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author:("hageman, M.")
1.  Ecological Genomics of Marine Picocyanobacteria†  
Summary: Marine picocyanobacteria of the genera Prochlorococcus and Synechococcus numerically dominate the picophytoplankton of the world ocean, making a key contribution to global primary production. Prochlorococcus was isolated around 20 years ago and is probably the most abundant photosynthetic organism on Earth. The genus comprises specific ecotypes which are phylogenetically distinct and differ markedly in their photophysiology, allowing growth over a broad range of light and nutrient conditions within the 45°N to 40°S latitudinal belt that they occupy. Synechococcus and Prochlorococcus are closely related, together forming a discrete picophytoplankton clade, but are distinguishable by their possession of dissimilar light-harvesting apparatuses and differences in cell size and elemental composition. Synechococcus strains have a ubiquitous oceanic distribution compared to that of Prochlorococcus strains and are characterized by phylogenetically discrete lineages with a wide range of pigmentation. In this review, we put our current knowledge of marine picocyanobacterial genomics into an environmental context and present previously unpublished genomic information arising from extensive genomic comparisons in order to provide insights into the adaptations of these marine microbes to their environment and how they are reflected at the genomic level.
PMCID: PMC2698417  PMID: 19487728
2.  Detection of the isiA Gene across Cyanobacterial Strains: Potential for Probing Iron Deficiency 
Applied and Environmental Microbiology  2001;67(11):5247-5253.
The use of isiA expression to monitor the iron status of cyanobacteria was investigated. Studies of laboratory cultures of the cyanobacterium Synechocystis sp. strain PCC 6803 showed that isiA expression is dependent on the organism's response to iron deficiency; isiA expression starts as soon as a decline in the rate of growth begins. isiA expression is switched on at concentrations of iron citrate of less than 0.7 μM. A PCR method was developed for the specific amplification of the iron-regulated isiA gene from a variety of cyanobacteria. After we developed degenerate primers, 15 new internal isiA fragments (840 bp) were amplified, cloned, and sequenced from strains obtained from algal collections, from new isolates, and from enriched field samples. Furthermore, isiA expression could be detected by means of reverse transcription-PCR when enriched field samples were exposed to restricted iron availability. These results imply that determining the level of iron-regulated isiA expression can serve to indicate iron deficiency in cyanobacterial samples of differing origins from the field.
PMCID: PMC93297  PMID: 11679352
3.  The stpA gene form synechocystis sp. strain PCC 6803 encodes the glucosylglycerol-phosphate phosphatase involved in cyanobacterial osmotic response to salt shock. 
Journal of Bacteriology  1997;179(5):1727-1733.
Mutations in a gene, stpA, had been correlated with the loss of tolerance to high NaCl concentrations in the cyanobacterium Synechocystis sp. strain PCC 6803. Genetic, biochemical, and physiological evidence shows that stpA encodes glucosylglycerol-phosphate phosphatase. stpA mutants are salt sensitive and accumulate glucosylglycerol-phosphate, the precursor of the osmoprotectant glucosylglycerol necessary for salt adaptation of Synechocystis. The consensus motif present in acid phosphatases was found in StpA; however, the homology with other sugar phosphatases is very poor. The amount of stpA mRNA was increased by growth of the cells in the presence of NaCl concentrations above 170 mM. Expression of stpA in Escherichia coli allowed the production of a 46-kDa protein which exhibited glucosylglycerol-phosphate phosphatase activity. The StpA-specific antibody revealed a protein of similar size in extracts of Synechiocystis, and the amount of this protein was increased in salt-adapted cells. The protein produced in E. coli had lost the requirement for activation by NaCl that was observed for the genuine cyanobacterial enzyme.
PMCID: PMC178888  PMID: 9045835
4.  The ggtA gene encodes a subunit of the transport system for the osmoprotective compound glucosylglycerol in Synechocystis sp. strain PCC 6803. 
Journal of Bacteriology  1997;179(3):714-720.
The ggtA gene was sequenced during the analysis of a mutant of Synechocystis sp. strain PCC 6803 with impaired salt tolerance. It showed striking sequence similarities to ATP-binding proteins of binding-protein-dependent transport systems (ABC transporters). Mutants of ggtA and three neighboring reading frames were constructed by inserting an aphII gene cassette and were physiologically and genetically characterized. The ggtA insertion mutant lost its glucosylglycerol (GG) uptake ability, but its salt tolerance did not change. Therefore, it was concluded that active transport of the osmoprotective compound GG in Synechocystis is mediated by an ABC transporter. The genes for the GG-specific ABC transporter are not organized in an operon as usually found for comparable transporters, since the other insertion mutants showed normal GG transport activity. After cultivation of the ggtA mutant at high salt concentrations, significant amounts of GG were found in the cultivation medium, indicating that GG transport is mainly necessary for recovery of GG leaked through the cytoplasmic membrane. The Northern blot technique revealed increased transcription of the ggtA gene in cells adapted to higher salt concentrations, whereas in cells from basal medium, its transcription was weak.
PMCID: PMC178752  PMID: 9006025

Results 1-4 (4)