Molecular evolution of the mammalian ribosomal protein gene, RPS14

Ribosomal protein S14 genes (RPS14) in eukaryotic species from protozoa to primates exhibit dramatically different intron-exon structures yet share homologous polypeptide-coding sequences. To recognize common features of RPS14 gene architectures in closely related mammalian species and to evaluate similarities in their noncoding DNA sequences, we isolated the intron-containing S14 locus from Chinese hamster ovary (CHO) cell DNA by using a PCR strategy and compared it with human RPS14. We found that rodent and primate S14 genes are composed of identical protein-coding exons interrupted by introns at four conserved DNA sites. However, the structures of corresponding CHO and human RPS14 introns differ significantly. Nonetheless, individual intron splice donor, splice acceptor, and upstream flanking motifs have been conserved within mammalian S14 homologues as well as within RPS14 gene fragments PCR amplified from other vertebrate genera (birds and bony fish). Our data indicate that noncoding, intronic DNA sequences within highly conserved, single-copy ribosomal protein genes are useful molecular landmarks for phylogenetic analysis of closely related vertebrate species.      

Enhancing denitrification using a carbon supplement generated from the wet oxidation of waste activated sludge

This study compared the effect of four pure carbon supplements on biological denitrification to a liquor derived as a by-product from the wet oxidation (WO) of waste activated sludge. Sequencing batch reactors were used to acclimate sludge biomass, which was used in batch assays. Acetate, WO liquor and ethanol-supplementation generated the fastest denitrification rates. Acetate and WO liquor were efficiently utilised by all acclimated biomass types, while poor rates were achieved with methanol and formate. When comparing an inoculum from an ethanol-supplemented and non-supplemented wastewater treatment plant (WWTP), the ethanol-acclimated sludge obtained superior denitrification rates when supplemented with ethanol. Similarly high nitrate removal rates were achieved with both sludge types with acetate and WO liquor supplementation, indicating that WO liquors could achieve excellent rates of nitrate removal. The performance of the WO liquor was attributed to the variety of organic carbon substrates (particularly acetic acid) present within the liquor.     

Nicotine self-medication of cognitive-attentional processing

This article selectively reviews research concerning nicotine's effects on cognition, including the neurobiological mechanism for these effects, task and experimental features that may be important for elucidating these effects, and why these effects may have amplified motivational significance among smokers with cognitive deficit. Nicotine has effects on various cognitive processes, though most studies in humans have focused on the amelioration of cognitive deficits experienced during drug withdrawal. The direct cognitive-enhancing effect of nicotine remains a controversial topic. The relationship between attentional and non-attentional cognitive effects of nicotine is discussed in the context of cognitive self-medication. Further research should include theory-driven examination of cognitive effects of nicotine, and develop targeted smoking cessation programs based on an improved understanding of the role of cognitive self-medication in high-risk individuals.     

Insights into the evolutionary origins of clostridial neurotoxins from analysis of the <Emphasis Type="Italic">Clostridium botulinum</Emphasis> strain A neurotoxin gene cluster

Background  

Clostridial neurotoxins (CNTs) are the most deadly toxins known and causal agents of botulism and tetanus neuroparalytic diseases. Despite considerable progress in understanding CNT structure and function, the evolutionary origins of CNTs remain a mystery as they are unique to Clostridium and possess a sequence and structural architecture distinct from other protein families. Uncovering the origins of CNTs would be a significant contribution to our understanding of how pathogens evolve and generate novel toxin families.     

Studies on the actin-binding protein HS1 in platelets

Background  

The platelet cytoskeleton mediates the dramatic change in platelet morphology that takes place upon activation and stabilizes thrombus formation. The Arp2/3 complex plays a vital role in these processes, providing the protrusive force for lamellipodia formation. The Arp2/3 complex is highly regulated by a number of actin-binding proteins including the haematopoietic-specific protein HS1 and its homologue cortactin. The present study investigates the role of HS1 in platelets using HS1^-/- mice.     

The economics of acetone-butanol fermentation: theoretical and market considerations

Acetone-butanol (AB) fermentation was once run commercially in many countries until these chemicals could be made more cheaply from fossil oil sources. Research into the revitalisation of the process has shown that the process could once again be run economically in niche markets if run in a relatively small industrial scale processing low-grade agricultural products. The following analysis is intended to help identify suitable niche markets.     

