Divergent gene expression responses in two Baltic Sea heterotrophic model bacteria to dinoflagellate dissolved organic matter.

Phytoplankton release massive amounts of dissolved organic matter (DOM) into the water column during recurring blooms in coastal waters and inland seas. The released DOM encompasses a complex mixture of both known and unknown compounds, and is a rich nutrient source for heterotrophic bacteria. The metabolic activity of bacteria during and after phytoplankton blooms can hence be expected to reflect the characteristics of the released DOM.

Cyanotoxins associated with macrophytes in Berlin (Germany) water bodies - Occurrence and risk assessment.

Fatal dog poisoning after uptake of neurotoxic cyanobacteria associated with aquatic macrophytes in Tegeler See (Berlin, Germany) raised concerns about critical exposure of humans, especially children, to cyanotoxins produced by macrophyte associated cyanobacteria during recreational activity. From 2017 to 2021 a total of 398 samples of macrophytes washed ashore at bathing sites located at 19 Berlin lakes were analysed for anatoxins, microcystins, and cylindrospermopsins, as were 463 water samples taken in direct proximity to macrophyte accumulations. Cyanotoxins were detected in 66 % of macrophyte samples and 50 % of water samples, with anatoxins being the most frequently detected toxin group in macrophyte samples (58 %) and cylindrospermopsins in water samples (41 %).

Cyanobacterial Genome Sequencing, Annotation, and Bioinformatics.

Cyanobacteria are collectively a globally important monophyletic phylum of bacteria. They have attracted a lot of attention, not only because they are rich sources of natural bioactive products, including toxic substances, but also because they play an important role in global nitrogen and carbon cycles, and are capable of maintaining versatile environmental niche adaptations. A vast number of cyanobacterial genomes have become available due to fast development of sequencing technologies, but effort is still needed to comprehensively understand the molecular basis of their diversity.

Deciphering Chemical Mediators Regulating Specialized Metabolism in a Symbiotic Cyanobacterium.

Genomes of cyanobacteria feature a variety of cryptic biosynthetic pathways for complex natural products, but the peculiarities limiting the discovery and exploitation of the metabolic dark matter are not well understood. Here we describe the discovery of two cell density-dependent chemical mediators, nostoclide and nostovalerolactone, in the symbiotic model strain Nostoc punctiforme, and demonstrate their pronounced impact on the regulation of specialized metabolism. Through transcriptional, bioinformatic and labeling studies we assigned two adjacent biosynthetic gene clusters to the biosynthesis of the two polyketide mediators.

Occurrence of cylindrospermopsin, anatoxin-a and their homologs in the southern Czech Republic - Taxonomical, analytical, and molecular approaches.

Water bloom-forming cyanobacteria have a severe impact on freshwater quality. Although some cyanobacterial toxins such as microcystins have been studied extensively, other toxins like anatoxin-a (ATX) and their structural analogs - as well as cyanobacterial taxa producing these toxins remain to be explored in detail. The present study investigated levels of ATX, CYN and their homologs along with the occurrence of anaC and cyrJ genes in water blooms in 16 sites in the Czech Republic that were pre-selected concerning the presence of potential toxin producers.

Effects of allochthonous dissolved organic matter input on microbial composition and nitrogen-cycling genes at two contrasting estuarine sites.

Heterotrophic bacteria are important drivers of nitrogen (N) cycling and the processing of dissolved organic matter (DOM). Projected increases in precipitation will potentially cause increased loads of riverine DOM to the Baltic Sea and likely affect the composition and function of bacterioplankton communities. To investigate this, the effects of riverine DOM from two different catchment areas (agricultural and forest) on natural bacterioplankton assemblages from two contrasting sites in the Baltic Sea were examined.

Insight into the genome and brackish water adaptation strategies of toxic and bloom-forming Baltic Sea Dolichospermum sp. UHCC 0315.

The Baltic Sea is a shallow basin of brackish water in which the spatial salinity gradient is one of the most important factors contributing to species distribution. The Baltic Sea is infamous for its annual cyanobacterial blooms comprised of Nodularia spumigena, Aphanizomenon spp., and Dolichospermum spp.

Coupling biogeochemical process rates and metagenomic blueprints of coastal bacterial assemblages in the context of environmental change.

Bacteria are major drivers of biogeochemical nutrient cycles and energy fluxes in marine environments, yet how bacterial communities respond to environmental change is not well known. Metagenomes allow examination of genetic responses of the entire microbial community to environmental change. However, it is challenging to link metagenomes directly to biogeochemical process rates.

Comparative Genomics of the Baltic Sea Toxic Cyanobacteria UHCC 0039 and Its Response to Varying Salinity.

Salinity is an important abiotic factor controlling the distribution and abundance of , the dominating diazotrophic and toxic phototroph, in the brackish water cyanobacterial blooms of the Baltic Sea. To expand the available genomic information for brackish water cyanobacteria, we sequenced the isolate UHCC 0039 using an Illumina-SMRT hybrid sequencing approach, revealing a chromosome of 5,294,286 base pairs (bp) and a single plasmid of 92,326 bp. Comparative genomics in showed pronounced genetic similarity among strains evidencing their short evolutionary history.

Strains of the toxic and bloom-forming Nodularia spumigena (cyanobacteria) can degrade methylphosphonate and release methane.

Nodularia spumigena is a nitrogen-fixing cyanobacterium that forms toxic blooms in the Baltic Sea each summer and the availability of phosphorous is an important factor limiting the formation of these blooms. Bioinformatic analysis identified a phosphonate degrading (phn) gene cluster in the genome of N. spumigena suggesting that this bacterium may use phosphonates as a phosphorus source.

Transcriptomic and Proteomic Profiling of Anabaena sp. Strain 90 under Inorganic Phosphorus Stress.

Inorganic phosphorus (Pi) is one of the main growth-limiting factors of diazotrophic cyanobacteria. Due to human activity, the availability of Pi has increased in water bodies, resulting in eutrophication and the formation of massive cyanobacterial blooms. In this study, we examined the molecular responses of the cyanobacterium Anabaena sp.