Geochemically distinct carbon isotope distributions in Allochromatium vinosum DSM 180T grown photoautotrophically and photoheterotrophically.

Anoxygenic, photosynthetic bacteria are common at redox boundaries. They are of interest in microbial ecology and geosciences through their role in linking the carbon, sulfur, and iron cycles, yet much remains unknown about how their flexible carbon metabolism-permitting either autotrophic or heterotrophic growth-is recorded in the bulk sedimentary and lipid biomarker records. Here, we investigated patterns of carbon isotope fractionation in a model photosynthetic sulfur-oxidizing bacterium, Allochromatium vinosum DSM180T . In one treatment, A. vinosum was grown with CO2 as the sole carbon source, while in a second treatment, it was grown on acetate. Different intracellular isotope patterns were observed for fatty acids, phytol, individual amino acids, intact proteins, and total RNA between the two experiments. Photoautotrophic CO2 fixation yielded typical isotopic ordering for the lipid biomarkers: δ13 C values of phytol > n-alkyl lipids. In contrast, growth on acetate greatly suppressed intracellular isotopic heterogeneity across all molecular classes, except for a marked 13 C-depletion in phytol. This caused isotopic "inversion" in the lipids (δ13 C values of phytol < n-alkyl lipids). The finding suggests that inverse δ13 C patterns of n-alkanes and pristane/phytane in the geologic record may be at least in part a signal for photoheterotrophy. In both experimental scenarios, the relative isotope distributions could be predicted from an isotope flux-balance model, demonstrating that microbial carbon metabolisms can be interrogated by combining compound-specific stable isotope analysis with metabolic modeling. Isotopic differences among molecular classes may be a means of fingerprinting microbial carbon metabolism, both in the modern environment and the geologic record.

Assessing the influence of physical, geochemical and biological factors on anaerobic microbial primary productivity within hydrothermal vent chimneys.

Chemosynthetic primary production supports hydrothermal vent ecosystems, but the extent of that productivity and its governing factors have not been well constrained. To better understand anaerobic primary production within massive vent deposits, we conducted a series of incubations at 4, 25, 50 and 90 °C using aggregates recovered from hydrothermal vent structures. We documented in situ geochemistry, measured autochthonous organic carbon stable isotope ratios and assessed microbial community composition and functional gene abundances in three hydrothermal vent chimney structures from Middle Valley on the Juan de Fuca Ridge. Carbon fixation rates were greatest at lower temperatures and were comparable among chimneys. Stable isotope ratios of autochthonous organic carbon were consistent with the Calvin-Benson-Bassham cycle being the predominant mode of carbon fixation for all three chimneys. Chimneys exhibited marked differences in vent fluid geochemistry and microbial community composition, with structures being differentially dominated by gamma (γ) or epsilon (ε) proteobacteria. Similarly, qPCR analyses of functional genes representing different carbon fixation pathways showed striking differences in gene abundance among chimney structures. Carbon fixation rates showed no obvious correlation with observed in situ vent fluid geochemistry, community composition or functional gene abundance. Together, these data reveal that (i) net anaerobic carbon fixation rates among these chimneys are elevated at lower temperatures, (ii) clear differences in community composition and gene abundance exist among chimney structures, and (iii) tremendous spatial heterogeneity within these environments likely confounds efforts to relate the observed rates to in situ microbial and geochemical factors. We also posit that microbes typically thought to be mesophiles are likely active and growing at cooler temperatures, and that their activity at these temperatures comprises the majority of endolithic anaerobic primary production in hydrothermal vent chimneys.

Isolation and characterization of novel psychrophilic, neutrophilic, Fe-oxidizing, chemolithoautotrophic alpha- and gamma-proteobacteria from the deep sea.

We report the isolation and physiological characterization of novel, psychrophilic, iron-oxidizing bacteria (FeOB) from low-temperature weathering habitats in the vicinity of the Juan de Fuca deep-sea hydrothermal area. The FeOB were cultured from the surfaces of weathered rock and metalliferous sediments. They are capable of growth on a variety of natural and synthetic solid rock and mineral substrates, such as pyrite (FeS(2)), basalt glass ( approximately 10 wt% FeO), and siderite (FeCO(3)), as their sole energy source, as well as numerous aqueous Fe substrates. Growth temperature characteristics correspond to the in situ environmental conditions of sample origin; the FeOB grow optimally at 3 to 10 degrees C and at generation times ranging from 57 to 74 h. They are obligate chemolithoautotrophs and grow optimally under microaerobic conditions in the presence of an oxygen gradient or anaerobically in the presence of nitrate. None of the strains are capable of using any organic or alternate inorganic substrates tested. The bacteria are phylogenetically diverse and have no close Fe-oxidizing or autotrophic relatives represented in pure culture. One group of isolates are gamma-Proteobacteria most closely related to the heterotrophic bacterium Marinobacter aquaeolei (87 to 94% sequence similarity). A second group of isolates are alpha-Proteobacteria most closely related to the deep-sea heterotrophic bacterium Hyphomonas jannaschiana (81 to 89% sequence similarity). This study provides further evidence for the evolutionarily widespread capacity for Fe oxidation among bacteria and suggests that FeOB may play an unrecognized geomicrobiological role in rock weathering in the deep sea.

