Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 5 de 5
Filter
Add more filters










Database
Language
Publication year range
1.
FEMS Microbiol Ecol ; 75(1): 111-22, 2011 Jan.
Article in English | MEDLINE | ID: mdl-21083579

ABSTRACT

The effects of sediment hypoxia, resulting from increased carbon loads or decreased dissolved oxygen (DO), on nitrogen cycling in estuarine environments is poorly understood. The important role played by bacterial and archaeal ammonia oxidizers in the eventual removal of nitrogen from estuarine environments is likely to be strongly affected by hypoxic events. In this study, an analysis of the effects of different levels of sediment hypoxia (5%, 20% and 75% DO) was performed in a microcosm experiment. Changes in the nutrient fluxes related to nitrification at 5% DO were observed after 4 h. Quantification of the key nitrification gene ammonium monooxygenase (amoA) in both DNA and RNA extracts suggests that bacterial amoA transcription was reduced at both of the lower DO concentrations, while changes in DO had no significant effect on archaeal amoA transcription. There was no change in the diversity of expressed archaeal amoA, but significant change in bacterial amoA transcriptional diversity, indicative of low- and high-DO phylotypes. This study suggests that groups of ammonia oxidizers demonstrate differential responses to changes in sediment DO, which may be a significant factor in niche partitioning of different ammonia oxidizer groups.


Subject(s)
Archaea/genetics , Bacteria/genetics , Nitrogen/metabolism , Oxidoreductases/genetics , Oxygen/analysis , Water Microbiology , Archaea/enzymology , Bacteria/enzymology , DNA, Archaeal/genetics , DNA, Bacterial/genetics , Geologic Sediments/analysis , Geologic Sediments/microbiology , Molecular Sequence Data , Nitrification , Phylogeny , Polymorphism, Restriction Fragment Length , Transcription, Genetic
2.
ISME J ; 4(2): 286-300, 2010 Feb.
Article in English | MEDLINE | ID: mdl-19798039

ABSTRACT

Nitrification and denitrification are key steps in nitrogen (N) cycling. The coupling of these processes, which affects the flow of N in ecosystems, requires close interaction of nitrifying and denitrifying microorganisms, both spatially and temporally. The diversity, temporal and spatial variations in the microbial communities affecting these processes was examined, in relation to N cycling, across 12 sites in the Fitzroy river estuary, which is a turbid subtropical estuary in central Queensland. The estuary is a major source of nutrients discharged to the Great Barrier Reef near-shore zone. Measurement of nitrogen fluxes showed an active denitrifying community during all sampling months. Archaeal ammonia monooxygenase (amoA of AOA, functional marker for nitrification) was significantly more abundant than Betaproteobacterial (beta-AOB) amoA. Nitrite reductase genes, functional markers for denitrification, were dominated by nirS and not nirK types at all sites during the year. AOA communities were dominated by the soil/sediment cluster of Crenarchaeota, with sequences found in estuarine sediment, marine and terrestrial environments, whereas nirS sequences were significantly more diverse (where operational taxonomic units were defined at both the threshold of 5% and 15% sequence similarity) and were closely related to sequences originating from estuarine sediments. Terminal-restriction fragment length polymorphism (T-RFLP) analysis revealed that AOA population compositions varied spatially along the estuary, whereas nirS populations changed temporally. Statistical analysis of individual T-RF dominance suggested that salinity and C:N were associated with the community succession of AOA, whereas the nirS-type denitrifier communities were related to salinity and chlorophyll-alpha in the Fitzroy river estuary.


Subject(s)
Ammonia/metabolism , Crenarchaeota/isolation & purification , Crenarchaeota/metabolism , Geologic Sediments/microbiology , Seawater/microbiology , Crenarchaeota/genetics , DNA, Archaeal/genetics , Ecosystem , Molecular Sequence Data , Nitrogen/metabolism , Queensland
3.
Mar Biotechnol (NY) ; 11(3): 410-8, 2009.
Article in English | MEDLINE | ID: mdl-18987913

ABSTRACT

The marine microalga Pavlova salina (Haptophyta, Pavlovophyceae) produces lipids containing approximately 50% n-3 long-chain polyunsaturated fatty acids including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). A full-length cDNA sequence, designated PsElo5, was isolated from P. salina. Sequence alignment showed that the gene was homologous to corresponding ELO-type elongases from other microalgae. Heterologous expression of PsElo5 in yeast and in higher plants confirmed that it encodes a specific Delta5-elongase activity as predicted and, furthermore, within the n-3 pathway, the elongation activity was confined exclusively to EPA.


