Cable bacteria regulate sedimentary phosphorus release in freshwater sediments.

Previous studies have demonstrated that e-SOx can regulate the sedimentary release of phosphorus (P) in brackish and marine sediments. When e-SOx is active, an iron (Fe) and manganese (Mn) oxide rich layer is formed near the sediment surface, which prevents P release. When e-SOx becomes inactive, the metal oxide layer is reduced via sulfide-mediated dissolution, and P is subsequently released to the water column. Cable bacteria have been shown to also occur in freshwater sediments. In these sediments, sulfide production is limited, and the metal oxide layer would thus dissolve less efficiently, leaving the P trapped at the sediment surface. This lack of an efficient dissolution mechanism implies that e-SOx could play an important role in the regulation of P availability in eutrophied freshwater streams. To test this hypothesis, we incubated sediments from a eutrophic freshwater river to investigate the impact of cable bacteria on sedimentary cycling of Fe, Mn and P. High-resolution depth profiling of pH, O2 and ΣH2S complemented with FISH analysis and high-throughput gene sequencing showed that the development of e-SOx activity was closely linked to the enrichment of cable bacteria in incubated sediments. Cable bacteria activity caused a strong acidification in the suboxic zone, leading to the dissolution of Fe and Mn minerals and consequently a strong release of dissolved Fe2+ and Mn2+ to the porewater. Oxidation of these mobilized ions at the sediment surface led to the formation of a metal oxide layer that trapped dissolved P, as shown by the enrichment of P-bearing metal oxides in the top layer of the sediment and low phosphate in the pore and overlying water. After e-SOx activity declined, the metal oxide layer did not dissolve and P remained trapped at the surface. Overall, our results suggested cable bacteria can play an important role to counteract eutrophication in freshwater systems.

A systematic review and quantitative meta-analysis of the relationships between driving forces and cyanobacterial blooms at global scale.

The global expansion of cyanobacterial blooms poses a major risk to the safety of freshwater resources. As a result, many explorations have been performed at a regional scale to determine the underlying impact mechanism of cyanobacterial blooms for one or several waterbodies. However, two questions still need to be answered quantitatively at a global scale to assist the water management. One is to specify which factors were often selected as the driving forces of cyanobacterial blooms, and the other is to estimate their quantitative relationships. For that, this paper applied a systematic literature review for 41 peer-reviewed studies published before May 2021 and a statistical meta-analysis based on the Pearson's or Spearman's correlation coefficients from 27 studies. These results showed that the water quality, hydraulic conditions, meteorological conditions and nutrient levels were often considered the driving forces of cyanobacterial blooms in global freshwater systems. Among these, meteorological conditions and nutrient level had the highest probability of being chosen as the driving force. In addition, knowledge of the quantitative relationships between these driving forces and cyanobacterial blooms was newly synthesized based on the correlation coefficients. The results indicated that, at a global scale, meteorological conditions were negatively related to cyanobacterial blooms, and other driving forces, such as water quality, hydraulic conditions and nutrient levels, were positively related to cyanobacterial blooms. In addition, the measurement indicators of these driving forces had diverse forms. For example, the nutrient level can be measured by the concentration of different forms of nitrogen or phosphorus, which may lead to different results in correlation analysis. Thus, a subgroup meta-analysis was necessary for the subdivided driving forces and cyanobacterial blooms, which had a better accuracy. Overall, the synthesized knowledge can help guide advanced cyanobacteria-centered water management, especially when the necessary cyanobacterial data of targeting waterbodies are inaccessible.

[Elucidation of Phenomena Involving Cyanobacteria in Freshwater Ecosystem by Chemically Ecological Approach].

