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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cell coloration changes from normal blue-green to yellow or yellow-green when the cyanobacterium Synechococcus sp. strain PCC 7942 is deprived of an essential nutrient. We found that this bleaching process (chlorosis) in cells deprived of sulfur (S) was similar to that in cells deprived of nitrogen (N), but that cells deprived of phosphorus (P) bleached differently. Cells divided once after N deprivation, twice after S deprivation, and four times after P deprivation. Chlorophyll (Chl) accumulation stopped almost immediately upon N or S deprivation but continued for several hours after P deprivation. There was no net Chl degradation during N, S, or P deprivation, although cellular Chl content decreased because cell division continued after Chl accumulation ceased. Levels of the light-harvesting phycobiliproteins declined dramatically in a rapid response to N or S deprivation, reflecting an ordered breakdown of the phycobilisomes (PBS). In contrast, P-deprived cultures continued to accumulate PBS for several hours. Whole PBS were not extensively degraded in P-deprived cells, although the PBS contents of P-deprived cells declined because of continued cell division after PBS accumulation ceased. Levels of mRNAs encoding PBS polypeptides declined by 90 to 95% in N- or S-deprived cells and by 80 to 85% in P-deprived cells. These changes in both the synthesis and stability of PBS resulted in a 90% decline in the PC/Chl ratio of N- or S-deprived cells and a 40% decline in the PC/Chl ratio of P-deprived cells. Therefore, although bleaching appears to be a general response to nutrient deprivation, it is not the same under all nutrient-limited conditions and is probably composed of independently controlled subprocesses.
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PMID:Chlorosis induced by nutrient deprivation in Synechococcus sp. strain PCC 7942: not all bleaching is the same. 162 59

We observed the ultrastructural (PCC) changes in the adrenal zona fasciculata (ZF) and zona reticularis (ZR) and plasma corticosterone levels after phosphorus burn in rats within 15 days. We found that the PCC in the burnt rats increased remarkably with 3 peaks, and all the organelles or the surface structures (filopodia and cytoplasmic processes) in ZF and ZR cells showed various changes, which we considered as variant forms of secretion and synthesis hyperfunction of the adrenal cortical cells. There were also degenerative changes in the membrane structure.
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PMID:[An experimental study on pathological changes in adrenal cortex in rats after phosphorus burn. I. Ultrastructural changes]. 203 81

A stable DNA/protein complex having an apparent molecular mass of approximately 150 kDa was purified from nitrate-limited cultures of the cyanobacterium Synechococcus sp. strain PCC 7942. Amino-terminal peptide sequencing indicated that the polypeptide was structurally similar to the Dps protein of Escherichia coli; Dps is also known as the product of the starvation- and stationary-phase-inducible gene, pexB. The 150-kDa complex dissociated into a 22-kDa protein monomer after boiling in 2% SDS. The 150-kDa complex preparation had approximately a 10% nucleic acid content and upon dissociation released DNA fragments that were sensitive to S1 nuclease digestion. Immunoblot data indicated that the complex accumulates during stationary phase and during nitrogen, sulfur, and phosphorus limitation. DNA-binding assays indicated that the protein nonspecifically binds both linear and supercoiled DNA. Circular dichroism spectroscopy revealed that the Synechococcus sp. Dps-like protein contains extensive regions of alpha-helical secondary structure. We propose that the 150-kDa complex represents a hexameric aggregate of the Dps-like protein complexed with single-stranded DNA and serves to bind a portion of the chromosomal DNA under nutrient-limited conditions.
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PMID:Purification and characterization of a Synechococcus sp. strain PCC 7942 polypeptide structurally similar to the stress-induced Dps/PexB protein of Escherichia coli. 779 1

