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7 result(s) for "Chronopoulou, P. -M."
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Generalist hydrocarbon‐degrading bacterial communities in the oil‐polluted water column of the North Sea
Summary The aim of this work was to determine the effect of light crude oil on bacterial communities during an experimental oil spill in the North Sea and in mesocosms (simulating a heavy, enclosed oil spill), and to isolate and characterize hydrocarbon‐degrading bacteria from the water column. No oil‐induced changes in bacterial community (3 m below the sea surface) were observed 32 h after the experimental spill at sea. In contrast, there was a decrease in the dominant SAR11 phylotype and an increase in Pseudoalteromonas spp. in the oiled mesocosms (investigated by 16S rRNA gene analysis using denaturing gradient gel electrophoresis), as a consequence of the longer incubation, closer proximity of the samples to oil, and the lack of replenishment with seawater. A total of 216 strains were isolated from hydrocarbon enrichment cultures, predominantly belonging to the genus Pseudoaltero monas; most strains grew on PAHs, branched and straight‐chain alkanes, as well as many other carbon sources. No obligate hydrocarbonoclastic bacteria were isolated or detected, highlighting the potential importance of cosmopolitan marine generalists like Pseudoalteromonas spp. in degrading hydrocarbons in the water column beneath an oil slick, and revealing the susceptibility to oil pollution of SAR11, the most abundant bacterial clade in the surface ocean. A permitted release of light crude oil into the North Sea resulted in no change in bacterial community composition 3 m beneath the spill. In contrast, there was a decrease in the dominant SAR11 phylotype and an increase in Pseudoalteromonas spp. in oiled mesocosms on board the ship (simulating a heavy spill in a harbour), as a consequence of the longer incubation, closer proximity of the samples to oil, and the lack of replenishment with seawater. Pseudoalteromonas spp. were enriched in media with hydrocarbons, whereas obligate hydrocarbonclastic bacteria were not; suggesting that generalist oil‐degrading bacteria may be important in the water column beneath an oil slick.
16S and 18S rRNA Gene Metabarcoding Provide Congruent Information on the Responses of Sediment Communities to Eutrophication
Metabarcoding analyses of bacterial and eukaryotic communities have been proposed as efficient tools for environmental impact assessment. It has been unclear, however, to which extent these analyses can provide similar or differing information on the ecological status of the environment. Here, we used 16S and 18S rRNA gene metabarcoding to compare eutrophication-induced shifts in sediment bacterial and eukaryotic community structure in relation to a range of porewater, sediment and bottom-water geochemical variables, using data obtained from six stations near a former rainbow trout farm in the Archipelago Sea (Baltic Sea). Shifts in the structure of both community types were correlated with a shared set of variables, including porewater ammonium concentrations and the sediment depth-integrated oxygen consumption rate. Distance-based redundancy analyses showed that variables typically employed in impact assessments, such as bottom water nutrient concentrations, explained less of the variance in community structure than alternative variables (e.g., porewater NH 4 + inventories and sediment depth-integrated O 2 consumption rates) selected due to their low collinearity (up to 40 vs. 58% of the variance explained, respectively). In monitoring surveys where analyses of both bacterial and eukaryotic communities may be impossible, either 16S or 18S rRNA gene metabarcoding can serve as reliable indicators of wider ecological impacts of eutrophication.
Delineation of the functional and structural properties of the glutathione transferase family from the plant pathogen Erwinia carotovora
Erwinia carotovora, a widespread plant pathogen that causes soft rot disease in many plants, is considered a major threat in agriculture. Bacterial glutathione transferases (GSTs) play important roles in a variety of metabolic pathways and processes, such as the biodegradation of xenobiotics, protection against abiotic stress, and resistance against antimicrobial drugs. The GST family of canonical soluble enzymes from Erwinia carotovora subsp. atroseptica strain SCRI1043 (EcaGSTs) was investigated. Genome analysis showed the presence of six putative canonical cytoplasmic EcaGSTs, which were revealed by phylogenetic analysis to belong to the well-characterized GST classes beta, nu, phi, and zeta. The analysis also revealed the presence of two isoenzymes that were phylogenetically close to the omega class of GSTs, but formed a distinct class. The EcaGSTs were cloned and expressed in Escherichia coli, and their catalytic activity toward different electrophilic substrates was elucidated. The EcaGSTs catalyzed different types of reactions, although all enzymes were particularly active in reactions involving electrophile substitution. Gene and protein expression profiling conducted under normal culture conditions as well as in the presence of the herbicide alachlor and the xenobiotic 1-chloro-2,4-dinitrobenzene (CDNB) showed that the isoenzyme EcaGST1, belonging to the omega-like class, was specifically induced at both the protein and mRNA levels. EcaGST1 presumably participates in counteracting the xenobiotic toxicity and/or abiotic stress conditions, and may therefore represent a novel molecular target in the development of new chemical treatments to control soft rot diseases.
