Identification and structural characterisation of novel trehalose dinocardiomycolates from n-alkane-grown Rhodococcus opacus 1CP

Rhodococcus opacus 1CP, a potent degrader of (chloro-) aromatic compounds was found to utilise C₁₀–C₁₆ n-alkanes as sole carbon sources. Highest conversion rates were observed with n-tetradecane and n-hexadecane, whereas the utilisation of n-dodecane and n-decane was considerably slower. Thin-layer chromatography of organic extracts of n-alkane-grown 1CP cultures indicated the growth-associated formation of a glycolipid which was characterised as a trehalose dimycolate by ¹H-NMR spectroscopy and mass spectrometry. Total chain lengths between 48 and 54 carbons classify the fatty acid residues as nocardiomycolic acids. The presence of two double bonds in each mycolic acid is another feature that distinguishes the corresponding trehalose dinocardiomycolates from trehalose dicorynomycolates reported for Rhodococcus erythropolis DSM43215 and Rhodococcus ruber IEGM231. R. opacus 1CP was not found, even under nitrogen limitation, to produce anionic trehalose tetraesters which have previously been reported for R. erythropolis DSM43215.     

Host Acceptance and Larval Competition in the Banded and European Elm Bark Beetles, <Emphasis Type="Italic">Scolytus schevyrewi</Emphasis> and <Emphasis Type="Italic">S. multistriatus</Emphasis> (Coleoptera: Scolytidae): Potential Mechanisms for Competitive Displacement between Invasive Species

A recent survey revealed that the newly invasive banded elm bark beetle, Scolytus schevyrewi, was much more abundant than the long-established European elm bark beetle, S. multistriatus, in areas of Colorado and Wyoming, USA. This study was initiated to determine whether competitive displacement of S. multistriatus by S. schevyrewi might be mediated by a sequence of behavioral interactions between the species on and below the bark surface. At the first step in the sequence, host acceptance behavior (i.e., time to tunnel into the host) was monitored among female S. schevyrewi and S. multistriatus. There was no substantial difference in host acceptance behavior when females were offered small cut logs (bolts) of Siberian elm, Ulmus pumila, infested with con- or heterospecific females. At the second step, mating and oviposition usually follow after a female has excavated a gallery. Mean oviposition per parental female in 1 wk was not significantly different among treatments: S. schevyrewi at medium density of 2.86 parental females per dm², at high density of 5.71 per dm²; S. multistriatus at medium density, at high density; and mixed species (i.e., S. schevyrewi and S. multistriatus combined, with each at medium density). At the third step, progeny production and progeny size were monitored among the same density treatments, but the number of parental beetles and size of bolts were doubled. Differences in progeny production would reflect larval competition, since the number of eggs initially laid was not different. Both S. schevyrewi and S. multistriatus were sensitive to intraspecific competition because size of progeny was smaller in high than medium density treatments, but total progeny production was similar at both densities. Scolytus schevyrewi was a stronger interspecific competitor than S. multistriatus. Smaller S. multistriatus progeny, and four-fold more S. schevyrewi progeny were produced when both species developed on the same host. The contributions of these proximal behavioral events toward the mechanism for competitive displacement are described in the context of the host colonization behavior of Scolytus spp. The competitive advantage of S. schevyrewi larvae established through this study, and the more rapid response of S. schevyrewi to elm hosts established through other investigations, may be the key mechanistic components that facilitate the displacement of S. multistriatus by S. schevyrewi.     

Ultradian and circadian rhythms of sleep-wake and food-intake behavior during early infancy

The early development of sleep-wake and food-intake rhythms in human infants is reviewed. The development of a 24h day-night rhythm contains two observable developmental processes: the alterations in the periodic structure of behavior (decreased ultradian, increased circadian components) and the process of synchronization to external time (entrainment). The authors present the results of their studies involving 26 German children and compare them with previous investigations. In their research, it became evident that, during the first weeks of life, the time pattern of sleep-wake and food-intake behavior is characterized by different ultradian periodicities, ranging from 2h to 8h. In the course of further ontogenesis, the share of ultradian rhythms in the sleep-wake behavior decreases, while it remains dominant for food-intake behavior. The circadian component is established as early as the first weeks of life and increases in the months that follow. Besides, the authors' study supports the notion of broad interindividual variation in ultradian rhythms and in the development of a day-night rhythm. Examples of free-running rhythms of sleep-wake and food-intake behavior by various authors are strong indicators of the endogenous nature of the circadian rhythms in infants and show that the internal clock is already functioning at birth. It is still uncertain when the process of synchronization to external and social time cues begins and how differences in the maturation of perceptive organs affect the importance of time cues for the entrainment. Prepartally, the physiological maternal entrainment factors and mother-fetus interactions may be most important; during the first weeks of life, the social time cues gain importance, while light acts as a dominant “zeitgeber” at a later time only.     

