Phenotypic and Genotypic Methods for the Identification and Quantification of Cyanobacteria in Lake Water.

Early monitoring of Microcystis, a cyanobacterium that produces microcystin, is paramount in order to confirm the presence of Microcystis spp. Both phenotypic and genotypic methods have been used. The phenotypic methods provide the presence of the microcystis but do not confirm its species type and toxin produced. Additionally, phenotypic methods cannot differentiate toxigenic from non-toxigenic Microcystis. Therefore, the current protocol also describes genetic methods based on PCR to detect toxigenic Microcystis spp. based on microcystin synthetase E (mcy E) gene and 16-23S RNA genes for species-specific identification, which can effectively comprehend distinct lineages and discrimination of potential complexity of microcystin populations. The presence of these microcystin toxins in blood, in most cases, indicates contamination of drinking water by cyanobacteria. The methods presented herein are used to identify microcystin toxins in drinking water and blood.

Microbial Diversity Impacts Non-Protein Amino Acid Production in Cyanobacterial Bloom Cultures Collected from Lake Winnipeg.

Lake Winnipeg in Manitoba, Canada is heavily impacted by harmful algal blooms that contain non-protein amino acids (NPAAs) produced by cyanobacteria: N-(2-aminoethyl)glycine (AEG), ß-aminomethyl-L-alanine (BAMA), ß-N-methylamino-L-alanine (BMAA), and 2,4-diaminobutyric acid (DAB). Our objective was to investigate the impact of microbial diversity on NPAA production by cyanobacteria using semi-purified crude cyanobacterial cultures established from field samples collected by the Lake Winnipeg Research Consortium between 2016 and 2021. NPAAs were detected and quantified by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) using validated analytical methods, while Shannon and Simpson alpha diversity scores were determined from 16S rRNA metagenomic sequences. Alpha diversity in isolate cultures was significantly decreased compared to crude cyanobacterial cultures (p < 0.001), indicating successful semi-purification. BMAA and AEG concentrations were higher in crude compared to isolate cultures (p < 0.0001), and AEG concentrations were correlated to the alpha diversity in cultures (r = 0.554; p < 0.0001). BAMA concentrations were increased in isolate cultures (p < 0.05), while DAB concentrations were similar in crude and isolate cultures. These results demonstrate that microbial community complexity impacts NPAA production by cyanobacteria and related organisms.

Bacterial Communities Along Environmental Gradients in Tropical Soda Lakes.

Soda lake environments are known to be variable and can have distinct differences according to geographical location. In this study, we investigated the effects of different environmental conditions of six adjacent soda lakes in the Pantanal biome (Mato Grosso do Sul state, Brazil) on bacterial communities and their functioning using a metagenomic approach combined with flow cytometry and chemical analyses. Ordination analysis using flow cytometry and water chemistry data from two sampling periods (wet and dry) clustered soda lakes into three different profiles: eutrophic turbid (ET), oligotrophic turbid (OT), and clear vegetated oligotrophic (CVO). Analysis of bacterial community composition and functioning corroborated this ordination; the exception was one ET lake, which was similar to one OT lake during the wet season, indicating drastic shifts between seasons. Microbial abundance and diversity increased during the dry period, along with a considerable number of limnological variables, all indicative of a strong effect of the precipitation-evaporation balance in these systems. Cyanobacteria were associated with high electric conductivity, pH, and nutrient availability, whereas Actinobacteria, Alphaproteobacteria, and Betaproteobacteria were correlated with landscape morphology variability (surface water, surface perimeter, and lake volume) and with lower salinity and pH levels. Stress response metabolism was enhanced in OT and ET lakes and underrepresented in CVO lakes. The microbiome dataset of this study can serve as a baseline for restoring impacted soda lakes. Altogether, the results of this study demonstrate the sensitivity of tropical soda lakes to climate change, as slight changes in hydrological regimes might produce drastic shifts in community diversity.

Studies on the Mechanism of the Volatile Oils from Caoguo-4 Decoction in Regulating Spleen Deficiency Diarrhea by Adjusting Intestinal Microbiota.

