Browsing by Subject "inorganic phosphorus"
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(2013)Cyanobacteria are phototrophic organisms. They usually occur in water but many species also live in terrestrial habitats, e.g. in symbiotic relationships with fungus. Inorganic phosphorus (Pi) is usually considered to be a limiting factor for the growth of cyanobacteria living in water, since cyanobacteria can use only Pi as a direct source of phosphorus. It has been shown that cyanobacteria have pho-regulon similar to that of Escherichia coli. Pho-regulon can transport and assimilate inorganic phosphate. Cyanobacteria usually produce a wide range of bioactive compounds, which can e.g. be toxic or prevent growth of other bacteria, fungi or yeast. Many of these compounds are produced by non-ribosomal peptide synthetases (NRPS). The aim of this study was to investigate changes in Anabaena sp. 90 proteome, and differences in amounts of bioactive compounds produced by the strain, while growing it in media with high (5,5 mg/l) or low (0,05 mg/ml) Pi concentration. Before moving the culture into two different Pi media, phosphorus storages of the culture were emptied by growing the strain in the media without Pi. In this study, 2D differential gel electrophoresis (2D-DIGE) coupled with LC/MS was used to study proteomes of the organism. Bioactive compounds were also analyzed by LC/MS. Anabaena sp. 90 was chosen because of its fully sequenced and annotated genome. The strain has been found to produce microcystins, anabaenopeptins and anabaenopeptilides. Eleven protein spots with significantly increased or decreased protein quantities were identified in the low Pi media. Ten of them were identified as proteins, which participate in bacterial stringent response. Stringent response is activated when culture is achieving the stationary phase. These stringent response proteins participate in the amino-acid metabolism and translation. One of the proteins was shown to be a ribosomal protein. In addition, the identified proteins included ribulose-bisphosphate carboxylase oxygenase (RuBisCO), which had a significantly lower concentration in the cells in low-phosphorous media. There were no significant differences in amounts of bioactive compounds when growing the culture in low and high Pi media. More replicates could be used, when the study of bioactive compounds is repeated.
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(2018)Inorganic phosphate (Pi) is the only readily utilizable form of phosphorus for toxic diazotrophic cyanobacterium Nodularia spumigena (N. spumigena). Pi is one of the limiting nutrients in the Baltic Sea where surprisingly N. spumigena are highly abundant especially during the summer. This indicates that N. spumigena possibly has an alternative pathway to fulfill its phosphorus requirement. The Baltic Sea, like most aquatic environments, is enriched with organic phosphorus compounds among which phosphonates may constitute a significant fraction. Interestingly, the Baltic Sea N. spumigena strains UHCC 0039 and CCY9414 have been found to carry phosphonate degrading gene cluster (phnC-M) implying that these cyanobacteria could assimilate phosphonates as a phosphorus source. However, the significance of the presence of phn gene cluster in N. spumigena for phosphonate utilization has not been investigated in detail. Here, I aimed to understand how N. spumigena copes with Pi limitation and utilizes phosphonates in laboratory conditions using biochemical assays, PCR-based methods and bioinformatics tools. This would aid in finding a suitable marker for Pi deficiency in cyanobacterial blooms in the Baltic Sea. In this study, bioinformatics and PCR screening showed that phn gene cluster was conserved in the Baltic Sea N. spumigena strains. The studied N. spumigena strains UHCC 0039 and UHCC 0060 were found to utilize naturally produced low molecular weight phosphonates, methylphosphonate (MPn), ethylphosphonate (EPn) and 2-aminoethylphosphonate (2APn). Among these phosphonates, MPn seemed to be the most preferred phosphorus source. Alkaline phosphatase activity, an indicator of Pi limitation, was found to be elevated in the media with Pi and 2APn questioning its suitability as a marker for phosphorus limitation. In addition, growth on MPn released methane indicating that massive blooms of N. spumigena might contribute to an elevated methane supersaturation in the Baltic Sea. Reverse transcriptase quantitative PCR (RT-qPCR) in N. spumigena strains did not show expected upregulation of high-affinity phosphate transporter pstS in Pi limitation. It demonstrated an induction of phosphonate transporter gene phnD in media lacking Pi and supplemented by 2APn. The phosphonate lyase gene phnJ was however, upregulated only in the presence of MPn suggesting that phnJ gene could be used as a marker for phosphonate bioavailability. The findings from this study suggest that the presence of phn gene cluster could provide N. spumigena a competitive advantage in Pi-limited cyanobacterial blooms in the Baltic Sea. The molecular detection methods designed in this study thus could be used in future to monitor the expression of genes induced during Pi limitation and the presence of phosphonates, and the method could be further optimized for screening natural water samples.
Now showing items 1-2 of 2