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Cyanobacterial and algal mass development, or blooms, have severe effects on freshwater and marine systems around the world. Many of these phototrophs produce a variety of potent toxins, contribute to oxygen depletion, and affect water quality in several ways. Coexisting antagonists, such as cyanolytic bacteria, hold the potential to suppress, or even terminate, such blooms, yet the nature of this interaction is not well studied. We isolated 31 cyanolytic bacteria affiliated with the genera Pseudomonas, Stenotrophomonas, Acinetobacter, and Delftia from three eutrophic freshwater lakes in Sweden and selected four phylogenetically diverse bacterial strains with strong-to-moderate lytic activity. To characterize their functional responses to the presence of cyanobacteria, we performed RNA sequencing (RNA-Seq) experiments on coculture incubations, with an initial predator-prey ratio of 1:1. Genes involved in central cellular pathways, stress-related heat or cold shock proteins, and antitoxin genes were highly expressed in both heterotrophs and cyanobacteria. Heterotrophs in coculture expressed genes involved in cell motility, signal transduction, and putative lytic activity. L,D-Transpeptidase was the only significantly upregulated lytic gene in Stenotrophomonas rhizophila EK20. Heterotrophs also shifted their central metabolism from the tricarboxylic acid cycle to the glyoxylate shunt. Concurrently, cyanobacteria clearly show contrasting antagonistic interactions with the four tested heterotrophic strains, which is also reflected in the physical attachment to their cells. In conclusion, antagonistic interactions with cyanobacteria were initiated within 24 h, and expression profiles suggest varied responses for the different cyanobacteria and studied cyanolytes. IMPORTANCE Here, we present how gene expression profiles can be used to reveal interactions between bloom-forming freshwater cyanobacteria and antagonistic heterotrophic bacteria. Species-specific responses in both heterotrophs and cyanobacteria were identified. The study contributes to a better understanding of the interspecies cellular interactions underpinning the persistence and collapse of cyanobacterial blooms. [ABSTRACT FROM AUTHOR]

Prochlorothrix hollandica is filamentous non-heterocystous cyanobacterium which possesses the chlorophyll a/b light-harvesting complexes. Despite the growing interest in unusual green-pigmented cyanobacteria (prochlorophytes) to date only a few sequenced genome from prochlorophytes genera have been reported. This study sequenced the genome of Prochlorothrix hollandica CCAP 1490/1T (CALU1027). The produced draft genome assembly (5.5 Mb) contains 3737 protein-coding genes and 114 RNA genes. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that microorganisms well-adapted to survival in extreme ecosystems could be considered as new sources of biomolecules that have biotechnological importance. On French Polynesian atolls, microbial mats are developing in water ponds exposed to fluctuations in physical and chemical parameters. In these microbial mats, which are called “kopara” by the inhabitants, bacteria coexist with cyanobacteria, and a synergistic relationship may exist between these two types of living microorganisms. A large number of cyanobacteria and bacteria have been isolated from different mats. Under laboratory conditions, these microorganisms were shown to produce various exopolymers, including exopolysaccharides and poly-β-hydroxyalkanoates, along with pigments for further commercial developments. This manuscript gives an overview of substances isolated and characterized from these bacteria and cyanobacteria and discusses their potential applications in biotechnology. [ABSTRACT FROM AUTHOR]

The mechanisms of gold bioaccumulation by cyanobacteria (Plectonema boryanum UTEX 485) from gold(III)-chloride solutions have been studied at three gold concentrations (0.8, 1.7, and 7.8 mM) at 25 °C, using both fixed-time laboratory and real-time synchrotron radiation absorption spectroscopy (XAS) experiments. Interaction of cyanobacteria with aqueous gold(III)-chloride initially promoted the precipitation of nanoparticles of amorphous gold(I)-sulfide at the cell walls, and finally deposited metallic gold in the form of octahedral (111) platelets (∼10 nm to 6 μm) near cell surfaces and in solutions. The XAS results confirm that the reduction mechanism of gold(III)-chloride to metallic gold by cyanobacteria involves the formation of an intermediate Au(I) species, gold(I)-sulfide. [ABSTRACT FROM AUTHOR]