BACKGROUND: The Caoguo-4 decoction, a classical Mongolian medicine formula, is widely used to treat spleen deficiency diarrhea (SDD) in Mongolian for decades. Previously, the Caoguo-4 decoction volatile oil has been confirmed to be effective in ameliorating symptoms of spleen deficiency diarrhea in an animal model. However, the underlying mechanism of the Caoguo-4 decoction volatile oil is yet to be established. The aim of the current study was to investigate the antidiarrheal effects and mechanism of the Caoguo-4 decoction volatile oil. METHOD: Wistar rats were randomly divided into 5 groups of 10 animals including control, model, positive, Caoguo-4 decoction, and Caoguo-4 decoction volatile oil groups (10 rats in each group). All the rats, besides those in the control group, were induced to develop SDD by a bitter-cold purgation method with Xiaochengqi decoction. The antidiarrheal effect of Caoguo-4 decoction volatile oil was evaluated by pathological section, serum D-xylose and AMS content, plasma MTL content, and gut microbiota analysis via 16S rRNA sequencing. RESULTS: The results showed that the developed SDD rat model (model group) had decreased food intake, increased weight loss, soft stool, and bad hair color. When compared with the control group, serum was significantly reduced serum D-xylose and AML but increased MTL levels in the model group (p < 0.05). However, after treatment with either the Caoguo-4 decoction (the decoction group) or Smecta (the positive group) or volatile oil from the Caoguo-4 decoction (the volatile oil group), a significant increase in the serum D-xylose levels was observed. Additionally, AML levels significantly increased in the positive and volatile oil groups, and MTL levels significantly decreased in the decoction and volatile oil groups, when compared with the model group (p < 0.05). The pathological changes of the intestinal mucosa showed that the structure of the epithelium in the villi of the small intestine was affected, deformed, and incomplete in the model group when compared with the control group. However, either the decoction group or the volatile oil group recovered the villous morphology. The results of OTU analysis and alpha diversity analysis of intestinal bacteria showed that the intestinal microbiota of the SDD model rats showed an obvious decrease in richness and diversity of intestinal microbiota. But the intervention treatment of decoction and volatile oil could significantly recover the richness and diversity of intestinal microbiota. CONCLUSION: The intestinal microbiota destroyed in SDD modelling could be significantly improved by the Caoguo-4 decoction volatile oils, which provides reference for clinical medication.

Thainema gen. nov. (Leptolyngbyaceae, Synechococcales): A new genus of simple trichal cyanobacteria isolated from a solar saltern environment in Thailand.

Simple trichal types constitute a group of cyanobacteria with an abundance of novel, often cryptic taxa. Here, we investigated material collected from wet surface-soil in a saline environment in Petchaburi Province, central Thailand. A morphological comparison of the isolated strain with similar known species, as well as its phylogenetic and species delimitation analyses based on the combined datasets of other related organisms, especially simple trichal cyanobacteria, revealed that the material of this study represented an independent taxon. Using a multifaceted method, we propose that this material represents a new genus, Thainema gen. nov., belonging to the family Leptolyngbyaceae, with the type species Thainema salinarum sp. nov. This novel taxon shares similar ecological habitats with strains previously placed in the same lineage.

Oral Cyanobacteria and Hepatocellular Carcinoma.

BACKGROUND: Gut microbial alterations have been linked to chronic liver disease and hepatocellular carcinoma (HCC). The role of the oral microbiome in liver cancer development has not been widely investigated. METHODS: Bacterial 16S rRNA sequences were evaluated in oral samples from 90 HCC cases and 90 controls who were a part of a larger U.S. case-control study of HCC among patients diagnosed from 2011 to 2016. RESULTS: The oral microbiome of HCC cases showed significantly reduced alpha diversity compared with controls (Shannon P = 0.002; Simpson P = 0.049), and beta diversity significantly differed (weighted Unifrac P = 0.004). The relative abundance of 30 taxa significantly varied including Cyanobacteria, which was enriched in cases compared with controls (P = 0.018). Cyanobacteria was positively associated with HCC [OR, 8.71; 95% confidence interval (CI), 1.22-62.00; P = 0.031] after adjustment for age, race, birthplace, education, smoking, alcohol, obesity, type 2 diabetes, Hepatitis C virus (HCV), Hepatitis B virus (HBV), fatty liver disease, aspirin use, other NSAID use, laboratory batch, and other significant taxa. When stratified by HCC risk factors, significant associations of Cyanobacteria with HCC were exclusively observed among individuals with negative histories of established risk factors as well as females and college graduates. Cyanobacterial genes positively associated with HCC were specific to taxa producing microcystin, the hepatotoxic tumor promotor, and other genes known to be upregulated with microcystin exposure. CONCLUSIONS: Our study provides novel evidence that oral Cyanobacteria may be an independent risk factor for HCC. IMPACT: These findings support future studies to further examine the causal relationship between oral Cyanobacteria and HCC risk.

