Bacteria Micrococcus Luteus Research Articles

Different forms of apolipophorin III in Galleria mellonella larvae challenged with bacteria and fungi

Apolipophorin III (apoLp-III), a lipid-binding protein and an insect homolog of human apolipoprotein E, plays an important role in lipid transport and immune response in insects. In the present study, we have demonstrated a correlation in time between changes in the apoLp-III abundance occurring in the hemolymph, hemocytes, and fat body after immunization of Galleria mellonella larvae with Gram-negative bacteria Escherichia coli, Gram-positive bacteria Micrococcus luteus, yeast Candida albicans, and a filamentous fungus Fusarium oxysporum. Using two-dimensional electrophoresis (IEF/SDS-PAGE) and immunoblotting with anti-apoLp-III antibodies, the profile of apoLp-III forms in G. mellonella larvae challenged with the bacteria and fungi has been analyzed. Besides the major apoLp-III protein (pI=6.5), one and three additional apoLp-III forms differing in the pI value have been detected, respectively, in the hemolymph, hemocytes, and fat body of non-immunized insects. Also, evidence has been provided that particular apoLp-III-derived polypeptides appear after the immune challenge and are present mainly in the hemolymph and hemocytes. The time of their appearance and persistence in the hemolymph was dependent on the pathogen used. At least two of the apoLp-III forms detected in hemolymph bound to the microbial cell surface. The increasing number of hemolymph apoLp-III polypeptides and differences in their profiles observed in time after the challenge with different immunogens confirmed the important role of apoLp-III in discriminating between pathogens by the insect defense system and in antibacterial as well as antifungal immune response.

Candida and Fusarium species known as opportunistic human pathogens from customer-accessible parts of residential washing machines

Energy constraints have altered consumer practice regarding the use of household washing machines. Washing machines were developed that use lower washing temperatures, smaller amounts of water and biodegradable detergents. These conditions may favour the enrichment of opportunistic human pathogenic fungi. We focused on the isolation of fungi from two user-accessible parts of washing machines that often contain microbial biofilms: drawers for detergents and rubber door seals. Out of 70 residential washing machines sampled in Slovenia, 79% were positive for fungi. In total, 72 strains belonging to 12 genera and 26 species were isolated. Among these, members of the Fusarium oxysporum and Fusarium solani species complexes, Candida parapsilosis and Exophiala phaeomuriformis represented 44% of fungi detected. These species are known as opportunistic human pathogens and can cause skin, nail or eye infections also in healthy humans. A machine learning analysis revealed that presence of detergents and softeners followed by washing temperature, represent most critical factors for fungal colonization. Three washing machines with persisting malodour that resulted in bad smelling laundry were analysed for the presence of fungi and bacteria. In these cases, fungi were isolated in low numbers (7.5 %), while bacteria Micrococcus luteus, Pseudomonas aeruginosa, and Sphingomonas species prevailed.

Carboxymethylcellulose acetate butyrate/poly(4-vinyl-N-pentyl pyridinium bromide) blends as antimicrobial coatings

Blends of carboxymethyl cellulose acetate butyrate (CMCAB), a cellulose derivative, and poly(4-vinyl-N-pentyl pyridinium bromide) (QPVP-C5), an antimicrobial polymer, were prepared by casting method and characterized by means of Fourier transform infrared vibrational spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and contact angle measurements. Miscibility between CMCAB and QPVP-C5 was evidenced by DSC measurements of blends, which showed a single thermal event of Tg, and SEM images, which revealed homogenous morphology, regardless the blend composition. Moreover, thermal stability of QPVP-C5 was substantially enhanced, when it was mixed with CMCAB. Upon increasing the QPVP-C5 content in the blend the wettabil- ity and antimicrobial activity against Gram-positive bacteria Micrococcus luteus increased, indicating the surface enrich- ment by pyridinium groups. In fact, blends with 70 wt% QPVP-C5 reduced 5 log and 4 log the colony-forming units of Micrococcus luteus and Escherichia coli, respectively.

