Iron-Utilization System in Vibrio vulnificus M2799.

Vibrio vulnificus is a Gram-negative pathogenic bacterium that causes serious infections in humans and requires iron for growth. A clinical isolate, V. vulnificus M2799, secretes a catecholate siderophore, vulnibactin, that captures ferric ions from the environment. In the ferric-utilization system in V. vulnificus M2799, an isochorismate synthase (ICS) and an outer membrane receptor, VuuA, are required under low-iron conditions, but alternative proteins FatB and VuuB can function as a periplasmic-binding protein and a ferric-chelate reductase, respectively. The vulnibactin-export system is assembled from TolCV1 and several RND proteins, including VV1_1681. In heme acquisition, HupA and HvtA serve as specific outer membrane receptors and HupB is a sole periplasmic-binding protein, unlike FatB in the ferric-vulnibactin utilization system. We propose that ferric-siderophore periplasmic-binding proteins and ferric-chelate reductases are potential targets for drug discovery in infectious diseases.

Application of electrolysis for inactivation of an antiviral drug that is one of possible selection pressure to drug-resistant influenza viruses.

The recent development of antiviral drugs has led to concern that the release of the chemicals in surface water due to expanded medical use could induce drug-resistant mutant viruses in zoonosis. Many researchers have noted that the appearance of an oseltamivir (Tamiflu(®))-resistant avian influenza mutant virus, which may spread to humans, could be induced by oseltamivir contamination of surface water. Although past studies have reported electrolysis as a possible method for degradation of antineoplastics and antibacterials in water, the validity of the method for treatment of antiviral drugs is unknown. In this study, electrolysis was used to degrade an antiviral prodrug, oseltamivir, and a stable active form, oseltamivir carboxylate, and the degradation process was monitored with HPLC-UV and the neuraminidase inhibitory assay. HPLC-UV-detectable oseltamivir and oseltamivir carboxylate were decomposed by electrolysis within 60 min, and inhibitory activity of neuraminidase decreased below the detection limit of the assay used. Cytotoxic and genotoxic activity were not detected in electrolyzed fluid. These results indicate that electrolysis is a possible treatment for inactivation of the antiviral drug oseltamivir.

Proteomic analysis of Vibrio vulnificus M2799 grown under iron-repleted and iron-depleted conditions.

Vibrio vulnificus is an opportunistic marine bacterium that causes a serious, often fatal, infection in human. An important factor that determines the survival of V. vulnificus in the human body is the ability to acquire iron. The differential expression of proteins in whole-cell lysates of V. vulnificus M2799, a clinical isolate, was evaluated under iron-repleted and iron-depleted conditions during the early, mid and late logarithmic growth phases. A total of 32, 53 and 42 iron-regulated spots were detected by two-dimensional differential gel electrophoresis (2D-DIGE) in the early, mid and late logarithmic growth phases, respectively. Of these, 18 (early logarithmic growth phase), 31 (mid logarithmic growth phase) and 26 (late logarithmic growth phase) proteins were subsequently identified by matrix-assisted laser desorption/ionization-time of flight analysis. These proteins were classified into 10 functional categories, including inorganic ion transport and metabolism, carbohydrate transport and metabolism, and amino acid transport and metabolism. Based on this classification, the expression of proteins involved in the iron acquisition system increased from the early to the mid logarithmic growth phases, while that of proteins involved in other metabolic pathways increased from the mid to the late logarithmic growth phases. Furthermore, when the protein expression profile of the wild type bacterium was compared with that of the fur mutant grown under the iron-repleted condition, the expression of 18 proteins was found to be regulated by iron and Fur.

Structure-activity relationship and biological property of cortistatins, anti-angiogenic spongean steroidal alkaloids.