Genome Streamlining, Plasticity, and Metabolic Versatility Distinguish Co-occurring Toxic and Nontoxic Cyanobacterial Strains of Microcoleus.

Harmful cyanobacterial bloom occurrences have increased worldwide due to climate change and eutrophication, causing nuisance and animal deaths. Species from the benthic cyanobacterial genus Microcoleus are ubiquitous and form thick mats in freshwater systems, such as rivers, that are sometimes toxic due to the production of potent neurotoxins (anatoxins). Anatoxin-producing (toxic) strains typically coexist with non-anatoxin-producing (nontoxic) strains in mats, although the reason for this is unclear. To determine the genetic mechanisms differentiating toxic and nontoxic Microcoleus, we sequenced and assembled genomes from 11 cultures and compared these to another 31 Microcoleus genomes. Average nucleotide identities (ANI) indicate that toxic and nontoxic strains are distinct species (ANI, <95%), and only 6% of genes are shared across all 42 genomes, suggesting a high level of genetic divergence among Microcoleus strains. Comparative genomics showed substantial genome streamlining in toxic strains and a potential dependency on external sources for thiamine and sucrose. Toxic and nontoxic strains are further differentiated by an additional set of putative nitrate transporter (nitrogen uptake) and cyanophycin (carbon and nitrogen storage) genes, respectively. These genes likely confer distinct competitive advantages based on nutrient availability and suggest nontoxic strains are more robust to nutrient fluctuations. Nontoxic strains also possess twice as many transposable elements, potentially facilitating greater genetic adaptation to environmental changes. Our results offer insights into the divergent evolution of Microcoleus strains and the potential for cooperative and competitive interactions that contribute to the co-occurrence of toxic and nontoxic species within mats. IMPORTANCE Microcoleus autumnalis, and closely related Microcoleus species, compose a geographically widespread group of freshwater benthic cyanobacteria. Canine deaths due to anatoxin-a poisoning, following exposure to toxic proliferations, have been reported globally. While Microcoleus proliferations are on the rise, the mechanisms underpinning competition between, or coexistence of, toxic and nontoxic strains are unknown. This study identifies substantial genetic differences between anatoxin-producing and non-anatoxin-producing strains, pointing to reduced metabolic flexibility in toxic strains, and potential dependence on cohabiting nontoxic strains. Results provide insights into the metabolic and evolutionary differences between toxic and nontoxic Microcoleus, which may assist in predicting and managing aquatic proliferations.

Vertical structure of the bacterial diversity in meromictic Fayetteville Green Lake.

The permanently stratified water columns in euxinic meromictic lakes produce niche environments for phototrophic sulfur oxidizers and diverse sulfur metabolisms. While Green Lake (Fayetteville, New York, NY) is known to host a diverse community of ecologically important sulfur bacteria, analyses of its microbial communities, to date, have been largely based on pigment analysis and smaller datasets from Sanger sequencing techniques. Here, we present the results of next-generation sequencing of the eubacterial community in the context of the water column geochemistry. We observed abundant purple and green sulfur bacteria, as well as anoxygenic photosynthesis-capable cyanobacteria within the upper monimolimnion. Amidst the phototrophs, we found other sulfur-cycling bacteria including sulfur disproportionators and chemotrophic sulfur oxidizers, further detailing our understanding of the sulfur cycle and microbial ecology of euxinic, meromictic lakes.

