Biological Role of Pigment Production for the Bacterial Phytopathogen Pantoea stewartii subsp. stewartii

Pantoea stewartii subsp. stewartii, the causal agent of Stewart's wilt of sweet corn, produces a yellow carotenoid pigment. A nonpigmented mutant was selected from a bank of mutants generated by random transposon mutagenesis. The transposon insertion site was mapped to the crtB gene, encoding a putative phytoene synthase, an enzyme involved in the early steps of carotenoid biosynthesis. We demonstrate here that the carotenoid pigment imparts protection against UV radiation and also contributes to the complete antioxidant pathway of P. stewartii. Moreover, production of this pigment is regulated by the EsaI/EsaR quorum-sensing system and significantly contributes to the virulence of the pathogen in planta.     

Pantoea stewartii subsp. stewartii produces an endoglucanase that is required for full virulence in sweet corn

Pantoea stewartii subsp. stewartii, a xylem-dwelling bacterium, is the causal agent of Stewart's wilt and blight of sweet corn. The goal of this study was to characterize the only gene in the P. stewartii subsp. stewartii genome predicted to encode an endoglucanase (EGase); this gene was designated engY. Culture supernatants from P. stewartii subsp. stewartii and Escherichia coli expressing recombinant EngY protein possessed both EGase and xylanase activities. Deletion of engY abolished EGase and xylanase activity, demonstrating that EngY appears to be the major EGase or xylanase produced by P. stewartii subsp. stewartii. Most importantly, our results show that EngY contributes to movement in the xylem and disease severity during the wilting phase of Stewart's wilt but is not required for water-soaked lesion formation.     

Biotransformation of methyl tert-butyl ether by human cytochrome P450 2A6

Methyl tert-butyl ether (MTBE) is widely used as gasoline oxygenate and octane number enhancer for more complete combustion in order to reduce the air pollution caused by motor vehicle exhaust. The possible adverse effects of MTBE on human health are of major public concern. However, information on the metabolism of MTBE in human tissues is scarce. The present study demonstrates that human cytochrome P450 2A6 is able to metabolize MTBE to tert-butyl alcohol (TBA), a major circulating metabolite and marker for exposure to MTBE. As CYP2A6 is known to be constitutively expressed in human livers, we infer that it may play a significant role in metabolism of gasoline ethers in liver tissue.     

Variation of nitrogenase activity, photosynthesis and pigmentation of the cyanobacterium Fischerella ambigua strain FS18 under different irradiance and pH values

Summary Our objective was to evaluate the physiological response of Fischerella ambigua FS18 to the combined influence of pH (5, 7 and 9) and light intensity (3 and 300 μmol photon m⁻² s⁻¹). Growth rates were similar at pH 9 and pH 7. There was no growth at pH 5. Increasing light intensity did not have any considerable influence on growth rates. Chlorophyll concentration was higher at pH 7 at all light intensities. Chlorophyll concentration decreased with increasing light intensity from 3 to 300 μmol photon m⁻² s⁻¹. Synthesis of the phycobiliproteins (PBP), phycocyanin (PC) and allophycocyanin (APC) had the highest rate in pH 7. Increasing irradiance decreased the concentrations of all PBPs. The light-saturated photosynthetic rate was clearly higher at high light intensity. With respect to nitrogenase activity, the highest rate was at pH 9 and 300 μmol photon m⁻² s⁻¹. Irradiance did not affect significantly this activity at pH 7. This cyanobacterium seems to be alkalophilic with maximum nitrogenase activity and photosynthesis at pH 9. It can also adapt its photosynthetic apparatus to the variable factors that are found in rice fields.     

Hydrogen production by sorption-enhanced steam reforming of glycerol

Catalytic steam reforming of glycerol for H₂ production has been evaluated experimentally in a continuous flow fixed-bed reactor. The experiments were carried out under atmospheric pressure within a temperature range of 400–700 °C. A commercial Ni-based catalyst and a dolomite sorbent were used for the steam reforming reactions and in situ CO₂ removal. The product gases were measured by on-line gas analysers. The results show that H₂ productivity is greatly increased with increasing temperature and the formation of methane by-product becomes negligible above 500 °C. The results suggest an optimal temperature of ∼500 °C for the glycerol steam reforming with in situ CO₂ removal using calcined dolomite as the sorbent, at which the CO₂ breakthrough time is longest and the H₂ purity is highest. The shrinking core model and the 1D-diffusion model describe well the CO₂ removal under the conditions of this work.     

