Conidia production of Beauveria sp. by solid-state fermentation for biocontrol of Ilex paraguariensis caterpillars.

Conidia production of Beauveria sp. strain LAG by solid-state fermentation (SSF) using blends of agro-industrial residues (residual potatoes and sugar-cane bagasse) was optimized with respect to cultivation conditions and the composition of substrate mixture in Erlenmeyer flasks and column-type bioreactor. With a blend of 60 % residual potatoes and 40 % sugar-cane bagasse the optimum conditions achieved were: incubation temperature 26 degrees C, initial substrate pH 6, inoculum concentration 10(7) conidia per g substrate; optimal initial moisture of the substrate was 70 % for Erlenmeyer flasks, in column-type bioreactor (with forced aeration) the optimal initial moisture of the substrate was 65 % with airflow of 60 mL/min. The highest production (1.07 x 10(10) conidia per g dry substrate) was achieved after a 10-d fermentation. The conidia were used in laboratory assays against Thelosia camina and Hylesia sp., caterpillars that are serious pests of mate plants. The mortality of T. camina was >90 % 10 d after spraying caterpillars with 1 mL conidia suspension at a concentration 10(5)-10(8)/mL. For Hylesia sp., the mortality was 70 %, 7 d after immersion in the conidia suspension containing 108 conidia per mL. Therefore, the Beauveria sp. LAG can be considered to be an important biocontrol instrument in the prospect of the Integrated Pest Management for mate plants.

Synthesis and antimicrobial activity of the symmetric dimeric form of Temporin A based on 3-N,N-di(3-aminopropyl)amino propanoic acid as the branching unit.

Dimeric derivative of antimicrobial peptide amide Temporin A (TA) was synthesized by using a new branching unit 3-N,N-di(3-aminopropyl)amino propanoic acid (DAPPA), which allows building of the parallelly symmetric alpha-helical structures. Antimicrobial effect of the original peptide amide, its monomeric carboxy (TAc) and novel dimeric (TAd) analogues were tested against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). Both TA and TAd completely inhibited the growth of S. aureus at the concentrations of 5 and 10 microM, respectively, whereas TAc did not show any inhibitory activity. The activities of TAc, TA and TAd correlate directly with the net charges of the molecules, +1, +2 and +4, respectively. Interestingly, TAd displayed antibacterial effect against E. coli at a concentration of 10 microM, where as monomeric TA did not show any activity at concentration as high as 20 microM. The results indicate that the novel structural modification improves the antibacterial properties of Temporin A especially towards Gram-negative bacteria.

Folding of alpha(r)beta and epsilonbeta reverse turns; a nanosecond molecular dynamics simulation of the hexapeptide MSALNT and the octapeptide NMSALNTL in water.

Folding of the hexapeptide MSALNT and the octapeptide NMSALNTL were investigated using 2.8 ns molecular dynamics (MD) simulations in aqueous solution. In the simulation, the central sequence SALN of the hexapeptide folded rapidly within 200 ps into an alpha(r)beta turn conformation (type VIII conformation) and remained in this conformation for the rest of the trajectory. The sequence SALN of the octapeptide needed 2 ns to fold via epsilonbeta conformations into a similar conformation. The results join the sequences into a growing group of sequences which have a tendency to form secondary structures and thereby to direct protein folding. The structures of the reverse turn conformations were in accordance with the experimental results (Hakalehto et al., Eur J. Biochem. 250, 19-29 (1997)). The main driving force of folding seems to be the hydrophobic interaction between the side chains of Ala and Leu at the i+1 and i+2 positions of the beta-turn.

A bovine dander allergen, comparative modeling, and similarities and differences in folding with related proteins.

The most important allergenic protein in cow dander and urine is Bos d 2. It is proposed to belong to the family of lipocalins, which are proteins capable of binding small hydrophobic molecules. The allergenic properties of Bos d 2 indicate an interaction between the accessible regions of the native protein and IgE. In this work, a three-dimensional model was created for Bos d 2 by comparative modeling, and features characteristic of outlier lipocalins were observed. The protruding regions of the surface were characterized and used in predicting the possible B-cell epitopes. There is a pocket inside the core and its size is appropriate for small molecules. The model shows a hydrophilic amino acid side chain of glutamic acid 115 on the inner surface of the hole and a phenylalanine as the "gatekeeper" instead of tyrosine, which is common in experimentally modeled lipocalins.

Comparison of the lethal effects of different actinomycins on a repair-deficient strain of Escherichia coli.

We report here the isolation and purification of a genotoxic antibiotic from the culture medium of a Streptomyces strain. The antibiotic was identified as actinomycin X2 by using a database search (AntiBase). In the previous studies a related compound, actinomycin D, has been shown to be non-mutagenic in the salmonella/microsome assay and several other bacterial systems. The fact that an actinomycin was detected by a bacterial repair assay seems to contradict these results. Therefore we tested several actinomycins by differential killing assay based on the same Escherichia coli strains that were used in our screening bioassays. According to our results the uvrA, recA double mutant sensitizes E. coli to the genotoxic effects of actinomycins.

Identification of a common structural motif in the disordered N-terminal region of bacterial flagellins--evidence for a new class of fibril-forming peptides.

Flagellin proteins lacking the N- or C-terminus form polymers of reduced filament stability and straight morphology, in contrast to the coiled native flagella. In the present study, the N-terminal amino acid sequence of flagellins of the anaerobic beer spoilage bacteria Pectinatus cerevisiiphilus and Pectinatus frisingiensis as well as Enterobacter aerogenes and Pseudomonas sp. were determined. Sequence similarity was revealed between these and the N-termini of all known eubacterial flagellins. Synthetic peptides corresponding to the first 15 amino acid residues of the flagellins of Pectinatus, Campylobacter jejuni, E. aerogenes or Proteus mirabilis flagellins had a spontaneous tendency under physiological conditions to form 4-6 nm broad, 1-2 microm long fibrillar structures that had a tendency to form clusters. In contrast, the Pectinatus peptide missing residues 1-3 did not form fibrils. The peptide missing residues 13-15 formed fibrils less easily, and the peptide missing residues 11-15 formed fibrils almost without clustering. In electron micrographs, the fibrillisation of the bacterial flagellar peptides resembled that of beta-amyloid and prion peptides. 1H-NMR and infrared spectroscopy studies with homology analysis indicate that although the flagellar N-terminal peptides are flexible with many conformational minima, they have a significant tendency to form beta-type structures and a loop in the middle of the peptide. The hydrophobic character of the N-terminus together with the property of forming a conserved beta-strand-loop-beta-strand motif may be related to a mechanism involved in attaining the proper morphology and stability of the flagellar filament, by providing a device for facilitating the attachment of the flagellin monomers to each other. The flagellar peptides represent a new class of fibril-forming peptides.

Reactions of hydrated formaldehyde in nasal mucus.

Formaldehyde is a well known toxic air impurity affecting the upper respiratory tract. It rapidly forms methylene glycol in water. Reactions of the hydrated formaldehyde with nasal mucus were studied by C-13 NMR spectroscopy. In the NMR spectra methylene glycol dominated and only minor signals from possible reactions were observed. This finding suggests that nasal mucus effectively protects nasal epithelium against formaldehyde.