Novel Gloeobacterales spp. from Diverse Environments across the Globe.

Photosynthetic Cyanobacteria and their descendants are the only known organisms capable of oxygenic photosynthesis. Their metabolism permanently changed the Earth's surface and the evolutionary trajectory of life, but little is known about their evolutionary history. Genomes of the Gloeobacterales, an order of deeply divergent photosynthetic Cyanobacteria, may hold clues about the evolutionary process. However, there are only three published genomes within this order, and it is difficult to make broad inferences based on such little data. Here, I describe five species within the Gloeobacterales retrieved from publicly available databases and examine their photosynthetic gene content and the environments in which Gloeobacterales genomes and 16S rRNA gene sequences are found. The Gloeobacterales contain reduced photosystems and inhabit cold, wet-rock, and low-light environments. They are likely present in low abundances due to their low growth rate. Future searches for Gloeobacterales should target these environments, and samples should be deeply sequenced to capture the low-abundance taxa. Publicly available databases contain undescribed taxa within the Gloeobacterales. However, searching through all available data with current methods is computationally expensive. Therefore, new methods must be developed to search for these and other evolutionarily important taxa. Once identified, these novel photosynthetic Cyanobacteria will help illuminate the origin and evolution of oxygenic photosynthesis. IMPORTANCE Early branching photosynthetic Cyanobacteria such as the Gloeobacterales may provide clues into the evolutionary history of oxygenic photosynthesis, but there are few genomes or cultured taxa from this order. Five new metagenome-assembled genomes suggest that members of the Gloeobacterales all contain reduced photosystems and lack genes associated with thylakoids and circadian rhythms. Their distribution suggests that they may thrive in environments that are marginal for other species, including wet-rock and cold environments. These traits may aid in the discovery and cultivation of novel species in this clade.

Molecular detection of some toxogenic cyanobacteria in Tigris River in Baghdad-Iraq.

Cyanobacteria and their pollution are being increasingly commonly reported worldwide that cause a serious hazard to environmental and human health. Cyanotoxin was the most algal toxin reported to be produced by several orders of cyanobacteria. This study aimed to provide a technique to detect cylindrosprmopsin and saxitoxin biosynthesis genes in the river. In November, December 2019, and January 2020. Cyanobacteria were isolated from freshwater of Tigris River and identified by compound microscope also conventional PCR. Five isolates of cyanobacteria that successfully amplified a gene fragment from the phycocyanin were found in all cyanobacteria (Microcystis flosaquae, Microcystis sp, anabaena circinalis, nostoc commune and westiellopsis prolifica) and all isolates successfully amplified aoaC gene to detecting the cylidrospemopsin and the saxitoxin. Our results concluded that PCR assay can be used for early detection of cylidrospemopsin and the saxitoxin producing cyanobacteria in river water that useful to stations responsible for the preparation of drinking water to public.

Make microalgal cultures axenic again - a fast and simple workflow utilizing fluorescence-activated cell sorting.

Since the removal of contaminations in microalgal cultures is extremely laborious and time-consuming, we developed a rapid workflow to obtain axenicity by a combination of fluorescence-activated cell sorting (FACS) and plate spreading. During method development, several cyanobacteria and green algae strains were successfully made axenic. At the end, method transferability to another FACS device was demonstrated. Our workflow offers great time-savings with less hands-on laboratory work compared to conventional isolation techniques.

Alborzia kermanshahica gen. nov., sp. nov. (Chroococcales, Cyanobacteria), isolated from paddy fields in Iran.

