Nitrification in hybrid bioreactors treating simulated domestic wastewater

Aim

To provide deeper insights into nitrification process within aerobic bioreactors containing supplemental physical support media (hybrid bioreactors).

Methods and Results

Three bench‐scale hybrid bioreactors with different media size and one control bioreactor were operated to assess how biofilm integrity influences microbial community conditions and bioreactor performance. The systems were operated initially at a 5‐day hydraulic retention time (HRT), and all reactors displayed efficient nitrification and chemical oxygen demand (COD) removal (>95%). However, when HRT was reduced to 2·5 days, COD removal rates remained high, but nitrification efficiencies declined in all reactors after 19 days. To explain reduced performance, nitrifying bacterial communities (ammonia‐oxidizing bacteria, AOB; nitrite‐oxidizing bacteria, NOB) were examined in the liquid phase and also on the beads using qPCR, FISH and DGGE. Overall, the presence of the beads in a reactor promoted bacterial abundances and diversity, but as bead size was increased, biofilms with active coupled AOB–NOB activity were less apparent, resulting in incomplete nitrification.

Conclusions

Hybrid bioreactors have potential to sustain effective nitrification at low HRTs, but support media size and configuration type must be optimized to ensure coupled AOB and NOB activity in nitrification.

Significance and Impact of the Study

This study shows that AOB and NOB coupling must be accomplished to minimize nitrification failure.     

Acidophilic microbial communities associated with a natural, biodegraded hydrocarbon seepage

Characterization of microbial communities present in a surface petroleum seep in which hydrocarbons have been biodegraded for thousands of years in order to improve the understanding on natural petroleum biodegradation. DNA was extracted from a natural, surface petroleum seep and subjected to culture independent analysis (rRNA gene-based denaturing gradient gel electrophoresis and phylogenetic analysis of clone libraries). Molecular analysis suggested dominance by acidophilic bacteria, especially Alphaproteobacteria (mainly bacteria related to Acidiphilium and Acidocella). Archaea were not detected, but fungi were present. pH of the samples was around 3.5. Acidophilic microbial communities are associated with an acidic petroleum seep. Microbial community structure analysis gives information on the environmental conditions under which petroleum biodegradation occurs. This knowledge could be applied to define conditions for specific cultivation or activity measurements. The activity of acidophilic micro-organisms deserves more attention with respect to their involvement in natural petroleum degradation. This knowledge will contribute to the design of oil bioremediation strategies for polluted acidic settings.     

Two low-molecular-weight Ca2+-binding proteins isolated from squid optic lobe by phenothiazine--Sepharose affinity chromatography.

We have isolated two Ca2+-binding proteins from squid optic lobes, each of which is also able to bind phenothiazines in a Ca2+-dependent manner. These proteins have each been purified and partly characterized. One of the proteins corresponds to calmodulin, in that it has a similar amino acid content to bovine brain calmodulin, including a single residue of trimethyl-lysine, it co-migrates with bovine calmodulin both on alkaline-urea- and on sodium dodecyl sulphate (SDS)/polyacrylamide-gel electrophoresis, and will activate calmodulin-dependent phosphodiesterase. The second protein has the same subunit molecular weight as calmodulin, as determined by SDS/polyacrylamide-gel electrophoresis, Mr 17 000, but migrates more slowly than this protein on alkaline-urea-gel electrophoresis. It has an amino acid composition distinct from calmodulin, containing no trimethyl-lysine, its CNBr fragments migrate on alkaline gels in a pattern distinct from those of calmodulin and it shows little ability to activate phosphodiesterase. The u.v.-absorption spectra of the proteins indicate the absence of tryptophan and the presence of a high phenylalanine/tyrosine ratio in each. Both proteins also bind 3-4 calcium ions/mol at 0.1 mM-free Ca2+ and each binds chlorpromazine in a Ca2+-dependent manner.     

PEG activation and ligand binding for the affinity partitioning of proteins in aqueous two-phase systems

Summary PEG has been activated using epoxy-oxirane, epichlorohydrin and periodate based reactions. The coupling to activated PEG of several protein ligands of different sizes was investigated. Glutathione, trypsin inhibitor, Protein A and anti-BSA have been bound to PEG and used to increase the selectivity of protein separation in aqueous two-phase systems.     

Nested genetic bit analysis (N-GBA) for mutation detection in the p53 tumor suppressor gene.