Fast biodegradation of long chain n-alkanes and crude oil at high concentrations with Rhodococcus sp. Moj-3449

Biodegradation of long chain n-alkanes and crude oil with fast rate and high concentration are desirable for bioremediation, especially in heavily oil-polluted areas, and enhanced oil recovery. We discovered Rhodococcus sp. Moj-3449 with such unique abilities by screening microorganisms for the growth on n-hexadecane at 30 mg/mL. The new strain grew very fast on 120 mg/mL of n-hexadecane giving a cell density of 14.7 g cdw/L after only 2 days’ incubation. During the growth with this strain, the oil–water phases were rapidly emulsified, giving rise to tolerance to high alkane concentration (250 mg/mL) and fast growth rate of 0.10–0.20 h^?1 for alkane concentration of 1–180 mg/mL. The degraded concentration of n-hexadecane increased linearly with the initial alkane concentration (1–250 mg/mL). Incubation on n-hexadecane at 250 mg/mL for 7 days gave a cell density of 13.5 g cdw/L and degraded 124 mg/mL of n-hexadecane. The strain grew also fast on n-dodecane (C12), n-tetradecane (C14), and n-octadecane (C18), with degradation preference of C14 (=C16) > C12 > C18. Different from many alkane-degrading strains, Rhodococcus sp. Moj-3449 was found to have subterminal oxidation pathway. Rhodococcus sp. Moj-3449 degraded also crude oil fast at 60–250 mg/mL, with a wide range of n-alkanes (C10–C35) as substrates in which C14–C19 are preferred. The degradation ability increased with initial oil concentration from 60 to 150 mg/mL and slightly decreased afterwards. Incubation on 150 mg/mL of crude oil for 7 days degraded 37% of n-alkanes. The outstanding ability of rapidly degrading long chain n-alkanes and crude oil at high concentration makes Rhodococcus sp. Moj-3449 potentially useful for bioremediation and microbial enhanced oil recovery.     

Survey of Flea Infestation in Dogs in Different Geographical Regions of Iran

Medically important arthropods, including fleas, play an important role in causing clinical disorders and disease in man and domestic animals. This study was conducted to determine the seasonal flea infestations for domestic dogs from different geographic regions of Iran. A total of 407 fleas, belonging to 5 different species, were recovered from 83 domestic dogs from 3 regions. There was a distinctive pattern of species distribution and infestations with the highest infestation rates observed in a temperate climate and higher rainfall. Additionally, fleas were observed over all seasons, except February and March, with the highest infestation rate observed in August (24.7%) and the lowest rate in January (1.7%). They also parasitize dogs with a different spectrum of species. The cat flea, Ctenocephalides felis (67.5%), exhibited the highest prevalence among all flea species found on dogs. Thus, climatic conditions and seasonal patterns impact on flea infestation and must be considered in developing control programs.     

Bioconversion of codeine to semi-synthetic opiate derivatives by the cyanobacterium <Emphasis Type="Italic">Nostoc muscorum</Emphasis>

Very limited studies have been done to investigate the algal biotransformation of codeine to its opioid derivatives. On the other hand, microalgae have been recently introduced as potential tools for green synthesis of various organic compounds. In the present work, the capability of biotransformation of codeine by a locally isolate strain of cyanobacterium, Nostoc muscorum, was evaluated. Incubation of the whole cells of Nostoc muscorum with codeine (I) under continuous light photoregime of 60 μmol photons/m²s at 25°C for 5 days gave rise to four transformation products. The bioproducts were separated by gas chromatography and identified as 6-acetylcodeine (II), oxycodone (III), norcodeine (IV), morphine (V) and based on their mass spectra. Observed modifications included O-demethylation, N-demethylation, C6-acetylation, C14-hydroxilation, Δ⁷-reduction, and C6-oxidation. The ability of N. muscorum to convert codeine to oxycodone (III) represents an uncommon pattern of codeine metabolism in microorganisms that may be of industrial importance.     

Derivation of new human embryonic stem cell lines from preimplantation genetic screening and diagnosis-analyzed embryos

In this study, we focused on the derivation of human embryonic stem cell (hESC) from preimplantation genetic screening (PGS)-analyzed and preimplantation genetic diagnosis (PGD)-analyzed embryos. Out of 62 fresh PGD/PGS-analyzed embryos, 22 embryos reached the blastocyst stage. From 12 outgrowth blastocysts, we derived four hESC lines onto a feeder layer. Surprisingly, karyotype analysis showed that hESC lines derived from aneuploid embryos had diploid female karyotype. One hESC line was found to carry a balanced Robertsonian translocation. All the cell lines showed hESC markers and had the pluripotent ability to differentiate into derivatives of the three embryonic germ layers. The established lines had clonal propagation with 22–31% efficiency in the presence of ROCK inhibitor. These results further indicate that hESC lines can be derived from PGD/PGS-analyzed embryos that are destined to be discarded and can serve as an alternative source for normal euploid lines.     

Nostoc muscorum: a regioselective biocatalyst for 17-carbonyl reduction of androst-4-en-3,17-dione and androst-1,4-dien-3,17-dione

Nostoc muscorum PTCC 1636 was examined for its ability to convert androst-4-en-3,17-dione (AD) and androst-1,4-dien-3,17-dione (ADD) to their 17-hydroxy related derivatives in BG-11 medium. Bioconversion procedures were carried out at 25 °C without shaking. The metabolites obtained were purified using chromatographic methods and characterized as testosterone and 1-dehydrotestosterone on the basis of their spectroscopic features. In both cases, the bioreaction characteristics observed were 17-carbonyl reduction.