Cultivation of the yeast candida lipolytica on hydrocarbons. I. Degradation of n-alkanes in batch fermentation of gas oil

The growth of batch-cultivated yeast Candida lipolytica on three kinds of gas oil using mineral medium was studied. A linear dependence was found between the production of yeast biomass and the consumption of n-alkanes, while the decrease of freezing point of gas oil during cultivation had a distinct course. This disproportion was explained by different degradation of individual n-alkanes contained in gas oil. The rate of degradation of pentadecane, hexadecane, and heptadecane was the same during the entire cultivation. On the contrary, in the first phase the utilization of shorter chain n-alkanes, nonane to tetradecane, was more rapid while that of longer chain homologs, octadecane to pentacosane, lagged. Rapid utilization of longer chain n-alkanes did not occur before the concentration of the other n-alkanes decreased. Only then the rapid decrease of freezing point appeared.     

Structural features of peptoid–peptide hybrids in lipid–water interfaces

The inclusion of peptoid monomers into antimicrobial peptides (AMPs) increases their proteolytic resistance, but introduces conformational flexibility (reduced hydrogen bonding ability and cis/trans isomerism). We here use NMR spectroscopy to answer how the insertion of a peptoid monomer influences the structure of a regular α-helical AMP upon interaction with a dodecyl phosphocholine (DPC) micelle. Insertion of [(2-methylpropyl)amino]acetic acid in maculatin-G15 shows that the structural change and conformational flexibility depends on the site of insertion. This is governed by the micelle interaction of the amphipathic helices flanking the peptoid monomer and the side chain properties of the peptoid and its preceding residue.     

Changes in plankton and fish larvae communities across hydrographic fronts off West Greenland

The variability in plankton community structure was studiedin Disko Bay and across important fishing banks off the westcoast of Greenland. The primary goal of the study was to investigatepossible linkages between hydrographical processes and planktonstructures, hypothesizing that hydrographic fronts would bepresent in the area, and that these to a large extent determineplankton distribution, composition and productivity. We sampledalong four cross-shelf transects, one covering Disko Bay andDisko Bank, while the other three covered Store Hellefiske Bank,Lille Hellefiske Bank and Sukkertop Bank. The hydrography wasexamined by CTD profiling, the phytoplankton by fluorescenceprofiling and water bottle sampling, while mesozooplankton andichthyoplankton were sampled by vertical or oblique net hauls,respectively. We observed distinct along-shelf flowing currentsin the area (e.g. the West Greenland Current, the Polar Currentand the Irminger Current), and the physical characteristicsindicated frontogenesis at the shelf slope, in regions of 80–100m water depth. Phytoplankton and ichthyoplankton showed a cross-shelfstructuring with apparent linkages to frontal characteristics,while a more diverse pattern was observed for the mesozooplanktonwhich were dominated by Calanus finmarchicus, Calanus glacialisand Calanus hyperboreus. The relationship between hydrographiccharacteristics and plankton distribution differed among species,and apparently specific plankton communities were establishedin different areas of the shelf. For example the larvae of Boreogadussaida, Ammodytes sp., Reinhardtius hippoglossoides and Stichaeuspunctatus differed markedly in distributional characteristics.In addition to the cross-shelf structuring, marked differencesin species composition and total plankton abundance were observedin the along-shelf (north–south) direction. The latitudinaldifferences in the unicellular plankton communities are interpretedlargely within a seasonal successional framework (i.e. an earlydominance of diatoms followed by increasing importance of smallerunicellular plankton), while the ichthyo- and zooplankton communitiesalso differed by the respective dominance of species with polarversus temperate origin. Our findings suggest that the flowof major currents and the establishment of hydrographical frontsare of primary importance to the plankton communities in theWest Greenland shelf area, influencing the early life of fishand the recruitment to the important fisheries resources.     

Resorption

Ohne Zusammenfassung     

Heteromorphe ammoniten aus dem unter-callovien („macrocephalen-schichten“) vom westrand der nördlichen frankenalb (s-deutschland)

Heteromorph Ammonites of the generaParapatoceras Spath,Paracuariceras Schindewolf undAcuariceras Spath from the Lower Callovian (“Macrocephalen-Schichten” of the Northern Franconian Alb are described. The species of the genusParapatoceras Spath are dominant. New finds of the generaParacuariceras Schindewolf andAcuariceras Spath show that their first occurence is in the Lower Callovian. The optimal biotope of the heteromorphs with vagile benthonic mode of life was probably, similar to the Swabian Dogger, in stillwater areas.     

Target cell lysis and IL-2 secretion by gamma/delta T lymphocytes after activation with bacteria

Peripheral blood T lymphocytes from healthy donors were stimulated with Mycobacterium tuberculosis in vitro and afterward analyzed phenotypically. Marked expansion of the gamma/delta T cell population (3- to 21-fold) was observed in 15/21 donors 7 to 10 days after stimulation. In addition to M. tuberculosis, Mycobacterium leprae (six of eight) as well as the gram-positive bacteria, Staphylococcus aureus (two of six), group A streptococci (seven of nine), and Listeria monocytogenes (four of eight) augmented gamma/delta TCR expression in peripheral blood T cells of many donors. gamma/delta T lymphocytes expressed IL-2R and secreted IL-2 upon restimulation with M. tuberculosis. Stimulation with M. tuberculosis evoked specific cytolytic activities in gamma/delta T lymphocytes because: gamma/delta T cells lysed M. tuberculosis pulsed but not unpulsed targets; high concentrations of TCR delta 1 mAb facilitated killing of unpulsed target cells; and low doses of anti-TCR delta 1 mAb blocked killing of pulsed targets. Furthermore, gamma/delta T cells from four donors, after activation with M. tuberculosis or with group A streptococci, respectively, only lysed targets pulsed with the homologous agents, whereas in other donors some cross-reactivity was observed. We conclude that, upon contact with mycobacteria and perhaps other microorganisms, gamma/delta T cells are activated which contribute to immunity against infection via IL-2 secretion and specific target cell lysis.     

Prey size spectra and prey availability of larval and small juvenile cod

The aim of the present study is to describe the prey preference characteristics of cod larvae and assess preference variability in relation to species and size composition of copepod prey. A further aim is to examine the hypothesis that dietary prey size spectra remain the same during the larval stage when viewed on a relative predator/prey size scale. The study is based on stomach analysis of larval/juvenile cod in the size range 10–35 mm from nursery grounds in the North Sea. Stomach contents (species, size) were compared to environmental composition and preference indices were calculated. Prey size spectra had the expected relationship to larval cod size, and preference for given copepod species could be ascribed to their relative size. Additional species-specific preferences were evident, for example the larger Pseudocalanus and the larger Calanus spp. were highly preferred. Available prey biomass was highest in the areas of a hydrographic front, where larvae have been shown to concentrate. Changes in prey availability with larval growth depend strongly on specific prey biomass spectra at a given location. Both increasing and decreasing prey availability at increasing larval size were indicated, dependent on location. The findings illustrate the usefulness of coupling dietary prey size spectra and biomass spectra of available prey sizes during studies of ichthyoplankton feeding ecology.