In Iran, polyphasic studies of unicellular cyanobacteria are still scarce, with more emphasis being placed on filamentous cyanobacteria in paddy fields and fresh water regions. In an effort to increase the knowledge of the diversity of unicellular cyanobacteria from paddy fields in Iran, we have isolated and characterized a new unicellular cyanobacterium strain. The strain was studied using a polyphasic approach based on morphological, ecological and phylogenetic analyses of the 16S-23S ITS rRNA gene region. Complementarily, we have searched for the presence of cyanotoxin genes and analysed the pigment content of the strain. Results showed that the strain was morphologically indistinguishable from the genus Chroococcus, but phylogenetic analyses based on the Bayesian inference and maximum-likelihood methods placed the strain in a separated monophyletic and highly supported (0.99/98, posterior probability/maximum-likelihood) genus-level cluster, distant from Chroococcus sensu stricto and with Chalicogloea cavernicola as sister taxa. The calculated p-distance for the 16S rRNA gene also reinforced the presence of a new genus, by showing 92 % similarity to C. cavernicola. The D1-D1', Box-B and V3 ITS secondary structures showed the uniqueness of this strain, as it shared no similar pattern with closest genera within the Chroococcales. For all these reasons, and in accordance with the International Code of Nomenclature for Algae, Fungi and Plants, we here proposed the description of a new genus with the name Alborzia gen. nov. along with the description of a new species, Alborzia kermanshahica sp. nov. (holotype: CCC1399-a; reference strains CCC1399-b; MCC 4116).

Amazonocrinis nigriterrae gen. nov., sp. nov., Atlanticothrix silvestris gen. nov., sp. nov. and Dendronalium phyllosphericum gen. nov., sp. nov., nostocacean cyanobacteria from Brazilian environments.

The cyanobacterial genus Nostoc is an important contributor to carbon and nitrogen bioavailability in terrestrial ecosystems and a frequent partner in symbiotic relationships with non-diazotrophic organisms. However, since this currently is a polyphyletic genus, the diversity of Nostoc-like cyanobacteria is considerably underestimated at this moment. While reviewing the phylogenetic placement of previously isolated Nostoc-like cyanobacteria originating from Brazilian Amazon, Caatinga and Atlantic forest samples, we detected 17 strains isolated from soil, freshwater, rock and tree surfaces presenting patterns that diverged significantly from related strains when ecological, morphological, molecular and genomic traits were also considered. These observations led to the identification of the evaluated strains as representative of three novel nostocacean genera and species: Amazonocrinis nigriterrae gen. nov., sp. nov.; Atlanticothrix silvestris gen. nov., sp. nov.; and Dendronalium phyllosphericum gen. nov., sp. nov., which are herein described according to the rules of the International Code of Nomenclature for algae, fungi and plants. This finding highlights the great importance of tropical and equatorial South American ecosystems for harbouring an unknown microbial diversity in the face of the anthropogenic threats with which they increasingly struggle.

Cyanobacteria and microalgae growing on monuments of UNESCO World Heritage site Champaner Pavagadh, India: biofilms and their exopolysaccharide composition.

The present study investigated the biofilm organisms growing on selected monuments of the Champaner Pavagadh complex (Gujarat, India), which is a UNESCO World Heritage Site. The cyanobacteria and microalgae were isolated from biofilms collected through non-destructive methods. The identification of these biological organisms was done using micro-morphological characters and confirmed by 16S rRNA gene sequencing. The exopolysaccharide of each of the isolated strains was extracted, hydrolysed and analysed by the HPTLC. Six isolated strains representing five cyanobacteria and one microalga belong to the genera Desmonostoc, Nostoc, Leptolyngbya, Chroococcidiopsis and Asterarcys. The relationships between substrates' specificity of these isolated biofilm organisms and those identified globally were evaluated using maximum parsimony analysis to generate a consensus phylogenetic tree. The five strains of cyanobacteria isolated were closely clustered with cyanobacteria belonging to a tropical region. At the generic level, no relationship between the species and substratum specificity was recorded. The exopolysaccharide analysis of the isolated strains revealed the presence of seven monosaccharides. While glucose was present in all the analysed species, the concentration of either fucose or arabinose was high. The current study presents a novel HPTLC-based method for determination of monosaccharides composition from the extracellular polymeric substances.

Removal of cyanobacteria from a water supply reservoir by sedimentation using flocculants and suspended solids as ballast: Case of Legedadi Reservoir (Ethiopia).