Tailoring, physicochemical characterization, antibacterial and DNA binding mode studies of Cu(II) Schiff bases amino acid bioactive agents incorporating 5-bromo-2-hydroxybenzaldehyde

Five novel Cu(II) complexes derived from the condensation between 5-bromosalicylaldehyde (bs) and α-amino acids (L-alanine, l-phenylalanine, L-aspartic acid, L-histidine and L-arginine) were synthesized and characterized by their elemental analyses, thermogravimetric analysis, IR, mass and electronic spectra, conductance and magnetic measurements. Moreover, the stoichiometry and the stability constants of the prepared complexes have been determined spectrophotometrically using continuous variation and molar ratio methods. The obtained results indicated that the Schiff bases of the amino acids: L-alanine, L-phenylalanine, L-histidine and L-arginine behave as tridentate ligands. The ligands are coordinating with the Cu(II) via azomethine nitrogen, deprotonated carboxylate oxygen and phenolic oxygen. However, in the case of L-aspartic, the ligand acts as tetradentate due to the coordination of the second carboxylate group. Based on the studies of magnetic moments and electronic spectra, a square planar geometry has been proposed for all Cu(II) complexes except bromsalicylaldehydine aspartate complex which has a distorted tetrahedral structure. The representative Schiff bases and their Cu(II) complexes were tested in vitro for their antibacterial activity against two Gram-positive bacteria (Micrococcus luteus and Bacillus cereus) and one Gram-negative bacteria (Pseudomonas aeruginosa). All the complexes showed activity against the organisms more than the free Schiff base ligands and the activity increases with the increase in concentration of test solution containing the new complexes. Moreover, the interaction of the prepared Schiff base amino acid Cu(II) complexes with calf thymus DNA has been investigated by absorption spectra, viscosity and gel electrophoresis measurement and the mode of CT-DNA binding to the complexes has been explored. The investigated complexes exhibit cooperative binding and presumably intercalate into DNA and follow the trend: bsarc>bshc>bsalc>bsphalc>bsasc.

Synthesis, characterization and antimicrobial activity of N,N-bis(hydroxymethyl)-N-[(2-mercaptoacetoxy)methyl]alkyl ammonium bromide surfactant and their Co(II), Zn(II) and Sn(II) complexes

Two-membered cationic surfactants namely: N,N-bis(hydroxymethyl)-N-[(2-mercaptoacetoxy)methyl)dodecane ammonium bromide (C12Q) and N,N-bis(hydroxymethyl)-N-[(2-mercaptoacetoxy)methyl]hexadecane ammonium bromide (C16Q) and their cobalt, tin and zinc complexes (C12QCo, C12QSn, C12QZn, C16QCo, C16QSn and C16QZn) were synthesized. The chemical structures of the synthesized compounds were confirmed using different spectroscopy tools. The surface activities of the synthesized surfactants were influenced by their chemical structures and the type of the transition metals. The synthesized cationic surfactants and their metal complexes were evaluated as biocides against Gram- positive bacteria (Bacillus subtilis and Micrococcus luteus), Gram-negative bacteria (Bordetella pertussis and Escherichia coli) and fungi (Candida albicans and Aspergillus niger), while the sulfate-reducing bacteria were tested against Desulfomonas pigra. The biological activity results showed that the cationic surfactants exhibit moderate to high efficiency against the tested microorganisms. The antimicrobial activity was strongly increased by complexation of these cationic surfactants with Co(II), Sn(II) and Zn(II) ions. The antimicrobial activity of the synthesized compounds against sulfate-reducing bacteria showed promising results in the field of biocides application.

Biosynthetically Distinct Cytotoxic Polyketides from Setophoma terrestris.

