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     

Amphiphilic cationic peptides mediate cell adhesion to plastic surfaces

Four amphiphilic peptides, each with net charges of +2 or more at neutrality and molecular weights under 4 kilodaltons, were found to mediate the adhesion of normal rat kidney fibroblasts to polystyrene surfaces. Two of these peptides, a model for calcitonin (peptide 1, MCT) and melittin (peptide 2, MEL), form amphiphilic alpha-helical structures at aqueous/nonpolar interfaces. The other two, a luteinizing hormone-releasing hormone model (peptide 3, LHM) and a platelet factor model (peptide 4, MPF) form beta-strand structures in amphiphilic environments. Although it contains only 10 residues, LHM mediated adhesion to surfaces coated with solutions containing as little as 10 pmoles/ml of peptide. All four of these peptides were capable of forming monolayers at air-buffer interfaces with collapse pressures greater than 20 dynes/cm. None of these four peptides contains the tetrapeptide sequence Arg-Gly-Asp-Ser, which has been associated with fibronectin-mediated cell adhesion. Ten polypeptides that also lacked the sequence Arg-Gly-Asp-Ser but were nonamphiphilic and/or had net charges less than +2 at neutrality were all incapable of mediating cell adhesion (Pierschbacher and Ruoslahti, 1984). The morphologies of NRK cells spread on polystyrene coated with peptide LHM resemble the morphologies on fibronectin-coated surfaces, whereas cells spread on surfaces coated with MCT or MEL exhibit strikingly different morphologies. The adhesiveness of MCT, MEL, LHM, and MPF implies that many amphiphilic cationic peptides could prove useful as well defined adhesive substrata for cell culture and for studies of the mechanism of cell adhesion.     

Steroid glucuronides as male pheromones in the reproduction of the African catfish Clarias gariepinus—a brief review

After ovulation, female African catfish are strongly attracted by the odor of male conspecifics. This attraction depends on the presence of the seminal vesicle, a part of the male reproductive organs. Removal of the seminal vesicle illustrates this fact. A low dose of seminal vesicle fluid, added to the water, appears to be highly attractive for catfish which have ovulated. Fractionation of the fluid and testing of the different fractions shows that steroid glucuronides could be responsible for the attraction. These steroid glucuronides can be identified with gas chromatographic-mass spectrometric analysis. A mixture of glucuronides, prepared to resemble the composition of the seminal vesicle fluid, evokes a dose-dependent attraction. The most potent odorant, observed by measuring electrical responses from the olfactory epithelium and from the olfactory tract appears to be 3α,17α-dihydroxy-5β-pregnan-20-one-3α-glucuronide.     

Effect of alpha-fetoprotein on isolated mouse oocytes

Data are presented which indicate a possible action of alpha-fetoprotein (AFP) on female germinal cells. The in vitro maturation of mature mice oocytes was significantly inhibited when mouse AFP replaced albumin in the culture medium. In addition, the degenerative aspect of oocytes cultured with AFP seemed to indicate that this me?otic inhibition was caused by a premature degeneration of oocytes rather than by a blockage at a specific stage of maturation. Thus AFP, perhaps through its ligands, may play a role in the reduction of germinal cells during fetal and immediate post-natal life rather than in the arrest of me?osis at the diplotene stage.     

Exon skipping in the sterol 27-hydroxylase gene leads to cerebrotendinous xanthomatosis

We report a new mutation in the sterol 27-hydroxylase (CYP 27) gene in a Dutch family with cerebrotendinous xanthomatosis: a G→A transition in the splice donor site in intron 4. This mutation leads to skipping of exon 4, resulting in a loss of 66 amino acids in the CYP 27 enzyme molecule. Received: 15 March 1997 / Accepted: 26 March 1997     

Differential induction of activation markers in macrophage cell lines by interferon-gamma

Macrophage cell lines were used in these studies as a model system to dissect the biochemical and functional mosaic of the macrophage activation process. In particular, the requirements for the induction of tumoricidal and bactericidal activity in the RAW 264.7 and WEHI-3 cell lines by interferon-gamma (IFN-gamma) and bacterial lipopolysaccharide (LPS) were determined. Changes in expression of a series of macrophage markers traditionally associated with macrophage activation were monitored during stimulation of the cells in order to determine whether a detectable pattern of activation-associated changes is associated with the development of a particular functional activity. These markers included changes in the cell surface expression of major histocompatibility complex-encoded Class I and Class II antigens and antigens in the Mac-1/LFA-1 family, alterations in the levels of membrane enzymes (5' nucleotidase and alkaline phosphodiesterase), and production of secretory products including hydrogen peroxide and the monokines interleukin-1, interferons-alpha/beta, and tumor necrosis factor-alpha. Our results demonstrate that a given homogeneous macrophage population expresses a distinct subset of functional activities in response to single, defined activating signals such as IFN-gamma and LPS. The display of a variety of macrophage surface antigens, enzymes, and secreted products is activated simultaneously by such treatment; however, the particular pattern of such activation-associated markers cannot reproducibly be used to predict the ability of an activated cell to perform a particular function. The results also suggest that macrophage cell lines expressing differential response patterns following IFN-gamma stimulation provide a valuable system for dissection of the molecular and cell biology of macrophage activation.