Growth of Dehalococcoides strains with chlorophenols as electron acceptors

Dehalococcoides strains reductively dechlorinate a wide variety of halogenated compounds including chlorinated benzenes, biphenyls, naphthalenes, dioxins, and ethenes. Recent genome sequencing of the two Dehalococcoides strains CBDB1 and 195 revealed the presence of 32 and 18 reductive dehalogenase homologous genes, respectively, and therefore suggested an even higher dechlorinating potential than previously anticipated. Here, we demonstrate reductive dehalogenation of chlorophenol congeners by Dehalococcoides strains CBDB1 and 195. Strain CBDB1 completely converted 2,3-dichlorophenol, all six trichlorophenols, all three tetrachlorophenols, and pentachlorophenol to lower chlorinated phenols. Observed dechlorination rates in batch cultures with cell numbers of 10(7) mL(-1) amounted up to 35 microM day(-1). Chlorophenols were preferentially dechlorinated in the ortho position, but also doubly flanked and singly flanked meta- or para-chlorine substituents were removed. We used a newly designed computer-assisted direct cell counting protocol and quantitative PCR to demonstrate that strain CBDB1 uses chlorophenols as electron acceptors for respiratory growth. The growth yield of strain CBDB1 with 2,3-dichlorophenol was 7.6 x 10(13) cells per mol of Cl- released, and the growth rate was 0.41 day(-1). For strain 195, fast ortho dechlorination of 2,3-dichlorophenol, 2,3,4-trichlorophenol, and 2,3,6-trichlorophenol was detected, with only the ortho chlorine removed. Because chlorinated phenolic compounds are widely distributed as natural components in anaerobic environments, our results reveal one mode in which the Dehalococcoides species could have survived through earth history.     

A pumping lemma for random permitting context languages

Random context grammars belong to the class of context-free grammars with regulated rewriting. Their productions depend on context that may be randomly distributed in a sentential form. Context is classified as either permitting or forbidding, where permitting context enables the application of a production and forbidding context inhibits it. For random context languages of finite index a generalization of the well-known pumping lemma for context-free languages has been proven. We drop the finite index restriction and concentrate on non-erasing grammars that use permitting context only. We prove a pumping lemma for their languages that generalizes and refines the existing one, and show that these grammars are strictly weaker than the non-erasing random context grammars.     

The role of electrical current mode in calcium carbonate deposition on conductive carbon nanofiber–epoxy coating

Calcium carbonate is one of the most common scaling minerals. In this paper we have used different electrical current modes (direct current [DC], pulsed DC, and alternating current [AC]) to control the amount, morphology, and distribution of calcium carbonate deposit on electroconductive epoxy/carbon nanofiber (CNF) coating. The effect of different current modes on surface scaling was visualized using scanning electron microscopy. It has been shown that both AC and DC anodic polarization limited scale deposition on epoxy/CNF coated surfaces, although the mechanisms of scale inhibition during AC and DC polarization were different. DC polarization of the coating at +2 V resulted in the smallest scale buildup without leading to coating degradation, while DC polarization at potentials as high as +5 V caused the coating to degrade. Interestingly, application of pulsed DC with high pulse frequency (50 Hz) inhibited the degradation. The type of current applied affected also the morphology of the precipitate at the cathode. The results presented in this work show, for the first time, how different modes of electrical current applied to electroconductive composite coatings can be used to control the morphology and distribution of calcium carbonate scale, and how the organic coating degradation at high polarization potentials can be avoided.     

Antibiotic susceptibility of Bifidobacterium thermophilum and Bifidobacterium pseudolongum isolates from animal sources

The widespread use of antimicrobial substances has led to resistant populations of microorganisms in several ecosystems. In animal husbandry, the application of antibiotics has contributed to resistance development in pathogenic and commensal bacteria. These strains or their resistance genes can be spread along several ecological routes, including the food chain. Antibiotic resistance is important in terms of the safety of industrial strains, such as probiotics for food and feed. Bifidobacterium thermophilum and Bifidobacterium pseudolongum are known to comprise the major part of the bifidobacterial microbiota in the gut and feces of cattle and pigs. In this study, the antimicrobial susceptibility in bifidobacterial isolates of these species was investigated. Isolates from the beef and pork production chain were identified and typed to strain level, and the antimicrobial susceptibility level was tested to a set of antibiotics. Isolates with low susceptibility levels were screened by PCR for already described resistance genes. Strains atypically resistant to clindamycin, erythromycin, and tetracycline were determined. The resistance genes tet(O), tet(W), and erm(X) were detected in the bifidobacterial species that were examined.     

Molecular Imaging of Apoptosis: The Case of Caspase-3 Radiotracers

The molecular imaging of apoptosis remains an important method for the diagnosis and monitoring of the progression of certain diseases and the evaluation of the efficacy of anticancer apoptosis-inducing therapies. Among the multiple biomarkers involved in apoptosis, activated caspase-3 is an attractive target, as it is the most abundant of the executioner caspases. Nuclear imaging is a good candidate, as it combines a high depth of tissue penetration and high sensitivity, features necessary to detect small changes in levels of apoptosis. However, designing a caspase-3 radiotracer comes with challenges, such as selectivity, cell permeability and transient caspase-3 activation. In this review, we discuss the different caspase-3 radiotracers for the imaging of apoptosis together with the challenges of the translation of various apoptosis-imaging strategies in clinical trials.     

Adaptive color segmentation-a comparison of neural and statisticalmethods

With the availability of more powerful computers it is nowadays possible to perform pixel based operations on real camera images even in the full color space. New adaptive classification tools like neural networks make it possible to develop special-purpose object detectors that can segment arbitrary objects in real images with a complex distribution in the feature space after training with one or several previously labeled image(s). The paper focuses on a detailed comparison of a neural approach based on local linear maps (LLMs) to a classifier based on normal distributions. The proposed adaptive segmentation method uses local color information to estimate the membership probability in the object, respectively, background class. The method is applied to the recognition and localization of human hands in color camera images of complex laboratory scenes.     

Symmetry and asymmetry of solutions in discrete variable structural optimization

In this paper symmetry and asymmetry of optimal solutions in symmetric structural optimization problems is investigated, based on the choice of variables. A group theory approach is used to define the symmetry of the structural problems in a general way. This approach allows the set of symmetric structures to be described and related to the entire search space of the problem. A relationship between the design variables and the likelihood of finding symmetric or asymmetric solutions to problems is established. It is shown that an optimal symmetric solution (if any) does not necessarily exist in the case of discrete variable problems, regardless of the size of the discrete, countable set from which variables can be chosen. Finally a number of examples illustrate these principles on simple truss structures with discrete topology and sizing variables.