Filamentous Anoxygenic Phototrophic Bacteria in Microbial Communities of the Kulunda Steppe Soda Lakes (Altai Krai,Russia)

Microbiology - Soda lakes are relic ecosystems inhabited by unique microorganisms, which are doubly extremophilic: both haloalkaliphilic and natronophilic. Two morphologically and physiologically...     

Participation of algal–bacterial community in the formation of modern stromatolites in Cock Soda Lake,Altai Region

Modern dolomite stromatolites are found in Cock Soda Lake (Kulunda Steppe) at a salinity of 100–200 g/L and pH of 10. The mineralogical analysis has revealed the presence in the stromatolites of Ca?Mg-carbonates of various compositions. The organisms–edificators of the phototrophic community developing in the lake are determined. They are identified as a part of the mineralized biota (cyanobacteria, bacteria, and eukaryotic alga Ctenocladus circinnatus). Morphological and ultrastructural features of exopolysaccharides secreted by cyanobacteria and bacteria dominant in the phototrophic community are characterized. It is shown that polysaccharides secreted primarily by cyanobacteria have the utmost importance for the formation of stromatolites in Petukhovskoe Soda Lake.     

Optimization of <Emphasis Type="Italic">Prochlorothrix hollandica</Emphasis> cyanobacteria culturing for obtaining myristoleic acid

Plankton filament cyanobacteria Prochlorothrix hollandica is characterized by a very high content of C₁₄ and C₁₆ fatty acids (FA) in the lipid membranes. Depending on culturing conditions of the cyanobacteria, total concentrations of myristic and myristoleic acids can reach 35% and those of palmitic and palmitoleic acids can reach 60% of all esterified FA cells. In P. hollandica, a variety of monounsaturated FA is represented by myristoleic and palmitic acids, and by hexadecenoic (C_16:1) acid with olefin bond of cis-configuration, located in the Δ4 position. The process of intensive culturing for P. hollandica cells to yield a maximal biomass in order to isolate the pure drug of myristoleic acid derivative has been optimized. The use of a threestage purification gives 30 mg of chromatographically pure myristoleic acid methyl ester from 17 g of P. hollandica raw biomass (dry mass is 3 g), which is 1% of dry cell mass.     

Characterization of a model cyanobacterium Synechocystis sp. PCC 6803 autotrophic growth in a flat‐panel photobioreactor

We characterized the photoautotrophic growth of glucose‐tolerant Synechocystis sp. PCC 6803 in a flat‐panel photobioreactor running on a semicontinuous regime under various lights, temperatures, and influx carbon dioxide concentrations. The maximum reached growth rate was 0.135 h^?1, which corresponds to a doubling time of 5.13 h—a growth speed never reported for Synechocystis before. Saturating red light intensity for the strain was 220–360 μmol(photons) m^?2 s^?1, and we did not observe any photoinhibition up to 660 μmol(photons) m^?2 s^?1. Synechocystis was able to grow under red light only; however, photons of wavelengths 405–585 and 670–700 nm further improved its growth. Optimal growth temperature was 35°C. Below 32°C, the growth rates decreased linearly with temperature coefficient (Q₁₀) 1.70. Semicontinuous cultivation is known to be efficient for growth characterization and optimization. However, the assumption of correct growth rates calculation—culture exponential growth—is often not fulfilled. The semicontinuous setup in this study was operated as a turbidostat. Accurate online OD measurements with high time‐resolution allowed fast and reliable growth rates determination. Repeating diluting frequencies (up to 18 dilutions per day) were essential for rapid growth stability evaluation. The presented setup provides improvement to previously published semicontinuous characterization strategies by decreasing experimental time requirements and maintaining the culture in exponential growth phase throughout the entire characterization procedure.     

The thylakoid carbonic anhydrase associated with photosystem II is the component of inorganic carbon accumulating system in cells of halo- and alkaliphilic cyanobacterium Rhabdoderma lineare

The organization of carbonic anhydrase (CA) system in halo- and alkaliphilic cyanobacterium Rhabdoderma lineare was studied by Western blot analysis and immunocytochemical electron microscopy. The presence of putative extracellular alpha-CA of 60 kDa in the glycocalyx, forming a tight sheath around the cell, and of two intracellular beta-CA is reported. We show for the first time that the beta-CA of 60 kDa is expressed constitutively and associated with polypeptides of photosystem II (beta-CA-PS II). Another soluble beta-CA of 25 kDa was induced in low-bicarbonate medium. Induction of synthesis of the latter beta-CA was accompanied by an increase in the intracellular pool of inorganic carbon, which suggests an important role of this enzyme in the functioning of a CO(2)-concentrating mechanism.     