Previously, bioassay-guided separation led us to isolate eleven novel steroidal alkaloids named cortistatins from the marine sponge Corticium simplex. These cortistatins were classified into three types based on the chemical structure of the side chain part, that is, isoquinoline, N-methyl piperidine or 3-methylpyridine units. From the structure-activity relationship study, the isoquinoline unit in the side chain was found to be crucial for the anti-angiogenic activity of cortistatins. Cortistatin A (1) showed cytostatic growth-inhibitory activity against human umbilical vein endothelial cells (HUVECs). Cortistatin A (1) also inhibited VEGF-induced migration of HUVECs and bFGF-induced tubular formation. Although cortistatin A (1) showed no effect on VEGF-induced phosphorylation of ERK1/2 and p38, which are one of the signaling pathways for migration and tubular formation, the phosphorylation of the unidentified 110kDa protein in HUVECs was inhibited by the treatment with cortistatin A.

Vibrio vulnificus damages macrophages during the early phase of infection.

Vibrio vulnificus is an estuarine bacterium that can cause primary septicemia as well as serious wound infections. Generally, clinical isolates have a high lethal effect compared with environmental isolates. However, little is known about the mechanisms by which V. vulnificus causes disease. In this study, we compared the pathogenicity of a clinical isolate, strain M2799, with that of an environmental isolate, strain JCM3731. The clinical isolate showed 100 times higher lethality in mice than the environmental isolate. In strain M2799-inoculated mice, the number of macrophages decreased significantly, whereas there was no appreciable change in the number of macrophages in strain JCM3731-inoculated mice. The clinical isolate showed high cytotoxic activity, especially to macrophages, compared with the environmental isolate in vitro. The growth of the clinical isolate was almost completely inhibited in the presence of macrophages. Moreover, the survival rate of the clinical isolate-inoculated mice increased by recruitment of macrophages. These results indicate that V. vulnificus infection progresses by damage to macrophages during the early phase of infection.

Biological activity of alpha-thujaplicin, the isomer of hinokitiol.

alpha-Thujaplicin, a minor component of Aomori Hiba (Thujopsis dolabrata SIEB. et ZUCC. var. hondai MAKINO), showed rather strong antifungal activity against seven kinds of plant-pathogenic fungi, their minimum inhibitory concentrations (MICs) being in the range of 12.0-50.0 microg/ml. alpha-Thujaplicin and hinokitiol (the major component of Aomori Hiba) also showed clear antibacterial activity against Legionella pneumophila SG 1 and L. pneumophila SG 3, and their MICs are in the range of 6.25-50 microg/ml. This compound showed strong insecticidal activity against Reticulitermes speratus [50%-lethal concentration (LC(50)): 0.02 g/m(2)], and it also had clear acaricidal activity against Dermatophagoides farinae (LC(50): 0.66 g/m(2)). At 24 h after treatment, alpha-thujaplicin at 0.63 microg/ml inhibited the cell growth of murine P388 lymphocytic leukemia by 78%, and its cytotoxic activity at a concentration higher than 0.63 microg/ml was as high as that of vincristine, used as a positive control. On the other hand, the cytotoxic effect of alpha-thujaplicin at 0.63 microg/ml was weaker than that of vinblastine. In this respect, the strong cytotoxic effect of alpha-thujaplicin on murine P388 lymphocytic leukemia cell line should be emphasized, considering that it has recently been found to be low in toxicity to mice.

Molecular characterization of a high-affinity xylobiose transporter of Streptomyces thermoviolaceus OPC-520 and its transcriptional regulation.

