Structural characterization of eight cyclic lipopeptides produced by Bacillus subtilis HSO121

Lipopeptides are amphiphilic compounds which contain both hydrophobic fatty acid moieties and amphiphilic peptide moieties. From the cell-free broth of Bacillus subtilis HSO121, eight cyclic lipopeptides were isolated by reversed-phase high performance liquid chromatography (RP-HPLC). The peptide part of each lipopeptide was elucidated according to electrospray ionization quadruple-time-of-flight mass spectrometry (ESI Q-TOF MS) and the fatty acid part was analyzed by electroionization gas chromatography/mass spectrometry (EI GC/MS). It showed that fractions 1-8 had molecular masses of 1007, 1021, 1021, 1035, 1035, 1035, 1063, and 1049, respectively. Analysis of hydrolyzed lipopeptides revealed that they had invariant amino acid compositions. The differences in molecular weights represent changes in the number of methylene groups and different types of branched chains in fatty acids. Peptide sequences of two of the eight lipopeptides appeared to be N-Asp-Leu-Leu-Val-Glu-Leu-Leu-C, which was different from previously reported lipopeptides. The remaining six had an identical peptide sequence of N-Glu-Leu-Leu-Val-Asp-Leu-Leu-C. The fatty acid parts were found to be mixtures of iso C(12), iso C(13), anteiso C(13), iso C(14), n C(14), iso C(15), anteiso C(15), n C(15), anteiso C(16) and anteiso C(17) beta-hydroxy fatty acids. The structure of each lipopeptide was determined to be the beta-hydroxy fatty acid bonded to the peptide chain.     

Caspase-mediated cleavage of the exosome subunit PM/Scl-75 during apoptosis

Recent studies have implicated the dying cell as a potential reservoir of modified autoantigens that might initiate and drive systemic autoimmunity in susceptible hosts. A number of subunits of the exosome, a complex of 3'→5' exoribonucleases that functions in a variety of cellular processes, are recognized by the so-called anti-PM/Scl autoantibodies, found predominantly in patients suffering from an overlap syndrome of myositis and scleroderma. Here we show that one of these subunits, PM/Scl-75, is cleaved during apoptosis. PM/Scl-75 cleavage is inhibited by several different caspase inhibitors. The analysis of PM/Scl-75 cleavage by recombinant caspase proteins shows that PM/Scl-75 is efficiently cleaved by caspase-1, to a smaller extent by caspase-8, and relatively inefficiently by caspase-3 and caspase-7. Cleavage of the PM/Scl-75 protein occurs in the C-terminal part of the protein at Asp369 (IILD³⁶⁹↓G), and at least a fraction of the resulting N-terminal fragments of PM/Scl-75 remains associated with the exosome. Finally, the implications of PM/Scl-75 cleavage for exosome function and the generation of anti-PM/Scl-75 autoantibodies are discussed.     

Improved bio-energy yields via sequential ethanol fermentation and biogas digestion of steam exploded oat straw

Using standard laboratory equipment, thermochemically pretreated oat straw was enzymatically saccharified and fermented to ethanol, and after removal of ethanol the remaining material was subjected to biogas digestion. A detailed mass balance calculation shows that, for steam explosion pretreatment, this combined ethanol fermentation and biogas digestion converts 85-87% of the higher heating value (HHV) of holocellulose (cellulose and hemicellulose) in the oat straw into biofuel energy. The energy (HHV) yield of the produced ethanol and methane was 9.5-9.8 MJ/(kg dry oat straw), which is 28-34% higher than direct biogas digestion that yielded 7.3-7.4 MJ/(kg dry oat straw). The rate of biogas formation from the fermentation residues was also higher than from the corresponding pretreated but unfermented oat straw, indicating that the biogas digestion could be terminated after only 24 days. This suggests that the ethanol process acts as an additional pretreatment for the biogas process.     

Determination of bioactive markers in Cleome droserifolia using cell-based bioassays for antidiabetic activity and isolation of two novel active compounds

The antidiabetic activities of the aqueous (AqEx) and ethanolic (AlEx) extracts of Cleome droserifolia (Forssk.) Del., were tested in cultured C2C12 skeletal muscle cells and 3T3-L1 adipocytes. An 18-h treatment with the AqEx increased basal glucose uptake by 33% [insulin equivalent (IE)=1.3±0.04] in muscle cells comparable to a 25.5% increase caused by 100 nM insulin (IE=1±0.03). Fractionation of the tested AqEx yielded hexane (HxFr), chloroform (ClFr) and ethyl acetate (EtFr) fractions which exerted 38, 52 and 35% increase in the glucose uptake corresponding to an IE of 1.5±0.06, 2.0±0.04 and 1.4±0.04, respectively. Only the ClFr and EtFr accelerated the triglyceride accumulation [rosiglitazone equivalent (RE) was 0.9±0.13 and 0.63±0.12, respectively] in pre-adipocytes undergoing differentiation comparably with 10 μM rosiglitazone. Six terpenoids (C1-C6) and three flavonol glycosides (F1-F3) were isolated from the active ClFr and EtFr, respectively, and identified. C5, C2 and C4 had an IE of 0.86±0.05, 1.01±0.04 and 0.9±0.08, while F1, F2 and F3 gave an IE of 1.3±0.05, 2.3±0.05 and 2.0±0.04, respectively. We could conclude that the reported antihyperglycemic activity of Cleome droserifolia is attributed to significant insulin-like effects in peripheral tissues, and that compounds F2 and F3, being highly active, could be used as bioactive markers to standardize the C. droserifolia herbal extract.     

Assessing predicted HIV-1 replicative capacity in a clinical setting

HIV-1 replicative capacity (RC) provides a measure of within-host fitness and is determined in the context of phenotypic drug resistance testing. However it is unclear how these in-vitro measurements relate to in-vivo processes. Here we assess RCs in a clinical setting by combining a previously published machine-learning tool, which predicts RC values from partial pol sequences with genotypic and clinical data from the Swiss HIV Cohort Study. The machine-learning tool is based on a training set consisting of 65000 RC measurements paired with their corresponding partial pol sequences. We find that predicted RC values (pRCs) correlate significantly with the virus load measured in 2073 infected but drug na?ve individuals. Furthermore, we find that, for 53 pairs of sequences, each pair sampled in the same infected individual, the pRC was significantly higher for the sequence sampled later in the infection and that the increase in pRC was also significantly correlated with the increase in plasma viral load and with the length of the time-interval between the sampling points. These findings indicate that selection within a patient favors the evolution of higher replicative capacities and that these in-vitro fitness measures are indicative of in-vivo HIV virus load.     

A revision of the purse-web spider genus Calommata Lucas, 1837 (Araneae, Atypidae) in the Afrotropical Region

The purse-web spider genus Calommata Lucas, 1837 is revised in the Afrotropical Region. Following examination of the female type material, Calommata transvaalica Hewitt, 1916 is removed from synonymy with Calommata simoni Pocock, 1903 and revalidated. The females of both species are redescribed and their males described for the first time. While Calommata simoni is very widespread across tropical Africa, Calommata transvaalica is endemic to northern South Africa. Four new species are described, all known only from males: Calommata megaesp. n. (Zimbabwe), Calommata meridionalissp. n. (South Africa), Calommata namibicasp. n. (Namibia) and Calommata tibialissp. n. (Ivory Coast and Togo). Notes are presented on the biology of each species.