The endophyte Enterobacter sp. FD17: a maize growth enhancer selected based on rigorous testing of plant beneficial traits and colonization characteristics

With the aim to select powerful microbial strains to be used for the enhancement of maize yield and resistance to abiotic and biotic stresses, we tested five endophytic bacterial strains previously isolated from maize roots. A range of different laboratory assays in regard to potential plant growth promotion was performed and strains were further evaluated for improving growth of five maize cultivars under axenic and natural soil conditions. Endophytic colonization was an additional component in our selection process as it is of high importance for an inoculant strain to efficiently colonize the plant environment. All strains had the potential to improve maize seedling growth under axenic conditions. Enterobacter sp. strain FD17 showed both the highest growth-promoting activity under axenic conditions as well as colonization capacity. FD17 was therefore selected for further plant tests in a net house, in which two different maize cultivars were grown in large pots until ripening and subjected to outdoor climatic conditions. Results showed that inoculation significantly increased plant biomass, number of leaves plant^?1, leaf area, and grain yield up to 39 %, 14 %, 20 %, and 42 %, respectively, as compared to the un-inoculated control. Similarly, inoculation also improved the photochemical efficiency of photosystem II (PSII) of maize plant and reduced the time needed for flowering. We also confirmed that strain FD17 is able to colonize the rhizosphere, roots and stems. Based on rigorous testing, Enterobacter sp. strain FD17 showed the highest potential to promote growth and health of maize grown under natural conditions. This study suggested that in vitro plant growth-promoting traits and potential of maize seedling growth promotion by bacterial endophytes could be used for the selection of potential inoculant strains subjected for further testing as bio-inoculant under field conditions.     

Invertase activity limits grain yield of maize under salt stress

Salt stress reduces grain yield of maize (Zea mays L.) due to poor kernel setting but not due to decreased grain filling. In the present study, it was tested whether acid invertase activity is decreased in developing kernels of maize under salt stress, and if assimilate supply is limited. The relatively salt‐sensitive maize hybrid Pioneer 3906 was compared with the more salt‐resistant hybrid SR 12. Salt stress caused a significant decrease in grain yield which was due to a 50% decrease in kernel number. No source limitation was observed, as the sucrose concentrations in kernels were significantly increased under salt stress for both genotypes. In contrast, glucose and fructose concentrations in kernels were significantly decreased. Salt stress caused a significant inhibition of soluble acid invertase activity to 19% in hydroponics 5 d after pollination (5 DAP) and to 50% in the soil culture experiment (2 DAP). The decrease in enzyme activity was the same for both genotypes. In the soil experiment, the highest soluble acid invertase activity was found 2 DAP with a steep decline until 8 DAP in Pioneer 3906. It is concluded that a decrease in acid invertase activity is a key factor associated with limited kernel setting under salt stress but additional factors may be responsible for genotypic differences.     

Rapid determination of domoic acid in serum and urine by liquid chromatography-electrospray tandem mass spectrometry

A rapid, selective, and sensitive LC-MS/MS method was developed for the quantitative determination of domoic acid in serum and urine samples. Samples were prepared for analysis using an Oasis HLB SPE column. Determination was by a reversed phase HPLC using a mixture of methanol, acetonitrile, and water containing 1% acetic acid and an electrospray ionization (ESI) ion-trap mass spectrometer (Finnigan LCQ). The method was validated by analyzing five replicates each of negative control bovine serum or urine fortified with domoic acid at the 0.005 microg/g method detection limit (MDL) and at the 0.05 microg/g level. Recoveries ranged from 90 to 95% for fortifications at the MDL and from 92 to 98% for fortifications 10 times higher than the MDL. The diagnostic utility of the method was tested by analyzing samples from live animals showing clinical signs suggestive of domoic acid poisoning submitted to the veterinary toxicology laboratory.     

Analysis of glycated and ascorbylated proteins by gas chromatography-mass spectrometry

Proteins or poly-L-lysine which were incubated in the presence of ascorbic acid, dehydroascorbic acid (ascorbylation), or various sugars (glycation) were analyzed by gas chromatography-mass spectrometry (GC-MS). To also detect more labile reaction products, the Maillard modified proteins or poly-L-lysine were enzymatically hydrolyzed and reacted with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide to form the N(O)-tert-butyldimethylsilyl (tBDMS) derivatives prior to GC analysis. Under these conditions, the known Maillard products N (epsilon)-(carboxymethyl)lysine (1), oxalic acid mono-N (epsilon)-lysinylamide (2), and N (epsilon)-(carboxyethyl)lysine (3) could be simultaneously detected and quantified in glycated and ascorbylated proteins. Additionally, N (epsilon)-(1-carboxy-3-hydroxypropyl)-L-lysine (4) was identified for the first time as a Maillard product of proteins. Under the conditions applied here, 4 was found only in ascorbylated proteins or poly-L-lysine, but not in glycated proteins. Maillard-modified poly-L-lysine was further subjected to high-performance liquid chromatography (HPLC) analysis after enzymatic hydrolysis and formation of the phenyl isothiocyanate derivatized amino acids. Using this method, N (epsilon)-formyl-L-lysine (5), which cannot be distinguished from 2 by GC-MS analysis, was identified for the first time as a glycation product. Compound 5 is mainly formed from ribose, lactose, and fructose. The indicated Maillard products were quantified in beta-lactoglobulin (GC-MS) or poly-L-lysine (HPLC) which were glycated or ascorbylated using different precursors.     