Subject(s)
Acetyltransferases/genetics , Eukaryota/enzymology , Fatty Acids, Unsaturated/metabolism , Acetyltransferases/metabolism , Arabidopsis , Base Sequence , DNA Primers/genetics , DNA, Complementary/genetics , Fatty Acid Elongases , Fatty Acids, Unsaturated/biosynthesis , Molecular Sequence Data , Reverse Transcriptase Polymerase Chain Reaction , Sequence Alignment , Sequence Analysis, DNA , Yeasts
4.
Phytochemistry ; 68(6): 785-96, 2007 Mar.
Article in English | MEDLINE | ID: mdl-17291553

ABSTRACT

The marine microalga Pavlova salina produces lipids containing approximately 50% omega-3 long chain polyunsaturated fatty acids (LC-PUFA) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Three cDNA sequences, designated PsD4Des, PsD5Des, PsD8Des, were isolated from P. salina and shown to encode three front-end desaturases with Delta4, Delta5 and Delta8 specificity, respectively. Southern analysis indicated that the P. salina genome contained single copies of all three front-end fatty acid desaturase genes. When grown at three different temperatures, analysis of fatty acid profiles indicated P. salina desaturation conversions occurred with greater than 95% efficiency. Real-Time PCR revealed that expression of PsD8Des was higher than for the other two genes under normal growth conditions, while PsD5Des had the lowest expression level. The deduced amino acid sequences from all three genes contained three conserved histidine boxes and a cytochrome b(5) domain. Sequence alignment showed that the three genes were homologous to corresponding desaturases from other microalgae and fungi. The predicted activities of these three front-end desaturases leading to the synthesis of LC-PUFA were also confirmed in yeast and in higher plants.


Subject(s)
Algal Proteins/genetics , Docosahexaenoic Acids/metabolism , Eukaryota/genetics , Fatty Acid Desaturases/genetics , Algal Proteins/metabolism , Base Sequence , Blotting, Southern , Chromatography, Gas , Cloning, Molecular , DNA, Complementary/chemistry , DNA, Complementary/genetics , Eukaryota/enzymology , Fatty Acid Desaturases/metabolism , Fatty Acids, Unsaturated/metabolism , Gas Chromatography-Mass Spectrometry , Gene Expression Regulation, Enzymologic , Isoenzymes/genetics , Isoenzymes/metabolism , Models, Biological , Molecular Sequence Data , Phylogeny , Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , Sequence Analysis, DNA
5.
Mar Biotechnol (NY) ; 8(2): 103-9, 2006.
Article in English | MEDLINE | ID: mdl-16372159

ABSTRACT

A large body of evidence suggests that there is a significant underconsumption of omega-3, long-chain, polyunsaturated fatty acids (LC-PUFAs) and that this is the cause of multiple chronic diseases and developmental aberrations. The scope for increasing omega-3 LC-PUFA consumption from seafood is limited because global wild fisheries are unable to increase their harvests, and aquaculture fisheries currently rely on wild fisheries as a source of LC-PUFAs. Agricultural production of oils is highly efficient and has the potential to be sustainable. The transfer of genes from marine microalgae and other microorganisms into oilseed crops has shown that the production of terrestrial omega-3 LC-PUFA oils is indeed possible. The specifications of these oils or whole seeds for use in human and Atlantic salmon (Salmo salar) aquaculture nutrition are discussed.


Subject(s)
Fatty Acids, Omega-3/biosynthesis , Food, Genetically Modified , Nutritional Physiological Phenomena/physiology , Plants, Genetically Modified , Animals , Aquaculture , Docosahexaenoic Acids/metabolism , Eicosapentaenoic Acid/biosynthesis , Eicosapentaenoic Acid/genetics , Fatty Acids, Omega-3/genetics , Humans
SELECTION OF CITATIONS
SEARCH DETAIL
...