Experimental and field evidence of Antarctic foraminiferal tolerance to anoxia and hydrogen sulfide

The common occurrence of foraminifera in strata deposited under anoxic environmental conditions throughout the geologic record raises the question of whether foraminifera actually survive anoxic or reducing conditions. To test this, benthic foraminifera from McMurdo Sound, Antarctica were exposed to anoxic or reducing conditions for 30 days. These Antarctic forms are known to be exposed to anoxic events in their natural environment. An adenosine triphosphate (ATP) assay was used to determine foraminiferal survival, and their ultrastructure was examined using transmission electron microscopy (TEM) to evaluate any possible effect that might have resulted from exposure to anoxic or reducing conditions. The experimental treatments did not have any statistically significant effects upon the foraminifers with regards to survival or average ATP content per individual including the four most common living species. Some ultrastructural evidence for encystment (fibrillar membrane-bound bodies in the cytoplasm of many specimens) was observed. Field data include the observation thatGlobocassidulina cf.G. biora resides in sediments to depths of 7 cm, as evidenced by ultrastructural investigations. A specimen ofGlobocassidulina cf.G. biora collected from sediments containing anoxic pore waters showed numerous bacteria within the confines of the organic lining. The occurrence of cytoplasmic inclusions similar in appearance to car☐ysomes within these bacteria suggest possible affinities to the chemolithotrophicThiobacillus. Bacteria of this type were not observed in specimens collected from oxygenated pore waters. These field and laboratory findings suggest that certain foraminifera may be facultative anaerobes able to withstand reducing conditions.     

Resveratrol causes arrest in the S-phase prior to Fas-independent apoptosis in CEM-C7H2 acute leukemia cells

Resveratrol (3,5,4'-trihydroxy-trans-stilbene), in the concentration range of 20 microM and above, induced arrest in the S-phase and apoptosis in the T cell-derived T-ALL lymphocytic leukemia cell line CEM-C7H2 which is deficient in functional p53 and p16. Expression of transgenic p16/INK4A, which causes arrest in G0/G1, markedly reduced the percentage of apoptotic cells. Antagonist antibodies to Fas or FasL, or constitutive expression of crmA did not diminish the extent of resveratrol-induced apoptosis. Furthermore, a caspase-8-negative, Fas-resistant Jurkat cell line was sensitive to resveratrol-induced apoptosis which could be strongly inhibited in the Jurkat as well as in the CEM cell line by z-VAD-fmk and z-IETD-fmk. The almost complete inhibition by z-IETD-fmk and the lack of inhibition by crmA suggested caspase-6 to be the essential initiator caspase. Western blots revealed the massive conversion of procaspase-6 to its active form, while caspase-3 and caspase-2 were proteolytically activated to a much lesser extent.     

Soil-air exchange of nitric oxide: An overview of processes, environmental factors, and modeling studies

Terrestrial ecosystems with their main elements soil and plants may act, in principle, as both source and sink for atmospheric nitric oxide (NO). The net exchange between ecosystems and the atmosphere, however, is globally dominated by biogenic emissions of NO from soils. Consequently the soil–air exchange of NO is the focus of the following overview. Particular emphasis is placed on the major processes that are responsible for NO production in soils (nitrification, denitrification) and their regulation by environmental factors (nitrogen availability, soil water content, soil temperature, ambient NO concentration). It is shown that interactions of these factors are a major reason for the broad range that exists in published data on NO fluxes. This variability makes it difficult to predict the magnitude of NO fluxes on relevant spatial and temporal scales. To overcome the problem various generalization procedures for scaling up in space and time have been developed, and the potential and limitations of the different approaches is discussed.     

Baeyer-Villiger oxidations of representative heterocyclic ketones by whole cells of engineered Escherichia coli expressing cyclohexanone monooxygenase

Whole cells of an Escherichia coli strain overexpressing Acinetobacter sp. NCIB 9871 cyclohexanone monooxygenase (CHMO; E.C. 1.14.13.22) have been used for the Baeyer-Villiger oxidation of representative heterocyclic six-membered ketones to probe the potential impact of nitrogen, sulfur and oxygen on the chemoselectivity of these reactions. The fact that all of these heterocyclic systems were accepted as substrates by the enzyme and gave normal Baeyer-Villiger products broadens the synthetic utility of the engineered E. coli strain and emphasizes the chemoselectivity achievable with enzymatic oxidation catalysts.     

