Reconstruction of Extracellular Respiratory Pathways for Iron(III) Reduction in Shewanella Oneidensis Strain MR-1

Shewanella oneidensis strain MR-1 is a facultative anaerobic bacterium capable of respiring a multitude of electron acceptors, many of which require the Mtr respiratory pathway. The core Mtr respiratory pathway includes a periplasmic c-type cytochrome (MtrA), an integral outer-membrane β-barrel protein (MtrB), and an outer-membrane-anchored c-type cytochrome (MtrC). Together, these components facilitate transfer of electrons from the c-type cytochrome CymA in the cytoplasmic membrane to electron acceptors at and beyond the outer-membrane. The genes encoding these core proteins have paralogs in the S. oneidensis genome (mtrB and mtrA each have four while mtrC has three) and some of the paralogs of mtrC and mtrA are able to form functional Mtr complexes. We demonstrate that of the additional three mtrB paralogs found in the S. oneidensis genome, only MtrE can replace MtrB to form a functional respiratory pathway to soluble iron(III) citrate. We also evaluate which mtrC/mtrA paralog pairs (a total of 12 combinations) are able to form functional complexes with endogenous levels of mtrB paralog expression. Finally, we reconstruct all possible functional Mtr complexes and test them in a S. oneidensis mutant strain where all paralogs have been eliminated from the genome. We find that each combination tested with the exception of MtrA/MtrE/OmcA is able to reduce iron(III) citrate at a level significantly above background. The results presented here have implications toward the evolution of anaerobic extracellular respiration in Shewanella and for future studies looking to increase the rates of substrate reduction for water treatment, bioremediation, or electricity production

What Genetics Offers Geobiology

For over 50 years, the Parker Brothers’ board game “Clue” has maintained its position as the classic family detective game. A murder has been committed in the mansion, but we don’t know where, by whom, or how. Was it Professor Plum in the study with a knife, or Miss Scarlett in the ballroom with a candlestick? Through rolls of the dice, fragments of information patiently accumulated piece-by-piece, and the application of logic, players construct a case to figure out “whodunit”. Because there are several potential solutions to the problem, the key challenge is to figure out what happened by understanding how it happened

Tensor transformation technique for the transport equation

A step-wise tensor transformation technique is presented for the transformation of the single energy group transport equation to an arbitrary spatial coordinate system. Both gradient and divergence forms of the equation are given and the same method is applied to the derivation of the diffusion approximation. It is demonstrated that using an orthogonal representation of the propagation vector will simplify the divergence form of the equation. The application of this technique is in the representation of the transport equation in coordinate systems other than the usual rectangular, cylindrical and spherical ones. Its use is demonstrated by transforming the transport equation to a toroidal coordinate system consisting of nested circular toroids. (auth

Transformation of the single energy group transport, equation to axissymmetric toroidal coordinates

The streaming term of the single energy group transport equation was derived for a general class of axisymmetric toroidal geometries using a tensor transformation formalism. The particular case of nested circular toroids treated previously by Pomraning and Stevens may be obtained by direct substitution into the equation. Other, more complicated geometries of interest to plasma physics and fusion reactor research are obtainable in the same manner. The cylindrical limit in which the azimuthal curvature is neglected may be obtained by taking the ratio of the poloidal curvature to X$sup 1$, the toroidal curvature, to zero. Similarly the planar limit results when both curvatures are small compared to the inverse of the physical dimension measured normal to the toroidal surface. (auth

Eating Disorders and Disordered Eating in Different Cultures

Clinical experience and research have moved the field toward greater recognition and differentiation of eating disorders as independent categories of mental disorder. Shorter's historical analysis, however, suggests that it may be useful to reconsider the relationship of AN and BN to the broader class of somatoform disorders. Also, by conferring legitimacy on this socially and culturally constructed disorder, mental health professionals may have seriously underestimated their unanticipated influence in propagating eating disorders with publicity aimed at preventing and curing them. Inasmuch as it offers an alternative or complement to the prevailing cultural hypothesis, which focuses on the effect of Western esthetics rather than the sociology of health care institutions, and has important implications for policy and publicity about eating disorders, the question of how culture and Westernization affect the epidemiology and experience of eating disorders also requires further study

