Evidence of oxygenic phototrophy in ancient phosphatic stromatolites from the Paleoproterozoic Vindhyan and Aravalli Supergroups, India.

Fossil microbiotas are rare in the early rock record, limiting the type of ecological information extractable from ancient microbialites. In the absence of body fossils, emphasis may instead be given to microbially derived features, such as microbialite growth patterns, microbial mat morphologies, and the presence of fossilized gas bubbles in lithified mats. The metabolic affinity of micro-organisms associated with phosphatization may reveal important clues to the nature and accretion of apatite-rich microbialites. Stromatolites from the 1.6 Ga Chitrakoot Formation (Semri Group, Vindhyan Supergroup) in central India contain abundant fossilized bubbles interspersed within fine-grained in situ-precipitated apatite mats with average δ13 Corg indicative of carbon fixation by the Calvin cycle. In addition, the mats hold a synsedimentary fossil biota characteristic of cyanobacterial and rhodophyte morphotypes. Phosphatic oncoid cone-like stromatolites from the Paleoproterozoic Aravalli Supergroup (Jhamarkotra Formation) comprise abundant mineralized bubbles enmeshed within tufted filamentous mat fabrics. Construction of these tufts is considered to be the result of filamentous bacteria gliding within microbial mats, and as fossilized bubbles within pristine mat laminae can be used as a proxy for oxygenic phototrophy, this provides a strong indication for cyanobacterial activity in the Aravalli mounds. We suggest that the activity of oxygenic phototrophs may have been significant for the formation of apatite in both Vindhyan and Aravalli stromatolites, mainly by concentrating phosphate and creating steep diurnal redox gradients within mat pore spaces, promoting apatite precipitation. The presence in the Indian stromatolites of alternating apatite-carbonate lamina may result from local variations in pH and oxygen levels caused by photosynthesis-respiration in the mats. Altogether, this study presents new insights into the ecology of ancient phosphatic stromatolites and warrants further exploration into the role of oxygen-producing biotas in the formation of Paleoproterozoic shallow-basin phosphorites.

Biogenicity of an Early Quaternary iron formation, Milos Island, Greece.

A ~2.0-million-year-old shallow-submarine sedimentary deposit on Milos Island, Greece, harbours an unmetamorphosed fossiliferous iron formation (IF) comparable to Precambrian banded iron formations (BIFs). This Milos IF holds the potential to provide clues to the origin of Precambrian BIFs, relative to biotic and abiotic processes. Here, we combine field stratigraphic observations, stable isotopes of C, S and Si, rock petrography and microfossil evidence from a ~5-m-thick outcrop to track potential biogeochemical processes that may have contributed to the formation of the BIF-type rocks and the abrupt transition to an overlying conglomerate-hosted IF (CIF). Bulk δ(13) C isotopic compositions lower than -25‰ provide evidence for biological contribution by the Calvin and reductive acetyl-CoA carbon fixation cycles to the origin of both the BIF-type and CIF strata. Low S levels of ~0.04 wt.% combined with δ(34) S estimates of up to ~18‰ point to a non-sulphidic depository. Positive δ(30) Si records of up to +0.53‰ in the finely laminated BIF-type rocks indicate chemical deposition on the seafloor during weak periods of arc magmatism. Negative δ(30) Si data are consistent with geological observations suggesting a sudden change to intense arc volcanism potentially terminated the deposition of the BIF-type layer. The typical Precambrian rhythmic rocks of alternating Fe- and Si-rich bands are associated with abundant and spatially distinct microbial fossil assemblages. Together with previously proposed anoxygenic photoferrotrophic iron cycling and low sedimentary N and C potentially connected to diagenetic denitrification, the Milos IF is a biogenic submarine volcano-sedimentary IF showing depositional conditions analogous to Archaean Algoma-type BIFs.

Deep-biosphere consortium of fungi and prokaryotes in Eocene subseafloor basalts.

The deep biosphere of the subseafloor crust is believed to contain a significant part of Earth's biomass, but because of the difficulties of directly observing the living organisms, its composition and ecology are poorly known. We report here a consortium of fossilized prokaryotic and eukaryotic micro-organisms, occupying cavities in deep-drilled vesicular basalt from the Emperor Seamounts, Pacific Ocean, 67.5 m below seafloor (mbsf). Fungal hyphae provide the framework on which prokaryote-like organisms are suspended like cobwebs and iron-oxidizing bacteria form microstromatolites (Frutexites). The spatial inter-relationships show that the organisms were living at the same time in an integrated fashion, suggesting symbiotic interdependence. The community is contemporaneous with secondary mineralizations of calcite partly filling the cavities. The fungal hyphae frequently extend into the calcite, indicating that they were able to bore into the substrate through mineral dissolution. A symbiotic relationship with chemoautotrophs, as inferred for the observed consortium, may be a pre-requisite for the eukaryotic colonization of crustal rocks. Fossils thus open a window to the extant as well as the ancient deep biosphere.

