferritin concentration, whilst waist circumference is positively but insignificantly associated with plasma iron, transferrin saturation, Hb and ferritin concentration. Binary regression analysis showed that obese or overweight people are more likely to have iron deficiency, whilst those with raised waist circumference are more likely to have iron overload. Multivariate analysis showed that body mass index is negatively and significantly associated with low iron status, while waist circumference is positively and insignificantly associated with iron status. This is supported by a comparison of plasma iron, transferrin saturation and ferritin concentrations in participants with high body mass index and normal waist circumference and participants with normal body mass index and high waist circumference to those participants having normal body mass index and normal waist circumference. The present study suggests that in women body mass index is associated with low plasma iron, transferrin saturation and ferritin concentrations, while waist circumference is associated with high plasma iron, transferrin saturation and ferritin concentrations.     

A histological and morphometric study on the tissue and cellular distribution of iron in carp Cyprinus carpio L. during chronic waterborne exposure

The effect of long-term (77 day) exposure of carp Cyprinus carpio to low concentrations of waterborne iron (1 mg Fe-dextran l⁻¹) on accumulation and cellular distribution of iron in the liver was assessed using Perl's staining and histological observations and morphometric measurements. Accumulation of iron in the liver occurred after 14 days of exposure, when the majority of the iron was found in the sinusoidal endothelium with lower amounts in the cytoplasm and nuclei of hepatocytes. Upon further treatment the iron was predominantly distributed in the cytoplasm of the hepatocytes either as granules or diffusive iron and in macrophages.     

Mercury in blood cells—Altered elemental profiles

The study was composed of 27 persons that displayed vague symptoms similar to those of the victims of Minamata and Iraq. Skew distributions of mercury were observed in individual erythrocytes and neutrophil granulocytes when measured by PIXE. Mercury could not be detected in the platelets. The erythrocytes also displayed lowered concentrations of magnesium and zinc, together with increased concentrations of calcium and strontium. The neutrophils displayed decreased concentrations of magnesium and zinc and increased concentrations of calcium, strontium, and iron. The presence of mercury and the altered elemental profiles in the erythrocytes and the neutrophil granulocytes are suggested as early signs of exposure.     

Application of PIXE analysis to the study of the regional distribution of trace elements in normal human brain

A particle-induced X-ray emission (PIXE) analysis method is presented, which allows measurement of eight elements (i.e., K, Ca, Mn, Fe, Cu, Zn, Se, and Rb) in human brain samples of only a few mg dry weight. The precision and accuracy of the method were investigated by analyzing animal brain matter with both PIXE and instrumental neutron activation analysis (INAA). The method was applied to measure the 8 elements in 46 different regions of 3 human brains. The sections analyzed originated from either the left or the right cerebral hemisphere, brain stem, and cerebellum. For one of the brains, sections were also analyzed from 26 corresponding regions of both hemispheres. For all elements, similar concentrations were found in the corresponding areas of the left and right sides of the brain. The concentrations (in μg/g dry weight) of the elements K, Fe, Cu, Zn, Se, and Rb were consistently higher in cortical structures than in white matter. Deep nuclei and brain stem, which have a mixed composition, showed intermediate values for K, Zn, Se, and Rb. A hierarchical cluster analysis indicated that the various brain regions clustered into two large groups, one comprising gray and mixed matter regions and the other, white and mixed matter brain areas.     

Diagnosis of iron deficiency in groundnut,Arachis hypogaea L.

Summary Investigations into iron deficiency have been hindered by the lack of a satisfactory diagnostic tissue test, which in turn results from the total iron content of plant tissue commonly being an unreliable index of the iron status. Our measurements of chlorotic and normal leaves of field grown groundnut (Arachis hypogaea L.) showed that total iron was unsatisfactory as the measure of iron status of plant tissue. It was found that iron status was better assessed from an estimate of the ferrous iron content of fresh leaf materials obtained by extraction with o-phenanthroline. Extractable iron content increased with leaf age. Chlorotic buds or the first fully opened leaf always contained less than 6μg extractable-Fe/g fresh tissue. Approved for publication as ICRISAT Journal Article No. 307.     

Experimental candidiasis in liver injury

In an attempt to evaluate effects of liver injury and roles of iron metabolism on systemic fungal infection, experimental systemicCandida infection was produced in mice with galactosamine-induced liver injury. Survival rate and extent of fungal lesion are compared between mice with liver injury (Group 1) and ones without liver injury (Group 2). Median survival was 7 and 18 days in Group 1 and 2 respectively after 21 days observation. Mortality rate of Group 1 was significantly higher (P=0.05) than that of Group 2. This difference was reflected to the extent of fungal lesions in that they were extensive and disseminated, involving the multiple organs in Group 1 but predominantly localized to the kidneys in Group 2. UIBC (unbound iron binding capacity) and TIBC (total iron binding capacity), i.e., serum transferrin as well as serum iron levels were significantly lower in Group 1 as compared with those in Group 2. These results indicate that hepatic injury promotesCandida infectionin vivo and suggest that increased susceptibility toCandida in the presence of liver injury is, at least partially, attributable to low UIBC and/or TIBC.