The cause of "acid-crash" and "acidogenic fermentations" during the batch acetone-butanol-ethanol (ABE-) fermentation process

Experiments were performed to determine the cause of "acid crash", a phenomenon which occasionally occurs in pH-uncontrolled batch fermentations resulting in premature cessation of ABE (acetone butanol) production. The results indicate that "acid crash" occurs when the concentration of undissociated acids in the broth exceeds 57 - 60 mmol/l. Prevention can be achieved by introducing some limited pH control to minimize the concentration of undissociated acids or by slowing the metabolic rate, and thus the rate of acid production, by, for example, lowering the fermentation temperature. "Acidogenic fermentations", which occur when batch fermentations are performed at pH values close to neutrality, are due to rapid production of acids followed by inhibition of solventogenesis when the total acid concentration reaches 240 - 250 mmol/l. Solventogenesis can be achieved at these pH values by lowering the glucose uptake rate / acid production rate by use of e.g. elevated glucose or lowered yeast extract concentrations in the growth medium.     

The acetone-butanol fermentation in pilot plant and pre-industrial scale

A summary of literature data concerning pilot or preindustrial scale trials of the acetone-butanol fermentation throughout its history is given. The recent pilot plant trials in Austria are also described for the first time. Some aspects of the current development of the acetone-butanol fermentation in general, especially from a technical point of view are also discussed.     

Aquatic metagenomes implicate Thaumarchaeota in global cobalamin production

Cobalamin (vitamin B₁₂) is a complex metabolite and essential cofactor required by many branches of life, including most eukaryotic phytoplankton. Algae and other cobalamin auxotrophs rely on environmental cobalamin supplied from a relatively small set of cobalamin-producing prokaryotic taxa. Although several Bacteria have been implicated in cobalamin biosynthesis and associated with algal symbiosis, the involvement of Archaea in cobalamin production is poorly understood, especially with respect to the Thaumarchaeota. Based on the detection of cobalamin synthesis genes in available thaumarchaeotal genomes, we hypothesized that Thaumarchaeota, which are ubiquitous and abundant in aquatic environments, have an important role in cobalamin biosynthesis within global aquatic ecosystems. To test this hypothesis, we examined cobalamin synthesis genes across sequenced thaumarchaeotal genomes and 430 metagenomes from a diverse range of marine, freshwater and hypersaline environments. Our analysis demonstrates that all available thaumarchaeotal genomes possess cobalamin synthesis genes, predominantly from the anaerobic pathway, suggesting widespread genetic capacity for cobalamin synthesis. Furthermore, although bacterial cobalamin genes dominated most surface marine metagenomes, thaumarchaeotal cobalamin genes dominated metagenomes from polar marine environments, increased with depth in marine water columns, and displayed seasonality, with increased winter abundance observed in time-series datasets (e.g., L4 surface water in the English Channel). Our results also suggest niche partitioning between thaumarchaeotal and cyanobacterial ribosomal and cobalamin synthesis genes across all metagenomic datasets analyzed. These results provide strong evidence for specific biogeographical distributions of thaumarchaeotal cobalamin genes, expanding our understanding of the global biogeochemical roles played by Thaumarchaeota in aquatic environments.     

Long-Term Continuous Cultivation of Clostridium beijerinckii in a Two-Stage Chemostat with On-Line Solvent Removal

A two-stage continuous cultivation experiment with Clostridium beijerinckii NRRL B592 is described. This strain maintained its ability to produce neutral solvents (acetone, n-butanol, and ethanol) at an overall dilution rate of 0.13 h(sup-1) and achieved an average overall solvent concentration of 9.27 g/liter and an overall solvent productivity of 1.24 g/liter/h for more than 100 overall retention times. The experiment was performed without pH control on a semisynthetic medium containing yeast extract, and product inhibition was the limiting factor. Solid carrier material was present in both stages, and the solvent productivity in both stages was similar. A membrane evaporation module integrated into the recirculation loop of a second-stage bioreactor after 2,166 h increased solvent productivity and improved the yield of solvents by about 40%. The membrane reduced the concentration of solvents, which would otherwise inhibit the fermentation. Additionally, the integrated membrane evaporation dampened metabolic oscillations, which are characteristic of continuous cultivation of clostridia. It was also demonstrated that a moderate concentration buildup (approximately 30% of bioreactor inflow) caused by water flux through the membrane caused no detrimental effects to the bacterial cells. However, much higher water fluxes through the membrane, associated with a much more dramatic increase in the concentration of salts in the medium, did appear to favor cell degeneration.