Electrogenic sulfur oxidation mediated by cable bacteria and its ecological effects.

At the sediment-water interfaces, filamentous cable bacteria transport electrons from sulfide oxidation along their filaments towards oxygen or nitrate as electron acceptors. These multicellular bacteria belonging to the family Desulfobulbaceae thus form a biogeobattery that mediates redox processes between multiple elements. Cable bacteria were first reported in 2012. In the past years, cable bacteria have been found to be widely distributed across the globe. Their potential in shaping the surface water environments has been extensively studied but is not fully elucidated. In this review, the biogeochemical characteristics, conduction mechanisms, and geographical distribution of cable bacteria, as well as their ecological effects, are systematically reviewed and discussed. Novel insights for understanding and applying the role of cable bacteria in aquatic ecology are summarized.

Cable Bacteria Skeletons as Catalytically Active Electrodes.

Cable bacteria are multicellular, filamentous bacteria that use internal conductive fibers to transfer electrons over centimeter distances from donors within anoxic sediment layers to oxygen at the surface. We extracted the fibers and used them as free-standing bio-based electrodes to investigate their electrocatalytic behavior. The fibers catalyzed the reversible interconversion of oxygen and water, and an electric current was running through the fibers even when the potential difference was generated solely by a gradient of oxygen concentration. Oxygen reduction as well as oxygen evolution were confirmed by optical measurements. Within living cable bacteria, oxygen reduction by direct electrocatalysis on the fibers and not by membrane-bound proteins readily explains exceptionally high cell-specific oxygen consumption rates observed in the oxic zone, while electrocatalytic water oxidation may provide oxygen to cells in the anoxic zone.

Cable bacteria: widespread filamentous electroactive microorganisms protecting environments.

Cable bacteria have been identified and detected worldwide since their discovery in marine sediments in Aarhus Bay, Denmark. Their activity can account for the majority of oxygen consumption and sulfide depletion in sediments, and they induce sulfate accumulation, pH excursions, and the generation of electric fields. In addition, they can affect the fluxes of other elements such as calcium, iron, manganese, nitrogen, and phosphorous. Recent developments in our understanding of the impact of cable bacteria on element cycling have revealed their positive contributions to mitigating environmental problems, such as recovering self-purification capacity, enhancing petroleum hydrocarbon degradation, alleviating phosphorus eutrophication, delaying euxinia, and reducing methane emission. We highlight recent research outcomes on their distribution, state-of-the-art findings on their physiological characteristics, and ecological contributions.

Indications for a genetic basis for big bacteria and description of the giant cable bacterium Candidatus Electrothrix gigas sp. nov.

Bacterial cells can vary greatly in size, from a few hundred nanometers to hundreds of micrometers in diameter. Filamentous cable bacteria also display substantial size differences, with filament diameters ranging from 0.4 to 8 µm. We analyzed the genomes of cable bacterium filaments from 11 coastal environments of which the resulting 23 new genomes represent 10 novel species-level clades of Candidatus Electrothrix and two clades that putatively represent novel genus-level diversity. Fluorescence in situ hybridization with a species-level probe showed that large-sized cable bacteria belong to a novel species with the proposed name Ca. Electrothrix gigas. Comparative genome analysis suggests genes that play a role in the construction or functioning of large cable bacteria cells: the genomes of Ca. Electrothrix gigas encode a novel actin-like protein as well as a species-specific gene cluster encoding four putative pilin proteins and a putative type II secretion platform protein, which are not present in other cable bacteria. The novel actin-like protein was also found in a number of other giant bacteria, suggesting there could be a genetic basis for large cell size. This actin-like protein (denoted big bacteria protein, Bbp) may have a function analogous to other actin proteins in cell structure or intracellular transport. We contend that Bbp may help overcome the challenges of diffusion limitation and/or morphological complexity presented by the large cells of Ca. Electrothrix gigas and other giant bacteria. IMPORTANCE In this study, we substantially expand the known diversity of marine cable bacteria and describe cable bacteria with a large diameter as a novel species with the proposed name Candidatus Electrothrix gigas. In the genomes of this species, we identified a gene that encodes a novel actin-like protein [denoted big bacteria protein (Bbp)]. The bbp gene was also found in a number of other giant bacteria, predominantly affiliated to Desulfobacterota and Gammaproteobacteria, indicating that there may be a genetic basis for large cell size. Thus far, mostly structural adaptations of giant bacteria, vacuoles, and other inclusions or organelles have been observed, which are employed to overcome nutrient diffusion limitation in their environment. In analogy to other actin proteins, Bbp could fulfill a structural role in the cell or potentially facilitate intracellular transport.

Persistent flocks of diverse motile bacteria in long-term incubations of electron-conducting cable bacteria, Candidatus Electronema aureum.

