Antimicrobial activity in the egg wax of the African cattle tick Amblyomma hebraeum (Acari: Ixodidae)

Eggs of the tick Amblyomma hebraeum Koch (Acari: Ixodidae) inhibited the growth of Escherichia coli and Serratia marcescens (Gram-negative bacteria) in solid culture, but not the growth of Staphylococcus epidermidis, and only marginally the growth of Bacillus subtilis (Gram-positive bacteria). When egg wax was extracted with chloroform/methanol (2:1), the extract contained antibacterial activity, but the denuded eggs did not. When assayed against bacteria in liquid culture, the aqueous phase inhibited the growth of S. epidermidis. However, the activity against E. coli was lost during extraction. The antimicrobial component of the aqueous phase was heat stable (100°C for 10 min), resistant to proteinase K (15 min at 55°C) and to pronase (30 min at 37°C). The antibacterial activity in the aqueous phase increased the permeability of the cell membrane of susceptible bacterial cells within 30 min. However, lysis of the cells was detected by optical density measurements (OD_{600 nm}) only after 1.5 h. The most evident cytological changes observed by transmission electron microscopy were a thickening of the cell wall and the appearance of numerous electron lucent areas within the cytoplasm of treated bacteria. Gené’s organ, the egg-waxing organ in ticks, grew enormously during the first 16 days post-engorgement, and gained antimicrobial activity by day 10 (when oviposition began). This suggests that Gené’s organ is the major source of the antibacterial substance in the egg wax. The vitellogenic hormone in A. hebraeum, 20-hydroxyecdysone, when injected into recently engorged females, did not stimulate growth of Gené’s organ or precocious secretion of antimicrobial activity.     

Enhancement of the inhibitory effect of an IL‐15 antagonist peptide by alanine scanning

IL‐15 is a proinflammatory cytokine that acts early in the inflammatory response and has been associated with several autoimmune diseases including rheumatoid arthritis, where it had been proposed as a therapeutic target. We recently reported an IL‐15 antagonist peptide corresponding to sequence 36–45 of IL‐15 (KVTAMKCFLL) named P8, which specifically binds to IL‐15Rα and inhibits IL‐15 biological activity with a half maximal inhibitory concentration (IC50) of 130 µ m in CTLL‐2 proliferation assay. In order to improve binding of peptide P8 to the receptor IL‐15Rα, we used an Ala scan strategy to study contribution of each individual amino acid to the peptide's antagonist effect. Here, we found that Phe and Cys are important for peptide binding to IL‐15Rα. We also investigated other single site mutations and replaced the second Lys in the sequence by the polar non‐charged amino acid threonine. The resulting peptide [K6T]P8 exhibited a higher activity than P8 with an IC50 of 24 µm . We also found that this peptide was more active than peptide P8 in the inhibition of TNFα secretion by synovial cells from rheumatoid arthritis patients. The peptide [K6T]P8 described in this work is a new type of IL‐15 antagonist and constitutes a potential therapeutic agent for rheumatoid arthritis. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.     

Assessing the Diversity of Marine Bacterial β-Glucosidases by Capillary Electrophoresis Zymography

We propose a new method for the fast separation and detection of β-glucosidases in environmental samples. With this approach, β-glucosidases extracted from bacteria are evidenced by substrate-incorporated capillary electrophoresis (CE zymography) and their kinetic parameters can be determined by repeated injections using different substrate concentrations. Preliminary results obtained with natural bacterial communities from the coastal North Sea suggest that the diversity of β-glucosidases in the marine environment might be much higher than previously observed.     

Methanol production from lignin-related substances by Phanerochaete chrysosporium

Methanol production resulting from the demethoxylation of lignin-related substances by Phanerochaete chrysosporium K-3 was studied in the presence or absence of glutamic acid in order to determine if methanol formation involved the ligninolytic system of the fungus. The general pattern was that methanol formation, calculated as percentage of theoretical yield, decreased in the order guaiacyl > syringyl > veratryl (3,4-dimethoxy) compounds. Methoxyhydroquinone and vanillic acid were most easily demethoxylated, while methanol production decreased with increasing molecular weight for the same type of structure (i.e. guaiacyl). Glutamic acid inhibited the demethoxylation of many of the compounds tested. The demethoxylation of the 4-methoxy group of veratric acid was particularly inhibited by glutamic acid suggesting a participation of the ligninolytic system, while the 3-methoxy group was influenced to a lesser extent.
The demethoxylating enzyme acting on lignin-related phenols is probably a peroxidase, while the identity of the enzyme demethoxylating dimethoxy compounds is not known with certainty, although a peroxidase type of enzyme reaction is anticipated also here.     

Solubilization of Iron-Containing Minerals by Soil Microorganisms

Eighty-eight strains of microorganisms were isolated from soils collected in northern and southern Chile, and 10 fungi which showed the highest solubilizing action upon the iron in granodiorite were then selected. These fungi were incubated with the following iron-containing minerals: augite, hornblende, biotite, magnetite, hematite, and the igneous rock granodiorite. The solubility of iron in these minerals depended on their nature, crystalline structure, the concentration of metabolic products, or all three. Complex formation could be the mechanism involved, as a strong cation-exchange resin was not able to extract Fe from culture solutions. This conclusion is also confirmed by the R(F) values obtained by thin-layer chromatography of iron-containing culture solutions.     

Recent Studies on Invasive Fungal Diseases in Children and Adolescents: an Update

The improved survival of fragile pediatric hosts such as those afflicted with primary or acquired immune deficiencies, prematurity, and surgical pathology – mainly gastrointestinal and trauma – has resulted in an increased number of children susceptible to invasive fungal infections. These infections are associated with significant morbidity and mortality. Newer, safer antifungal agents allow for preventive and empiric strategies in the management of patients at risk, such as premature infants, patients receiving chemotherapy, and bone marrow or solid-organ transplant recipients. Improved radiological and molecular techniques result in earlier diagnosis of fungal infections, allowing for preemptive therapy in these patients, minimizing exposure to antifungal agents and the risk of emergence of resistant fungal strains. A better understanding of the differences in pharmacokinetics between children and adults will allow for better utilization of existing antifungal agents and improved outcomes.