The massive growth of potentially toxic cyanobacteria in water supply reservoirs, such as Legedadi Reservoir (Ethiopia), poses a huge burden to water purification units and represents a serious threat to public health. In this study, we evaluated the efficiency of the flocculants/coagulants chitosan, Moringa oleifera seed (MOS), and poly-aluminium chloride (PAC) in settling cyanobacterial species present in the Legedadi Reservoir. We also tested whether coagulant-treated reservoir water promotes cyanobacteria growth. Our data showed that suspended solids in the turbid reservoir acted as ballast, thereby enhancing settling and hence the removal of cyanobacterial species coagulated with chitosan, Moringa oleifera seed, or their combination. Compared to other coagulants, MOS of 30 mg/L concentration, with the removal efficiency of 93.6%, was the most effective in removing cyanobacterial species without causing cell lysis. Contrary to our expectation, PAC was the least effective coagulant. Moreover, reservoir water treated with MOS alone or MOS combined with chitosan did not support any growth of cyanobacteria during the first two weeks of the experiment. Our data indicate that the efficacy of a flocculant/coagulant in the removal of cyanobacteria is influenced by the uniqueness of individual lakes/reservoirs, implying that mitigation methods should consider the unique characteristic of the lake/reservoir.

Removal of cyanobacteria and cyanotoxins by ferrate from polluted lake water.

Freshwater cyanobacterial blooms are becoming increasingly problematic microbiological pollutants, especially for the water resource and surface natural lakes. Cyanobacterial blooms, which produce toxins and microcystins, negatively affect the quality of water, animal, and human health, and they have also negative impact on recreational activities. The effect of electrochemically prepared potassium ferrate (green oxidation agent) on the water polluted by cyanobacteria and cyanotoxins was studied. The two most frequently occurring cyanobacterial genus Microcystis and Anabaena and the most toxic and abundant microcystin MC-LR were successfully inactivated and treated by ferrate. Potassium ferrates were applied at different conditions, such as varied hydrodynamics flow of samples, pH, and Fe(VI) concentrations. High detected elimination efficiency was consequently tested on the real water matrix from microbiological polluted natural lake Sastín-Gazárka in Slovakia. The ferrate application leads to the better chemical, biological, microbiological, and ecotoxicological outcomes.

The Effect of Abiotic Factors on Abundance and Photosynthetic Performance of Airborne Cyanobacteria and Microalgae Isolated from the Southern Baltic Sea Region.

Cyanobacteria and microalgae present in the aquatic or terrestrial environment may be emitted into the air and transported along with air masses over long distances. As a result of staying in the atmosphere, these organisms may develop a greater tolerance to stressful factors, but this topic is still relatively unknown. The main aim was to show an autecological characteristic of some airborne microalgae and cyanobacteria strains by a factorial laboratory experiment approach, including changes in irradiance, temperature, and salinity conditions. The additional purpose of this work was also to present part of the Culture Collection of Baltic Algae (CCBA) collection, which consists of airborne algae (AA) isolated from the atmospheric air of the southern Baltic Sea region. Altogether, 61 strains of airborne cyanobacteria and microalgae from the southern Baltic Sea region were isolated from May 2018 to August 2020. Selected microorganisms were tested in controlled laboratory conditions to identify their response to different irradiance (10-190 µmol photons m-2 s-1), temperature (13-23 °C), and salinity conditions (0-36 PSU). The highest numbers of cells (above 30 × 105 cell mL-1) were recorded for cyanobacterium Nostoc sp., and for diatoms Nitzschia sp., Amphora sp., and Halamphora sp. We found that for cyanobacterium Nostoc sp. as well as for green alga Coccomyxa sp. the maximum cell concentrations were recorded at the salinity of 0 PSU. Moreover, cyanobacteria Planktolyngbya contorta, Pseudanabaena catenata, Leptolyngbya foveolarum, Gloeocapsa sp., and Rivularia sp. were able to grow only at a salinity of 0 PSU. On the other hand, in the range of 16-24 PSU, the highest cell numbers of examined diatoms have been identified. Our research provided that deposited airborne microalgae and cyanobacteria showed full colonization potential. The present experiment suggests that the adaptive abilities of microorganisms, in particular those producing toxins, may contribute to the spread in the future. Thus, it may increase human exposure to their negative health effects. Any distinctive adaptations of the genera give them an additional competitive advantage and a greater chance for territorial expansion.