Vocal fold tissue failure: preliminary data and constitutive modeling

In human voice production (phonation), linear small-amplitude vocal fold oscillation occurs only under restricted conditions. Physiologically, phonation more often involves large-amplitude oscillation associated with tissue stresses and strains beyond their linear viscoelastic limits, particularly in the lamina propria extracellular matrix (ECM). This study reports some preliminary measurements of tissue deformation and failure response of the vocal fold ECM under large-strain shear The primary goal was to formulate and test a novel constitutive model for vocal fold tissue failure, based on a standard-linear cohesive-zone (SL-CZ) approach. Tissue specimens of the sheep vocal fold mucosa were subjected to torsional deformation in vitro, at constant strain rates corresponding to twist rates of 0.01, 0.1, and 1.0 rad/s. The vocal fold ECM demonstrated nonlinear stress-strain and rate-dependent failure response with a failure strain as low as 0.40 rad. A finite-element implementation of the SL-CZ model was capable of capturing the rate dependence in these preliminary data, demonstrating the model's potential for describing tissue failure. Further studies with additional tissue specimens and model improvements are needed to better understand vocal fold tissue failure.     

Complexation of metal ions by pseudotripeptides with different functionalized N-alkyl residues

Seven pseudotripeptides with the common structure Bz-His-[CO-N(CH₂)n-X]Gly-His-NH₂ were synthesized on the solid phase using the Fmoc-strategy, trityl protection for both His residues and Boc- or -OBu^t-protection for N-aminoalkyl- and N-carboxyalkyl residues, respectively. Functionalized N-alkyl glycyl peptides were formed on the solid phase by amination of a bromoacetyl dipeptide. All seven pseudotripeptides are able to form chelate complexes with the metal ions Zn²⁺, Ni²⁺, Cu²⁺ and Co²⁺. The existence of monomeric 1:1 complexes for these pseudopeptides was calculated from the MW estimated by MALDI-MS and from the isotope distribution pattern estimated by ESI.     

The role of regulatory T cells in antigen-induced arthritis: aggravation of arthritis after depletion and amelioration after transfer of CD4<Superscript>+</Superscript>CD25<Superscript>+</Superscript>T cells

It is now generally accepted that CD4⁺CD25⁺ T_reg cells play a major role in the prevention of autoimmunity and pathological immune responses. Their involvement in the pathogenesis of chronic arthritis is controversial, however, and so we examined their role in experimental antigen-induced arthritis in mice. Depletion of CD25-expressing cells in immunized animals before arthritis induction led to increased cellular and humoral immune responses to the inducing antigen (methylated bovine serum albumin; mBSA) and autoantigens, and to an exacerbation of arthritis, as indicated by clinical (knee joint swelling) and histological scores. Transfer of CD4⁺CD25⁺ cells into immunized mice at the time of induction of antigen-induced arthritis decreased the severity of disease but was not able to cure established arthritis. No significant changes in mBSA-specific immune responses were detected. In vivo migration studies showed a preferential accumulation of CD4⁺CD25⁺ cells in the inflamed joint as compared with CD4⁺CD25^- cells. These data imply a significant role for CD4⁺CD25⁺ T_reg cells in the control of chronic arthritis. However, transferred T_reg cells appear to be unable to counteract established acute or chronic inflammation. This is of considerable importance for the timing of T_reg cell transfer in potential therapeutic applications.     

Pseudomonas cepacia lipase: Studies on aggregation,purification and on the cleavage of olive oil

Summary To purify the extracellular lipase ofPseudomonas cepacia DSM 50181 and to disintegrate molecular aggregation, the presence of i-propanol (70% per volume) was necessary. The molecular weight was determined to be 33,000 D. Concerning the hydrolytic activity of the pure enzyme towards olive oil additional free fatty acids inhibited the reaction.     

Analysing overexpression of l-valine biosynthesis genes in pyruvate-dehydrogenase-deficient Corynebacterium glutamicum

l-Valine biosynthesis was analysed by comparing different plasmids in pyruvate-dehydrogenase-deficient Corynebacterium glutamicum strains in order to achieve an optimal production strain. The plasmids contained different combinations of the genes ilvBNCDE encoding for the l-valine forming pathway. It was shown that overexpression of the ilvBN genes encoding acetolactate synthase is obligatory for efficient pyruvate conversion and to prevent l-alanine as a by-product. In contrast to earlier studies, overexpression of ilvE encoding transaminase B is favourable in pyruvate-dehydrogenase-negative strains. Its amplification enhanced l-valine formation and avoided extra- and intracellular accumulation of ketoisovalerate.