Sixteen polyketides belonging to diverse structural classes, including monomeric/dimeric tetrahydroxanthones and resorcylic acid lactones, were isolated from an organic extract of a fungal culture Setophoma terrestris (MSX45109) using bioactivity-directed fractionation as part of a search for anticancer leads from filamentous fungi. Of these, six were new: penicillixanthone B (5), blennolide H (6), 11-deoxy blennolide D (7), blennolide I (9), blennolide J (10), and pyrenomycin (16). The known compounds were: secalonic acid A (1), secalonic acid E (2), secalonic acid G (3), penicillixanthone A (4), paecilin B (8), aigialomycin A (11), hypothemycin (12), dihydrohypothemycin (13), pyrenochaetic acid C (14), and nidulalin B (15). The structures were elucidated using a set of spectroscopic and spectrometric techniques; the absolute configurations of compounds 1-10 were determined using ECD spectroscopy combined with time-dependent density functional theory (TDDFT) calculations, while a modified Mosher's ester method was used for compound 16. The cytotoxic activities of compounds (1-15) were evaluated using the MDA-MB-435 (melanoma) and SW-620 (colon) cancer cell lines. Compounds 1, 4, and 12 were the most potent with IC50 values ranging from 0.16 to 2.14 μM. When tested against a panel of bacteria and fungi, compounds 3 and 5 showed promising activity against the Gram-positive bacterium Micrococcus luteus with MIC values of 5 and 15 μg/mL, respectively.

Multifunctional cellulose beads and their interaction with gram positive bacteria.

Cellulose beads with ∼3 mm of diameter and high circularity were obtained by dripping cellulose solutions (5, 6, and 7 wt %) dissolved in NaOH7%/urea12%, into HCl 2 M coagulation bath. Carboxylic groups were generated on beads surface through NaClO/NaClO2/TEMPO oxidation method, achieving total charge density of ∼0.77 mmol/g. Pristine (CB) and oxidized (OCB) beads were characterized by means of optical images analyses, scanning electron microscopy (SEM) and compression tests. Both types of beads, CB and OCB, were used as adsorbent for poly(4-vinyl-N-pentylpyridinium) bromide, QPVP-C5, a bactericidal agent. The adsorption of QPVP-C5 on CB and OCB was evaluated by means of FTIR-ATR, UV-vis, CHN elemental analyses, and X-ray photoelectron spectroscopy (XPS). The adsorbed amount of QPVP-C5 was remarkably higher on OCB than on CB due to ionic interactions. Desorption was less than 5%. The interaction between neat OCB or OCB coated and two different amounts of QPVP-C5 and Gram-positive bacteria Micrococcus luteus was assessed by changes in turbidimetry, SEM, and elemental analyses. Bacteria adsorbed on the surface of neat OCB and weakly QPVP-C5 coated OCB due to hydrogen bonding or ion-dipole interaction. Notorious bactericidal action was observed for OCB samples coated with large amount of QPVP-C5.

Efficient enzymatic systems for synthesis of novel α-mangostin glycosides exhibiting antibacterial activity against Gram-positive bacteria.

Two enzymatic systems were developed for the efficient synthesis of glycoside products of α-mangostin, a natural xanthonoid exhibiting anti-oxidant, antibacterial, anti-inflammatory, and anticancer activities. In these systems, one-pot reactions for the synthesis of UDP-α-D-glucose and UDP-α-D-2-deoxyglucose were modified and combined with a glycosyltransferase (GT) from Bacillus licheniformis DSM-13 to afford C-3 and C-6 position modified glucose and 2-deoxyglucose conjugated novel α-mangostin derivatives. α-Mangostin 3-O-β-D-glucopyranoside, α-mangostin 6-O-β-D-glucopyranoside, α-mangostin 3,6-di-O-β-D-glucopyranoside, α-mangostin 3-O-β-D-2-deoxyglucopyranoside, α-mangostin 6-O-β-D-2-deoxyglucopyranoside, and α-mangostin 3,6-di-O-β-D-2-deoxyglucopyranoside were successfully produced in practical quantities and characterized by high-resolution quadruple time-of-flight electrospray ionization-mass spectrometry (HR-QTOF ESI/MS), (1)H and (13)C NMR analyses. In excess of the substrate, the maximum productions of three α-mangostin glucopyranosides (4.8 mg/mL, 86.5 % overall conversion of α-mangostin) and three α-mangostin 2-deoxyglucopyronosides (4.0 mg/mL, 79 % overall conversion of α-mangostin) were achieved at 4-h incubation period. All the α-mangostin glycosides exhibited improved water solubility, and their antibacterial activity against three Gram-positive bacteria Micrococcus luteus, Bacillus subtilis, and Staphylococcus aureus was drastically enhanced by the glucosylation at C-3 position. In this study, diverse glycosylated α-mangostin were produced in significant quantities by using inexpensive starting materials and recycling co-factors within a reaction vessel without use of expensive NDP-sugars in the glycosylation reactions.