Lakes Sagami and Tsukui are reservoirs constructed by connecting to the Sagami River. Because of eutrophication of the lakes, cyanobacteria have appeared every year. This review deals with phenomena related to occurrence of cyanobacteria that have been observed for 40 years since 1974 at the lakes. These 40 years of observations raised three interesting issues including the retention of cyanobacteria on their surfaces. These phenomena have been attributed to the usual factors, such as illuminance, nutrition and water temperature, but our research results suggested that they cannot be resolved without the introduction of another factor. We have attempted to elucidate various phenomena involving cyanobacteria in lake ecosystems by chemical ecological methods using volatile organic compounds (VOCs) produced by the cyanobacteria as indicators. One of the VOCs, ß-cyclocitral, was significantly involved in the above phenomena, which was considered to be produced by the carotenoid cleavage dioxygenase (CCD) of the cyanobacteria. ß-Cyclocitral was not produced in the two known CCDs, but two additional CCDs to Microcystis aeruginosa participated to produce the ß-cyclocitral. These CCDs did not directly produce ß-cyclocitral, but it was accumulated in cells as their precursors. The released ß-cyclocitral underwent a Baeyer-Villiger-like oxidation. It was speculated that Microcystis activated the CCD genes through density stress and produced ß-cyclocitral, which acted as an allelopathic substance. As a result, the number of cells of cyanobacteria decreased, and the resulting nitrogen and phosphorus were fed to the living cyanobacteria. It is postulated that this "quorum sensing" was functioning in the above-mentioned issues.

The investigation of bioremediation potential of Bacillus subtilis and B. thuringiensis isolates under controlled conditions in freshwater.

Bioremediation is widely used to remove water pollution as environmentally friendly smart solutions. In this study, Bacillus isolates were investigated in terms of the effectiveness of single and multiple cultures in eliminating aquatic pollution related to aquaculture activities. In the established experimental setups, the environments where Bacillus isolates were inoculated with single and multiple cultures at 1 × 107 CFU/mL were evaluated comparatively with control groups without these isolates, and total aerobic mesophilic bacterial counts were performed in the petri dish by inoculation method. At the end of the 6 days of the experiment, in the environment in which single and multiple cultures of Bacillus isolates were presented with 17-20 ± 0.05 °C temperature and 5.1-8.1 pH 2-4.6 mg/l dissolved oxygen values (O2), 2% increase in total phosphorus (TP) value was observed. On the other hand, 4% removal of Ammonia-nitrogen (NH3-N), 80% removal of Nitrite-nitrogen (NO2-N), and 100% removal of Nitrate-nitrogen (NO3-N) were observed. In the changes in heavy metal concentrations, the removal of Ni, Cr, Se, Al, Cd, Mn, Fe, and B was observed from highest to lowest as 57%, 50%, 50%, 43%, 40%, 23%, 5%, and 2%, respectively. It also has been seen that B. thuringiensis isolate was observed to be more effective than B. subtilis in metal removal.

Xanthones from a lignicolous freshwater fungus (BCC 28210).

Four xanthones (1‒4) and a known compound, mansonone D (5), were isolated from the lignicolous freshwater fungus BCC 28210 (family, Chaetosphaeriaceae). The structures of these compounds were elucidated by extensive spectroscopic analysis. Among the isolated metabolites, compound 2 and the known mansonone D (5) displayed antimalarial activity against Plasmodium falciparum K1 with IC50 values of 7.75 and 0.55 µg/mL, respectively. Compound 4 displayed antibacterial activity against Bacillus cereus with an MIC value of 6.25 µg/mL.

Differential gene content and gene expression for bacterial evolution and speciation of Shewanella in terms of biosynthesis of heme and heme-requiring proteins.

BACKGROUND: Most species of Shewanella harbor two ferrochelatase paralogues for the biosynthesis of c-type cytochromes, which are crucial for their respiratory versatility. In our previous study of the Shewanella loihica PV-4 strain, we found that the disruption of hemH1 but not hemH2 resulted in a significant accumulation of extracellular protoporphyrin IX (PPIX), but it is different in Shewanella oneidensis MR-1. Hence, the function and transcriptional regulation of two ferrochelatase genes, hemH1 and hemH2, are investigated in S. oneidensis MR-1. RESULT: In the present study, deletion of either hemH1 or hemH2 in S. oneidensis MR-1 did not lead to overproduction of extracellular protoporphyrin IX (PPIX) as previously described in the hemH1 mutants of S. loihica PV-4. Moreover, supplement of exogenous hemins made it possible to generate the hemH1 and hemH2 double mutant in MR-1, but not in PV-4. Under aerobic condition, exogenous hemins were required for the growth of MR-1ΔhemH1ΔhemH2, which also overproduced extracellular PPIX. These results suggest that heme is essential for aerobic growth of Shewanella species and MR-1 could also uptake hemin for biosynthesis of essential cytochrome(s) and respiration. Besides, the exogenous hemin mediated CymA cytochrome maturation and the cellular KatB catalase activity. Both hemH paralogues were transcribed in wild-type MR-1, and the hemH2 transcription was remarkably up-regulated in MR-1ΔhemH1 mutant to compensate for the loss of hemH1. The periplasmic glutathione peroxidase gene pgpD, located in the same operon with hemH2, and a large gene cluster coding for iron, heme (hemin) uptake systems are absent in the PV-4 genome. CONCLUSION: Our results indicate that the genetic divergence in gene content and gene expression between these Shewanella species, accounting for the phenotypic difference described here, might be due to their speciation and adaptation to the specific habitats (iron-rich deep-sea vent versus iron-poor freshwater) in which they evolved and the generated mutants could potentially be utilized for commercial production of PPIX.