Streptomyces thermoviolaceus OPC-520 secretes two types of xylanases (StxI and StxII), an acetyl xylan esterase (StxIII), and an alpha-L-arabinofuranosidase (StxIV) in the presence of xylan. Xylan degradation products (mainly xylobiose) produced by the action of these enzymes entered the cell and were then degraded to xylose by an intracellular beta-xylosidase (BxlA). A gene cluster involved in xylanolytic system of the strain was cloned and sequenced upstream of and including a BxlA-encoding gene (bxlA). The gene cluster consisted of four different open reading frames organized in the order bxlE, bxlF, bxlG, and bxlA. Reverse transcriptase PCR analysis revealed that the gene cluster is transcribed as polycistronic mRNA. The deduced gene products, comprising BxlE (a sugar-binding lipoprotein), BxlF (an integral membrane protein), and BxlG (an integral membrane protein), showed similarity to components of the bacterial ATP-binding cassette (ABC) transport system; however, the gene for the ATP binding protein was not linked to the bxl operon. The soluble recombinant BxlE protein was analyzed for its binding activity for xylooligosaccharides. The protein showed high-level affinity for xylobiose (K(d) = 8.75 x 10(-9) M) and for xylotriose (K(d) = 8.42 x 10(-8) M). Antibodies raised against the recombinant BxlE recognized the detergent-soluble BxlE isolated from S. thermoviolaceus membranes. The deduced BxlF and BxlG proteins are predicted to be integral membrane proteins. These proteins contained the conserved EAA loop (between the fourth and the fifth membrane-spanning segments) which is characteristic of membrane proteins from binding-protein-dependent ABC transporters. In addition, the bxlR gene located upstream of the bxl operon was cloned and expressed in Escherichia coli. The bxlR gene encoded a 343-residue polypeptide that is highly homologous to members of the GalR/LacI family of bacterial transcriptional regulators. The purified BxlR protein specifically bound to a 4-bp inverted sequence overlapping the -10 region of the bxl operon. The binding of BxlR to the site was inhibited specifically by low concentrations of xylobiose. This site was also present in the region located between stxI and stxIV and in the upstream region of stxII. BxlR specifically bound to the regions containing the inverted sequence. These results suggest that BxlR might act as a repressor of the genes involved not only in the uptake system of xylan degradation products but also in xylan degradation of S. thermoviolaceus OPC-520.

A thermostable laccase from Streptomyces lavendulae REN-7: purification, characterization, nucleotide sequence, and expression.

We found a polyphenoloxidase (PPO) in the cell extract of Streptomyces lavendulae REN-7. About 0.8 mg of purified PPO was obtained from 200 g of the mycelia with a yield of 9.0%. REN-7-PPO showed broad substrate specificity toward various aromatic compounds. Moreover, this enzyme was capable of oxidation of syringaldazine, which is a specific substrate for laccase. Interestingly, REN-7-PPO retained its original activity after 20 min of incubation at even 70 degrees C. The gene encoding the PPO was cloned. Four copper-binding sites characteristics of laccases were contained in the deduced amino acid sequence. We constructed a high-level expression system of this gene in Escherichia coli. The properties of the recombinant enzyme were identical that of wild-type. In conclusion, this PPO is a thermostable laccase.

Biological activity of 4-acetyltropolone, the minor component of Thujopsis dolabrata SIeb. et Zucc. hondai Mak.

4-Acetyltropolone, a minor component of Thujopsis dolabrata SIEB. et Zucc. hondai MAKINO, showed antimicrobial activity against various microorganisms including wood-rotting fungi, a phytogrowth-inhibitory effect with chlorophyll biosynthesis inhibition, cytotoxic effect and inhibitory activity on metalloproteases. This compound had strong antifungal activity on Daedalea dickinsii IFO-4979 [minimum inhibitory concentration (MIC): 0.2 microg/ml] and Coriolus versicolor IFO-4940 (MIC: 0.39 microg/ml). Its cytotoxic effect at 20.0/microg/ml on human stomach cancer KATO-III and Ehrich's ascites carcinoma was stronger than those of podophyllotoxin, vincristine and vinblastine, the anticancer agents isolated from higher plants and used clinically. This compound also had potent antibacterial activity against Staphylococcus epidermidis IFO-12993, its MIC being 1.56 microg/ml. However, other biological activities of 4-acetyltropolone were lower than those of hinokitiol which is the main component of this plant, suggesting that the contribution of the acetyl group at C-4 to biological activity is smaller than that of the isopropyl group at that position. The acute toxicity of 4-acetyltropolone (LD50: 335.2 mg/kg) to mice was much lower than that of hinokitiol (LD50: 191 mg/kg).