The effects of dietary vitamin C on mucosal immune responses and growth performance in Caspian roach (Rutilus rutilus caspicus) fry.

This study was conducted to investigate the effects of different levels of dietary vitamin C on some skin mucus immune parameters, mucus antimicrobial activity and growth performance of Caspian roach (Rutilus rutilus caspicus) fry. Six hundred sixty Caspian roach (1.4 ± 0.02 g) fry were allocated to 12 tanks (55 fish per tank), and triplicate groups were fed diets containing 0, 1,000, 1,500 and 2,000 mg kg(-1) vitamin C for 60 days. At the end of the trial, the epidermal mucus protein level, alkaline phosphatase and antimicrobial activity against two gram-positive bacteria (Streptococcus faecium and Micrococcus luteus) and gram-negative bacteria (Escherichia coli and Serratia marcescens) as well as growth performance were measured. The results demonstrated that feeding on vitamin C significantly elevated skin mucus alkaline phosphatase and protein levels compared to the control group (P < 0.05). However, lysozyme activity was undetectable in both the vitamin C-fed roach fry and the control group. Skin mucus antimicrobial activity was increased following vitamin C administration, and the bacterial growth inhibition zones were significantly elevated in vitamin C-fed roach (P < 0.05). Similar results were obtained in case of the minimum inhibitory concentration of skin mucus. Also fish fed the control diet had a significantly lower weight gain, specific growth rate and condition factor compared to the other treatments (P < 0.05). These results revealed that dietary vitamin C beneficially affects the skin mucus immune parameters and growth performance of Caspian roach fry.

Characterization and function analysis of an anti-lipopolysaccharide factor (ALF) from the Chinese shrimp Fenneropenaeus chinensis

Anti-lipopolysaccharide factor (ALF) is one of the widely-studied antimicrobial peptides (AMPs) with broad-spectrum antibacterial activity and antiviral property. Previous studies show the existence of multiform of ALFs in crustacean which are important for immunity of the animals. In the present study, we characterized one isoform of ALF from the Chinese shrimp Fenneropenaeus chinensis (FcALF2). Tissue distribution analysis revealed that FcALF2 showed the highest expression level in the lymphoid organ (Oka) of the shrimp. The expression level of FcALF2 in shrimp was significantly up-regulated when they were injected with Micrococcus lysodeikticus and Vibrio anguillarum. A peptide corresponding to the LPS-binding domain of FcALF2 (FcALF2-LBD) was synthesized to analyze its antimicrobial activities. Data demonstrated that FcALF2-LBD possessed strong antibacterial activity against Gram-positive bacteria Micrococcus luteus and M.lysodeikticus with MIC ranges of 2–4μM and 1–2μM respectively and significant inhibition activity against white spot syndrome virus (WSSV). The antibacterial activities of the sequence modified peptides (FcALF2-LBDb, FcALF2-LBDv) were apparently enhanced and broadened after the amount of basic amino acids was increased in the synthetic LPS-binding domain. These data provide more insights into understanding the function of LPS-binding domain of ALF and the role of ALF in shrimp immunity.

Synthesis, Antimicrobial Evaluation, and Structure–Activity Relationship of α-Pinene Derivatives

Several (+)- and (-)-α-pinene derivatives were synthesized and evaluated for their antimicrobial activity toward Gram-positive bacteria Micrococcus luteus and Staphylococcus aureus, Gram-negative bacterium Escherichia coli, and the unicellular fungus Candida albicans using bioautographic assays. (+)-α-Pinene 1a showed modest activity against the test organisms, whereas (-)-α-pinene 1b showed no activity at the tested concentration. Of all the α-pinene derivatives evaluated, the β-lactam derivatives (10a and 10b) were the most antimicrobial. The increase in the antimicrobial activity of 10a compared to 1a ranged from nearly 3.5-fold (C. albicans) to 43-fold (S. aureus). The mean ± standard deviation for the zone of inhibition (mm) for 10a (C. albicans) was 31.9 ± 4.3 and that for S. aureus was 51.1 ± 2.9. Although (-)-α-pinene 1b was not active toward the test microorganisms, the corresponding β-lactam 10b, amino ester 13b, and amino alcohol 14b showed antimicrobial activity toward the test microorganisms. The increase in the antimicrobial activity of 10b compared to 1b ranged from 32-fold (S. aureus) to 73-fold (M. luteus). The mean ± standard deviation for the zone of inhibition (mm) for 10b (S. aureus) was 32.0 ± 0.60 and that for M. luteus was 73.2 ± 0.30.

