Do vertebrate neural crest and cranial placodes have a common evolutionary origin?

Two embryonic tissues-the neural crest and the cranial placodes-give rise to most evolutionary novelties of the vertebrate head. These two tissues develop similarly in several respects: they originate from ectoderm at the neural plate border, give rise to migratory cells and develop into multiple cell fates including sensory neurons. These similarities, and the joint appearance of both tissues in the vertebrate lineage, may point to a common evolutionary origin of neural crest and placodes from a specialized population of neural plate border cells. However, a review of the developmental mechanisms underlying the induction, specification, migration and cytodifferentiation of neural crest and placodes reveals fundamental differences between the tissues. Taken together with insights from recent studies in tunicates and amphioxus, this suggests that neural crest and placodes have an independent evolutionary origin and that they evolved from the neural and non-neural side of the neural plate border, respectively.     

Microbial degradation of nonylphenol and other alkylphenols—our evolving view

Because the endocrine disrupting effects of nonylphenol (NP) and octylphenol became evident, the degradation of long-chain alkylphenols (AP) by microorganisms was intensively studied. Most NP-degrading bacteria belong to the sphingomonads and closely related genera, while NP metabolism is not restricted to defined fungal taxa. Growth on NP and its mineralization was demonstrated for bacterial isolates, whereas ultimate degradation by fungi still remains unclear. While both bacterial and fungal degradation of short-chain AP, such as cresols, and the bacterial degradation of long-chain branched AP involves aromatic ring hydroxylation, alkyl chain oxidation and the formation of phenolic polymers seem to be preferential elimination pathways of long-chain branched AP in fungi, whereby both intracellular and extracellular oxidative enzymes may be involved. The degradation of NP by sphingomonads does not proceed via the common degradation mechanisms reported for short-chain AP, rather, via an unusual ipso-substitution mechanism. This fact underlies the peculiarity of long-chain AP such as NP isomers, which possess highly branched alkyl groups mostly containing a quaternary α-carbon. In addition to physicochemical parameters influencing degradation rates, this structural characteristic confers to branched isomers of NP a biodegradability different to that of the widely used linear isomer of NP. Potential biotechnological applications for the removal of AP from contaminated media and the difficulties of analysis and application inherent to the hydrophobic NP, in particular, are also discussed. The combination of bacteria and fungi, attacking NP at both the phenolic and alkylic moiety, represents a promising perspective.     

The Sweet Tooth of Adult Parasitoid Cotesia rubecula: Ignoring Hosts for Nectar?

Investing time and energy into survival and reproduction often presents a trade-off to many species of animals. In parasitic wasps, both hosts and sugar sources contribute to the forager's fitness but are often found in different locations. The decision to search for hosts or for food can have a strong impact on fitness when the forager's lifetime is short and resources are not abundant. We investigated the tendency of flowers and hosts to attract 1-day-old female Cotesia rubecula Marshall (Hymenoptera: Braconidae) with different feeding histories in a wind tunnel. Only well-fed wasps exhibited a preference for hosts. In comparison, unfed wasps visited hosts and flowers in equal proportions. Feeding experience had a strong impact on the searching behavior and the number of landings on both resources. Host and food stimuli seem to be equally attractive to hungry parasitic wasps such as C. rubecula. We expect that under field conditions the time available for active food searching in female C. rubecula is short and influenced by the presence of hosts.     

Proteomic analysis of exoproteins expressed by enterotoxigenic Staphylococcus aureus strains

Pathogenic bacteria excrete a variety of virulence factors into extracellular medium and to the cell surface which have essential roles in the colonization and insurrection of the host cells, and thus reflect the degree of bacterial pathogenicity. For the exploration of virulence factors expressed in the secreted proteome fraction, different Staphylococcus aureus strains were analyzed using gel-based bottom-up proteomic approach. A total of 119 distinct proteins were identified for the enterotoxin gene cluster (egc) negative and seb gene positive S. aureus American Type Culture Collection (ATCC) 14458 strain by the use of one- and 2-DE based proteomics. Detailed analysis of enterotoxin region of the 2-D map confirmed, beside the highly expressed staphylococcal enterotoxin B (SEB), the presence of enterotoxin-like proteins SElK and SElQ previously predicted by genotyping (Sergeev et al.., J. Clin. Microbiol. 2004, 42, 2134-2143). Exoprotein patterns at the late-exponential (7 h) and stationary (24 h) phases of cellular growth show a high-level similarity in this region. Comparative analysis of enterotoxin region of five S. aureus strains including two clinical isolates (RIMD 31092 and A900322), a food derived strain (AB-8802) with highly prevalent egc positive operon and a nonenterotoxigenic reference strain (ROS) revealed the presence of different known enterotoxins and other virulence factors along with a number of core exoproteins. In addition, production of SElL (RIMD 31092) and SElP (A900322) was demonstrated for the first time at the protein level. Under the experimental conditions applied none of the enterotoxins encoded by the genes of egc operon was identified.     

Feeding and survival in parasitic wasps: sugar concentration and timing matter

Sugar consumption can increase the longevity and lifetime fecundity of many species of parasitic wasps. Consequently, for these insects the availability of sugar sources in the field is important for their reproductive success. As sugar sources can be highly variable in quantity, space and time, the chances of finding a sufficient amount of sugar to increase longevity might be very low. Therefore, the reward from a single feeding event can be critical for the forager's fitness. We measured the longevity of the parasitoid Cotesia rubecula after a single honey meal differing in sugar concentration (25, 47, 86% w/w) and timing (day of emergence and 24 h later). Survival was analysed with Cox's Proportional Hazards Model. The risk of starving to death in sugar-fed wasps was reduced by 0–73% in comparison to unfed wasps, depending on sugar concentration and timing. Longevity was significantly increased by sugar concentration and by feeding later in life. Our results suggest that in the field, adult C. rubecula has to locate food at least once per day to avoid starvation.     

Morphological characterization of microencapsulated Penicillium raistrickii i 477

For the immobilization of spores of Penicillium raistrickii i 477 the formation of polyelectrolyte complexes using the sodium salt of cellulose sulphate as polyanion and poly-dimethyl-diallylammoniumchloride as polycation was used. Light and scanning electron microscopy have shown that during germination of spores the capsule walls do not cause effective limitations on hyphal growth and that there are no significant morphological changes of the mycelium detectable by an outgrowth of immobilized spores. By comparing the 15α-hydroxylation of 13-ethyl-gon-4-en-3,17-dione with free and encapsulated cells it was found that an increase of total dry biomass per immobilized system led to a higher product formation in relation to free cells.     

Mass spectrometric analysis of combinatorial peptide libraries derived from the tandem repeat unit of MUC2 mucin.

Four 19-member synthetic peptide libraries, based on the TX1TX2T epitope motif of the mucin-2 gastrointestinal glycoprotein (MUC2) and ranging in peptide length from dipeptides to 15-mers (XT, TXT, TQTXT and KVTPTPTPTGTQTXT), were synthesized by combinatorial solid phase peptide synthesis using the portioning-mixing combinatorial approach, and analysed by electrospray ionization mass spectrometry at different (1000-10000) resolutions. Most of the components of the individual libraries could be easily identified in a single-stage molecular mass screening experiment. The resolving power of the instrument becomes an important factor above 800-1000 Da molecular mass, when predominantly multiply charged molecular ions are formed. Approaches to the identification of isobars (glutamine/lysine), isomers leucine/isoleucine) and sequence variations by tandem mass spectrometry, and/or by high-performance liquid chromatography-mass spectrometry are outlined.