Endophenazines A-D, new phenazine antibiotics from the arthropod associated endosymbiont Streptomyces anulatus. I. Taxonomy, fermentation, isolation and biological activities.
(41/571)
Four new members of the phenazine family, endophenazines A-D, and the already known phenazine-1-carboxylic acid (tubermycin B) were detected in the culture broth of various endosymbiotic Streptomyces anulatus strains by chemical screening in a combination of TLC-staining reagents and HPLC-diode array analysis. The endosymbiotic strains were isolated from four different arthropod hosts at various sites. The new phenazine compounds showed antimicrobial activities against Gram-positive bacteria and some filamentous fungi, and herbicidal activity against Lemna minor (duckweed). (+info)
Endophenazines A-D, new phenazine antibiotics from the athropod associated endosymbiont Streptomyces anulatus II. Structure elucidation.
(42/571)
A detailed screening of the secondary metabolite pattern produced by different athropod associated strains of the species Streptomyces anulatus resulted in the isolation and structure elucidation of the endophenazines A-D (2, 4-6). The structures were assigned by spectroscopic methods and chemical transformations. 4 represents a chromophoric system based on a phenazin-7-one, 5 and 6 are new 5,10-dihydrophenazine derivatives. (+info)
Inactivation of gacS does not affect the competitiveness of Pseudomonas chlororaphis in the Arabidopsis thaliana rhizosphere.
(43/571)
Quorum-sensing-controlled processes are considered to be important for the competitiveness of microorganisms in the rhizosphere. They affect cell-cell communication, biofilm formation, and antibiotic production, and the GacS-GacA two-component system plays a role as a key regulator. In spite of the importance of this system for the regulation of various processes, strains with a Gac(-) phenotype are readily recovered from natural habitats. To analyze the influence of quorum sensing and the influence of the production of the antibiotic phenazine-1-carboxamide on rhizosphere colonization by Pseudomonas chlororaphis, a gnotobiotic system based on Arabidopsis thaliana seedlings in soil was investigated. Transposon insertion mutants of P. chlororaphis isolate SPR044 carrying insertions in different genes required for the production of N-acyl-homoserine lactones and phenazine-1-carboxamide were generated. Analysis of solitary rhizosphere colonization revealed that after prolonged growth, the population of the wild type was significantly larger than that of the homoserine lactone-negative gacS mutant and that of a phenazine-1-carboxamide-overproducing strain. In cocultivation experiments, however, the population size of the gacS mutant was similar to that of the wild type after extended growth in the rhizosphere. A detailed analysis of growth kinetics was performed to explain this phenomenon. After cells grown to the stationary phase were transferred to fresh medium, the gacS mutant had a reduced lag phase, and production of the stationary-phase-specific sigma factor RpoS was strongly reduced. This may provide a relative competitive advantage in cocultures with other bacteria, because it permits faster reinitiation of growth after a change to nutrient-rich conditions. In addition, delayed entry into the stationary phase may allow more efficient nutrient utilization. Thus, GacS-GacA-regulated processes are not absolutely required for efficient rhizosphere colonization in populations containing the wild type and Gac(-) mutants. (+info)
Gram stain, culture, and histopathological examination findings for heart valves removed because of infective endocarditis.
(44/571)
Retrospective chart review was undertaken for 480 patients who underwent a total of 506 valve replacements or repair procedures for infective endocarditis. The influence of preoperative antimicrobial treatment on culture, Gram stain, and histopathological examination findings for resected valve specimens was examined. When valves were removed before the end of treatment, organisms were seen on the Gram stain of ground valve material performed in the microbiology laboratory and on Gram-stained histopathological sections in 231 (81%) of 285 and 140 (67%) of 208 specimens, respectively (P=.0007). Gram-positive cocci were either cultured from or observed in excised valve tissue in 42 (67%) of 63 episodes involving negative preoperative blood cultures. Positive Gram stain results for microbiological specimens should be reintroduced into the definite pathological criteria for infective endocarditis. When deciding on how long to continue antimicrobial therapy after valve replacement for endocarditis, valve culture results should be the only laboratory finding taken into account, because it takes months for dead bacteria to be removed from sterile vegetations. (+info)
Comparison of Gram stain and Pap smear procedures in the diagnosis of bacterial vaginosis.
(45/571)
OBJECTIVE: The purpose of this study was to examine the characteristics of Gram stain versus Pap smear in diagnosis of bacterial vaginosis (BV). METHODS: One-thousand and sixty women were enrolled in this study. All cases with symptoms of BV were determined by Amsel's criteria, which were accepted as the gold standard for diagnosis of BV. Pap smear and Gram stain evaluations were compared according to Amsel's criteria, without viewing the clinical results of the patients. Gram stain and Pap smear results were determined as negative or positive according to Amsel's criteria. Sensitivity, specifity and positive predictive values were calculated. RESULTS: After accepting the cases that were diagnosed as BV according to Amsel's criteria as reference cases, the sensitivity of the Gram stain method was calculated as 97% and the sensitivity of the Pap smear method as 93%. Similar specificity rates were obtained with both methods in diagnosis of BV related to the clinical results. There were no statistically significant differences in diagnosis of BV between these two groups. CONCLUSION: If Amsel's criteria are accepted as the gold standard for diagnosis of BV, Gram stain and Pap smear methods will give similar results in diagnosis. (+info)
Root and stem hydraulic conductivity as determinants of growth potential in grafted trees of apple (Malus pumila Mill.).
