Microbial community changes during a toxic cyanobacterial bloom in an alkaline Hungarian lake

Diversity and Distribution Characteristics of Viruses from Soda Lakes

Viruses are the most abundant living things and a source of genetic variation. Despite recent research, we know little about their biodiversity and geographic distribution. We used different bioinformatics tools, MG-RAST, genome detective web tools, and GenomeVx, to describe the first metagenomic examination of haloviruses in Wadi Al-Natrun. The discovered viromes had remarkably different taxonomic compositions. Most sequences were derived from double-stranded DNA viruses, especially from Myoviridae, Podoviridae, Siphoviridae, Herpesviridae, Bicaudaviridae, and Phycodnaviridae families; single-stranded DNA viruses, especially from the family Microviridae; and positive-strand RNA viruses, especially from the family Potyviridae. Additionally, our results showed that Myohalovirus chaoS9 has eight Contigs and is annotated to 18 proteins as follows: tail sheath protein, tco, nep, five uncharacterized proteins, HCO, major capsid protein, putative pro head protease protein, putative head assembly protein, CxxC motive protein, terl, HTH domain protein, and terS Exon 2. Additionally, Halorubrum phage CGphi46 has 19 proteins in the brine sample as follows: portal protein, 17 hypothetical proteins, major capsid protein, etc. This study reveals viral lineages, suggesting the Virus's global dispersal more than other microorganisms. Our study clarifies how viral communities are connected and how the global environment changes.

The effect of graphene photocatalysis on microbial communities in Lake Xingyun, southwestern China

Graphene photocatalysis is a new method for harmful algae and water pollution control. However, microbial communities undergoing graphene photocatalysis treatment in freshwater lakes have been poorly studied. Here, using 16S rRNA and 18S rRNA gene high-throughput sequencing, the responses of microbial communities to graphene photocatalysis were analyzed in the eutrophic lake, Lake Xinyun, southwestern China. For microeukaryotes, we found that Arthropoda was dominant in summer, while its abundant level declined in spring under natural conditions. The evident reduction of Arthropods was observed after graphene photocatalysis treatment in summer and then reached a relatively stable level. For bacteria, Cyanobacteria decreased in summer due to the graphene photocatalysis-mediated inactivation. However, Cyanobacteria was higher in the treated group in spring with a genera group-shift. Functional analysis revealed that microeukaryotes showed higher potential for fatty acid oxidation and TCA cycle in the treated group in summer, but they were more abundant in control in spring. Pathways of starch and sucrose metabolism and galactose metabolism were more abundant in control in summer, while they were enriched in the treated group in spring for bacteria. This study offers insights into the effects of graphene photocatalysis on microbial communities and their functional potential in eutrophic lake.

Removal of phosphate at low concentration from water by porous PVA/Al2O3 composites

The porous polyvinyl alcohol (PVA)/Al₂O₃ composite by supporting activated alumina on the cross-linked network of PVA has been successfully prepared and its property for the removal of phosphate in aqueous solution was also evaluated. The structure of the PVA/Al₂O₃ was examined by scanning electron microscopy. It showed that the activated alumina particles with an average size of 1 μm were evenly dispersed and fixed in the cross-linked network structure of PVA. The effects of adsorption time, solution temperature, pH, initial concentration of phosphate, Al₂O₃ loading rate, dosage and coexisting ions on the phosphate removal were further studied. The results showed that the highest removal phosphate efficiency of 95% can be obtained with the Al₂O₃ loading rate of PVA/Al₂O₃ being 60 wt.% at pH of 4 at 30 °C. The maximum adsorption capacities of PO43- by PVA/Al₂O₃ suggested by the Langmuir isothermal model was 10.12 mg/g. The adsorption process of phosphate can be fit well with a pseudo-second-order model (R² = 0.9900). The PVA/Al₂O₃ composite exhibited a high selective adsorption of phosphate in the presence of commonly coexisting anions except the obvious effect of CO32- in water. Meanwhile, the PVA/Al₂O₃ composite can be easily separated and recovered due to the granulation of adsorbent. PVA/Al₂O₃ composite also shows the excellent properties of regeneration and recycling use with the removal efficiency of phosphate was 88.93%, 88.38% and 94.34% after three cycles, respectively. It can be proposed that the PVA/Al₂O₃ composite is a promising recyclable adsorbent for removing phosphate at low concentration from aqueous solution.