Feedback Regulation between Aquatic Microorganisms and the Bloom-Forming Cyanobacterium Microcystis aeruginosa.

The frequency and intensity of cyanobacterial blooms are increasing worldwide. Interactions between toxic cyanobacteria and aquatic microorganisms need to be critically evaluated to understand microbial drivers and modulators of the blooms. In this study, we applied 16S/18S rRNA gene sequencing and metabolomics analyses to measure the microbial community composition and metabolic responses of the cyanobacterium Microcystis aeruginosa in a coculture system receiving dissolved inorganic nitrogen and phosphorus (DIP) close to representative concentrations in Lake Taihu, China. M. aeruginosa secreted alkaline phosphatase using a DIP source produced by moribund and decaying microorganisms when the P source was insufficient. During this process, M. aeruginosa accumulated several intermediates in energy metabolism pathways to provide energy for sustained high growth rates and increased intracellular sugars to enhance its competitive capacity and ability to defend itself against microbial attack. It also produced a variety of toxic substances, including microcystins, to inhibit metabolite formation via energy metabolism pathways of aquatic microorganisms, leading to a negative effect on bacterial and eukaryotic microbial richness and diversity. Overall, compared with the monoculture system, the growth of M. aeruginosa was accelerated in coculture, while the growth of some cooccurring microorganisms was inhibited, with the diversity and richness of eukaryotic microorganisms being more negatively impacted than those of prokaryotic microorganisms. These findings provide valuable information for clarifying how M. aeruginosa can potentially modulate its associations with other microorganisms, with ramifications for its dominance in aquatic ecosystems.IMPORTANCE We measured the microbial community composition and metabolic responses of Microcystis aeruginosa in a microcosm coculture system receiving dissolved inorganic nitrogen and phosphorus (DIP) close to the average concentrations in Lake Taihu. In the coculture system, DIP is depleted and the growth and production of aquatic microorganisms can be stressed by a lack of DIP availability. M. aeruginosa could accelerate its growth via interactions with specific cooccurring microorganisms and the accumulation of several intermediates in energy metabolism-related pathways. Furthermore, M. aeruginosa can decrease the carbohydrate metabolism of cooccurring aquatic microorganisms and thus disrupt microbial activities in the coculture. This also had a negative effect on bacterial and eukaryotic microbial richness and diversity. Microcystin was capable of decreasing the biomass of total phytoplankton in aquatic microcosms. Overall, compared to the monoculture, the growth of total aquatic microorganisms is inhibited, with the diversity and richness of eukaryotic microorganisms being more negatively impacted than those of prokaryotic microorganisms. The only exception is M. aeruginosa in the coculture system, whose growth was accelerated.

Interplay between resistance and resilience governs the stability of a freshwater microbial food web under multiple stressors.

