Weak activity of haloalkane dehalogenase LinB with 1,2,3-trichloropropane revealed by X-Ray crystallography and microcalorimetry

1,2,3-Trichloropropane (TCP) is a highly toxic and recalcitrant compound. Haloalkane dehalogenases are bacterial enzymes that catalyze the cleavage of a carbon-halogen bond in a wide range of organic halogenated compounds. Haloalkane dehalogenase LinB from Sphingobium japonicum UT26 has, for a long time, been considered inactive with TCP, since the reaction cannot be easily detected by conventional analytical methods. Here we demonstrate detection of the weak activity (k(cat) = 0.005 s(-1)) of LinB with TCP using X-ray crystallography and microcalorimetry. This observation makes LinB a useful starting material for the development of a new biocatalyst toward TCP by protein engineering. Microcalorimetry is proposed to be a universal method for the detection of weak enzymatic activities. Detection of these activities is becoming increasingly important for engineering novel biocatalysts using the scaffolds of proteins with promiscuous activities.     

Studying recombination in heterozygous tandem duplications in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Our previous data showed that the principal pathway of the formation of selected recombinants in Escherichia coli strains carrying heterozygous tandem duplications is unequal crossing over between sister chromosomes. Data presented in this work showed that when DNA homology is not disturbed (due to transposon insertion), intragenic recombinants can occur directly in the region of recombination through intrachromomal exchange as well.     

Calceocrinids and a new Ramacrinid (Crinoidea,inaduanta)from the Lower Devonian of Bohemia and Armorican Massif

The calceocrinid crinoids Eohalysiocrinus latus and E. convexus, formerly considered as endemic in theBarrandian and restricted to organodetrital limestones, have been discovered in a shaly layer at the top of the Beg an Arreun Formation (upper Emsian, upper Zlichovian) in the western part of the Armorican massif. A new species, Ramacrinus brevis, found simultaneously in Bohemia and Brittany, is described. It is suggested that the incursions of hercynian faunal elements into the rhenish associations of the Brest area may be in relation with paleogeographical changes allowing communication between the Barrandian and the western part of Europe and migration of both pelagic and benthic organisms.     

Dispersions in hydrocarbon fermentation. A retrospective study

A nondimensionalized plot, obtained by normalizing the drop-size distribution in the hydrocarbon phase using the Sauter mean diameter, shows a tendency towards self-preservation of the distribution. Changes of distribution in time during the course of fermentation, initial dispersed phase fraction, speed of rotation, and reactor size were taken into account. Using this self-preserving property, an empirical (single parameter) equation has been proposed for drop-size distribution. Data, available from the literature, are presented for non-biological and biological systems (gas-oil, n-hexadecane, and n-hexadecane dissolved in dewaxed gas oil as dispersed phases). The parameter, Sauter mean diameter, has been correlated with the operating conditions, and a critical review presented. Cell density was found to have significant effect on Sauter mean diameter. This effect has also been empirically explained. The possibilities of using generalized distribution in predicting the performance of fermenters is outlined.     

Polygynous great reed warblers Acrocephalus arundinaceus suffer more cuckoo Cuculus canorus parasitism than monogamous pairs

There is increasing evidence that hosts within a population may not be parasitized by common cuckoos Cuculus canorus with equal probability. Such non‐randomness has been documented, for example, for host nest sites and host quality. In this study we demonstrate association between successful cuckoo parasitism and host social mating system. We found that nests of socially polygynous great reed warblers Acrocephalus arundinaceus were more often successfully parasitized than the nests of their monogamous counterparts. We hypothesize that lack of parental assistance provided by polygynous males to their mates during egg laying period and higher nest activity in their territories could contribute to this discrepancy. These data imply that social mating system should be taken into account in future studies of brood parasitism.     

Dissecting regulatory networks of filopodia formation in a Drosophila growth cone model

F-actin networks are important structural determinants of cell shape and morphogenesis. They are regulated through a number of actin-binding proteins. The function of many of these proteins is well understood, but very little is known about how they cooperate and integrate their activities in cellular contexts. Here, we have focussed on the cellular roles of actin regulators in controlling filopodial dynamics. Filopodia are needle-shaped, actin-driven cell protrusions with characteristic features that are well conserved amongst vertebrates and invertebrates. However, existing models of filopodia formation are still incomplete and controversial, pieced together from a wide range of different organisms and cell types. Therefore, we used embryonic Drosophila primary neurons as one consistent cellular model to study filopodia regulation. Our data for loss-of-function of capping proteins, enabled, different Arp2/3 complex components, the formin DAAM and profilin reveal characteristic changes in filopodia number and length, providing a promising starting point to study their functional relationships in the cellular context. Furthermore, the results are consistent with effects reported for the respective vertebrate homologues, demonstrating the conserved nature of our Drosophila model system. Using combinatorial genetics, we demonstrate that different classes of nucleators cooperate in filopodia formation. In the absence of Arp2/3 or DAAM filopodia numbers are reduced, in their combined absence filopodia are eliminated, and in genetic assays they display strong functional interactions with regard to filopodia formation. The two nucleators also genetically interact with enabled, but not with profilin. In contrast, enabled shows strong genetic interaction with profilin, although loss of profilin alone does not affect filopodia numbers. Our genetic data support a model in which Arp2/3 and DAAM cooperate in a common mechanism of filopodia formation that essentially depends on enabled, and is regulated through profilin activity at different steps.