High-throughput sequencing approach to reveal the bacterial diversity of traditional yak jerky from the Tibetan regions.

A high-throughput sequencing approach was used to investigate the bacterial community diversity of traditional Tibetan yak jerky, which was collected from three different regions in Tibet and with different natural drying times. Tibetan yak jerky from different regions had different bacterial communities, which was mainly reflected in the relative abundance levels of unclassified Cyanobacteria, Psychrobacter and Acinetobacter. The unclassified Cyanobacteria was the dominant genus of Qamdo yak jerky, Acinetobacter was the dominant genus of Shigatse yak jerky, and Psychrobacteria was the dominant genus of Nyingchi yak jerky. With increasing natural drying time, the diversity of bacterial communities in yak jerky decreased, and unclassified Cyanobacteria become the dominant genus. Spearman's correlation analysis and canonical correspondence analysis revealed that physicochemical factors (moisture content, water activity, shear force and pH) were significantly correlated with bacterial community. Our results will be beneficial to improve and standardize the safety and quality of traditional Tibetan yak jerky.

Dynamic Change of Sedimental Microbial Community During Black Bloom-an In Situ Enclosure Simulation Study.

Black bloom is a worldwide environmental problem. Sediment microbes play important roles in the process of black bloom. The dynamic change of sedimental microbial community and their potential link between taste and odor compounds during black bloom was investigated in an in situ black bloom enclosure simulation experiment. Through high-throughput sequencing and analysis, pronounced shifts of sedimental microbial community were observed on the 3rd and 7th day in the black bloom group. Microbes in Cyanobacteria, Verrucomicrobia, Planctomycetes, and Actinobacteria were obviously increased, while microbes from the phyla OP8, Chloroflexi, and Acidobacteria were decreased significantly. RDA analysis revealed that the concentrations of chlorophyll a (Chla), total phosphorus (TP), and turbidity (NTU) in the water and the TP, TN concentrations in the sediment were the main environmental factors that affect the microbial community in the sediment. Correlation analysis revealed that microbes Dechloromonas sp. (OTU003567 and OTU000093), Desulfococcus sp. (OTU000911), Chromatiaceae (OTU001222), and Methanosaeta sp. (OTU004809) were positively correlated with the taste and odor substances in the sediment, such as dimethyl sulfide (DMS), ß-ionone, ß-cyclocitral and geosmin. The sedimental microbial community gradually recovered in the late phase of black bloom, indicating the stability and self-recovery ability of the sedimental microbial community during black bloom. Noteworthily, we observed many possible pathogens increased significantly during the black bloom, which alerts us to keep away from contaminated sediment when black bloom occurred.

Colonization of toxic cyanobacteria on the surface and inside of leafy green: A hidden source of cyanotoxin production and exposure.

Cyanobacteria are a threat to the safety of water sources for drinking, recreation, and food production, because some cyanobacteria, such as Microcystis, produce cyanotoxins. However, the colonization of plants by Microcystis and the fate of their toxin, microcystins (MCs), in agricultural environments have not been thoroughly studied. This study examined the colonization of lettuce, as a representative of leafy greens, by Microcystis and its potential impact on food safety and crop health. The surfaces of lettuce leaves were exposed to environmentally relevant concentrations of M. aeruginosa (104, 106, and 108mcyE gene copies/mL) by mimicking contamination scenarios during cultivation, such as spraying irrigation with contaminated water or deposits of airborne Microcystis. Scanning electron microscope (SEM) and droplet digital PCR were used. The results showed that M. aeruginosa colonized the surface of leaves and MCs accumulated in the edible part of the lettuce (>20 µg/kg of lettuce). Crop productivity (length, weight, and number of leaves) was negatively affected. The SEM images provide evidence that M. aeruginosa deposited on the lettuce surface can be internalized via natural opening sites of the leaves and then proliferate within the plants. Our findings imply that toxic cyanobacteria contamination in agricultural environments can be a significant cyanotoxin exposure pathway.