Parasitic Diseases and Psychiatric Illness

Distinguishing parasitic diseases from other infections and tropical medical disorders based on microbiological classification is a matter of convenience. Organic brain syndromes are associated with both protozoan and helminthic infections; side-effects of drugs commonly used to treat parasitoses may impair mood and cause anxiety, agitation or psychosis. Emotional states may in turn affect the experience of medical illness. Psychiatrically significant features of medical illness are determined both by pathophysiology and by the personal and social context in which they occur. Many factors affect mental health in the tropics where the synergy of infection, emotional strengths, vulnerabilities, social supports and stressors is critical. This review discusses parasitic diseases of psychiatric interest by virtue of their effects on thinking, mood and behaviour; and it distinguishes issues that apply mainly to indigenous populations and visitors to endemic areas. In some paradoxical instances the psychiatric influence of parasitic diseases does not require infection; the review concludes by considering the prime example, delusions of parasitosis, which is a primary psychiatric disorder

Cultural epidemiology: An introduction and overview

Although the value of interdisciplinary collaboration between epidemiology and anthropology is both widely acknowledged and hotly contested, effective international health policy and multicultural health programmes require it. The EMIC framework for cultural studies of illness was developed in response to such needs, and a cultural epidemiology emerged from that framework as an interdisciplinary field of research on locally valid representations of illness and their distributions in cultural context. These representations are specified by variables, descriptions, and narrative accounts of illness experience, its meaning, and associated illness behaviour. Specialized interactive qualitative and quantitative research methods provide a descriptive account, facilitate comparisons, and clarify the cultural basis of risk, course, and outcomes of practical significance for clinical practice and public health. This paper discusses the theoretical underpinnings of cultural epidemiology and an operational formulation for examining patterns of distress, perceived causes, and help-seeking. Five additional papers in this special issue of Anthropology and Medicine indicate how the EMIC has been used and has engendered an ethnographically grounded cultural epidemiology. Although this overview and these papers are concerned exclusively with mental health, a complementary stream of active research on leprosy, tuberculosis, epilepsy, and other tropical infectious, neurological, and medical disorders is ongoing. Next steps for cultural epidemiology in mental health research are discussed, including (1) further clinic-based studies of psychiatric disorders, (2) studies of deliberate self-harm in clinic and community settings, (3) complementary cultural components of psychiatric epidemiological surveys, (4) baseline assessments to guide community programmes, and (5) contributions to intervention studies

Mechanisms Underlying the Morning Increase in Platelet Aggregation: A Flow Cytometry Study

ObjectivesMechanisms underlying the morning increase in platelet aggregation produced by arising and assuming the upright posture were studied by examining 1) the expression on the platelet surface of activation-dependent markers; 2) platelet aggregation in whole blood; and 3) hematologic factors likely to influence aggregation.BackgroundThe morning increase in thrombotic cardiovascular events has been attributed, in part, to the morning surge in platelet aggregability, but its mechanisms are poorly understood.MethodsExpression of seven platelet surface antigens (including P-selectin, activated GPIIb-IIIa and GPIb-IX), whole-blood platelet aggregation, platelet count and hematocrit were measured before and after arising in 17 normal volunteers. The fibrinolytic variables, tissue-type plasminogen activator, plasminogen activator inhibitor 1 and catecholamine levels were also measured.ResultsOn arising and standing, platelet aggregation increased by 71% (p ≤ 0.01) and 27% (p ≤ 0.03) in response to collagen and adenosine diphosphate, respectively. However, there was no change in any of the activation-dependent platelet surface markers. Whole-blood platelet count and hematocrit increased by 15% and 7% (both p < 0.0001), respectively. Norepinephrine and epinephrine levels increased by 189% (p < 0.0001) and 130% (p < 0.01), respectively. Tissue-type plasminogen activator antigen increased (31%, p < 0.01), but there was no significant increase in plasminogen activator inhibitor 1, suggesting an overall increase in fibrinolysis on standing. Prothrombin fragment 1.2 increased by 28% (p < 0.02), indicating a small increase in thrombin generation. The increases in hematocrit and platelet count that occurred on standing were carefully mimicked in vitro and resulted in a 115% (p < 0.05) increase in platelet aggregation in response to adenosine diphosphate.ConclusionsThese data demonstrate that the morning increase in platelet aggregation is not accompanied by expression of activation-dependent platelet surface receptors and suggest that the increase in whole-blood aggregation may be primarily due to the increases in catecholamine levels, platelet count and hemocon-centration