Analysis of hopanes and steranes in single oil-bearing fluid inclusions using time-of-flight secondary ion mass spectrometry (ToF-SIMS).

Steranes and hopanes are organic biomarkers used as indicators for the first appearance of eukaryotes and cyanobacteria on Earth. Oil-bearing fluid inclusions may provide a contamination-free source of Precambrian biomarkers, as the oil has been secluded from the environment since the formation of the inclusion. However, analysis of biomarkers in single oil-bearing fluid inclusions, which is often necessary due to the presence of different generations of inclusions, has not been possible due to the small size of most inclusions. Here, we have used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to monitor in real time the opening of individual inclusions trapped in hydrothermal veins of fluorite and calcite and containing oil from Ordovician source rocks. Opening of the inclusions was performed by using a focused C(60)(+) ion beam and the in situ content was precisely analysed for C(27)-C(29) steranes and C(29)-C(32) hopanes using Bi(3)(+) as primary ions. The capacity to unambiguously detect these biomarkers in the picoliter amount of crude oil from a single, normal-sized (15-30 mum in diameter) inclusion makes the approach promising in the search of organic biomarkers for life's early evolution on Earth.

Fossilized microorganisms associated with zeolite-carbonate interfaces in sub-seafloor hydrothermal environments.

In this paper we describe carbon-rich filamentous structures observed in association with the zeolite mineral phillipsite from sub-seafloor samples drilled and collected during the Ocean Drilling Program (ODP) Leg 197 at the Emperor Seamounts. The filamentous structures are approximately 5 microm thick and approximately 100-200 microm in length. They are found attached to phillipsite surfaces in veins and entombed in vein-filling carbonates. The carbon content of the filaments ranges between approximately 10 wt% C and 55 wt% C. They further bind to propidium iodide (PI), which is a dye that binds to damaged cell membranes and remnants of DNA. Carbon-rich globular microstructures, 1-2 microm in diameter, are also found associated with the phillipsite surfaces as well as within wedge-shaped cavities in phillipsite assemblages. The globules have a carbon content that range between approximately 5 wt% C and 55 wt% C and they bind to PI. Ordinary globular iron oxides found throughout the samples differ in that they contain no carbon and do not bind to the dye PI. The carbon-rich globules are mostly concentrated to a film-like structure that is attached to the phillipsite surfaces. This film has a carbon content that ranges between approximately 25 wt% C and 75 wt% C and partially binds to PI. EDS analyses show that the carbon in all structures described are not associated with calcium and therefore not bound in carbonates. The carbon content and the binding to PI may indicate that the filamentous structures could represent fossilized filamentous microorganisms, the globules could represent fossilized microbial cells and the film-like structures could represent a microbially produced biofilm. Our results extend the knowledge of possible habitable niches for a deep biosphere in sub-seafloor environments and suggests, as phillipsite is one of the most common zeolite mineral in volcanic rocks of the oceanic crust, that it could be a common feature in the oceanic crust elsewhere.

Fossilized microorganisms from the Emperor Seamounts: implications for the search for a subsurface fossil record on Earth and Mars.

We have observed filamentous carbon-rich structures in samples drilled at 3 different seamounts that belong to the Emperor Seamounts in the Pacific Ocean: Detroit (81 Ma), Nintoku (56 Ma), and Koko Seamounts (48 Ma). The samples consist of low-temperature altered basalts recovered from all 3 seamounts. The maximum depth from which the samples were retrieved was 954 meters below seafloor (mbsf). The filamentous structures occur in veins and fractures in the basalts, where they are attached to the vein walls and embedded in vein-filling minerals like calcite, aragonite, and gypsum. The filaments were studied with a combination of optical microscopy, environmental scanning electron microscopy (ESEM), Raman spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Minerals were identified by a combination of optical microscopy, X-ray diffraction, Raman spectrometry, and energy dispersive spectrometry on an environmental scanning electron microscope. Carbon content of the filaments ranges between approximately 10 wt % and approximately 50 wt % and is not associated with carbonates. These results indicate an organic origin of the carbon. The presence of C(2)H(4), phosphate, and lipid-like molecules in the filaments further supports a biogenic origin. We also found microchannels in volcanic glass enriched in carbon (approximately 10-40 wt %) compatible with putative microbial activity. Our findings suggest new niches for life in subseafloor environments and have implications for further exploration of the subseafloor biosphere on Earth and beyond.