Energy (photosynthetically active [PAR] and ultraviolet [UVR] radiation) and matter (organic and inorganic nutrients) fluxes regulate the ecosystem's stability. However, the mechanisms underpinning the potential interplay between resistance and resilience to shifts in nutrient inputs and UVR are poorly understood. To assess how the UVR × nutrients interaction alters ecosystem stability, we exposed in situ a microbial food web from an oligotrophic ecosystem to: (1) two light (UVR + PAR and PAR), and (2) four nutrient (ambient concentrations, phosphorus [P], carbon [C] and C × P addition) treatments for three weeks. During this period, we quantified the community composition and biomass, sestonic P and C:P ratio, primary [PP] and bacterial [BP] production, community [CR] and bacterial [BR] respiration, excreted organic carbon [EOC], as well as the commensalistic phytoplankton-bacteria interaction (i.e. bacterial carbon demand [BCD]:EOC ratio) and the metabolic balance of the ecosystem (i.e. [PP:R] ratio). The stability of all response variables under the four environmental scenarios tested (i.e. UVR, UVR × C, UVR × P, and UVR × C × P) was quantified by means of the resistance and resilience indexes. The microbial community was dominated by phototrophs during the experimental period regardless of the treatment considered. The most complex scenario, i.e. UVR × C × P, decreased the resistance for all variables, except for BR and the PP:R ratio. Despite that PP:R ratio showed the highest resistance under such scenario, it was >1 in all environmental scenarios (i.e. net autotrophic), except under the UVR × C interaction, where, concomitant with increased resilience, the balance shifted towards net heterotrophy (PP:R < 1). Under the UVR × C × P scenario, the metabolic balance of the ecosystem proved strongly resistant due mainly to high resistance of bacterial respiration and a firm stability of the commensalistic interaction. Our results evidence that the high resilience of phototrophs (favoring their predominance over mixo- and heterotrophs) may lead to the maintenance of the autotrophic nature and carbon (C) sink capacity of the ecosystem.

Culturing the ubiquitous freshwater actinobacterial acI lineage by supplying a biochemical 'helper' catalase.

The actinobacterial acI lineage is among the most successful and ubiquitous freshwater bacterioplankton found on all continents, often representing more than half of all microbial cells in the lacustrine environment and constituting multiple ecotypes. However, stably growing pure cultures of the acI lineage have not been established despite various cultivation efforts based on ecological and genomic studies on the lineage, which is in contrast to the ocean from which abundant microorganisms such as Prochlorococcus, Pelagibacter, and Nitrosopumilus have been isolated. Here, we report the first two pure cultures of the acI lineage successfully maintained by supplementing the growth media with catalase. Catalase was critical for stabilizing the growth of acI strains irrespective of the genomic presence of the catalase-peroxidase (katG) gene. The two strains, representing two novel species, displayed differential phenotypes and distinct preferences for reduced sulfurs and carbohydrates, some of which were difficult to predict based on genomic information. Our results suggest that culture of previously uncultured freshwater bacteria can be facilitated by a simple catalase-supplement method and indicate that genome-based metabolic prediction can be complemented by physiological analyses.

Pollutant removal and bioelectricity generation from urban river sediment using a macrophyte cathode sediment microbial fuel cell (mSMFC).

Sediment microbial fuel cell (SMFC) efficacy depends highly on organic matter flux and dissolved oxygen (DO) at the anode and cathode, respectively. However, utilizing floating-macrophyte for elevated DO supply at the cathode has not been fully explored. Therefore, a novel floating-macrophyte implanted biocathode single-chamber SMFC (mSMFC) was developed for the simultaneous removal of pollutant and bioelectricity generation from polluted urban river sediment. With Lemna minor L. employed in mSMFC, high pollutant removal was feasible as opposed to the control bioreactor. Total COD, nitrate and sulfate removal reached 57%, 99%, and 99%, respectively. Maximum voltage output, power density, columbic efficiency, normalized energy recovery, and net energy production observed was 0.56 ±â€¯0.26 V, 86.06 mW m-3, 24.7%, 0.033 kWh m-3 and 0.020 kWh m-3, respectively. Alternatively, when floating-macrophyte (predominantly Pistia stratiotes) was employed in the catholyte, DO increased significantly to about 10 mg L-1 in the mSMFC. 16S rRNA gene sequencing revealed Euryarchaeota-(90.91%) and Proteobacteria-(59.68%) as the dominant phyla affiliated to archaea and bacteria, respectively. Pollutant removal mechanisms observed within the mSMFC included bioelectrochemical oxidation at the anode and reduction reaction and macrophyte hyperaccumulation at the cathode. The novel mSMFC system provided an effective approach for the removal of pollutant and bioelectricity generation.

