Effect of substrate type on bacterial community composition in biofilms from the Great Barrier Reef

Natural and anthropogenic impacts such as terrestrial runoff, influence the water quality along the coast of the Great Barrier Reef (GBR) and may in turn affect coral reef communities. Associated bacterial biofilms respond rapidly to environmental conditions and are potential bioindicators for changes in water quality. As a prerequisite to study the effects of water quality on biofilm communities, appropriate biofilm substrates for deployment in the field must be developed and evaluated. This study investigates the effect of different settlement substrates (i.e. glass slides, ceramic tiles, coral skeletons and reef sediments) on bacterial biofilm communities grown in situ for 48 days at two locations in the Whitsunday Island Group (Central GBR) during two sampling times. Bacterial communities associated with the biofilms were analysed using terminal restriction fragment length polymorphism (T-RFLP) and clone library analyses of 16S rRNA genes. Findings revealed that substrate type had little influence on bacterial community composition. Of particular relevance, glass slides and coral skeletons exhibited very similar communities during both sampling times, suggesting the suitability of standardized glass slides for long-term biofilm indicator studies in tropical coral reef ecosystems.     

Essential role of neutrophil mobilization in concanavalin A-induced hepatitis is based on classic IL-6 signaling but not on IL-6 trans-signaling

Neutrophil depleted mice are protected from concanavalin A-mediated hepatitis, showing that neutrophils are critical for cellular liver damage. Interleukin-6 has pro- and anti-inflammatory properties and mediates neutrophil recruitment in diseases such as rheumatoid arthritis. In classic signaling, interleukin-6 binds to the membrane-bound interleukin-6-receptor and initiates signaling via gp130. In interleukin-6 trans-signaling, the agonistic soluble interleukin-6-receptor can form a soluble interleukin-6/interleukin-6-receptor complex and stimulate cells which only express gp130 but no interleukin-6-receptor. Interleukin-6 trans-signaling was shown to be important for liver regeneration and development of liver adenomas. Here, we show that blocking classic interleukin-6 signaling but not interleukin-6 trans-signaling reduced concanavalin A-induced liver damage in mice, with reduced liver STAT3 phosphorylation and liver neutrophil accumulation. However, the level of neutrophil-attracting chemokine KC is only reduced by inhibition of interleukin-6 trans-signaling. Analysis of circulating neutrophils after concanavalin A challenge revealed that classic interleukin-6 signaling is required for the mobilization of blood neutrophils. Reduced neutrophil infiltration was accompanied by increased levels of hepatoprotective monocyte chemoattractant protein-1 and reduced level of hepatodestructive interleukin-4. Abrogated classic interleukin-6 signaling in concanavalin A-mediated hepatitis exhibited liver-protective effects indicating that interleukin-6 classic but not interleukin-6 trans-signaling is responsible for liver damage. Classic interleukin-6 signaling is required to mount an efficient neutrophilia during concanavalin A-induced immune response, which might have clinical implications in the regard that blocking global interleukin-6 signaling pathways is a treatment option in different chronic inflammatory diseases.     

Synthesis of new functionalized aziridine-2- and azetidine-3-carboxylic acid derivatives of potential interest for biological and foldameric applications

A short synthesis of alkyl 2-(bromomethyl)aziridine-2-carboxylates and alkyl 3-bromoazetidine-3-carboxylates was developed involving amination, bromination, and base-induced cyclization of alkyl 2-(bromomethyl)acrylates. The aziridines are the kinetically favored cyclization products and could be transformed into 3-bromoazetidine-3-carboxylic acid derivatives via thermal isomerization. The new small-membered azaheterocyclic α- and β-amino acid derivatives contain a bromo-substituted carbon center as a useful moiety for functionalization. Transformation of these functionalized azaheterocycles via nucleophilic substitution with carbon, sulfur, oxygen, and nitrogen nucleophiles and via elaboration of the amino and carboxyl group provided a broad range of new conformationally constrained aziridine-2- and azetidine-3-carboxylic acid derivatives, which are of interest from a biological point-of-view as well as for applications in the field of foldamers.     