Modification of a synthetic LPS-binding domain of anti-lipopolysaccharide factor from shrimp reveals strong structure-activity relationship in their antimicrobial characteristics

Anti-lipopolysaccharide factor (ALF) is a small protein with broad-spectrum antimicrobial activities and certain antiviral property. Its putative lipopolysaccharide (LPS) binding domain was deduced to be important for its activities. However, there is still no report revealing how the structure of the LPS-binding domain affects its biological function until now. In the present study, we designed and synthesized a peptide corresponding to the LPS-binding domain of ALF from the Chinese shrimp (designated as FcALF-LBDc) and its structure-modified isoforms in order to analyze the relationship between its structure and antimicrobial activities. Results showed that FcALF-LBDc exhibited apparent antibacterial activities against both Gram-negative bacteria Escherichia coli and Vibrio anguillarum and Gram-positive bacteria Micrococcus luteus and Micrococcus lysodeikticus with MIC ranges of 32–64, 2–4, 1–2, and 32–64μM, respectively. The disulfide loop and the basic amino acids in the LPS-binding domain (LBD) of ALF played key roles in its antibacterial activities. In addition, FcALF-LBDc could reduce the propagation of white spot syndrome virus (WSSV) in vivo, and its lysine residue is indispensable for its antiviral property. This is the first attempt to testify the effects of the sequence features of the LPS-binding domain on its antimicrobial activities.

Capillary electrophoresis of microbial aggregates

Uncontrolled aggregation of bacterial cells is a significant disadvantage of electrophoretic separations. Various aspects of the electrophoretic behavior of different strains of Gram-positive Bacillus cereus, Bacillus subtilis, Sarcina lutea, Staphylococcus aureus(1), and Micrococcus luteus bacteria and Gram-negative Escherichia coli bacteria were investigated in this study. Our findings indicate that bacteria can be rapidly analyzed by CZE with surface charge modification by calcium ions (Ca(2+)). Bound Ca(2+) ions increase zeta potential to more than 2.0 mV and significantly reduce repulsive forces. Under the above conditions, bacterial cells create compact aggregates, and fewer high-intensity signals are observed in electropherograms. The above can be attributed to the bridging effect of Ca(2+) between bacterial cells. CE was performed to analyze bacterial aggregates in an isotachophoretic mode. A single peak was observed in the electropherogram.

Transcriptome Profiling Analysis on Whole Bodies of Microbial Challenged Eriocheir sinensis Larvae for Immune Gene Identification and SNP Development

To study crab immunogenetics of individuals, newly hatched Eriocheir sinensis larvae were stimulated with a mixture of three pathogen strains (Gram-positive bacteria Micrococcus luteus, Gram-negative bacteria Vibrio alginolyticus and fungi Pichia pastoris; 108 cfu·mL-1). A total of 44,767,566 Illumina clean reads corresponding to 4.52 Gb nucleotides were generated and assembled into 100,252 unigenes (average length: 1,042 bp; range: 201-19,357 bp). 17,097 (26.09%) of 65,535 non-redundant unigenes were annotated in NCBI non-redundant protein (Nr) database. Moreover, 23,188 (35.38%) unigenes were assigned to three Gene Ontology (GO) categories, 15,071 (23.00%) to twenty-six Clusters of orthologous Groups (COG) and 8,574 (13.08%) to six Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, respectively. Numerous genes were further identified to be associated with multiple immune pathways, including Toll, immune deficiency (IMD), janus kinase (JAK)-signal transducers and activators of transcription (STAT) and mitogen-activated protein kinase (MAPK) pathways. Some of them, such as tumor necrosis factor receptor associated factor 6 (TRAF6), fibroblast growth factor (FGF), protein-tyrosine phosphatase (PTP), JNK-interacting protein 1 (JIP1), were first identified in E. sinensis. TRAF6 was even first discovered in crabs. Additionally, 49,555 single nucleotide polymorphisms (SNPs) were developed from over 13,309 unigenes. This is the first transcriptome report of whole bodies of E. sinensis larvae after immune challenge. Data generated here not only provide detail information to identify novel genes in genome reference-free E. sinensis, but also facilitate our understanding on host immunity and defense mechanism of the crab at whole transcriptome level.

