Shifting microbial communities sustain multiyear iron reduction and methanogenesis in ferruginous sediment incubations.

Reactive Fe(III) minerals can influence methane (CH4 ) emissions by inhibiting microbial methanogenesis or by stimulating anaerobic CH4 oxidation. The balance between Fe(III) reduction, methanogenesis, and CH4 oxidation in ferruginous Archean and Paleoproterozoic oceans would have controlled CH4 fluxes to the atmosphere, thereby regulating the capacity for CH4 to warm the early Earth under the Faint Young Sun. We studied CH4 and Fe cycling in anoxic incubations of ferruginous sediment from the ancient ocean analogue Lake Matano, Indonesia, over three successive transfers (500 days in total). Iron reduction, methanogenesis, CH4 oxidation, and microbial taxonomy were monitored in treatments amended with ferrihydrite or goethite. After three dilutions, Fe(III) reduction persisted only in bottles with ferrihydrite. Enhanced CH4 production was observed in the presence of goethite, highlighting the potential for reactive Fe(III) oxides to inhibit methanogenesis. Supplementing the media with hydrogen, nickel and selenium did not stimulate methanogenesis. There was limited evidence for Fe(III)-dependent CH4 oxidation, although some incubations displayed CH4 -stimulated Fe(III) reduction. 16S rRNA profiles continuously changed over the course of enrichment, with ultimate dominance of unclassified members of the order Desulfuromonadales in all treatments. Microbial diversity decreased markedly over the course of incubation, with subtle differences between ferrihydrite and goethite amendments. These results suggest that Fe(III) oxide mineralogy and availability of electron donors could have led to spatial separation of Fe(III)-reducing and methanogenic microbial communities in ferruginous marine sediments, potentially explaining the persistence of CH4 as a greenhouse gas throughout the first half of Earth history.

Coevolution of metal availability and nitrogen assimilation in cyanobacteria and algae.

Marine primary producers adapted over eons to the changing chemistry of the oceans. Because a number of metalloenzymes are necessary for N assimilation, changes in the availability of transition metals posed a particular challenge to the supply of this critical nutrient that regulates marine biomass and productivity. Integrating recently developed geochemical, biochemical, and genetic evidence, we infer that the use of metals in N assimilation - particularly Fe and Mo - can be understood in terms of the history of metal availability through time. Anoxic, Fe-rich Archean oceans were conducive to the evolution of Fe-using enzymes that assimilate abiogenic NH(4)(+) and NO(2)(-). The N demands of an expanding biosphere were satisfied by the evolution of biological N(2) fixation, possibly utilizing only Fe. Trace O(2) in late Archean environments, and the eventual 'Great Oxidation Event' c. 2.3 Ga, mobilized metals such as Mo, enabling the evolution of Mo (or V)-based N(2) fixation and the Mo-dependent enzymes for NO(3)(-) assimilation and denitrification by prokaryotes. However, the subsequent onset of deep-sea euxinia, an increasingly-accepted idea, may have kept ocean Mo inventories low and depressed Fe, limiting the rate of N(2) fixation and the supply of fixed N. Eukaryotic ecosystems may have been particularly disadvantaged by N scarcity and the high Mo requirement of eukaryotic NO(3)(-) assimilation. Thorough ocean oxygenation in the Neoproterozoic led to Mo-rich oceans, possibly contributing to the proliferation of eukaryotes and thus the Cambrian explosion of metazoan life. These ideas can be tested by more intensive study of the metal requirements in N assimilation and the biological strategies for metal uptake, regulation, and storage.

The association of pauciarticular juvenile arthritis and myasthenia gravis.

We encountered two children with fluorescent antinuclear antibody-positive pauciarticular juvenile arthritis who later developed myasthenia gravis. Acetylcholine receptor binding, blocking, and modulating antibodies, retrospectively tested on frozen serum, yielded negative results before the onset of myasthenic symptoms but all yielded strongly positive results coincident with the onset of weakness. In both children, myasthenia gravis responded to thymectomy, and one child had a beneficial response to plasmapheresis. Although, to our knowledge, only two patients with juvenile arthritis and myasthenia gravis have been described in the past, the presence of two additional children with both diseases in a single clinic population suggests that the association may be more prevalent than previously suspected.

The treatment of female borderlines.

Failure to complete needed operations in the separation-individuation process during early childhood development is increasingly suspected of being a major source of borderline pathology. Building on Mahler's descriptions of this process as an interpersonal operation between child and mother, we have directly intervened in the patient-mother relationship in a small group of adult female borderlines. All patients displayed rapid and apparently complete clearing of borderline symptoms following limited conjoint therapy. Although neuroses remained, the criteria for a borderline diagnosis were no longer met. Treatment results with six women who had pretreatment and posttreatment psychological testing are reported. Testing confirmed clinical impressions of significant shifts in psychological defenses as well as perceptions of self and others. Fundamentals of this approach are discussed briefly, and observations regarding possible borderline pathology, mother-daughter interactions, family dynamics, and therapeutic philosophy are made. This approach appears not only to be effective but offers promise of simplifying both the role of the therapist and the therapy itself.