Effect of Homeopathic Medicines on Intestinal Coccidia and Immune Response Cells in Spotted Rose Snapper (Lutjanus guttatus).

BACKGROUND: Homeopathy has been widely applied in freshwater species but rarely in marine fish. Farm stress destabilises host-pathogen equilibrium, favouring parasites and disease. Coccidian endoparasites cause intestinal infections and cell degeneration. MATERIALS AND METHODS: Naturally parasite-infested juvenile snapper Lutjanus guttatus (n = 430; weight 1.9 ± 0.01 g; length 4.9 ± 0.03 cm) specimens were distributed in group sizes of 43, in 10 fiberglass tanks (100 L) with aeration and continuous water change. Five groups in duplicate were assessed: Passival (PaV); Passival and Phosphoricum acid Similia (PaV-PhA); Passival and Silicea terra Similia (PaV-SiT); Endecto and Infecçoes (End-Inf) and a control (Ethanol) for 45 days. Feed was sprinkled with treatment (5% v/w) and dried to avoid ethanol side-effects. Statistical results were expressed as mean ± standard error of the mean. RESULTS: Intestinal coccidia were recorded histopathologically, with the least incidence attained at T45 with End-Inf treatment (p < 0.001), coinciding with the highest lymphocyte (p = 0.015) count. Fish treated with PaV-PhA recorded a higher percentage of neutrophils (p = 0.015), and those treated with PaV-PhA, PaV-SiT and End-Inf revealed a decrease in lesions, degree of alteration and change in intestine and stomach tissues (p < 0.05). The number of mucous cells in gills was greater (p < 0.001) for End-Inf (43 ± 0.58), PaV-SiT (40 ± 2.89) and PaV-PhA (39 ± 3.46) as compared respectively with T0 and control (19 ± 0.58 and 28 ± 2.31). PaV and PaV-SiT increased carbohydrate reserves in liver (28.4 ± 1.39% and 22.4 ± 0.12%, respectively) compared with T0 and control (3.4 ± 0.32 and 5.6 ± 0.66%). The highest survival rate was 97.7 ± 0.16% in fish treated with PaV and End-Inf. CONCLUSION: Homeopathic treatments had a positive effect on fish health. Besides the accumulation of metabolic reserves in the liver, homeopathic treatment was associated with mucin increase in gills as well as raised production of lymphocytes and neutrophils in blood, which could act as macrophages against intestinal coccidia.

Gene Expansion and Positive Selection as Bacterial Adaptations to Oligotrophic Conditions.

We examined the genomic adaptations of prevalent bacterial taxa in a highly nutrient- and ion-depleted freshwater environment located in the secondary cooling water system of a nuclear research reactor. Using genome-centric metagenomics, we found that none of the prevalent bacterial taxa were related to typical freshwater bacterial lineages. We also did not identify strong signatures of genome streamlining, which has been shown to be one of the ecoevolutionary forces shaping the genome characteristics of bacterial taxa in nutrient-depleted environments. Instead, focusing on the dominant taxon, a novel Ramlibacter sp. which we propose to name Ramlibacter aquaticus, we detected extensive positive selection on genes involved in phosphorus and carbon scavenging pathways. These genes were involved in the high-affinity phosphate uptake and storage into polyphosphate granules, metabolism of nitrogen-rich organic matter, and carbon/energy storage into polyhydroxyalkanoate. In parallel, comparative genomics revealed a high number of paralogs and an accessory genome significantly enriched in environmental sensing pathways (i.e., chemotaxis and motility), suggesting extensive gene expansions in R. aquaticus The type strain of R. aquaticus (LMG 30558T) displayed optimal growth kinetics and productivity at low nutrient concentrations, as well as substantial cell size plasticity. Our findings with R. aquaticus LMG 30558T demonstrate that positive selection and gene expansions may represent successful adaptive strategies to oligotrophic environments that preserve high growth rates and cellular productivity.IMPORTANCE By combining a genome-centric metagenomic approach with a culture-based approach, we investigated the genomic adaptations of prevalent populations in an engineered oligotrophic freshwater system. We found evidence for widespread positive selection on genes involved in phosphorus and carbon scavenging pathways and for gene expansions in motility and environmental sensing to be important genomic adaptations of the abundant taxon in this system. In addition, microscopic and flow cytometric analysis of the first freshwater representative of this population (Ramlibacter aquaticus LMG 30558T) demonstrated phenotypic plasticity, possibly due to the metabolic versatility granted by its larger genome, to be a strategy to cope with nutrient limitation. Our study clearly demonstrates the need for the use of a broad set of genomic tools combined with culture-based physiological characterization assays to investigate and validate genomic adaptations.