Sulfur-containing components of supercritical garlic extracts and their synthetic analogs as potential biocides

We have shown that a specific component of supercritical (SC) garlic extract and some synthetic disulfide analogs are active as antimicrobials. In the course of this study, six compounds (diallyl disulfide, 1-propenylallyl disulfide, methylallyl disulfide, diallyl trisulfide, 2-vinyl-4H-1,3-dithiin, and 3-vinyl-4H-1,2-dithiin) were isolated from SC garlic extract and identified. Also, two novel sulfoxide-containing garlic analogs were synthesized. All isolated and synthetic substances were tested as potential antimicrobials against gram-positive bacteria Bacillus cereus, Mycobacterium smegmatis, and Micrococcus luteus and gram-negative bacteria Pseudomonas aurantiaca. Diallyl disulfide and diallyl trisulfide exhibited the best activity against both gram-positive and gram-negative bacteria.

Transcriptome Analysis and Discovery of Genes Involved in Immune Pathways from Hepatopancreas of Microbial Challenged Mitten Crab Eriocheir sinensis

BackgroundThe Chinese mitten crab Eriocheir sinensis is an important economic crustacean and has been seriously attacked by various diseases, which requires more and more information for immune relevant genes on genome background. Recently, high-throughput RNA sequencing (RNA-seq) technology provides a powerful and efficient method for transcript analysis and immune gene discovery.Methods/Principal FindingsA cDNA library from hepatopancreas of E. sinensis challenged by a mixture of three pathogen strains (Gram-positive bacteria Micrococcus luteus, Gram-negative bacteria Vibrio alginolyticus and fungi Pichia pastoris; 108 cfu·mL−1) was constructed and randomly sequenced using Illumina technique. Totally 39.76 million clean reads were assembled to 70,300 unigenes. After ruling out short-length and low-quality sequences, 52,074 non-redundant unigenes were compared to public databases for homology searching and 17,617 of them showed high similarity to sequences in NCBI non-redundant protein (Nr) database. For function classification and pathway assignment, 18,734 (36.00%) unigenes were categorized to three Gene Ontology (GO) categories, 12,243 (23.51%) were classified to 25 Clusters of Orthologous Groups (COG), and 8,983 (17.25%) were assigned to six Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Potentially, 24, 14, 47 and 132 unigenes were characterized to be involved in Toll, IMD, JAK-STAT and MAPK pathways, respectively.Conclusions/SignificanceThis is the first systematical transcriptome analysis of components relating to innate immune pathways in E. sinensis. Functional genes and putative pathways identified here will contribute to better understand immune system and prevent various diseases in crab.

A Novel Beta-Defensin Antimicrobial Peptide in Atlantic Cod with Stimulatory Effect on Phagocytic Activity