Phycobilisomes are the multiprotein complexes predominantly responsible for harvesting light energy in cyanobacteria and some eukaryotic algae. When the cyanobacterium Synechococcus sp. strain PCC 7942 is deprived of an essential nutrient, the phycobilisomes are specifically and rapidly degraded. Degradation may be either partial (after phosphorus deprivation) or complete (after sulfur or nitrogen deprivation). We have developed a visual screen to obtain mutants unable to degrade their phycobilisomes upon nutrient starvation. Complementation of one of these mutants led to the identification of a gene, designated nblA, that encodes a 59 amino acid polypeptide essential for phycobilisome degradation. Transcription of nblA increases dramatically in sulfur- or nitrogen-deprived cells and moderately in phosphorus-deprived cells. Using the phosphorus-regulated alkaline phosphatase (phoA) promoter as a tool, we engineered constructs from which we could control the expression of either sense or antisense nblA. Increased expression of sense nbLA caused complete phycobilisome degradation during phosphorus deprivation, while expression of antisense nblA prevented phycobilisome degradation. Hence, nblA is necessary, and may be sufficient, for the degradation of phycobilisomes under adverse environmental conditions. Further investigation of the mechanism by which nblA causes phycobilisome destruction may reveal general principles that govern the specificity of macromolecular complex degradation.
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PMID:A small polypeptide triggers complete degradation of light-harvesting phycobiliproteins in nutrient-deprived cyanobacteria. 813 38

The identity of a number of phosphorus-containing metabolites present in Synechocystis sp. PCC 6308 has been confirmed by 31P NMR spectroscopy. The presence of D-ribulose 1,5-bisphosphate (RuBP); DL-glyceraldehyde 3-phosphate (GlyP); D(-)3-phosphoglyceric acid (3PGA); D-ribulose 5-phosphate (Ru5P);6-phosphogluconic acid (6PGA); phosphoenolpyruvate (PEP); inorganic phosphate (Pi); uridine diphosphoglucose (UDPG); ADP and ATP were demonstrated by the pH dependence of their 31P NMR chemical shifts in spectra of perchloric acid cell extracts. Intracellular pH of cells was determined to be 7.5-7.7.
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PMID:31P NMR identification of metabolites and pH determination in the cyanobacterium Synechocystis sp. PCC 6308. 909 27

Recombinant sucrose-6-phosphate synthase (SpsA) was synthesized in Escherichia coli BL21DE3 by using the spsA gene of the cyanobacterium Synechocystis sp. strain PCC 6803. Transformants exhibited a 10,000-fold increase in survival compared to wild-type cells following either freeze-drying, air drying, or desiccation over phosphorus pentoxide. The phase transition temperatures and vibration frequencies (P==O stretch) in phospholipids suggested that sucrose maintained membrane fluidity during cell dehydration.
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PMID:Engineering desiccation tolerance in Escherichia coli. 1074 60

The Synechococcus sp. strain PCC 7942 dpsA gene encodes a stress-inducible DNA-binding protein whose transcription increases in the stationary phase. Such transcription is likely under the control of an alternative sigma factor. Our current work indicated that dpsA transcription is also important under metal-ion limitation, because dpsA mRNA levels increased 12-fold under low-iron conditions, and that dpsA function is essential for growth under iron-limiting conditions. Promoter activity of the dpsA-promoter-lacZ reporter gene constructs implied that a region of dyad symmetry centered 28 nucleotides from the transcription start is required for metal-dependent repression, as judged by the level of lacZ induction following treatment of cultures with the chelator 2,2'-dipyridyl. This potential operator sequence is distinct from the site recognized by the cyanobacterial Fur repressor homologue. No other nutrient stresses (nitrogen, sulfur, phosphorus) yielded the high level of induction seen following chelator treatment. These studies suggest that there may be more than one class of metal-dependent repressor in cyanobacteria.
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PMID:Growth phase and metal-dependent regulation of the dpsA gene in Synechococcus sp. strain PCC 7942, USA. 1089 14