Sulfur cycling in freshwater sediments: A cryptic driving force of iron deposition and phosphorus mobilization.

Sulfur cycling in freshwater ecosystems has been previously considered minor, and the direct evidence of its impacts on iron and phosphorus cycles in freshwater sediments remains unclear. In this study, mesocosms with amended acetate and various sulfate concentrations (1.5-3.0 mmol L-1) were set up to investigate sulfur cycling and its influences on iron-rich freshwater sediments. Acetate addition induced hypoxia and provided substrates, which stimulated the sulfur cycling with evidence of SO42- decline, ΣS2-, S0 increase and corresponding variations of sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria. Meanwhile, the growth of iron-reducing bacteria (IRB) was suppressed, and lower Fe(II) release was correspondingly related to larger SRB abundance at higher sulfate level, indicating that microbial iron reduction might be blocked by SRB activities. However, continuous dissolution of Fe(III) oxides and generation of iron sulfides were observed, suggesting that sulfide-mediated chemical iron reduction (SCIR) became the dominant iron-reducing pathway, and Fe(II) was buried as iron sulfides instead of released to water column, which resulted in a transition of iron cycling into unidirectional SCIR. Consequently, continuous dissolution of Fe(III) oxides led to significant increase of PO43- concentration in the water column and sediment pore-water, revealing the phosphorus mobility in sediments derived from the SCIR process. To note, sustained accumulation of iron sulfides was observed even without ΣS2- presence, suggesting that ΣS2- precipitation occurred prior to diffusion. Thus, ΣS2--missing sulfur cycling seemed "cryptic" in this study. To highlight, the transition of the iron-reducing pathway and resulting PO43- release can be induced even under current sulfate level of Lake Taihu, and elevated sulfate levels could significantly intensify SCIR and phosphorus mineralization. Thus, the stimulated iron deposition and the resulting phosphorus release derived from the sulfur cycling should be paid more attention to in the treatment of eutrophic freshwater ecosystems.

Delitpyrones: α-Pyrone Derivatives from a Freshwater Delitschia sp.

In research focused on the discovery of new chemical diversity from freshwater fungi, a peak library was built and evaluated against a prostate cancer cell line, E006AA-hT, which was derived from an African American, as this population is disproportionately affected by prostate cancer. The chemical study of the bioactive sample accessioned as G858 (Delitschia sp.) led to the isolation of eight new α-pyrone derivatives (1:  - 7: , and 11: ), as well as the new 3S*,4S*-7-ethyl-4,8-dihydroxy-3,6-dimethoxy-3,4-dihydronaphthalen-1(2H)-one (15: ). In addition, the known compounds 5-(3-S-hydroxybutyl)-4-methoxy-6-methyl-2H-pyran-2-one (8: ), 5-(3-oxobutyl)-4-methoxy-6-methyl-2H-pyran-2-one (9: ), pyrenocine I (10: ), 5-butyl-6-(hydroxymethyl)-4-methoxy-2H-pyran-2-one (12: ), sporidesmin A (13: ), 6-ethyl-2,7-dimethoxyjuglone (14: ), artrichitin (16: ), and lipopeptide 15G256ε (17: ) were also obtained. The structures of the new compounds were elucidated using a set of spectroscopic (NMR) and spectrometric (HRMS) methods. The absolute configuration of the most abundant member of each subclass of compounds was assigned through a modified Mosher's ester method. For 15: , the relative configuration was assigned based on analysis of 3 J values. Compounds 1, 2, 5:  - 14, 16: , and 17: were evaluated against the cancer cell line E006AA-hT under hypoxic conditions, where compound 13: inhibited cell proliferation at a concentration of 2.5 µM.

Air and waterborne microbiome of a pharmaceutical plant provide insights on spatiotemporal variations and community resilience after disturbance.