A novel defensin antimicrobial peptide gene was identified in Atlantic cod, Gadus morhua. This three exon/two intron defensin gene codes for a peptide precursor consisting of two domains: a signal peptide of 26 amino acids and a mature peptide of 40 residues. The mature cod defensin has six conserved cysteine residues that form 1–5, 2–4 and 3–6 disulphide bridges. This pattern is typical of beta-defensins and this gene was therefore named cod beta-defensin (defb). The tertiary structure of Defb exhibits an α/β fold with one α helix and β1β2β3 sheets. RT-PCR analysis indicated that defb transcripts were present mainly in the swim bladder and peritoneum wall but could also be detected at moderate to low levels in skin, head- and excretory kidneys. In situ hybridisation revealed that defb was specifically expressed by cells located in the swim bladder submucosa and the oocytes. During embryonic development, defb gene transcripts were detectable from the golden eye stage onwards and their expression was restricted to the swim bladder and retina. Defb was differentially expressed in several tissues following antigenic challenge with Vibrio anguillarum, being up-regulated up to 25-fold in head kidney. Recombinant Defb displayed antibacterial activity, with a minimal inhibitory concentration of 0.4–0.8 µM and 25–50 µM against the Gram-(+) bacteria Planococcus citreus and Micrococcus luteus, respectively. In addition, Defb stimulated phagocytic activity of cod head kidney leucocytes in vitro. These findings imply that beta-defensins may play an important role in the innate immune response of Atlantic cod.

Bacterial infection activates the immune system response and dysregulates microRNA expression in honey bees

In insects, a rapid and massive synthesis of antimicrobial peptides (AMPs) is activated through signaling pathways (Toll and Imd) to combat invading microbial pathogens. However, it is still unclear whether different types of bacteria provoke specific responses. Immune response mechanisms and the activation of specific genes were investigated by challenging Apis mellifera workers with the Gram-negative bacterium Serratia marcescens or the Gram-positive bacterium Micrococcus luteus. The immune system responded by activating most genes of the Toll and Imd pathways, particularly AMP genes. However, genes specifically regulated by M. luteus or S. marcescens were not detected, suggesting an interaction between the signaling pathways that lead to immune effectors synthesis. Despite this finding, kappaB motifs in the 5′-UTRs of selected genes suggest a pathway-specific control of AMP and transferrin-1 gene expression. Regulation by miRNAs was also investigated and revealed a number of candidates for the post-transcriptional regulation of immune genes in bees.

English

Tecoma stans of the Bignoniaceae family, is an important medicinal plant. Different extracts of the leaves and branches of T. stans were evaluated as antibacterial potential against the growth of some human bacterial strains using the disc diffusion and minimum inhibitory concentration (MIC) methods as well as the antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Total phenolic and total flavonoid contents weredetermined. The different extracts of T. stans were obtained by successive solvent extraction with methanol and its fractions; ethyl acetate (EtOAc), chloroform (CHCl3), n-butanol and aqueous. The methanol, EtOAc and CHCl3 extracts of T. stans showed significant effect against the tested bacteria (Bacillus subtilis, Micrococcus luteus,Sarcina lutea, Staphylococcus aureus, Escherichia coli, Serratia marcescens,Salmonella typhi, Proteus vulgaris and Pseudomonas aeruginosa). The methanol extract of the leaves exhibited the highest amount of total phenolics (50.3±3 mg gallic acid equivalents/g extract) and flavonoids (40.66±5.03 mg catechin equivalents/g extract). The EtOAc fraction of leaves and branches extracts showed the highest total antioxidant activity (%) with 83.4±0.31 and 82.06±0.54%, respectively followed by CHCl3 fraction of leaves extracts (79.17±0.20%). These findings provide scientific evidence to support traditional medicinal uses of T. stans and indicate a promising potential for the development of an antibacterial and antioxidant agent from T. stans trees. Key words: Antioxidant activity, antibacterial activity, total phenolics, total flavonoids,Tecoma stans

Structure determination of the bioactive depsipeptide xenobactin from Xenorhabdus sp. PB30.3

A new hexadepsipeptide called xenobactin (1) was isolated from Xenorhabdus sp. PB30.3. Structure elucidation was performed after isolation by extensive 1D- and 2D-NMR experiments. To determine the absolute configuration of the amino acids, modifications of the advanced Marfey's method were applied avoiding racemization and additionally allowing the stereochemical assignment of tryptophan. Moreover, the three dimensional structure was modeled by ROE derived constraints and molecular dynamics runs. The major conformation was verified by comparison of the modeled and experimentally predicted hydrogen bonds. Moreover, bioactivity testing of 1 revealed good antiprotozoal activity against Plasmodium falciparum and a specific antibiotic activity against the Gram positive bacterium Micrococcus luteus, whereas no cytotoxicity could be observed.