Comparison of atherosclerosis in alaska Natives and nonnatives.

OBJECTIVE: To test the hypothesis that Alaska Natives have fewer atherosclerotic lesions in the coronary arteries and aorta than nonnative Alaska residents. DESIGN: Systematic standardized collection and evaluation of coronary arteries and aortas collected at autopsy. SETTING: Forensic autopsy service in Alaska. SUBJECTS: One hundred thirty Alaska Natives and 115 Alaska nonnatives who underwent forensic autopsy between February 1989 and December 1993. INTERVENTION: None. MAIN OUTCOME MEASURES: Prevalence and extent of atherosclerotic lesions in the aortas and coronary arteries in both populations studied. RESULTS: Alaska Natives had significantly lower prevalence and extent of raised atherosclerotic lesions in the abdominal aorta and coronary arteries than nonnative Alaska residents. CONCLUSIONS: Differences in coronary heart disease mortality between Alaska Natives and nonnatives are, at least in part, the result of fewer atherosclerotic lesions in Alaska Natives.

Accidental fatal monochloroacetic acid poisoning.

A case of accidental lethal monochloroacetic acid poisoning is presented, along with a brief review of the mechanisms of intoxication. Although lethal skin exposures have been previously reported, this case appears to be the first instance of oral-route poisoning to be documented.

Atherosclerosis in Alaska Natives and non-natives.

Low mortality from coronary heart disease (CHD) among Eskimos has been attributed to less atherosclerosis in the coronary arteries because of a high dietary intake of omega-3 fatty acids. Other investigators attribute this low mortality to the fact that Eskimos have a high mortality from other causes before middle age, when CHD is common. However, most studies have been epidemiological, either by death-certificate review or risk-factor evaluation. We evaluated the extent of atherosclerotic lesions in the coronary arteries and aortas from Alaska Natives. Standardised comparisons between samples from 103 Native and 101 non-native residents show that the extent of raised lesions increases with age in both groups, but the prevalence of raised lesions in native specimens was consistently lower than in those from non-natives. This difference was statistically significant. The data suggest that the differences in CHD mortality between Alaska Natives and non-natives are, at least in part, the result of less atherosclerosis in natives.

Wounds caused by contact with muzzle-lift relief ports (Mag-Na-Port).

Fan-shaped stippled burns were produced on the skin when a revolver whose barrel had been modified by the Mag-Na-Port process was fired twice with the side of the muzzle in contact. A grazing wound was produced by one bullet, and an oblique entry was produced by the other. The characteristics of Mag-Na-Port wounds and test shots are described, and these are compared with test shots from two other higher power revolvers.

Simultaneous temporal and frontal suicidal gunshots.

A white man in a remote area of Alaska shot himself simultaneously with two revolvers--a .41 magnum and a .44 magnum. Only three examples of two-gun suicides are described in the literature.

Autoamputation of the left arm--a bizarre suicide.

A 24-year-old woman committed suicide by amputating her left arm immediately below the shoulder joint with a small kitchen knife. No references to such a suicide were found in an extensive literature search.

Wounds caused by tight contact with the barrel-cylinder gap of revolvers.

A case is presented in which the recognition of a tight cylinder gap contact wound was crucial. Experiments were carried out to reproduce the wound which was noted on the hand of a robbery suspect. Tight contact with the cylinder gap of a revolver produces a characteristic, readily recognizable wound. It is characterized by an L-shaped pattern of powder residue. Along one axis a searing burn may occur which may be deep and which may lead to significant tissue destruction.

Epithelial-nerve intermingling in benign breast lesions.

Intimate intermingling of benign ductal epithelium and nerves was observed in two specimens of breast tissue with extensive adenosis and papillomatosis. The ducts were not situated within lymphatic channels. Rencent investigations have cast doubt on the very existence of "perineural-lymphatics." And while perineural and intraneural spread of malignant cells is unquestionably frequent, growth and extension seemingly occur along loose connective tissue spaces and not within preformed channels. We suggest that the designation "epithelial-nerve intermingling" appropriately describes this phenomenon, and, whereas this is most frequently found with carcinomatous cells, benign epithellum may and, occasionally does, participate. Thus, epithelial-nerve intermingling is neither necessarily indicative of malignant neoplasia nor should it be a decisive criterion in determining the extension of known malignant neoplasm, unless the epithelial cells are clearly atypical.