In the cyanobacterium Synechococcus elongatus (PCC 7942) the kai genes A, B, and C and the sasA gene encode the functional protein core of the timing mechanism essential for circadian clock regulation of global gene expression. The Kai proteins comprise the central timing mechanism, and the sensor kinase SasA is a primary transducer of temporal information. We demonstrate that the circadian clock also regulates a chromosome compaction rhythm. This chromosome compaction rhythm is both circadian clock-controlled and kai-dependent. Although sasA is required for global gene expression rhythmicity, it is not required for these chromosome compaction rhythms. We also demonstrate direct control by the Kai proteins on the rate at which the SasA protein autophosphorylates. Thus, to generate and maintain circadian rhythms in gene expression, the Kai proteins keep relative time, communicate temporal information to SasA, and may control access to promoter elements by imparting rhythmic chromosome compaction. [ABSTRACT FROM AUTHOR]

Two chromium-resistant bacterial strains, Bacillus cereus S-6 and Ochrobactrum intermedium CrT-1, and two cyanobacterial strains, Oscillatoria sp. and Synechocystis sp., were used in this study. At initial chromate concentrations of 300 and 600 μg K2CrO4 mL−1, and an inoculum size of 9.6×107 cells mL−1, B. cereus S-6 completely reduced Cr(VI), while O. intermedium CrT-1 reduced Cr(VI) by 98% and 70%, respectively after 96 h. At 100 μg K2CrO4 mL−1, Synechocystis sp. MK(S) and Oscillatoria sp. BJ2 reduced 62.1% and 39.9% of Cr(VI), respectively, at 30°C and pH 8. Application of hexavalent chromate salts adversely affected wheat seedling growth and anatomical characters. However, bacterial inoculation alleviated the toxic effects, as reflected by significant improvements in growth as well as anatomical parameters. Cyanobacterial strains also led to some enhancement of various growth parameters in wheat seedlings. [ABSTRACT FROM AUTHOR]

The proteins present in gas vesicles of the cyanobacteria Anabaena flos-aquae and Microcystis sp. were separated by SDS-polyacrylamide gel electrophoresis. Each contained a protein of Mr 22 K whose N-terminal amino acid sequences showed homology with that of the Calothrix sp. PCC 7601 gvpC gene product. The gvpC gene from A. flos-aquae was cloned and sequenced. The derived amino acid sequence for the gene product indicated a protein, GVPc, of 193 residues and Mr 21985 containing five highly conserved 33 amino acid repeats. The sequence was identical at the N-terminus to that of the Mr 22K protein present in gas vesicles and showed correspondence to seven tryptic peptides isolated from gas vesicles. This establishes that GVPc forms a second protein component of the gas vesicle, in addition to the main constituent, the 70 residue GVPa. Quantitative amino acid analysis of entire gas vesicles reveals that GVPc accounts for only 2.9% of the protein molecules and 8.2% of the mass present: this is insufficient to form the conical end caps of the gas vesicles. It is suggested that GVPc provides the hydrophilic outer surface of the gas vesicle wall; the 33 amino acid repeats may interact with the periodic structure provided by GVPa. [ABSTRACT FROM AUTHOR]

Reports on the importance of extracellular polysaccharide (EPS) in the biology of cyanobacteria according to a research in the U.S. Function of EPS; Characteristics of the cyanobacterial EPS; Significance of the findings for the research industry in general.

Plants and their green cousins cyanobacteria and algae use sunlight to drive the chemistry that lets them grow, survive and perform an amazing range of biochemical reactions. The ability of these organisms to use a freely available energy source makes them attractive as sustainable and renewable platforms for more than just food production. They are also a source of metabolic tools for engineering microbes for "green" chemistry. This Thematic Minireview Series discusses how green organisms capture light and protect their photosynthetic machinery from too much light; new structural snapshots of the clock complex that orchestrates signaling during the light/dark cycle; challenges for improving stress responses in crops; harnessing cyanobacteria as biofactories and efforts to engineer microbes for "green" biopolymer production. [ABSTRACT FROM AUTHOR]