There is a growing and significant demand for reliable, simple and sensitive methods for repeated scanning of a given gene or gene fragment for detection and characterization of mutations. Solid-phase sequencing by single base primer extension of nested GBATM primers on miniaturized DNA arrays can be used to effectively scan targeted sequences for missense, insertion and deletion mutations. This paper describes the use of N-GBA arrays designed to scan the sequence of a 33 base region of exon 8 of the p53 gene (codons 272-282) encompassing a hot spot for mutations associated with the development of cancer. Synthetic DNA templates containing various missense, insertion and deletion mutations, as well as DNA prepared from pancreatic and biliary tumor cells, were genotyped using the exon 8 arrays.     

A gene for speed: contractile properties of isolated whole EDL muscle from an alpha-actinin-3 knockout mouse

The actin-binding protein -actinin-3 is one of the two isoforms of -actinin that are found in the Z-discs of skeletal muscle. -Actinin-3 is exclusively expressed in fast glycolytic muscle fibers. Homozygosity for a common polymorphism in the ACTN3 gene results in complete deficiency of -actinin-3 in about 1 billion individuals worldwide. Recent genetic studies suggest that the absence of -actinin-3 is detrimental to sprint and power performance in elite athletes and in the general population. In contrast, -actinin-3 deficiency appears to be beneficial for endurance athletes. To determine the effect of -actinin-3 deficiency on the contractile properties of skeletal muscle, we studied isolated extensor digitorum longus (fast-twitch) muscles from a specially developed -actinin-3 knockout (KO) mouse. -Actinin-3-deficient muscles showed similar levels of damage to wild-type (WT) muscles following lengthening contractions of 20% strain, suggesting that the presence or absence of -actinin-3 does not significantly influence the mechanical stability of the sarcomere in the mouse. -Actinin-3 deficiency does not result in any change in myosin heavy chain expression. However, compared with -actinin-3-positive muscles, -actinin-3-deficient muscles displayed longer twitch half-relaxation times, better recovery from fatigue, smaller cross-sectional areas, and lower twitch-to-tetanus ratios. We conclude that -actinin-3 deficiency results in fast-twitch, glycolytic fibers developing slower-twitch, more oxidative properties. These changes in the contractile properties of fast-twitch skeletal muscle from -actinin-3-deficient individuals would be detrimental to optimal sprint and power performance, but beneficial for endurance performance. extensor digitorum longus     

Distribution and Numbers of Pygmies in Central African Forests

Pygmy populations occupy a vast territory extending west-to-east along the central African belt from the Congo Basin to Lake Victoria. However, their numbers and actual distribution is not known precisely. Here, we undertake this task by using locational data and population sizes for an unprecedented number of known Pygmy camps and settlements (n = 654) in five of the nine countries where currently distributed. With these data we develop spatial distribution models based on the favourability function, which distinguish areas with favourable environmental conditions from those less suitable for Pygmy presence. Highly favourable areas were significantly explained by presence of tropical forests, and by lower human pressure variables. For documented Pygmy settlements, we use the relationship between observed population sizes and predicted favourability values to estimate the total Pygmy population throughout Central Africa. We estimate that around 920,000 Pygmies (over 60% in DRC) is possible within favourable forest areas in Central Africa. We argue that fragmentation of the existing Pygmy populations, alongside pressure from extractive industries and sometimes conflict with conservation areas, endanger their future. There is an urgent need to inform policies that can mitigate against future external threats to these indigenous peoples’ culture and lifestyles.     

Neurotransmitter Specific,Cellular-Resolution Functional Brain Mapping Using Receptor Coated Nanoparticles: Assessment of the Possibility

Receptor coated resonant nanoparticles and quantum dots are proposed to provide a cellular-level resolution image of neural activities inside the brain. The functionalized nanoparticles and quantum dots in this approach will selectively bind to different neurotransmitters in the extra-synaptic regions of neurons. This allows us to detect neural activities in real time by monitoring the nanoparticles and quantum dots optically. Gold nanoparticles (GNPs) with two different geometries (sphere and rod) and quantum dots (QDs) with different sizes were studied along with three different neurotransmitters: dopamine, gamma-Aminobutyric acid (GABA), and glycine. The absorption/emission spectra of GNPs and QDs before and after binding of neurotransmitters and their corresponding receptors are reported. The results using QDs and nanorods with diameter 25nm and aspect rations larger than three were promising for the development of the proposed functional brain mapping approach.