Descriptive and experimental evidence for timing-mediated polygyny risk in a pied flycatcher Ficedula hypoleuca population

In polygynous species with biparental care, mates are often acquired in succession. Most research has focussed on the cost of polygyny in secondary females, but primary females may also suffer from reduced paternal care. The likelihood of sharing a male may be higher for early laying females, which could counteract the fitness benefits of breeding early. In this study, we use 12 years of data on pied flycatchers Ficedula hypoleuca, to show that the likelihood of becoming a primary female of a polygynous male declines over the season. Moreover, we provide experimental evidence that early breeding elevates polygyny risk, through an experimental manipulation that introduced early breeding females to a population with later breeding phenology. We found that, independently of breeding date, primary females slightly more often experienced complete brood failures than monogamous females, but did not differ in number of fledged offspring among successful broods or number of locally returning recruits. However, apparent survival in subsequent years was substantially lower in primary females, indicating that they may compensate for reduced male care at the expense of future reproduction. Our study reveals that polygyny risk indeed increases with early breeding and entails a local survival cost for primary females. However, this cost is likely largely outweighed by fitness benefits of early breeding in most years. Hence it is unlikely that the increased polygyny risk of early breeding counteracts the fitness benefits, but it may reduce selection for breeding extremely early.     

Involvement of CD44v6 in InlB-dependent Listeria invasion

Listeria monocytogenes , a Gram-positive bacterium, is the causative agent for the disease called listeriosis. This pathogen utilizes host cell surface proteins such as E-cadherin or c-Met in order to invade eukaryotic cells. The invasion via c-Met depends on the bacterial protein InlB that activates c-Met phosphorylation and internalization mimicking in many regards HGF, the authentic c-Met ligand. In this paper, we demonstrate that the activation of c-Met induced by InlB is dependent on CD44v6, a member of the CD44 family of transmembrane glycoproteins. Inhibiting CD44v6 by means of a blocking peptide, a CD44v6 antibody or CD44v6-specific siRNA prevents the activation of c-Met induced by InlB. Subsequently, signalling, scattering and the entry of InlB-coated beads into host cells are also impaired by CD44v6 blocking reagents. For the entry process, ezrin, a protein that links the CD44v6 cytoplasmic domain to the cytoskeleton, is required as well. Most importantly, this collaboration between c-Met and CD44v6 contributes to the invasion of L. monocytogenes into target cells as demonstrated by a drastic decrease in bacterial invasion in the presence of blocking agents such as the CD44v6 peptide or antibody.     

Adeno-cosmid cloning vectors for regulated gene expression

Background

Adenovectors are widely used for efficient delivery of genes into a variety of cell types and organisms. However, the construction of the desired vector/genes combination, especially if it involves the cloning of several gene cassettes, can be laborious due to the large size of these vectors. New methods are needed to simplify the construction of complex combinations of gene cassettes into adenovectors.

Methods

Using simple cloning techniques and exploiting the λ‐phage packaging system, we devised efficient methods for the ‘selection’ of the desired vector constructs. Thus we generated a series of cosmids containing the adeno helper dependent (HD) backbone in which we inserted cis‐ and trans‐acting tetracycline (tet) elements for the regulation of any gene of interest. One of these cosmids has been used to produce an HD adenovirus carrying a tetracycline‐regulated gene expressing β‐galactosidase.

Results

We have demonstrated that the adeno‐cosmid system allows rapid and efficient cloning of genes of interest in helper dependent vectors, and described a prototype ‘ready‐to‐use’ vector in which any gene of interest can be easily expressed under the control of the tet system. The HD viruses produced with this novel methodology can be grown at high titers, can be easily separated from the helper adenovirus, and allow delivery and regulated gene expression in a variety of tissues.

Conclusions

Exploiting the λ‐packaging system, complex adeno constructs can be generated with a simple and reproducible protocol, which allows selection of the desired size construct, counterselecting for the frequently observed intramolecular recombinations and deletions. Copyright © 2002 John Wiley & Sons, Ltd.

     

Enzyme-catalyzed synthesis of alkyl β-D-glycosides with crude homogenate ofSulfolobus solfataricus

Summary Crude homogenate of thermophilic archaebacteriumSulfolobus solfataricus, possessing a -glycosidase, has been used to synthesize different alkyl -D-glycosides starting from phenyl -D-glucoside, phenyl -D-galactoside and lactose as carbohydrate donors. High product yield (95% with respect to the carbohydrate donor) of octyl -D-glucoside has been obtained in a two-phase system containing 5% of water. The enantioselection for the galactosyl transfer to the secondary hydroxyl group of propane-1,2-diol is higher than that found using -galactosidase fromE. coli.     

Halomonas alkaliantarctica sp. nov., isolated from saline lake Cape Russell in Antarctica, an alkalophilic moderately halophilic, exopolysaccharide-producing bacterium

The taxomony of strain CRSS (DSM 15686(T)=ATCC BAA-848(T)) isolated from Cape Russell in Antarctica (Ross Sea, 74 52.35 S 163 53.03 E) was investigated in a polyphasic approach. The morphological, physiological and genetic characteristics were compared with that of related species of the genus Halomonas. The isolate grew optimally at pH 9.0, 10% NaCl at 30 degrees C. The cells were Gram-negative aerobic rods able to produce exopolysaccharide. They accumulated glycine-betaine, as a major osmolyte, with minor components ectoine and glutamate. The strain CRSS biosynthetised alpha-glucosidase. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol as major components. Ubiquinone with nine repetitive unities (Q9) was the only quinone found and the fatty acid composition was dominated by C18:1 (53%). The G+C content of DNA was 55.0mol% and its phylogenetic position was established by 16S rRNA gene sequencing as a member of the genus Halomonas. For physiological, chemotaxonomic and genetic features (DNA-DNA hybridisation) it is proposed to classify the isolate as a new species for which we propose the name Halomonas alkaliantarctica sp. nov.     