The health consequences of racial discrimination: a study of African Americans.

This investigation focuses on the relationship between racial discrimination and health. Many studies have shown a link between race and differential health outcomes, but few have actually measured racial discrimination. Such studies leave unanswered the question of exactly how the experience of racial discrimination might affect health. Racial discrimination is argued to act in the same fashion as other chronic stressors by increasing blood pressure. However, racial discrimination may also give rise to the sense of thwarted aspirations, itself a stressor, and make the active coping style of "John Henryism" more likely. In these data, we measure perceived racial discrimination for a sample of African Americans and find that experiencing racially-based discriminatory treatment does not impact health. There is no relationship between doctor-diagnosed hypertension and cardiovascular disease, and being the victim of racially biased treatment. We discuss possible reasons for this, and argue that greater conceptualization about the postulated link between discrimination and health is necessary, as well as explicitly designed studies for the purpose of examining this postulated relationship.

Racism and the mental health of African Americans: the role of self and system blame.

The research on external (social system) and internal (personal) attributions to mental health outcomes for African Americans is reviewed. Although many blacks have aspirations that they are unable to achieve, the motivational and mental health consequences of this situation are unclear. Several researchers have suggested that it is adaptive for African Americans to reduce striving effort and bring personal goals more in line with the objective realities of an unfair opportunity structure. Others have proposed that because an unjust system is to blame, the most appropriate response is to work collectively with other group members to make the system more open to opportunities for advancement. Epidemiologic research on the relationship of internal-external locus of control to mental disorder has generally found that being internal has positive mental health effects; while having an external orientation is detrimental. This paper addresses these issues by demonstrating that the psychiatric-epidemiologic and the race-consciousness literatures lead to opposite predictions about the relationship of external attributions (fatalism and system blame) to mental health. The article concludes with a series of issues that need to be addressed in order to advance knowledge about social and psychological risk factors for psychiatric disorders in African Americans.

Race, gender, and the response to stress: autoworkers' vulnerability to long-term unemployment.

A three-wave panel study of auto plant closings focused on the mental health effects of unemployment on blue-collar workers. This paper explores how the impact of long-term unemployment varies across race and gender. We also examine whether other demographic factors can themselves modify the impacts of race and gender. Dependent variables include two measures of distress and two drinking measures. Results showed that the effect of long-term unemployment on distress and drinking was more severe among less educated workers, and responses of blacks were especially sensitive to level of education. In addition, men showed a greater association of long-term unemployment with depression (and to some extent anxiety) than did women. Marriage affected the responses of men but not of women, and of whites but not of blacks. Explanatory variables--the worker's experiences of financial hardship, other negative life events, and lack of a confidant--largely accounted for male-female differences. We conclude by discussing theoretical implications of these effects and address the limitations of the traditional term "vulnerability" in describing them.

Leisure-time physical activity in an African-American population.

Despite the many important benefits of leisure-time physical exercise on health, many Americans do not engage in exercise. This is more the case for the African-American population. This study assesses the impact of efficacy cognitions on leisure-time physical activity (LTPA) in an African-American sample. Our findings show that LTPA is predicted by the sense of efficacy in this African-American sample. Further analyses address significant factors in the prediction of the sense of efficacy. We find that the general sense of mastery predicts efficacy in this African-American sample. This may be especially significant for the African-American population. Also, analysis reveals surprising findings concerning characteristics predictive of efficacy cognitions. The highly educated are least likely to believe in the efficacy of preventive health behavior.

Impact of mental health services use on subsequent mental health of autoworkers.

Collecting three waves of panel data offered an unusual opportunity to examine the long-term outcomes of the use of mental health services. Data are drawn from a panel study of autoworkers. Waves 1, 2, and 3 consisted of 1,597, 1,288, and 1,136 workers, respectively, from four closing and 12 non-closing plants in Southeastern Michigan. Our results revealed a surprising finding: use of mental health services, whether in the general or specialty sectors, had a negative impact on the subsequent mental health of autoworkers in our sample. The use of mental health services is associated with increased levels of psychological distress. Further, we show that the negative association between use of mental health services and distress was greater for certain demographic groups, notably Blacks, men, older workers, the poorly educated, and the unemployed, depending upon the type of service used. Finally, we sought to uncover the reasons for the negative impact of services use. Results suggest that self-blame, for one, contributed to the negative impact of using mental health services.