Generalist hydrocarbon‐degrading bacterial communities in the oil‐polluted water column of the N orth S ea
The aim of this work was to determine the effect of light crude oil on bacterial communities during an experimental oil spill in the N orth S ea and in mesocosms (simulating a heavy, enclosed oil spill), and to isolate and characterize hydrocarbon‐degrading bacteria from the water column. No oil‐induced changes in bacterial community (3 m below the sea surface) were observed 32 h after the experimental spill at sea. In contrast, there was a decrease in the dominant SAR 11 phylotype and an increase in P seudoalteromonas spp. in the oiled mesocosms (investigated by 16 S rRNA gene analysis using denaturing gradient gel electrophoresis), as a consequence of the longer incubation, closer proximity of the samples to oil, and the lack of replenishment with seawater. A total of 216 strains were isolated from hydrocarbon enrichment cultures, predominantly belonging to the genus P seudoaltero monas ; most strains grew on PAHs , branched and straight‐chain alkanes, as well as many other carbon sources. No obligate hydrocarbonoclastic bacteria were isolated or detected, highlighting the potential importance of cosmopolitan marine generalists like P seudoalteromonas spp. in degrading hydrocarbons in the water column beneath an oil slick, and revealing the susceptibility to oil pollution of SAR 11, the most abundant bacterial clade in the surface ocean.
Biological effects of milk proteins and their peptides with emphasis on those related to the gastrointestinal ecosystem
The protein fraction of milk contains several components with physiological significance for the development of the newborn. Among them, immunomodulatory peptides and lactoferrin exemplify the complexity of biologically active substances of milk. Immunomodulatory peptides have latent activity within the native protein and are generated after proteolysis during gastrointestinal transit. Once they are generated, they modulate mucosal immunity, possibly by guiding the local immune system until it develops its full functionality. Lactoferrin is another milk bioactive compound with nutritional and health promoting properties; it modulates the microbial intestinal environment, displays anti-microbial activity against various pathogens and stimulates the establishment of beneficial microflora. The following overview focuses on the importance of immunomodulatory peptides and lactoferrin for the maturation of intestine and immune system that are functionally immature in the newborn.
Generalist marine hydrocarbon‐degrading bacteria
The aim of this work was to determine the effect of light crude oil on bacterial communities during an experimental oil spill in the North Sea and in mesocosms (simulating a heavy, enclosed oil spill), and to isolate and characterize hydrocarbon‐degrading bacteria from the water column. No oil‐induced changes in bacterial community (3 m below the sea surface) were observed 32 h after the experimental spill at sea. In contrast, there was a decrease in the dominant SAR11 phylotype and an increase in Pseudoalteromonas spp. in the oiled mesocosms (investigated by 16S rRNA gene analysis using denaturing gradient gel electrophoresis), as a consequence of the longer incubation, closer proximity of the samples to oil, and the lack of replenishment with seawater. A total of 216 strains were isolated from hydrocarbon enrichment cultures, predominantly belonging to the genus Pseudoaltero monas; most strains grew on PAHs, branched and straight‐chain alkanes, as well as many other carbon sources. No obligate hydrocarbonoclastic bacteria were isolated or detected, highlighting the potential importance of cosmopolitan marine generalists like Pseudoalteromonas spp. in degrading hydrocarbons in the water column beneath an oil slick, and revealing the susceptibility to oil pollution of SAR11, the most abundant bacterial clade in the surface ocean.
Biological effects of milk proteins and their peptides with emphasis on those related to the gastrointestinal ecosystem
The protein fraction of milk contains several components with physiological significance for the development of the newborn. Among them, immunomodulatory peptides and lactoferrin exemplify the complexity of biologically active substances of milk. Immunomodulatory peptides have latent activity within the native protein and are generated after proteolysis during gastrointestinal transit. Once they are generated, they modulate mucosal immunity, possibly by guiding the local immune system until it develops its full functionality. Lactoferrin is another milk bioactive compound with nutritional and health promoting properties; it modulates the microbial intestinal environment, displays anti-microbial activity against various pathogens and stimulates the establishment of beneficial microflora. The following overview focuses on the importance of immunomodulatory peptides and lactoferrin for the maturation of intestine and immune system that are functionally immature in the newborn.