Maternal provisioning of an obligate symbiont in a sponge.

The transmission of microbes from mother to offspring is an ancient, advantageous, and widespread feature of metazoan life history. Despite this, little is known about the quantitative strategies taken to maintain symbioses across generations. The quantity of maternal microbes that is provided to each offspring through vertical transmission could theoretically be stochastic (no trend), consistent (an optimal range is allocated), or provisioned (a trade-off with fecundity). Examples currently come from animals that release free-living eggs (oviparous) and suggest that offspring are provided a consistent quantity of symbionts. The quantity of maternal microbes that is vertically transmitted in other major reproductive strategies has yet to be assessed. We used the brooding (viviparous) sponge Halichondria panicea to test whether offspring receive quantitatively similar numbers of maternal microbes. We observed that H. panicea has a maternal pool of the obligate symbiont Candidatus Halichondribacter symbioticus and that this maternal pool is provisioned proportionally to reproductive output and allometrically by offspring size. This pattern was not observed for the total bacterial community. Experimental perturbation by antibiotics could not reduce the abundance of Ca. H. symbioticus in larvae, while the total bacterial community could be reduced without affecting the ability of larvae to undergo metamorphosis. A trade-off between offspring size and number is, by definition, maternal provisioning and parallel differences in Ca. H. symbioticus abundance would suggest that this obligate symbiont is also provisioned.

Site specific and localized structural displacements in open structured multimetallic oxides.

The structures of solids can locally differ from the macroscopic picture obtained by structural averaging techniques. This difference significantly influences the performance of any functional material. Measurements of these local structures are challenging. Thus, the description of defects is often disregarded. However, in order to understand the functionality, such irregularities have to be investigated. Here, we present a high resolution scanning transmission electron microscopic (STEM) study revealing local structural irregularities in open structured oxides using catalytically active orthorhombic (Mo,V,Te,Nb)Ox as a complex example. Detailed analysis of annular dark field- and annular bright field-STEM images reveal site specific local structural displacements of individual framework and channel sites in the picometer range. These experimental observables can be considered as an important structural addendum for theoretical modelling and should be implemented into the existing data in order to quantify site specific potential energies and stresses. This information can further be used to describe the impact of the structure on the catalytic performance in greater detail.

Homomeric and Heteromeric Aß Species Exist in Human Brain and CSF Regardless of Alzheimer's Disease Status and Risk Genotype.

Background: A fundamental question in Alzheimer's disease (AD) is whether amyloid-ß (Aß) peptides and their deposition in the brain signify a direct pathological role or they are mere outcome of the disease pathophysiological events affecting neuronal function. It is therefore important to decipher their physiological role in the brain. So far, the overwhelming focus has been on the potential toxicity of Aß, often studied outside the crucial AD characteristics, i.e.: (i) the slow, decades-long disease progression that precedes clinical symptoms; (ii) the link to apolipoprotein-E ε4 allele as major risk factor; (iii) the selective early degeneration of cholinergic neurons. Previous studies, in vitro and cerebrospinal fluid (CSF) only, indicated one possible native function of Aß peptides is the allosteric modulation of acetylcholine homeostasis, via molecular interactions between Aß, apolipoprotein-E, and the acetylcholine-degrading enzymes, cholinesterases, resulting in the formation of acetylcholine-hydrolyzing complexes (BAßACs). Methods: Here, by combining sucrose-density gradient fractionation of post-mortem brains and in-house developed sensitive ELISA assays on the obtained fractions, we investigated the presence, levels and molecular interactions between Aß, apolipoprotein-E and cholinesterases for the first time in brain tissues. We examined three distinct brain regions of Alzheimer and non-demented subjects, plus a large number of Alzheimer CSF samples. Results: We report that both monomeric and oligomeric (homomeric and heteromeric) forms of Aß peptides are present in the brain of Alzheimer and non-demented individuals. Heteromeric Aß was found in stable complexes with apolipoprotein-E and/or cholinesterases, irrespective of APOE genotype or disease status, arguing in favor of a physiological dynamic formation and function for these complexes in the brain. The patterns and molecular sizes of the detected soluble Aß forms were closely matched between CSF and brain samples. This evinces that the detected Aß-apolipoprotein-E complexes and BAßACs in CSF most likely originate from the interstitial fluids of the brain. Conclusions: In conclusion, both light homomeric Aß oligomers and heteromeric Aß-ApoE and BAßACs are present and readily detectable in the brain, regardless of disease status and APOE4 genotype. Deeper knowledge of the physiological function of Aß is crucial for better understanding the early pathological events that decades later lead to manifestation of AD.

Influence of the photoperiod on redox regulation and stress responses in Arabidopsis thaliana L. (Heynh.) plants under long- and short-day conditions.

Arabidopsis thaliana L. (Heynh.) plants were grown in low light (150 micromol photons m(-2) s(-1) and 20 degrees C) either in short days (7.5 h photoperiod) or long days (16 h photoperiod), and then transferred into high light and low temperature (350-800 micromol photons m(-2) s(-1) at 12 degrees C). Plants grown in short days responded with a rapid increase in NADP-malate dehydrogenase (EC 1.1.1.82) activation state. However, persisting overreduction revealed a new level of regulation of the malate valve. Activity measurements and Northern-blot analyses indicated that NADP-malate dehydrogenase transcript and protein levels increased within a few hours. Using macroarrays, additional changes in gene expression were identified. Transcript levels for several enzymes of glutathione metabolism and of some photosynthetic genes increased. The cellular glutathione level increased, but its redox state remained unchanged. A different situation was observed in plants grown in long-day conditions. Neither NADP-malate dehydrogenase nor glutathione content changed, but the expression of several antioxidative enzymes increased strongly. We conclude that the endogenous systems that measure day length interact with redox regulation, and override the interpretation of the signals, i.e. they redirect redox-mediated acclimation signals to allow for more efficient light usage and redox poising in short days to systems for the prevention of oxidative damages when grown under long-day conditions.

Heterologous expression of enterocin A, a bacteriocin from Enterococcus faecium, fused to a cellulose-binding domain in Escherichia coli results in a functional protein with inhibitory activity against Listeria.

The genes for the bacteriocins enterocin A and B were isolated from Enterococcus faecium ATB 197a. Using the pET37b(+) vector, the enterocin genes were fused to an Escherichia coli specific export signal sequence, a cellulose-binding domain (CBD(cenA)) and a S-tag under the control of a T7lac promotor. The constructs were subsequently cloned into E. coli host cells. The expression of the recombinant enterocins had different effects on both the host cells and other Gram-positive bacteria. The expression of entA in Esc. coli led to the synthesis and secretion of functional active enterocin A fusion proteins, which were active against some Gram-positive indicator bacteria, but did not influence the viability of the host cells. In contrast, the expression of enterocin B fusion proteins led to a reduced viability of the host cells, indicating a misfolding of the protein or interference with the cellular metabolism of Esc. coli. Indicator strains of Gram-positive bacteria were not inhibited by purified enterocin B fusion proteins. However, recombinant enterocin B displayed inhibitory activity after the proteolytic cleavage of the fused peptides.