BACKGROUND: The presence of microrganisms in pharmaceutical production plant environments is typically monitored by cultural methods, however these cannot detect the unculturable fraction of the microbial community. To get more accurate information on the composition of these indoor microbial communities, both water and air microbiome from a pharmaceutical production plant were profiled by 16S amplicon sequencing. RESULTS: In the water system, we found taxa which typically characterize surface freshwater, groundwater and oligotrophic environments. The airborne microbiome resulted dominated by taxa usually found in outdoor air in combination with human-associated taxa. The alpha- and beta- diversity values showed that the heat-based sanitization process of the water plant affects the composition of the water microbiome by transiently increasing both diversity and evenness. Taxonomic compositional shifts were also detected in response to sanitization, consisting in an increase of Firmicutes and α-Proteobacteria. On the other hand, seasonality seems to be the main driver of bacterial community composition in air of this work environment. CONCLUSIONS: This approach resulted useful to describe the taxonomy of these indoor microbiomes and could be further applied to other built environments, in which the knowledge of the microbiome composition is of relevance. In addition, this study could assist in the design of new guidelines to improve microbiological quality control in indoor work environments.

Carbon sequestration in macroalgal mats of brackish-water habitats in Indian Sunderbans: Potential as renewable organic resource.

Large influx of excess nutrients into sub-tropical brackish-water habitats is expected to radically affect the algal populations in the heavily populated Sunderbans brackish-water ecozone. Twelve selected brackish-water sites in the Indian Sunderbans were surveyed to investigate the growth performance of mat-forming dominant algal/cyanobacterial macrophytes and their potential for carbon (C) sequestration into hydrologic and pedologic pools. The mats were dominated by particular taxa at different seasons related to physico-chemical properties of the wetland habitats. Different environmental variables and biomass productivity parameters were measured on fortnightly basis to assess the carbon cycle related to dominant algal blooms of the study area. The dominating species at the twelve sites included seven genera (Spirogyra, Rhizoclonium, Ulva, Cladophora, Pithophora, Chaetomorpha) belonging to Chlorophyta, three genera (Polysiphonia, Gracilaria, Catenella) belonging to Rhodophyta and Lyngbya majuscula from cyanobacteria. Multivariate statistical methods indicated that nutrient availability, particularly dissolved P concentration and N:P ratio in the water column, along with salinity in the water column mainly affected biomass yield and C sequestration of mat-forming macrophytes and OC input into water column. However, OC contents of underlying muck proved to be very stable, though small influxes of OC occurred at each bloom. High biomass yields (34-3107 g/m2) of the dominant mat components accumulated enormous stocks of OC, very little of which reaches the pedologic pool. This transient biomass might be utilized as dietary supplements or biofuel feedstocks. Availability of important dietary fatty acids in Spirogyra punctulata, Gracilaria sp., Polysiphonia mollis, Rhizoclonium riparium, R. tortuosum, Pithophora oedogonia and Ulva lactuca was considered as suitability of these species as nutraceuticals. Fatty acid compositions of L. majuscula, Catenella repens, R. tortuosum and Cladophora crystallina were estimated to be applicable for producing biodiesel for usage in sub-tropical climates.

Seasonal dynamics of the bacterioplankton community in a large, shallow, highly dynamic freshwater lake.

The spatiotemporal shifts of the bacterioplankton community can mirror their transition of functional traits in an aquatic ecosystem. However, the spatiotemporal variation of the bacterioplankton community composition structure (BCCS) within a large, shallow, highly dynamic freshwater lake is still poorly understood. Here, we examined the seasonal and spatial variability of the BCCs within Poyang Lake by sequencing the 16S rRNA gene amplicon to explore how hydrological changes affect the BCCs. Principal coordinate analysis showed that the BCCs varied significantly among four sampling seasons, but not spatially. The seasonal changes of the BCCs were mainly attributed to the differences between autumn and spring-winter. Higher α diversity indices were observed in autumn. Redundancy analysis indicated that the BCCs co-variated with water level, pH, temperature, total phosphorus, ammoniacal nitrogen, electrical conductivity, total nitrogen, and turbidity. Among them, water level was the key determinant separating autumn BCCs from the BCCs in other seasons. A significantly lower relative abundance of Burkholderiales (betI and betVII) and a higher relative abundance of Actinomycetales (acI, acTH1, and acTH2) were found in autumn than in other seasons. Overall, our results suggest that water level changes associated with pH, temperature, and nutrient status shaped the seasonal patterns of the BCCs within Poyang Lake.