Pretreatment strategies for microbial valorization of bio‐oil fractions produced by fast pyrolysis of ash‐rich lignocellulosic biomass

This work evaluates a biorefinery approach for microbial valorization of bio‐oil fractions produced by fast pyrolysis of ash‐rich lignocellulosic biomass. Different methods are presented for the pretreatment of the low‐sugar complex bio‐oil consisting of organic condensate (OC) and aqueous condensate (AC) to overcome their strong inhibitory effects and unsuitability for common analytical methods. Growth of Pseudomonas putida KT2440, which was chosen as a reference system, on untreated bio‐oil fractions was only detectable using solid medium with OC as sole carbon source. Utilization of a pretreated OC which was filtered, autoclaved, neutralized and centrifuged enabled growth in liquid medium with significant remaining optical instability. By subjecting the pretreated fractions to solid phase extraction, more stable and less inhibitory bio‐oil fractions could be obtained enabling the appliance of common analytical methods. Furthermore, this pretreatment facilitated growth of the applied reference organism Pseudomonas putida KT2440. As there is currently no convincing strategy for reliable application of bio‐oil as a sole source of carbon in industrial biotechnology, the presented work depicts a first step toward establishing bio‐oil as a future sustainable feedstock for a bio‐based economy.     

Purification of the ADP-ribosylating enzyme from S. solfataricus by SDS-polyacrylamide gel electrophoresis and electroelution

The ADPribosylating enzyme from the thermophilic archaeon S. solfataricus was purified by a simple procedure which included preparative electrophoresis on a 0.1% SDS- polyacrylamide gel. The gel slice containing the enzymatic protein was cut out and the enzyme was solubilized by electroelution. The pure enzyme was obtained by chromatography of the electroeluted sample on a DNA-Sepharose column. The purified enzyme retained both its full activity and the structuring ability as a function of temperature increase.     

PIC1, an ancient permease in Arabidopsis chloroplasts, mediates iron transport

In chloroplasts, the transition metals iron and copper play an essential role in photosynthetic electron transport and act as cofactors for superoxide dismutases. Iron is essential for chlorophyll biosynthesis, and ferritin clusters in plastids store iron during germination, development, and iron stress. Thus, plastidic homeostasis of transition metals, in particular of iron, is crucial for chloroplast as well as plant development. However, very little is known about iron uptake by chloroplasts. Arabidopsis thaliana PERMEASE IN CHLOROPLASTS1 (PIC1), identified in a screen for metal transporters in plastids, contains four predicted alpha-helices, is targeted to the inner envelope, and displays homology with cyanobacterial permease-like proteins. Knockout mutants of PIC1 grew only heterotrophically and were characterized by a chlorotic and dwarfish phenotype reminiscent of iron-deficient plants. Ultrastructural analysis of plastids revealed severely impaired chloroplast development and a striking increase in ferritin clusters. Besides upregulation of ferritin, pic1 mutants showed differential regulation of genes and proteins related to iron stress or transport, photosynthesis, and Fe-S cluster biogenesis. Furthermore, PIC1 and its cyanobacterial homolog mediated iron accumulation in an iron uptake-defective yeast mutant. These observations suggest that PIC1 functions in iron transport across the inner envelope of chloroplasts and hence in cellular metal homeostasis.     

GENETIC POPULATION STRUCTURE OF PSEUDO‐NITZSCHIA PUNGENS (BACILLARIOPHYCEAE) FROM THE PACIFIC NORTHWEST AND THE NORTH SEA1

Several species of the diatom Pseudo‐nitzschia produce the neurotoxin domoic acid (DA). Consumption of fish and shellfish that have accumulated this potent excitotoxin has resulted in severe illness and even death in humans, marine mammals, and seabirds. Pseudo‐nitzschia pungens (Grunow ex Cleve) Hasle is a cosmopolitan diatom commonly occurring in the waters of the Pacific Northwest (PNW) and the eastern North Atlantic, including the North Sea. However, genetic and physiological relationships among populations throughout this large geographic distribution have not been assessed. Population genetic parameters (e.g., Hardy–Weinberg equilibrium, linkage equilibrium, F_ST) calculated for P. pungens collected from the Juan de Fuca eddy region in the PNW indicated the presence of two distinct groups that were more divergent from each other than either was from a P. pungens sample from the North Sea. Geographic heterogeneity was also detected within each of the two PNW groups. These results suggested that the populations of P. pungens recently mixed in the Juan de Fuca eddy region (a seasonally retentive feature off the coasts of Washington State, USA, and Vancouver Island, Canada) but did not exchange genetic material by sexual reproduction. Alternatively, these two groups may be cryptic (morphologically identical, but reproductively isolated) species. Identifying cryptic diversity in Pseudo‐nitzschia is important for bloom prediction and aiding the identification of molecular markers that can be used for rapid detection assay development.