Thiosulfate, polythionates and elemental sulfur assimilation and reduction in the bacterial world

Abstract Among sulfur compounds, thiosulfate and polythionates are present at least transiently in many environments. These compounds have a similar chemical structure and their metabolism appears closely related. They are commonly used as energy sources for photoautotrophic or chemolithotrophic microorganisms, but their assimilation has been seldom studied and their importance in bacterial physiology is not well understood. Almost all bacterial strains are able to cleave these compounds since they possess thiosulfate sulfur transferase, thiosulfate reductace or S -sulfocysteine synthase activities. However, the role of these enzymes in the assimilation of thiosulfate or polythionates has not always been clearly established.
Elemental sulfur is, on the contrary, very common in the environmental. It is an energy source for sulfur-reducing eubacteria and archaebacteria and many sulfur-oxidizing archaebacteria. A phenomenon still not well understood is the 'excessive assimilatory sulfur metabolism' as observed in methanogens which perform a sulfur reduction which exceeds their anabolic needs without any apparent benefit. In heterotrophs, assimilation of elemental sulfur is seldom described and it is uncertain whether this process actually has a physiological significance.
Thus, reduction of thiosulfate and elemental sulfur is a common by incompletely understood feature among bacteria. These activities could give bacteria a selective advantage, but futher investigations are needed to clarify this possibility. Presence of thiosulfate, polythionates and sulfur reductase activities does not imply obligatorily that these activities play a role in thiosulfate, polythionates or sulfur assimilation as these compounds could be merely intermediates in bacterial metabolism. The possibility also exists that the assimilation of these sulfur compounds is just a side effect of an enzymatic activity with a completely different function.     

Tree growth and water-use in hyper-arid Acacia occurs during the hottest and driest season

Oecologia - Drought-induced tree mortality has been recently increasing and is expected to increase further under warming climate. Conversely, tree species that survive under arid conditions might...     

A new polymorphic restriction site at the human atrial natriuretic peptide (hANP) gene locus

A unique two allele polymorphism for both HpaII and SmaI is described in the second intron of the human atrial natriuretic peptide gene. It should be a useful marker of this candidate gene in familial susceptibility to hypertension.     

Ambient ammonia effect on catalytic potential of muscle and gill AMP deaminase in fish

AMP deaminase activity was inhibited in gill and muscle of Sarotherodon mossambicus, subjected to a week-long exposure to sublethal concentration of ambient ammonia. pH-dependent kinetic studies revealed decreased catalytic efficiency of the enzyme due to altered active site density and ionization pattern in the fish tissues at different phases of ammonia exposure.     

How the CIOMS guidelines contribute to fair inclusion of pregnant women in research

As early as 2002, CIOMS stated that pregnant women should be presumed eligible for participation in research. Despite this position and calls of other well‐recognized organizations, the health needs of pregnant women in research remain grossly under‐researched. Although the presumption of eligibility remains unchanged, the revision of the 2002 CIOMS International ethical guidelines for biomedical research involving human subjects involved a substantive rewrite of the guidance on research with pregnant women and related guidelines, such as those on fair inclusion and vulnerability. However, close reading of the guidelines reveals morally relevant different approaches to fair inclusion of pregnant women and other under‐represented groups, such as children and incompetents. Where CIOMS sets out that children and adolescents must be included unless a good scientific reason justifies their exclusion, no such claim of having to justify exclusion appears in the guideline on pregnant women. Instead, CIOMS claims that research relevant to pregnant women’s health needs must be promoted. This paper analyses how and to what extent the guideline on pregnant women differs from other guidance on fair inclusion in the document. Accordingly, the paper evaluates to what extent the current phrasing may contribute to fair inclusion of pregnant women in research. We will conclude that a system change towards a learning health system is essential to break down the status quo of knowledge generation in the field of medication use during pregnancy and argue that the CIOMS guidelines allow for this system change.     

Non-photochemical quenching-dependent acclimation and thylakoid organization of Chlamydomonas reinhardtii to high light stress

Light is essential for all photosynthetic organisms while an excess of it can lead to damage mainly the photosystems of the thylakoid membrane. In this study, we have grown Chlamydomonas reinhardtii cells in different intensities of high light to understand the photosynthetic process with reference to thylakoid membrane organization during its acclimation process. We observed, the cells acclimatized to long-term response to high light intensities of 500 and 1000 µmol m^?2 s^?1 with faster growth and more biomass production when compared to cells at 50 µmol m^?2 s^?1 light intensity. The ratio of Chl a/b was marginally decreased from the mid-log phase of growth at the high light intensity. Increased level of zeaxanthin and LHCSR3 expression was also found which is known to play a key role in non-photochemical quenching (NPQ) mechanism for photoprotection. Changes in photosynthetic parameters were observed such as increased levels of NPQ, marginal change in electron transport rate, and many other changes which demonstrate that cells were acclimatized to high light which is an adaptive mechanism. Surprisingly, PSII core protein contents have marginally reduced when compared to peripherally arranged LHCII in high light-grown cells. Further, we also observed alterations in stromal subunits of PSI and low levels of PsaG, probably due to disruption of PSI assembly and also its association with LHCI. During the process of acclimation, changes in thylakoid organization occurred in high light intensities with reduction of PSII supercomplex formation. This change may be attributed to alteration of protein–pigment complexes which are in agreement with circular dichoism spectra of high light-acclimatized cells, where decrease in the magnitude of psi-type bands indicates changes in ordered arrays of PSII–LHCII supercomplexes. These results specify that acclimation to high light stress through NPQ mechanism by expression of LHCSR3 and also observed changes in thylakoid protein profile/supercomplex formation lead to low photochemical yield and more biomass production in high light condition.

     

Effect of dieldrin on catalytic potential of field mouse Mus booduga brain acetylcholinesterase

Substrate kinetics of acetylcholinesterase (AChE) were investigated in control and dieldrin-treated Mus booduga brains. Non competitive inhibition with respect to activation by acetylcholine was indicated by decreased maximal velocity (V) without change in Michaelis-Menten constant (Km). Activation energies (delta E) were found to be increased suggesting decreased efficiency of enzyme in dieldrin-treated mouse brains. Fall in the activity potential of AChE may account for the interference of dieldrin or its metabolites with the acetylcholine (ACh)--AChE system and deserve consideration in contributing to the neurotoxicity.     

A Step Towards a General Framework for Consequential Life Cycle Assessment

At the core of consequential life cycle assessment (CLCA) is a model of the economic system of which the activity that motivates the CLCA is a part. While there are several applications of CLCA in the literature, there does not appear to exist a formal, general mathematical framework. To address this gap, this article presents a general multi‐market equilibrium framework, which could be adapted to an arbitrary level of complexity depending on the context and data availability. A general expression for total pollution (of a given type) is derived, which highlights different factors that determine the impact on emissions. It is then illustrated how microeconomic theory can help predict the direction of price and quantity changes for each commodity within the modeled system simply based on an activity's relationship to the ultimate activity or service, which motivates the CLCA. The steps involved in converting the multi‐market framework to general equilibrium are also discussed.