Production of type 5 capsular polysaccharide by Staphylococcus aureus grown in a semi-synthetic medium

The concentration of the type 5 capsular polysaccharide (CP) antigen of Staphylococcus aureus can be measured directly in cultures or cell suspensions by a two-step inhibition enzyme-linked immunosorbent assay (ELISA), using monoclonal antibodies. CP was synthesized during growth on a variety of carbon substrates and its production was not affected by the nature of the carbon source. High levels of yeast extract inhibited CP formation. CP was synthesized in batch culture at the same rate during exponential growth as in the post-exponential phase. Post-exponential CP production contributed at least half the final amount of CP measured. This phenomenon was observed in different culture media, although the specific yield of polysaccharide varied from one medium to another. Post-exponential CP production was observed in the pH range 6-7, but not at pH 8. Post-exponential production was strictly dependent on oxygen availability and did not occur under anaerobic conditions.     

Anesthetic inhibition of firefly luciferase, a protein model for general anesthesia, does not exhibit pressure reversal.

The surprising observation that pressures of the order of 150 atmospheres can restore consciousness to an anesthetized animal has long been central to theories of the molecular mechanisms underlying general anesthesia. We have constructed a high-pressure gas chamber to test for "pressure reversal" of the best available protein model of general anesthetic target sites: the pure enzyme firefly luciferase, which accounts extremely well for animal potencies (over a 100,000-fold range). We found no significant pressure reversal for a variety of anesthetics of differing size and polarity. It thus appears that either firefly luciferase is not an adequate model for general anesthetic target sites or that pressure and anesthetics act at different molecular sites in the central nervous system.     

Heat-sensitive DNA-binding activity of thecI product of bacteriophage lambda

Summary The binding of genecI product to DNA was studied at temperatures from 0°C to 46° C. Binding activity of the products ofcIts mutants was higher at 22° C than at 0° C, 26° C or 30° C. BothcI⁺ andcIts products lost DNA-binding activity at 46° C, but after subsequent cooling to 22° C, they regained 50–100% of their activity.     

Shifts in Antarctic megabenthic structure after ice-shelf disintegration in the Larsen area east of the Antarctic Peninsula

The aim of this study was to contribute to a general understanding of the response of the Antarctic macrobenthos to environmental variability and climate-induced changes. The change in population size of selected macrobenthic organisms was investigated in the Larsen A area east of the Antarctic Peninsula in 2007 and 2011 using ROV-based imaging methods. The results were complemented by data from the Larsen B collected in 2007 to allow a conceptual reconstruction of the environment-driven changes before the period of investigation. Both Larsen areas are characterised by ice-shelf disintegration in 1995 and 2002, respectively, as well as high inter-annual variability in sea-ice cover and oceanographic conditions. In 2007 one ascidian species, Molgula pedunculata, was abundant north and south of the stripe of remaining ice shelf between Larsen A and B. Population densities decreased drastically in the Larsen A between 2007 and 2011, coincident with the decrease in Corella eumyota, another ascidian. Among the ophiuroids, the population of deposit feeders increased, while suspension feeders halved their abundance. Current measurements indicated a northward flow between the Larsen B and Larsen A, suggesting that a major physical forcing on benthic population development comes from the South. The results demonstrate that Antarctic macrobenthic populations can exhibit dramatic population dynamics. Analyses of sea-ice dynamics, salinity, temperature and surprisingly ice-shelf disintegration history, however, did not provide any clear evidence for environmental drivers underlying the apparent changes.     

Family Aggregation and Risk Factors in Phobic Disorders over Three-Generations in a Nation-Wide Study

Objective

This nation-wide register-based study investigated how often phobic disorders (PHO) and co-morbid disorders occur in affected families compared to control families. Furthermore, the study addressed the impact of sex, year of birth, and degree of urbanization in terms of risk factors.

Method

A total of N = 746 child and adolescent psychiatric participants born between 1969 and 1986 and registered in the Danish Psychiatric Central Research Register (DPCRR) with a diagnosis of a mental disorder before the age of 18, and developed PHO at some point during their life-time until a maximum age of 40 years were included. In addition, N = 2229 controls without any diagnosis of mental disorders before age 18 and that were matched for age, sex, and residential region were included. Diagnoses of mental disorders were also obtained from the first- degree relatives as a part of the Danish Three Generation Study (3GS). A family load component was obtained by using various mixed regression models.

Results

PHO occurred significantly more often in case than in control families, in particular, in mothers and siblings. Substance use disorders (SUD), Depressive disorders (DEP), anxiety disorders (ANX) and personality disorders (PERS) in the family were significantly associated with specific phobia in the case-probands. After controlling for various mental disorders comorbid to PHO it was found that some of the family transmission could be caused by various other mental disorders in family members rather than the PHO itself. Female sex and more recent year of birth were further risk factors while region of residence was not related to the manifestation of PHO. Case-relatives did not develop PHO earlier than control relatives. After adjusting for various additional explanatory variables, the family load explained only 0.0013% of the variance in the manifestation of PHO in the case-probands

Discussion

These findings, based on a very large and representative dataset, provide evidence for the family aggregation and further risk factors in PHO. In contrast to anxiety disorders and other major mental disorders the family load of PHO in this nation-wide study was rather low.     

Minireview: Recent progress in hemocyanin research

This review summarizes recent highlights of our joint work on the structure, evolution, and function of a family of highly complex proteins, the hemocyanins. They are blue-pigmented oxygen carriers, occurring freely dissolved in the hemolymph of many arthropods and molluscs. They are copper type-3 proteins and bind one dioxygen molecule between two copper atoms in a side-on coordination. They possess between 6 and 160 oxygen-binding sites, and some of them display the highest molecular cooperativity observed in nature. The functional properties of hemocyanins can be convincingly described by either the Monod-Wyman-Changeux (MWC) model or its hierarchical extension, the Nested MWC model; the latter takes into account the structural hierarchies in the oligomeric architecture. Recently, we applied these models to interpret the influence of allosteric effectors in detailed terms. Effectors shift the allosteric equilibria but have no influence on the oxygen affinities characterizing the various conformational states. We have shown that hemocyanins from species living at different environmental temperatures have a cooperativity optimum at the typical temperature of their natural habitat. Besides being oxygen carriers, some hemocyanins function as a phenoloxidase (tyrosinase/catecholoxidase) which, however, requires activation. Chelicerates such as spiders and scorpions lack a specific phenoloxidase, and in these animals activated hemocyanin might catalyse melanin synthesis in vivo. We propose a similar activation mechanism for arthropod hemocyanins, molluscan hemocyanins and tyrosinases: amino acid(s) that sterically block the access of phenolic compounds to the active site have to be removed. The catalysis mechanism itself can now be explained on the basis of the recently published crystal structure of a tyrosinase. In a series of recent publications, we presented the complete gene and primary structure of various hemocyanins from different molluscan classes. From these data, we deduced that the molluscan hemocyanin molecule evolved ca. 740 million years ago, prior to the separation of the extant molluscan classes. Our recent advances in the 3D cryo-electron microscopy of hemocyanins also allow considerable insight into the oligomeric architecture of these proteins of high molecular mass. In the case of molluscan hemocyanin, the structure of the wall and collar of the basic decamers is now rapidly becoming known in greater detail. In the case of arthropod hemocyanin, a 10-? structure and molecular model of the Limulus 8 × 6mer shows the amino acids at the various interfaces between the eight hexamers, and reveals histidine-rich residue clusters that might be involved in transferring the conformational signals establishing cooperative oxygen binding.