Enzymes involved in the anaerobic degradation of meta-substituted halobenzoates

Organohalides are environmentally relevant compounds that can be degraded by aerobic and anaerobic microorganisms. The denitrifying Thauera chlorobenzoica is capable of degrading halobenzoates as sole carbon and energy source under anaerobic conditions. LC‐MS/MS‐based coenzyme A (CoA) thioester analysis revealed that 3‐chloro‐ or 3‐bromobenzoate were preferentially metabolized via non‐halogenated CoA‐ester intermediates of the benzoyl‐CoA degradation pathway. In contrast, 3‐fluorobenzoate, which does not support growth, was converted to dearomatized fluorinated CoA ester dead‐end products. Extracts from cells grown on 3‐chloro‐/3‐bromobenzoate catalysed the Ti(III)‐citrate‐ and ATP‐dependent reductive dehalogenation of 3‐chloro/3‐bromobenzoyl‐CoA to benzoyl‐CoA, whereas 3‐fluorobenzoyl‐CoA was converted to a fluorinated cyclic dienoyl‐CoA compound. The reductive dehalogenation reactions were identified as previously unknown activities of ATP‐dependent class I benzoyl‐CoA reductases (BCR) present in all facultatively anaerobic, aromatic compound degrading bacteria. A two‐step dearomatization/H‐halide elimination mechanism is proposed. A halobenzoate‐specific carboxylic acid CoA ligase was characterized in T. chlorobenzoica; however, no such enzyme is present in Thauera aromatica, which cannot grow on halobenzoates. In conclusion, it appears that the presence of a halobenzoate‐specific carboxylic acid CoA ligase rather than a specific reductive dehalogenase governs whether an aromatic compound degrading anaerobe is capable of metabolizing halobenzoates.     

Treatment of volatile organic contaminants in a vertical flow filter: Relevance of different removal processes

Vertical flow filters and vertical flow constructed wetlands are established wastewater treatment systems and have also been proposed for the treatment of contaminated groundwater. This study investigates the removal processes of volatile organic compounds in a pilot-scale vertical flow filter. The filter is intermittently irrigated with contaminated groundwater containing benzene, MTBE and ammonium as the main contaminants. The system is characterized by unsaturated conditions and high contaminant removal efficiency. The aim of the present study is to evaluate the contribution of biodegradation and volatilization to the overall removal of benzene and MTBE. Tracer tests and flow rate measurements showed a highly transient flow and heterogeneous transport regime. Radon-222, naturally occurring in the treated groundwater, was used as a gas tracer and indicated a high volatilization potential. Radon-222 behavior was reproduced by numerical simulations and extrapolated for benzene and MTBE, and indicated these compounds also have a high volatilization potential. In contrast, passive sampler measurements on top of the filter detected only low benzene and MTBE concentrations. Biodegradation potential was evaluated by the analysis of catabolic genes involved in organic compound degradation and a quantitative estimation of biodegradation was derived from stable isotope fractionation analysis. Results suggest that despite the high volatilization potential, biodegradation is the predominant mass removal process in the filter system, which indicates that the volatilized fraction of the contaminants is still subject to subsequent biodegradation. In particular, the upper filter layer located between the injection tubes and the surface of the system might also contribute to biodegradation, and might play a crucial role in avoiding the emission of volatilized contaminants into the atmosphere.     