The formal description of Prochlorococcus marinus Chisholm et al. 1992, 299 was based on the non-axenic nomenclatural type, strain CCMP 1375T. The purification and properties of the axenic strain PCC 9511, derived from the same primary culture (SARG) as the type species, are reported here. Prochlorococcus PCC 9511 differs from the latter in possessing horseshoe-shaped thylakoids, exhibiting a low chlorophyll b2 content and lacking phycoerythrin, but shares these phenotypic properties with Prochlorococcus strain CCMP 1378. This relationship was confirmed by 16S rRNA sequence analyses, which clearly demonstrated that the axenic isolate is not co-identic with the nomenclatural type. Strain PCC 9511 has a low mean DNA base composition (32 mol% G+C) and harbours the smallest genome of all known oxyphotobacteria (genome complexity 1.3 GDa = 2 Mbp). Urea and ammonia are the preferred sources of nitrogen for growth, whereas nitrate is not utilized. Several different organic phosphorus compounds efficiently replace phosphate in the culture medium, indicative of ecto-phosphohydrolase activity. In order to distinguish strain PCC 9511 from the nomenclatural type, a new subspecies is proposed, Prochlorococcus marinus Chisholm et al. 1992 subsp. pastoris subsp. nov.
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PMID:Prochlorococcus marinus Chisholm et al. 1992 subsp. pastoris subsp. nov. strain PCC 9511, the first axenic chlorophyll a2/b2-containing cyanobacterium (Oxyphotobacteria). 1103 95

The physiological regulation of glutamine synthetase (GS; EC 6.3.1.2) in the axenic Prochlorococcus sp. strain PCC 9511 was studied. GS activity and antigen concentration were measured using the transferase and biosynthetic assays and the electroimmunoassay, respectively. GS activity decreased when cells were subjected to nitrogen starvation or cultured with oxidized nitrogen sources, which proved to be nonusable for Prochlorococcus growth. The GS activity in cultures subjected to long-term phosphorus starvation was lower than that in equivalent nitrogen-starved cultures. Azaserine, an inhibitor of glutamate synthase, provoked an increase in enzymatic activity, suggesting that glutamine is not involved in GS regulation. Darkness did not affect GS activity significantly, while the addition of diuron provoked GS inactivation. GS protein determination showed that azaserine induces an increase in the concentration of the enzyme. The unusual responses to darkness and nitrogen starvation could reflect adaptation mechanisms of Prochlorococcus for coping with a light- and nutrient-limited environment.
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PMID:In vivo regulation of glutamine synthetase activity in the marine chlorophyll b-containing cyanobacterium Prochlorococcus sp. strain PCC 9511 (oxyphotobacteria). 1131 1

Nitrogen (N) limitation in cyanobacteria is well documented: a reduced growth rate is observed, accompanied by a cessation of phycobiliprotein synthesis and an ordered degradation of phycobilisomes (PBS). This leads to a dramatic bleaching phenomenon known as chlorosis. In Synechococcus strain PCC 7942, bleaching due to PBS degradation is also observed under sulfur (S) or phosphorus (P) limitation, and all three are under the control of the nblA gene product, a 59-amino-acid polypeptide which is overexpressed under N, S, and P starvation (J. L. Collier, and A. R. Grossman, EMBO J. 13:1039-1047, 1994). Cyanobase sequence data for Synechocystis strain PCC 6803 indicate the presence of two tandem open reading frames (sll0452 and sll0453) homologous to nblA. We cloned the two genes, identified a unique 5' mRNA end suggestive of a single transcription start site, and studied nblA expression under conditions of N or S starvation by Northern hybridization: transcripts were detected only under N starvation (no signal is detected in replete medium or with S starvation), whether nblA1 or nblA2 was used as a probe. Mutations in nblA1 and nblA2 were constructed by insertion of a kanamycin cassette; both mutations were nonbleaching under N starvation. Synechocystis strain PCC 6803 does not bleach under S starvation, consistent with the absence of nblA induction in these conditions. These results were confirmed by analysis of the PBS components: sequential degradation of phycocyanin and associated linkers was observed only under conditions of N starvation. This indicates differences between Synechocystis strain PCC 6803 and Synechococcus strain PCC 7942 in their regulatory and signaling pathways leading to N- and S-starved phenotypes.
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PMID:Nitrogen or sulfur starvation differentially affects phycobilisome degradation and expression of the nblA gene in Synechocystis strain PCC 6803. 1132 25


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