In leather tanning industrial areas sulphide management represents a major problem. However, biological sulphide oxidation to sulphur represents a convenient solution to this problem. Elemental ...sulphur is easy to separate and the process is highly efficient in terms of energy consumption and effluent quality. As the oxidation process is performed by specialized bacteria, selection of an appropriate microbial community is fundamental for obtaining a good yield. Sulphur oxidizing bacteria (SOB) represent a wide-ranging and highly diversified group of microorganisms with the capability of oxidizing reduced sulphur compounds. Therefore, it is useful to select new microbes that are able to perform this process efficiently. For this purpose, an experimental membrane bioreactor for sulphide oxidation was set up, and the selected microbial community was characterized by constructing 16S rRNA gene libraries and subsequent screening of clones. Fluorescence
in situ hybridization (FISH) was then used to assess the relative abundance of different bacterial groups. Sulphide oxidation to elemental sulphur proceeded in an efficient (up to 79% conversion) and stable way in the bioreactor. Both analysis of clone libraries and FISH experiments revealed that the dominant operational taxonomic unit (OTU) in the bioreactor was constituted by
Gammaproteobacteria belonging to the
Halothiobacillaceae family. FISH performed with the specifically designed probe tios_434 demonstrated that this OTU constituted 90.6±1.3% of the bacterial community. Smaller fractions were represented by bacteria belonging to the classes
Betaproteobacteria,
Alphaproteobacteria,
Deltaproteobacteria,
Clostridia,
Mollicutes,
Sphingobacteria,
Bacteroidetes and
Chlorobia. Phylogenetic analysis revealed that clone sequences from the dominant OTU formed a stable clade (here called the TIOS44 cluster), within the
Halothiobacillaceae family, with sequences from many organisms that have not yet been validly described. The data indicated that bacteria belonging to the TIOS44 cluster were responsible for the oxidation process.
The production and characterization of Arabidopsis plants containing a transgene in which the Arabidopsis tAPX is inserted in antisense orientation, is described. tAPX activity in these transgenic ...tAPX plants is around 50% of control level. The tAPX antisense plants are phenotypically indistinguishable from control plants under normal growth conditions; they show, however, enhanced sensitivity to the superoxide-generating herbicide, Paraquat. Interestingly, the tAPX antisense plants show enhanced symptoms of damage when cell death is triggered through treatment with the nitric oxide-donor, SNP. These results are in accordance with the ones recently obtained with transgenic plants overexpressing tAPX; altogether, they suggest that tAPX, besides the known ROS scavenging role, is also involved in the fine changes of H2O2 concentration during signaling events.
A reduced scale e.m. calorimeter prototype for the AMS-02 experiment Cervelli, F.; Chen, G.; Coignet, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2002, Letnik:
490, Številka:
1
Journal Article
Recenzirano
A reduced scale prototype of the Pb–SciFi sampling e.m. calorimeter for the AMS-02 experiment was tested at CERN SPS beam line X5 at energies from 5 to
250
GeV
. The detector was equalized with ...minimum ionizing particles and calibrated with electron beams. Effective sampling thickness, linearity and energy resolution were measured.
The rice
Osmyb4 gene, coding for a MYB transcription factor, is expressed at low levels in rice coleoptiles under normal conditions and strongly induced at 4
°C. Its overexpression in
Arabidopsis ...thaliana plants increases biotic and abiotic stress tolerance and results in the accumulation of several metabolites, essential in defence response. The heterologous expression of the Myb4 transcription factor represents a promising potential approach to improve stress tolerance in crops, avoiding endogenous mechanisms that often co-suppress the transgene of interest.
In order to explore the potential of the
Osmyb4 gene to enhance tolerance toward multiple stresses in different host plant genomes, we generated transgenic tomato (
Solanum lycopersicum L. cv. Tondino) plants. Like Arabidopsis, tomato plants overexpressing
Osmyb4 acquired a higher tolerance to drought stress and to virus disease. However, the transgenic plants did not appear to be more cold tolerant than the WT, in any tested condition. The data obtained indicate that the specificity and the degree of
Osmyb4 activity depend on the host genomic background.