Role for cER and Mmr1p in anchorage of mitochondria at sites of polarized surface growth in budding yeast

Mitochondria accumulate at neuronal and immunological synapses and yeast bud tips and associate with the ER during phospholipid biosynthesis, calcium homeostasis, and mitochondrial fission. Here we show that mitochondria are associated with cortical ER (cER) sheets underlying the plasma membrane in the bud tip and confirm that a deletion in YPT11, which inhibits cER accumulation in the bud tip, also inhibits bud tip anchorage of mitochondria. Time-lapse imaging reveals that mitochondria are anchored at specific sites in the bud tip. Mmr1p, a member of the DSL1 family of tethering proteins, localizes to punctate structures on opposing surfaces of mitochondria and cER sheets underlying the bud tip and is recovered with isolated mitochondria and ER. Deletion of MMR1 impairs bud tip anchorage of mitochondria without affecting mitochondrial velocity or cER distribution. Deletion of the phosphatase PTC1 results in increased Mmr1p phosphorylation, mislocalization of Mmr1p, defects in association of Mmr1p with mitochondria and ER, and defects in bud tip anchorage of mitochondria. These findings indicate that Mmr1p contributes to mitochondrial inheritance as a mediator of anchorage of mitochondria to cER sheets in the yeast bud tip and that Ptc1p regulates Mmr1p phosphorylation, localization, and function.     

Ubp15p, a ubiquitin hydrolase associated with the peroxisomal export machinery

Peroxisomal matrix protein import is facilitated by cycling receptors shuttling between the cytosol and the peroxisomal membrane. One crucial step in this cycle is the ATP-dependent release of the receptors from the peroxisomal membrane. This step is facilitated by the peroxisomal AAA (ATPases associated with various cellular activities) proteins Pex1p and Pex6p with ubiquitination of the receptor being the main signal for its export. Here we report that the AAA complex contains dislocase as well as deubiquitinating activity. Ubp15p, a ubiquitin hydrolase, was identified as a novel constituent of the complex. Ubp15p partially localizes to peroxisomes and is capable of cleaving off ubiquitin moieties from the type I peroxisomal targeting sequence (PTS1) receptor Pex5p. Furthermore, Ubp15p-deficient cells are characterized by a stress-related PTS1 import defect. The results merge into a picture in which removal of ubiquitin from the PTS1 receptor Pex5p is a specific event and might represent a vital step in receptor recycling.     

Ion channels in autoimmune neurodegeneration

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system characterized by widespread inflammation, focal demyelination and a variable degree of axonal and neuronal loss. Ionic conductances regulate T cell activation as well as neuronal function and thus have been found to play a crucial role in MS pathogenesis. Since present therapeutical approaches are only partially effective so far, ion channel modulation as a future strategy was brought into focus. Here, we review the status quo concerning recent findings from ion channel research in MS and its animal model, experimental autoimmune encephalomyelitis.     

Mice with disrupted type I protein kinase A anchoring in T cells resist retrovirus-induced immunodeficiency

Type I protein kinase A (PKA) is targeted to the TCR-proximal signaling machinery by the A-kinase anchoring protein ezrin and negatively regulates T cell immune function through activation of the C-terminal Src kinase. RI anchoring disruptor (RIAD) is a high-affinity competitor peptide that specifically displaces type I PKA from A-kinase anchoring proteins. In this study, we disrupted type I PKA anchoring in peripheral T cells by expressing a soluble ezrin fragment with RIAD inserted in place of the endogenous A-kinase binding domain under the lck distal promoter in mice. Peripheral T cells from mice expressing the RIAD fusion protein (RIAD-transgenic mice) displayed augmented basal and TCR-activated signaling, enhanced T cell responsiveness assessed as IL-2 secretion, and reduced sensitivity to PGE(2)- and cAMP-mediated inhibition of T cell function. Hyperactivation of the cAMP-type I PKA pathway is involved in the T cell dysfunction of HIV infection, as well as murine AIDS, a disease model induced by infection of C57BL/6 mice with LP-BM5, a mixture of attenuated murine leukemia viruses. LP-BM5-infected RIAD-transgenic mice resist progression of murine AIDS and have improved viral control. This underscores the cAMP-type I PKA pathway in T cells as a putative target for therapeutic intervention in immunodeficiency diseases.