Social relationships and health-related behavior.

The relationship of social ties to health behavior is studied in this paper. The general hypothesis tested is that those with social relationships are more likely to avoid health damaging behavior. Patterns regarding specific social ties and particular health behaviors are examined. Findings indicate the relationships of spouse, organization member, and friend are related to preventive health behavior; spouses are less likely smokers, drinkers, and heavy drinkers. The friend relationship is related to decreased smoking behavior, while the employee relationship is related to increased drinking. A consistent predictor of health behaviors is the social tie of organization member. People with relationships as organization members are more likely always to wear seat belts, smoke and drink less, and consume lower amounts of these substances.

Unemployment, distress, and coping: a panel study of autoworkers.

This study of coping with unemployment traces the distress levels of workers in 4 closing and 12 nonclosing General Motors (GM) plants. Workers were interviewed 3 months before plants closed, 1 year after, and 2 years after (final N = 1,136). Tested were (a) effects of unemployment on symptoms of depression, anxiety, and somatization; (b) linkages between depression and subsequent unemployment, controlling for workers' gender, race, marital status, age, education, prior income, and seniority; and (c) the relationship between workers' coping decisions and subsequent depression. Results showed that unemployment at Waves 2 and 3 was related to prior frequency of symptoms of depression. Depression, in turn, was alleviated for workers whose coping decisions at Wave 2 fit with their Wave 3 outcomes: those who both wanted and found a job, lost a job they disliked, or remained unemployed as planned.

Hard times and vulnerable people: initial effects of plant closing on autoworkers' mental health.

Large-scale 1987 General Motors plant shutdowns offered an unusual opportunity to study effects of actual and anticipated unemployment on mental health. Workers from four closing and 12 nonclosing plants (Ns = 831 and 766 respectively) were interviewed approximately three months before scheduled plant closings. Dependent variables were baseline frequencies of somatic, depressive, and anxiety symptoms. The quasi-experimental design made it possible to explore systematically the mental health problems of individual autoworkers as a function of their employment status, their demographic characteristics, and the interaction of the two. Three groups were formed by dividing workers at closing plants into those already laid off and those anticipating layoff; the third group consisted of workers in nonclosing plants. Results revealed a pattern of interaction between unemployment and demographic variables, showing differential vulnerability to job loss. Less educated blacks were especially affected; follow-up analyses showed that their more distressed mental health could not be attributed entirely to other, prior stressors.

Social mobility and hypertension among blacks.

This paper considers the role of social mobility to hypertension among blacks. Using a nationally representative sample of the adult black population, this research finds no effects of intergenerational socioeconomic mobility. Minimal effects are found for geographic mobility; geographic moves bears a small positive relationship to hypertension. The implications for a theory of mobility effects on black health are discussed.

Anger expression and life stress among blacks: their role in physical health.

This study examines the relationship between anger expression and life stress in a nationally representative sample of black adults. Recent research of mostly white subjects has shown that anger-hostility, one of the components of the Type A behavioral pattern, is an important predictor of health problems. The findings of the present inquiry indicate that anger-hostility is an important predictor of life stress, and that people with higher levels of anger conflict are more likely to experience negative life events. Moreover, negative life events and anger are shown to be independent predictors of health problems among blacks. The implications of these results for future studies of the health of black Americans are discussed.

Race differences in professional help seeking.

Using data from two national surveys, findings from this research indicated that blacks were more likely than whites to seek help from mental health professionals, particularly for economic and physical health problems. Blacks also sought help more often than whites from other sources of professional help, such as teachers, lawyers, social workers and emergency rooms. On the other hand, whites were more likely to seek help from medical sources for all types of problems, and from clergy members.

The relationship of anger expression to health problems among black Americans in a national survey.

This study examined the relationship between anger expression, other psychosocial measures, and health problems in a nationally representative, cross-sectional sample of 1277 black adults. Subjects indicating a high level of outwardly expressed anger during a period in which they experienced a severe personal problem had a significantly higher number of health problems than their counterparts who expressed low and moderate levels of anger. Anger expression also significantly interacted with a measure of life strain (employment status) to predict health problems. Blacks who were unemployed were more likely to have a higher number of health problems if anger was expressed outwardly at a high level. The relationship was found to be independent of age, gender, urbanicity, smoking, and drinking problems. The overall pattern of the findings suggests that blacks who are at increased risk for health problems may be identified by how often anger is experienced and expressed during periods of emotional distress.