Posidonia oceanica meadows are among the most valuable coastal systems in the Mediterranean basin. They provide nursery and forage areas for many commercially important species, including juvenile ...mollusc, finfish, and crustaceans. In the Mediterranean Sea,
P. oceanica beds have recently suffered from progressive die-offs attributed to lower light availability from elevated water turbidity. In order to understand adaptive low-light responses of this seagrass, we compared the protein expression in plants collected from turbid waters (low-light) with plants collected from pristine-clear waters (high-light). More than 2600 proteins were detected in leaves from both sites. Among them, 26 proteins were differentially expressed in low-light conditions, 12 of which were identified through MASCOT analyses. The remaining 14 proteins, did not receive significant identity scores due to a lack of genomic and proteomic information in available databases. Nevertheless, we observed a 30% down-regulation of RuBisCo large subunit in low-light acclimated leaves. Whereas, enzymes involved in carbohydrate cleavage (1-fructose-bisphosphate aldolase, nucleoside diphosphate kinase, and beta-amylase) were upregulated in low-light conditions. Electron microscopy studies also revealed substantial changes in the stroma lamellae/grana ratios in chloroplasts receiving low-light, possibly as a mechanism for re-establishing optimal PSI/PSII ratios. Furthermore, under low-light conditions, four components of the ubiquitin/mediated proteolysis pathway (26 S proteasome regulatory, proteasome beta type 1, proteasome 7 D beta type, and proteasome alpha 7), and the perchloric acid soluble translation inhibitor protein, were upregulated. This suggests that, in
P. oceanica leaves, enhanced protein turnover mediates acclimation to low-light conditions. Also, enzymes involved in defending against cellular stress (superoxide dismutase, pyridoxine, and 2-caffeic-acido-methyl transferase) were differentially expressed in low-light regime. Subsequent aquaria studies involving
P. oceanica transplants maintained in low- and high-light conditions, also demonstrate RuBisCo down-regulation and proteasomes upregulation in low-light acclimated plants.
. We have found a Polynucleobacter bacterium in the cytoplasm of Euplotes harpa, a species living in a brackish‐water habitat, with a cirral pattern not corresponding to that of the freshwater ...Euplotes species known to harbor this type of bacteria. The symbiont has been found in three strains of the species, obtained by clonal cultures from ciliates collected in different geographic regions. The 16S rRNA gene sequence of this bacterium identifies it as a member of the β‐proteobacterial genus Polynucleobacter. This sequence shares a high similarity value (98.4–98.5%) with P. necessarius, the type species of the genus, and is associated with 16S rRNA gene sequences of environmental clones and bacterial strains included in the Polynucleobacter cluster (>95%). An oligonucleotide probe was designed to corroborate the assignment of the retrieved sequence to the symbiont and to detect similar bacteria rapidly. Antibiotic experiments showed that the elimination of the bacteria stops the reproductive cycle in E. harpa, as has been shown for the freshwater Euplotes species.
A symbiotic relationship between the marine ciliate Euplotes magnicirratus and an alpha-proteobacterium has recently been described. The bacterial symbiont, identified by molecular analysis as a new ...species of the genus Devosia, is referred to with the provisional name `Candidatus Devosia euplotis'. This association is constant (it was found in different ciliate strains sampled in different geographical regions), and durable (it persisted in laboratory conditions for years). The physiological significance of this association was investigated through antibiotically produced aposymbiotic E. magnicirratus and attempts to grow the endosymbionts outside their host. Aposymbiotic protozoa completely lost the ability to digest the green alga Dunaliella tertiolecta, their usual food in laboratory conditions, and died. An investigation into the different steps of the digestive process showed that acidification of the digestive vacuoles occurred normally in both symbiotic and aposymbiotic ciliates, but that subsequent activation of acid phosphatase did not occur in aposymbiotic cells. Therefore, the ciliate depends on the symbiont for digestion of its green algal food and, as a consequence, for its survival. Attempts to grow bacterial endosymbionts on diluted culture media and on ciliate homogenate were unsuccessful. The results indicate that this represents a new type of symbiosis between prokaryotes and ciliates, which is mutualistic, and most likely obligatory for both partners.
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