Isolation and Characterization of Toxic Cyanobacteria from Different Natural Sources

We isolated seven algologically and five bacteriologically pure cultures of toxin-producing cyanobacteria from Turgen gorge (Kazakhstan), Karlovy Vary (Czech Republic), and Shar-Nuur Lake, Bayan Ulgiiregion (Mongolia) springs. According to the Daphnia magna test, Desertifilum sp. and Nostoc sp. strains were the most toxic in the test of isolated strains (complete death of all test organisms was detected after 48 h). These strains possessed the highest inhibitory effect on proliferation of the HeLa cancer cell line. The Anabaena sp. 35 and Nostoc sp. 4 strains were also high toxic. Model strains Synechocystis PCC 6803 and Synechococcus elongates PCC 7942, as well as the strain isolated in the present work, Synechococcus sp. 55, were less toxic. Mass spectrometry made it possible to assign cyanobacterial toxins to cyclic depsipeptides. Two cyclic depsipeptides, micropeptin T and oscillapeptin, were detected in Desertifilum sp. extracts. Cryptophycin and small amounts of cyclic depsipeptide micropeptin SD were detected in Nostoc sp. extract.     

Distribution and functional role of carbonic anhydrase Cah3 associated with thylakoid membranes in the chloroplast and pyrenoid of <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

Localization of lumenal carbonic anhydrase Cah3 in thylakoid membranes of Chlamydomonas reinhardtii was studied using wild-type algae and photosynthetic mutants with different composition of chlorophyll-protein complexes in the photosystems. In addition, the photosynthetic characteristics of wild-type C. reinhardtii and cia3 mutants lacking the activity of carbonic anhydrase Cah3 were examined. Western blot analysis revealed the lack of cross reaction with antibodies to Cah3 in the mutant lacking the photosystem II (PSII) reaction center, in contrast to the mutant deficient in light-harvesting complex of PSII. These data show that the lumenal Cah3 is associated with polypeptides on the donor side of PSII reaction center. Using immunoelectron microscopy and antibodies to Cah3 from C. reinhardtii, we showed for the first time that the major part of thylakoid Cah3 is localized in the pyrenoid where the bulk of Rubisco is located. The rate of photosynthetic oxygen evolution and PSII photochemical efficiency were lower in C. reinhardtii cia3 mutant than in the wild type, especially in the cells grown at limiting CO₂ concentrations. These observations show that Cah3 takes part in CO₂-concentrating mechanism of the chloroplast. The results support our hypothesis [1, 2] that the carboxylation reaction in microalgae proceeds in the pyrenoid, a specific Rubisco-containing part of the chloroplast, which acquires CO₂ from the lumen of intrapyrenoid thylakoids. We discuss significance of the pyrenoid as an autonomous metabolic microcompartment, in which Cah3 plays a key role in the production and concentration of CO₂ for Rubisco. These functions may promote the photosynthetic efficiency owing to the effective CO₂ supply for the Calvin cycle.     

Cyanofuels: biofuels from cyanobacteria. Reality and perspectives

Photosynthesis Research - Cyanobacteria are represented by a diverse group of microorganisms that, by virtue of being a part of marine and freshwater phytoplankton, significantly contribute to the...     

Far-red light-regulated efficient energy transfer from phycobilisomes to photosystem I in the red microalga Galdieria sulphuraria and photosystems-related heterogeneity of phycobilisome population

Phycobilisomes (PBS) are the major photosynthetic antenna complexes in cyanobacteria and red algae. In the red microalga Galdieria sulphuraria, action spectra measured separately for photosynthetic activities of photosystem I (PSI) and photosystem II (PSII) demonstrate that PBS fraction attributed to PSI is more sensitive to stress conditions and upon nitrogen starvation disappears from the cell earlier than the fraction of PBS coupled to PSII. Preillumination of the cells by actinic far-red light primarily absorbed by PSI caused an increase in the amplitude of the PBS low-temperature fluorescence emission that was accompanied by the decrease in PBS region of the PSI 77 K fluorescence excitation spectrum. Under the same conditions, fluorescence excitation spectrum of PSII remained unchanged. The amplitude of P700 photooxidation in PBS-absorbed light at physiological temperature was found to match the fluorescence changes observed at 77 K. The far-red light adaptations were reversible within 2-5min. It is suggested that the short-term fluorescence alterations observed in far-red light are triggered by the redox state of P700 and correspond to the temporal detachment of the PBS antenna from the core complexes of PSI. Furthermore, the absence of any change in the 77 K fluorescence excitation cross-section of PSII suggests that light energy transfer from PBS to PSI in G. sulphuraria is direct and does not occur through PSII. Finally, a novel photoprotective role of PBS in red algae is discussed.