Differential effects of ferulic acid and p-coumaric acid on S phase distribution and length of S phase in the human colonic cell line Caco-2

Ferulic acid (FA) and para-coumaric acid (p-CA) may mediate the protective effects of whole-grain cereals against colon cancer. Therefore, the effects of FA and p-CA on the metabolic activity, proliferation, cell cycle phase distribution, and kinetics of the colonic endothelial tumor cell line Caco-2 was studied. Both compounds at 1500 microM decreased the number of cells to 43-75% of control after 2-3 days of treatment. Cell cycle phase distribution and cell cycle kinetics were determined by flow cytometric analysis after bromodeoxyuridine labeling. Each compound at 1500 microM decreased the proportion of cells in the G(1) phase and increased the proportion of cells in the S and G(2) phases. Treatment with 1500 microM FA significantly increased the length of the S phase, while p-CA did not. It was concluded that FA and p-CA inhibited cell proliferation by presumably affecting different cell cycle phases, and this warrants further investigations because this inhibition may be one explanation for the diet-related protection against cancer.     

Calcarides A–E,Antibacterial Macrocyclic and Linear Polyesters from a Calcarisporium Strain

Bioactive compounds were detected in crude extracts of the fungus, Calcarisporium sp. KF525, which was isolated from German Wadden Sea water samples. Purification of the metabolites from the extracts yielded the five known polyesters, 15G256α, α-2, β, β-2 and π (1–5), and five new derivatives thereof, named calcarides A–E (6–10). The chemical structures of the isolated compounds were elucidated on the basis of one- and two-dimensional NMR spectroscopy supported by UV and HRESIMS data. The compounds exhibited inhibitory activities against Staphylococcus epidermidis, Xanthomonas campestris and Propionibacterium acnes. As the antibacterial activities were highly specific with regard to compound and test strain, a tight structure-activity relationship is assumed.     

Distribution,structure and function of Nordic eelgrass (Zostera marina) ecosystems: implications for coastal management and conservation

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Methicillin-resistant Staphylococcus aureus (MRSA) in veterinary medicine: a "new emerging pathogen"?

The problem of nosocomial infections is of increasing importance in veterinary medicine. As an example, this review summarizes current knowledge regarding methicillin-resistant Staphylococcus aureus (MRSA) as a typical example, as these pathogens are the most important agents of nosocomial infections in human medicine worldwide and are being increasingly reported in veterinary medicine. MRSA are classified by their ability to be resistant against oxacillin/methicillin, this feature being confered by mecA, a gene which was acquired by horizontal gene transfer of the staphylococcal gene cassette (SCCmec). It is this genetic information that enables MRSA to be resistant against all penicillins, cehalosporins and carbapenems. In addition, MRSA are often resistant against a variety of other antiinfectives, i.e. aminoglycosides, macrolides, lincosamide, streptomycins, tetracyclin, chloramphenicol, but also against fluorquinolones and rifampicin. Presumably, these highly adapted strains are particularly able to acquire resistance genes located on plasmids or transposons.They are also able to develop point mutations, further leading to resistant phenotypes. If these pathogens are leading to infectious diseases, veterinarians may be confronted with a worst-case scenario, being left without any antiinfective therapeutic. As Staphylococcus aureus is highly tenacid, professional hygiene management is of utmost importance. The increasing number of published sporadic MRSA infections, MRSA-infectious diseases as well as MRSA outbreaks in veterinary medicine justifies their recognition as a "New Emerging Pathogen". So far, horses and dogs are mostly affected by MRSA. Although transmission between humans and animals has been reported occasionally, the sources, routes of transmission or the epidemiological relevance of MRSA infections in animals are far from being understood. Therefore, epidemiological investigations utilizing molecular typing tools are mandatory. Typing tools like multilocus-sequence-typing (MLST), pulsefield-gelelectrophoresis (PFGE), sequence analysis of the gene encoding protein A (spa-typing) as well as SCCmec-typing are all at hand.