Tanzawaic acid derivatives from freshwater sediment-derived fungus Penicillium sp.

Chemical investigation of a freshwater sediment-derived fungus, Penicillium sp. (S1a1), led to the isolation of three new tanzawaic acid derivatives, including penitanzchroman (1), tanzawaic acids Y (2) and Z (3), along with six known tanzawaic acid analogues (4-9), three known isochromans (10-12) and two known benzoquinones (13 and 14). The structures of the new compounds were established based on high-resolution mass spectrometry, and detailed analysis of one- and two-dimensional NMR spectroscopy. The relative configuration of the new compounds was assigned on the basis of NMR spectroscopic data including ROESY spectra. The absolute configuration was determined based on the specific optical rotation, in addition to biogenetic considerations in comparison with related co-isolated known metabolites. Penitanzchroman (1) constitutes a hitherto unprecedented skeleton, formed of tanzawaic acid A (5) and (3S)-6-hydroxy-8-methoxy-3,5-dimethylisochroman (10) linked by a CC bond. Moreover, all compounds were evaluated for their antibacterial and cytotoxic activities.

Incidence of bacterial diseases associated with irrigation methods on onions (Allium cepa).

BACKGROUND: In the last decade, diseases of bacterial origin in onions have increased and this has led to significant losses in production. These diseases are currently observed in both the Old and New Worlds. The present study aimed to evaluate whether the irrigation method influences the incidence of diseases of bacterial origin. RESULTS: In cases where the inoculum was natural, the initial incidence of soft bacterial rot did not manifest in any treatment in the first year, whereas, at the end of the conservation period, all treatments had increased incidences of infection. Sprinkler irrigation (8%) was statistically differentiated from the other treatments, for which the final incidence was similar (4.5%). For all irrigation treatments, the final incidence of bacterial soft rot decreased or remained stable towards the end of the cycle, with the exception of sprinkler irrigation in 2015, which increased. CONCLUSION: From the results of the present study, it can be inferred that the irrigation method does have an influence on the incidence of diseases of bacterial origin in the post-harvest stage for onions. © 2018 Society of Chemical Industry.

Pond bank access as an approach for managing toxic cyanobacteria in beef cattle pasture drinking water ponds.

Forty-one livestock drinking water ponds in Alabama beef cattle pastures during were surveyed during the late summer to generally understand water quality patterns in these important water resources. Since livestock drinking water ponds are prone to excess nutrients that typically lead to eutrophication, which can promote blooms of toxigenic phytoplankton such as cyanobacteria, we also assessed the threat of exposure to the hepatotoxin, microcystin. Eighty percent of the ponds studied contained measurable microcystin, while three of these ponds had concentrations above human drinking water thresholds set by the US Environmental Protection Agency (i.e., 0.3 µg/L). Water quality patterns in the livestock drinking water ponds contrasted sharply with patterns typically observed for temperate freshwater lakes and reservoirs. Namely, we found several non-linear relationships between phytoplankton abundance (measured as chlorophyll) and nutrients or total suspended solids. Livestock had direct access to all the study ponds. Consequently, the proportion of inorganic suspended solids (e.g., sediment) increased with higher concentrations of total suspended solids, which underlies these patterns. Unimodal relationships were also observed between microcystin and phytoplankton abundance or nutrients. Euglenoids were abundant in the four ponds with chlorophyll concentrations > 250 µg/L (and dominated three of these ponds), which could explain why ponds with high chlorophyll concentrations would have low microcystin concentrations. Based on observations made during sampling events and available water quality data, livestock-mediated bioturbation is causing elevated total suspended solids that lead to reduced phytoplankton abundance and microcystin despite high concentrations of nutrients, such as phosphorus and nitrogen. Thus, livestock could be used to manage algal blooms, including toxic secondary metabolites, in their drinking water ponds by allowing them to walk in the ponds to increase turbidity.