Microbial communities of soda lakes and pans in the Carpathian Basin: a review

In this review, I would like to summarize the current knowledge on the microbiology of soda lakes and pans of the Carpathian Basin. First, the characteristic physical and chemical features of these sites are described. Most of the microbiological information presented deals with prokaryotes and algae, but protists and viruses are also mentioned. Planktonic bacterial communities are dominated by members of the phyla Actinobacteria, Bacteroidetes and Proteobacteria; small-sized trebouxiophycean green algae and Synechococcus/Cyanobium picocyanobacteria are the most important components of phytoplankton. Based on the current knowledge, it seems that mainly temperature, salinity, turbidity and grazing pressure regulate community composition and the abundance of individual microbial groups, but the external nutrient load from birds also has a significant impact on the ecological processes.

Community composition and functional genes explain different ecological roles of heterotrophic bacteria attached to two bloom-forming cyanobacterial genera

Eutrophication leads to frequent outbreaks of cyanobacterial blooms, however, the effect of heterotrophic bacteria attached to cyanobacterial cells is unclear. Field investigations were carried out to gain a deeper understanding of the community composition and functional role of heterotrophic bacteria attached to Dolichospermum and Microcystins cells. The significantly positive relationships between Dolichospermum density and total nitrogen (TN) and between Microcystins density and particle nitrogen (PN) indicated the strong nitrogen (N) demand of these two species. The lack of functional genes that mediate the nitrification process in bacteria attached to both Microcystins and Dolichospermum cells indicated that these two genera preferred ammonium (NH₄⁺-N). Dolichospermum cells obtained more available N through N₂ fixation, which was expressed by high nitrogenase gene abundance. Bacteria attached to Microcystins cells showed a higher activity of leucine aminopeptidase and a significantly higher abundance of functional genes that mediate dissimilatory nitrate reduction to ammonium (DNRA) than those attached to Dolichospermum cells. The significantly higher abundance of carbon degradation genes and β-glucosidase activity of bacteria attached to Microcystins cells compared with those of bacteria attached to Dolichospermum cells suggested that abundant organic carbon was bound to Microcystins cells, which is a prerequisite for DNRA. In addition, Microcystins cells exhibited a great advantage in soluble reactive phosphorus (SRP) production through high levels of organic phosphorus (P) hydrolysis associated with high levels of phosphatase genes of attached bacteria. In conclusion, bacteria attached to Microcystins cells performed more important functions on NH₄⁺-N and SRP production through ammonification and DNRA, as well as phosphatase hydrolysis respectively, compared to those attached to Dolichospermum. Thus, algal growth is the result of different variables such as nutrient concentration, their ratio and the microbial ability.

A Large-Scale Survey of the Bacterial Communities in Lakes of Western Mongolia with Varying Salinity Regimes

In recent years, climate change coupled with anthropogenic activities has led to monumental changes in saline lakes which are rapidly drying up across the globe and particularly in Central Asia. The landlocked country of Mongolia is rich in lakes which have remained primarily undisturbed by human impact, and many of these lakes have varying salinity regimes and are located across various geographical landscapes. In this study, we sampled 18 lakes with varying salinity regimes (hyperhaline, mesohaline, oligohaline, and polyhaline) covering 7000 km of western Mongolia and its various geographical landscapes (Gobi Desert, forests, and steppe). We identified that the bacterial communities that dominate these lakes are significantly influenced by salinity (p < 0.001) and geographical landscape (p < 0.001). Further, only five zOTUs were shared in all the lakes across the salinity regimes, providing evidence that both local and regional factors govern the community assembly and composition. Furthermore, the bacterial communities of hyperhaline lakes were significantly positively correlated with salinity (ANOVA, p < 0.001) and arsenic concentrations (ANOVA, p < 0.001), whereas bacterial communities of mesohaline and polyhaline lakes situated in forest and steppe landscapes were positively correlated with temperature (ANOVA, p < 0.001) and altitude (ANOVA, p < 0.001), respectively. Functional predictions based on the 16S rRNA gene indicated enrichment of KEGG Ontology terms related to transporters for osmoprotection and -regulation. Overall, our study provides a comprehensive view of the bacterial diversity and community composition present in these lakes, which might be lost in the future.

Prokaryotic community composition in a great shallow soda lake covered by large reed stands (Neusiedler See/Lake Fertő) as revealed by cultivation- and DNA-based analyses

Little is known about the detailed community composition of heterotrophic bacterioplankton in macrophyte-dominated littoral systems, where a considerable amount of dissolved organic carbon originates from aquatic macrophytes instead of phytoplankton. The aim of the present study was to reveal the effect of macrophytes on the microbial community and to elucidate their role in a macrophyte-dominated shallow soda lake, which can be characterised by a mosaic of open waters and reed marsh. Therefore, 16S rRNA gene amplicon sequencing, the most probable number method, cultivation of bacterial strains, EcoPlate and cultivation-based substrate utilisation techniques were applied. Differences in the structures of microbial communities were detected between the water and the sediment samples and between vegetated and unvegetated water samples. Planktonic bacterial communities of an inner pond and a reed-covered area showed significant similarities to each other. Woesearchaeia was the dominant archaeal taxon in the water samples, while Bathyarchaeia, 'Marine Benthic Group D' and 'DHVEG-1' were abundant in the sediment samples. The most probable number of heterotrophic bacteria was lower in the open water than in the reed-associated areas. The vast majority (83%) of the isolated bacterial strains from the water samples of the reed-covered area were able to grow on a medium containing reed extract as the sole source of carbon.

