Respiratory components in acidophilic bacteria that respire on iron

Abstract

Microorganisms capable of aerobic respiration on ferrous ions are spread throughout eubacterial and archaebacterial phyla. Phylogenetically distinct organisms were shown to express spectrally distinct redox‐active biomolecules during autotrophic growth on soluble iron. A new iron‐oxidizing eubacterium, designated as strain Funis, was investigated. Strain Funis was judged to be different from other known iron‐oxidizing bacteria on the bases of comparative lipid analyses, 16S rRNA sequence analyses, and cytochrome composition studies. When grown autotrophically on ferrous ions, Funis produced conspicuous levels of a novel acid‐stable, acid‐soluble yellow cytochrome with a distinctive absorbance peak at 579 nm in the reduced state.

Stopped‐flow spectrophotometric kinetic studies were conducted on respiratory chain components isolated from cell‐free extracts of Thiobacillus ferrooxidans. Experimental results were consistent with a model where the primary oxidant of ferrous ions is a highly aggregated c‐type cytochrome that then reduces the periplasmic rusticyanin. The Fe(II)‐dependent, cytochrome c‐catalyzed reduction of the rusticyanin possessed three kinetic properties in common with corresponding intact cells that respire on iron: the same anion specificity, a similar dependence of the rate on the concentration of ferrous ions, and similar rates at saturating concentrations of ferrous ions     

Fluorometric, Chromatographic, and Spectronic Evidence for the Non-indolic Nature of Citrus Auxin

Evidence for the non-indolic nature of the new citrus auxinis presented on the basis of fluorometric properties, thin-layerchromatography, Ehrlich's colour reaction, paper electrophoresis,and the infra-red spectra determinations. Citrus auxin had alower Rf in TLC than IAA, did not give the typical indole reactionwith Ehrlich's reagent, and behaved differently in electrophoresis.The infra-red spectra also provided preliminary informationconcerning chemical structure. The hypothesis that indolic compoundsconstitute the only natural auxins in higher plants should berevised in view of this evidence that a non-indole auxin existsin higher plants.     

Involvement of the 2'-5' A pathway in the augmentation of natural killer activity

Pretreatment of human large granular lymphocytes (LGL) or unseparated peripheral blood mononuclear cells with interferon (IFN) resulted in a significant augmentation of natural killer (NK) activity. This increase was paralleled by an increase in the 2'-5'A synthetase activity. In order to investigate the possibility that IFN might be inducing augmentation of NK cells via the 2'-5'A pathway, we tested the effects of nonphosphorylated core material [(A2'p)2A] and of the triphosphorylated form of the 2'-5'A [ppp(A2'p)2A]. The core material had no detectable effect on NK activity. In contrast, when experiments were performed with the triphosphorylated form of 2'-5'A, NK activity was stimulated. In order to achieve activation, permeabilization of LGL with calcium chloride was necessary and, under these conditions, a dose-dependent augmentation of NK activity was seen. However, the calcium treatment had considerable toxic effects on basal levels of NK activity. Collectively, these results suggest that IFN may be inducing augmentation of NK activity via the 2'-5'A pathway. Further studies will be necessary to determine the effects of IFN and/or 2'-5'A on subsequent activation steps in the process leading to cytotoxicity by NK cells.     

Major histocompatibility (B) complex and sex effects on the phytohaemagglutinin wattle response

The influence of the major histocompatibility (B) complex and sex on the phytohaemagglutinin (PHA) wattle response was studied in 136 segregants (B2/B2, B2/B5 and B5/B5) of a fourth generation cross between inbred lines 6(1) and 15(1). At 6 weeks of age, chickens were injected with 100 micrograms purified PHA-P. Wattle thickness measurements were taken 4, 24, 48, 72 and 96 h after injection. Analysis of variance showed that 4 h after injection, males had a significantly higher response than females but the sex-genotype interaction was also significant. Females had higher responses than males 24 and 48 h after injection as a consequence of more rapid development and earlier resolution of the reaction in males. B2/B2 chickens had significantly lower responses than B5/B5 chickens 72 and 96 h after injection, signifying a faster late resolution phase in the B2/B2 genotype. The developmental and early resolution phases of the PHA wattle response were influenced by sex while the late resolution phase was influenced by B genotype.     

Allometric Root/Shoot Relationships and Predicted Water Uptake for Desert Succulents

Root morphology, shoot morphology, and water uptake for Agavedeserti and Ferocactus acanthodes of various sizes were studiedusing allometric relationships (y = ax^b) and a previously developedwater uptake model. Shoot surface area increased with shootvolume with an exponent b of 0.75 for both species. Root lengthand the ground area explored by the roots increased with shootsurface area with b's of 0.72 for A. deserti and 0.92 for F.acanthodes. Various sized individuals had about the same ratioof root length to explored ground area, with higher values occurringfor A. deserti. Predicted water uptake averaged over the exploredground area was approximately constant over a 10⁴-fold rangein shoot surface area, suggesting that shoot size confers nointraspecific competitive advantage for water uptake. For theroot lengths per explored ground area observed in the field,water uptake was predicted to be 85 per cent of maximal; wateruptake could be increased by the production of more rain roots.When differences in shoot volume were accounted for by allometry,small plants had relatively less shoot surface area and relativelymore root length per shoot volume than did large plants, whichmay be important for the water relations of seedling establishment. Agave deserti, Ferocactus acanthodes, allometry, desert succulents, root distribution, root length, seedling growth, seedling establishment, shoot surface area, shoot volume, water uptake     

IFN-gamma treatment of K562 cells inhibits natural killer cell triggering and decreases the susceptibility to lysis by cytoplasmic granules from large granular lymphocytes

Pretreatment of human K562 leukemia cells with rIFN-alpha and rIFN-gamma resulted in decreased susceptibility to lysis by human peripheral blood NK cells. The reduction of NK-susceptibility after IFN treatment was not due to a general effect of IFN on the stability of the cell membrane because the susceptibility of K562 cells to lysis by antibodies plus C, distilled water, or lysolecithin was unaffected. Binding studies with effector cell preparations enriched for NK cells with large granular lymphocyte morphology revealed no difference in binding to control and IFN-gamma-treated target cells. The sensitivity to soluble NK cytotoxic factors was not affected significantly by the IFN treatment. In contrast, the susceptibility of IFN-treated target cells to the cytotoxic activity of purified cytoplasmic granules from a rat large granular lymphocyte tumor was significantly reduced, indicating that the IFN-induced resistance acted at the level of susceptibility to the lytic mechanism of NK cells. However, IFN-alpha was more effective than IFN-gamma in inducing resistance to the cytoplasmic granules although resulting in only a weak resistance in the cell-mediated cytotoxic assay. IFN-gamma but not IFN-alpha caused a reduction in the frequency of effector cells that had reoriented their Golgi apparatus toward their bound target cell. In addition, IFN-gamma treated K562 cells failed to elicit an influx of Ca2+ into effector cells. Taken together, the results suggest that IFN-gamma in addition to an increased resistance to the lytic molecules released by NK cells can also induce changes in the target cells which prevent the triggering and activation of the effector cell.