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     

Mapping and characterization of a novel human myc-like (MYCLK1) sequence.

The myc family of proto-oncogenes consists of several members that possess regions of sequence homology and some have known similarities in structure and function. We have isolated an 8.8-kb EcoRI fragment from a human genomic library by hybridization to a 28-base oligonucleotide probe derived from a region of the second exon of MYC, which is highly conserved in the myc gene family. Sequence analysis of this myc-like (MYCLK1) DNA fragment has revealed the existence of a region with 85% homology to the 28-base oligonucleotide probe. An open reading frame of 207 nucleotides containing the region of homology was found. We have mapped MYCLK1 to human chromosome 7 at band p15 by chromosome in situ hybridization; this site is distinct from the map location of previously characterized myc genes. Whether MYCLK1 represents a new functional member of the myc family of proto-oncogenes remains to be determined.     

Successful infection of the common marmoset (Callithrix jacchus) with human varicella-zoster virus.

The common marmoset, Callithrix jacchus, can be infected with human varicella-zoster virus (VZV), both wild-type strain KMcC and attenuated vaccine strain Oka/Merck. Infection was accomplished with either whole-cell-associated or cell extract VZV by combined oral-nasal-conjunctival application and was characterized by substantial and persistent anti-VZV antibody responses. The infectivity of VZV for marmosets was destroyed by treatment of inocula with heat or UV light. Diluted inocula with as few as 40 PFU/ml were infectious for marmosets. The lungs were demonstrated to be a major site of viral replication; both the presence of viral antigens and signs of pneumonia were demonstrated in lung tissues. Four serial passages of VZV KMcC were carried out in C. jacchus by a process of in vitro isolation and culturing of VZV from infected lung tissue and reapplication of the cultured isolates to fresh animals. The isolated viruses were identified as VZV both serologically and by restriction endonuclease analyses. The C. jacchus infectivity model should prove useful for determining the efficacy of subunit and live recombinant VZV vaccines as well as for the study of zoster.     

Changing time perspective and mental health among Southeast Asian refugees

Little is known about the psychological mechanisms people employ in adapting to extreme circumstances such as becoming refugees. Case studies of refugees making up part of a sample of 1348 persons relocated from Southeast Asia to Vancouver, British Columbia, suggest that altering one's perception of time may be an adaptive strategy. During periods of acute stress, refugees seem to focus on the present to the relative exclusion of past and future. The reemergence of past and future into consciousness brings about a risk for developing depression. Epidemiological data corroborate inferences from case material, demonstrating that refugees are more present-oriented than the indigenous population. A Nostalgic time orientation, preoccupation with the past, is associated with elevated depression scores. Contrasts are drawn between nostalgia, a maladaptive pattern, and memory, which is an inevitable part of the process of personality integration.     

The enzyme defect in bovine protoporphyria. Studies with purified ferrochelatase

Ferrochelatase was purified from the livers of normal and protoporphyria cattle by chromatography on Blue Sepharose CL-6B in order to investigate the enzyme defect in this disorder. The increase in specific activity (up to 2900-fold) indicated that the normal and protoporphyria enzymes were purified to a similar degree. The mutant enzyme had catalytic activity which was 10 to 15% of normal ferrochelatase, although the Michaelis constants for protoporphyrin and iron were similar. The molecular mass of the normal and protoporphyria enzyme protein was 40 kDa as evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In the presence of 15 mM sodium cholate, gel filtration demonstrated a similar size. However, at a lower concentration of sodium cholate (4 mM) the molecular mass was about 240 kDa, suggesting that the purified enzymes aggregate under this condition. Polyvalent antibodies were raised in rabbits using as antigens purified normal native enzyme and normal 40-kDa protein which had been further purified by preparative SDS-PAGE. In Western blots these antibodies complexed with both the normal and mutant 40-kDa proteins. The amount of 40-kDa protein in normal and protoporphyria mitochondrial fractions was also similar as evaluated by Western blots. These studies indicate that the ferrochelatase defect in bovine protoporphyria probably results from a point gene mutation that causes a minor change in enzyme structure.     

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.