The microbiota as a candidate biomarker for SPA pools and SPA thermal spring stability after seismic events

Worldwide, the location of thermal springs overlaps seismic areas, and the higher occurrence of earthquakes may impact on water stability and safety. The hydrogeological perturbations pose environmental and public health risks that can be monitored by well-established chemical, physical and biological parameters. Specific health concerns involve the exposure of the population to the medical or wellness uses of SPA thermal waters, e.g. in respiratory or hydropinic treatments as well as during rehabilitative or recreational activities in pools. Since SPA waters are characterized by their own microbiota, we analysed by 16S amplicon sequencing the dynamics of water microbial communities after the August 2017 Ischia island earthquake. For the first time, we report the impact of a seismic event on a thermal spring water, whose microbiota was deeply characterized before and immediately after the natural disaster. The biodiversity stability of the water underwent a dramatic disturbance following the earthquake, as summarized by a Shannon index moving from 1.300 during May 2016-July 2017, up to 1.600 during the first 20-70 h after the event and slightly slowing down to 1.500 after 30 days and to 1.400 after 6 months. Microbiota analysis showed a sudden reduction of the relative abundance of autochthone thermophilic species within the first 20 h and a parallel increase of other thermophilic species as well as of ectopic bacteria from soil, sediments, sea, freshwater and wastewaters. Cultivable mesophilic bacteria were observed only in the first 20 h sample (7 × 10³/L), even if the presence of faecal contamination traces was detected by Real Time PCR also up to 70 h after the disaster. OTUs analysis of putative metabolic functions showed several changes between pre and post event, such as in the distribution of Sulphur metabolizing and Carbon fixation species. The restoration of the original pattern followed a slow trend, requiring over six months. The observed results confirm the impact of the earthquake on the microbiota structure of the underground thermal spring water, suggesting further perspectives for monitoring water stability and safety issues by a metagenomic approach.

A Review and Perspective of eDNA Application to Eutrophication and HAB Control in Freshwater and Marine Ecosystems

Changing ecological communities in response to anthropogenic activities and climate change has become a worldwide problem. The eutrophication of waterbodies in freshwater and seawater caused by the effects of human activities and nutrient inputs could result in harmful algae blooms (HABs), decreases water quality, reductions in biodiversity and threats to human health. Rapid and accurate monitoring and assessment of aquatic ecosystems are imperative. Environmental DNA (eDNA) analysis using high-throughput sequencing has been demonstrated to be an effective and sensitive assay for detecting and monitoring single or multiple species in different samples. In this study, we review the potential applications of eDNA approaches in controlling and mitigating eutrophication and HABs in freshwater and marine ecosystems. We use recent studies to highlight how eDNA methods have been shown to be a useful tool for providing comprehensive data in studies of eutrophic freshwater and marine environments. We also provide perspectives on using eDNA techniques to reveal molecular mechanisms in biological processes and mitigate eutrophication and HABs in aquatic ecosystems. Finally, we discuss the feasible applications of eDNA for monitoring biodiversity, surveying species communities and providing instructions for the conservation and management of the environment by integration with traditional methods and other advanced techniques.

Microcystis Chemotype Diversity in the Alimentary Tract of Bigheaded Carp

Most cyanobacterial organisms included in the genus Microcystis can produce a wide repertoire of secondary metabolites. In the mid-2010s, summer cyanobacterial blooms of Microcystis sp. occurred regularly in Lake Balaton. During this period, we investigated how the alimentary tract of filter-feeding bigheaded carps could deliver different chemotypes of viable cyanobacteria with specific peptide patterns. Twenty-five Microcystis strains were isolated from pelagic plankton samples (14 samples) and the hindguts of bigheaded carp (11 samples), and three bloom samples were collected from the scums of cyanobacterial blooms. An LC-MS/MS-based untargeted approach was used to analyze peptide patterns, which identified 36 anabaenopeptin, 17 microginin, and 13 microcystin variants. Heat map clustering visualization was used to compare the identified chemotypes. A lack of separation was observed in peptide patterns of Microcystis that originated from hindguts, water samples, and bloom-samples. Except for 13 peptides, all other congeners were detected from the viable and cultivated chemotypes of bigheaded carp. This finding suggests that the alimentary tract of bigheaded carps is not simply an extreme habitat, but may also supply the cyanobacterial strains that represent the pelagic chemotypes.