(46/571)
The anatomy of the graft tissue between a rootstock and its shoot (scion) can provide a mechanistic explanation of the way dwarfing Malus rootstocks reduce shoot growth. Considerable xylem tissue disorganization may result in graft tissue having a low hydraulic conductivity (k(h)), relative to the scion stem. The graft may influence the movement of substances in the xylem such as ions, water and plant-growth-regulating hormones. Measurements were made on 3-year-old apple trees with a low-pressure flow system to determine k(h) of root and scion stem sections incorporating the graft tissue. A range of rootstocks was examined, with different abilities of dwarfing; both ungrafted and grafted with the same scion shoot cultivar. The results showed that the hydraulic conductivity (k(hroot)) of roots from dwarfing rootstocks was lower compared with semi-vigorous rootstocks, at least for the size class of root measured (1.5 mm diameter). Scion hydraulic conductivity (k(hs)) was linked to leaf area and also to the rootstock on to which it was grafted, i.e. hydraulic conductivity was greater for the scion stem on the semi-vigorous rootstock. Expressing conductivities relative to xylem cross-sectional areas (k(s)) did not remove these differences suggesting that there were anatomical changes induced by the rootstock. The calculated hydraulic conductivity of the graft tissue was found to be lower for grafted trees on dwarfing rootstocks compared to invigorating rootstocks. These observations are discussed in relation to the mechanism(s) by which rootstock influences shoot growth in grafted trees. (+info)
A flow-cytometric gram-staining technique for milk-associated bacteria.
(47/571)
A Gram-staining technique combining staining with two fluorescent stains, Oregon Green-conjugated wheat germ agglutinin (WGA) and hexidium iodide (HI) followed by flow-cytometric detection is described. WGA stains gram-positive bacteria while HI binds to the DNA of all bacteria after permeabilization by EDTA and incubation at 50 degrees C for 15 min. For WGA to bind to gram-positive bacteria, a 3 M potassium chloride solution was found to give the highest fluorescence intensity. A total of 12 strains representing some of the predominant bacterial species in bulk tank milk and mixtures of these were stained and analyzed by flow cytometry. Overall, the staining method showed a clear differentiation between gram-positive and gram-negative bacterial populations. For stationary-stage cultures of seven gram-positive bacteria and five gram-negative bacteria, an average of 99% of the cells were correctly interpreted. The method was only slightly influenced by the growth phase of the bacteria or conditions such as freezing at -18 degrees C for 24 h. For any of these conditions, an average of at least 95% of the cells were correctly interpreted. When stationary-stage cultures were stored at 5 degrees C for 14 days, an average of 86% of the cells were correctly interpreted. The Gram-staining technique was applied to the flow cytometry analysis of bulk tank milk inoculated with Staphylococcus aureus and Escherichia coli. These results demonstrate that the technique is suitable for analyzing milk samples without precultivation. (+info)
Phenazine-1-carboxylic acid, a secondary metabolite of Pseudomonas aeruginosa, alters expression of immunomodulatory proteins by human airway epithelial cells.
(48/571)
Pseudomonas aeruginosa is a gram-negative bacterium that causes both acute and chronic lung disease in susceptible patient populations. P. aeruginosa secretes numerous proteins and secondary metabolites, many of which have biological effects that likely contribute to disease pathogenesis. An unidentified small-molecular-weight factor was previously reported to increase IL-8 release both in vitro and in vivo. To identify this factor, we subjected the <3-kDa fraction from P. aeruginosa-conditioned medium to HPLC analysis. A peak fraction that stimulated IL-8 release was found by mass spectrometry to have a molecular mass (MM) of 224 Da. On the basis of this MM and other biochemical properties, we hypothesized that the factor was phenazine-1-carboxylic acid (PCA). Subsequent studies and comparison with purified PCA confirmed this hypothesis. Purified PCA exhibited a number of biological effects in human airway epithelial cells, including increasing IL-8 release and ICAM-1 expression, as well as decreasing RANTES and monocyte chemoattractant protein-1 (MCP-1) release. PCA also increased intracellular oxidant formation as measured by electron paramagnetic resonance and by an intracellular oxidant-sensitive probe. Antioxidants inhibited PCA-dependent increases in IL-8 and ICAM-1, suggesting that oxidants contributed to these effects. However, in contrast to the related phenazine compound pyocyanin, PCA did not oxidize NAD(P)H at physiologically relevant pH, providing preliminary evidence that PCA and pyocyanin may have distinct redox chemistries within the cell. Thus PCA is a biologically active factor secreted by P. aeruginosa that has several activities that could alter the host immune and inflammatory response and thereby contribute to bacterial disease pathogenesis. (+info)