A cyclophilin-like peptidyl-prolyl cis/trans isomerase from Legionella pneumophila – characterization, molecular cloning and overexpression

Legionella pneumophila is the causative agent of a severe form of pneumonia in humans (Legionnaires’disease). A major virulence factor, the Mip protein (FK506-binding protein, FKBP25mem), belongs to the enzyme family of peptidyl-prolyl cis/trans isomerases (PPIases). Here we show that L. pneumophila Philadelphia I possesses an additional cytoplasmic PPiase at a level of enzyme activity comparable to that of FKBP25mem. The N-terminal amino acid sequence of the purified protein was obtained by Edman degradation and showed that the protein is a member of the cyclophilin family of PPIases. The Icy gene (Legionella cycophn) was cloned and sequenced. It encodes a putative 164-amino-acid protein with a molecular mass of 17 968 Da called L. pneumophila cyclophilin 18 (L. p. Cyp18). Amino acid sequence comparison displays considerable similarity to the cytoplasmic and the periplasmic cyclophilins of Escherichia coll with 60.5% and 51.5% identity, respectively. The substrate specificity and inhibition by cyclosporin A revealed a pattern that is typically found for other bacterial cyclophilins. An L. pneumophila Cyp18 derivative with a 19-amino-acid polypeptide extension including a 6-histi-dine tag and an enterokinase cleavage site exhibits     

Metabolic Consequences of Altered PhosphoenolpyruvateCarboxykinase Activity in Corynebacterium glutamicum Reveal Anaplerotic Regulation Mechanisms in Vivo

Corynebacterium glutamicum possesses high in vivo activity of the gluconeogenic phosphoenolpyruvate carboxykinase (PEPCk) during growth on glucose, resulting together with anaplerotic carboxylation reactions in a PEP/pyruvate/oxaloacetate substrate cycle. The present study investigated the changes in intracellular fluxes and metabolite concentrations that are caused by altered PEPCk activity in L-lysine-producing C. glutamicum MH20-22B, applying a recently developed (13)C labeling-based strategy for anaplerotic flux resolution and quantification. Abolition of PEPCk activity by deletion of the respective pck gene resulted in increased intracellular concentrations of oxaloacetate L-aspartate, alpha-ketoglutarate, pyruvate, and L-lysine and in a 60% enhanced flux toward L-lysine biosynthesis, whereas increasing the PEPCk activity by pck overexpression had opposite effects. The results of the combined measurements of enzyme activities, in vivo fluxes, and metabolite concentrations were exploited to elucidate the in vivo regulation of anaplerotic reactions in C. glutamicum, and implications for the metabolic engineering of amino-acid-producing strains are discussed.     

Direct Profiling of Environmental Microbial Populations by Thermal Dissociation Analysis of Native rRNAs Hybridized to Oligonucleotide Microarrays

Oligonucleotide microarrays were used to profile directly extracted rRNA from environmental microbial populations without PCR amplification. In our initial inspection of two distinct estuarine study sites, the hybridization patterns were reproducible and varied between estuarine sediments of differing salinities. The determination of a thermal dissociation curve (i.e., melting profile) for each probe-target duplex provided information on hybridization specificity, which is essential for confirming adequate discrimination between target and nontarget sequences.     

Obesity and impairment in psychosocial functioning in women: the mediating role of eating disorder features

Objective: The objective was to test the hypothesis that, in women, the association between obesity and impairment in psychosocial functioning is mediated by levels of weight and shape concerns and/or binge‐eating frequency. Research Methods and Procedures: Self‐report measures of eating disorder psychopathology, mental health functioning, subjective quality of life in the psychological and social domains, and days “out‐of‐role” associated with any (physical or mental) health problem, were completed by a community sample of women classified as obese (BMI ≥30 kg/m², n = 639) or non‐obese (BMI <30 kg/m², n = 4253). For each of the dependent measures, regression models were used to test the hypothesis of mediation by comparing the strength of the relationship between independent and dependent variables with and without inclusion of the putative mediator in the regression model. Results: On each measure, the conditions for perfect mediation were satisfied when weight or shape concerns acted as the putative mediator, indicating that there was no association between obesity and functional impairment after controlling for weight or shape concerns. In contrast, associations between obesity and impairment in psychosocial functioning remained highly significant when binge‐eating frequency was the putative mediator. Discussion: The findings suggest that in women, weight and shape concerns are an important mediator of the relationship between obesity and impairment in psychosocial functioning, whereas binge eating may not be of primary importance. A greater focus on body acceptance in obesity treatment may be indicated.     

A deletion at the mouse Xist gene exposes trans-effects that alter the heterochromatin of the inactive X chromosome and the replication time and DNA stability of both X chromosomes

The inactive X chromosome of female mammals displays several properties of heterochromatin including late replication, histone H4 hypoacetylation, histone H3 hypomethylation at lysine-4, and methylated CpG islands. We show that cre-Lox-mediated excision of 21 kb from both Xist alleles in female mouse fibroblasts led to the appearance of two histone modifications throughout the inactive X chromosome usually associated with euchromatin: histone H4 acetylation and histone H3 lysine-4 methylation. Despite these euchromatic properties, the inactive X chromosome was replicated even later in S phase than in wild-type female cells. Homozygosity for the deletion also caused regions of the active X chromosome that are associated with very high concentrations of LINE-1 elements to be replicated very late in S phase. Extreme late replication is a property of fragile sites and the 21-kb deletions destabilized the DNA of both X chromosomes, leading to deletions and translocations. This was accompanied by the phosphorylation of p53 at serine-15, an event that occurs in response to DNA damage, and the accumulation of gamma-H2AX, a histone involved in DNA repair, on the X chromosome. The Xist locus therefore maintains the DNA stability of both X chromosomes.