Cable bacteria are centimeters-long filamentous bacteria that oxidize sulfide in anoxic sediment layers and reduce oxygen at the oxic-anoxic interface, connecting these reactions via electron transport. The ubiquitous cable bacteria have a major impact on sediment geochemistry and microbial communities. This includes diverse bacteria swimming around cable bacteria as dense flocks in the anoxic zone, where the cable bacteria act as chemotactic attractant. We hypothesized that flocking only appears when cable bacteria are highly abundant and active. We set out to discern the timing and drivers of flocking over 81 days in an enrichment culture of the freshwater cable bacterium Candidatus Electronema aureum GS by measuring sediment microprofiles of pH, oxygen, and electric potential as a proxy of cable bacteria activity. Cable bacterial relative abundance was quantified by 16S rRNA amplicon sequencing, and microscopy observations to determine presence of flocking. Flocking was always observed at some cable bacteria, irrespective of overall cable bacteria rRNA abundance, activity, or sediment pH. Diverse cell morphologies of flockers were observed, suggesting that flocking is not restricted to a specific, single bacterial associate. This, coupled with their consistent presence supports a common mechanism of interaction, likely interspecies electron transfer via electron shuttles. Flocking appears exclusively linked to the electron conducting activity of the individual cable bacteria.

Clinical characteristics of hospitalized patients with paracetamol poisoning before and after restrictions of over-the-counter sale of paracetamol.

INTRODUCTION: Paracetamol poisoning is a frequent cause of hospitalization in Denmark. On 30 September 2013, the Danish authorities restricted packages available without a prescription in pharmacy outlets to contain a maximum of 10 g of paracetamol. We aimed to investigate the effects of this regulation. METHODS: This was a cross-sectional study of two groups of patients admitted consecutively to a Danish University Hospital due to poisoning with paracetamol in 365 days in 2012-13 before 30 September 2013, and a corresponding 365-day period in 2017-18. Data were extracted from patient records. RESULTS: In 2012-2013 and 2017-18, 156 and 92 admissions in 127 and 78 unique patients, respectively, were identified. Ingestion of more than 20 g paracetamol occurred in a significantly higher proportion of cases in 2012-13 compared to 2017-18 (29% vs 13%, P < 0.01). In accordance, there were no cases of international normalized ratio >1.5 or alanine aminotransferase activity >1000 U/L in the post-legislation period, and seven and five cases in the pre-legislation period, respectively. Females accounted for 80% and 78% of patients in the two periods, respectively, and were considerably younger than males (median [interquartile range]: 22 [17-40] vs. 47 [30-56], P < 0.01 in 2012-13, and 23 [18-46] vs. 43 [27-49] years, P = 0.02 in 2017-18). Furthermore, in 2012-13, intentional poisonings occurred in a higher proportion of females than males 2012-13 (97% vs 85%, P < 0.01). CONCLUSIONS: The present study demonstrated a lower number of paracetamol poisonings, a decreased proportion of poisonings involving ingestion of more than 20 g of paracetamol, and a lower occurrence of hepatotoxicity after the regulation. However, circumstances other than pack size restrictions, such as increased public awareness of the danger of paracetamol poisonings, may affect these associations. Furthermore, the study showed that females and males constitute two distinct groups in terms of age and intentional poisoning.

Cable bacteria with electric connection to oxygen attract flocks of diverse bacteria.

Cable bacteria are centimeter-long filamentous bacteria that conduct electrons via internal wires, thus coupling sulfide oxidation in deeper, anoxic sediment with oxygen reduction in surface sediment. This activity induces geochemical changes in the sediment, and other bacterial groups appear to benefit from the electrical connection to oxygen. Here, we report that diverse bacteria swim in a tight flock around the anoxic part of oxygen-respiring cable bacteria and disperse immediately when the connection to oxygen is disrupted (by cutting the cable bacteria with a laser). Raman microscopy shows that flocking bacteria are more oxidized when closer to the cable bacteria, but physical contact seems to be rare and brief, which suggests potential transfer of electrons via unidentified soluble intermediates. Metagenomic analysis indicates that most of the flocking bacteria appear to be aerobes, including organotrophs, sulfide oxidizers, and possibly iron oxidizers, which might transfer electrons to cable bacteria for respiration. The association and close interaction with such diverse partners might explain how oxygen via cable bacteria can affect microbial communities and processes far into anoxic environments.

Highly Selective Microsensor for Monitoring Trace Phosphine in the Environment.

Monitoring P flux at the Earth's surface-atmosphere interface has many challenges. Therefore, the development of a technology with high selectivity and high sensitivity to in situ trace PH3 in aquatic or sedimentary environments has become a priority. Herein, an amperometric PH3 microsensor meeting the above conditions is developed. The sensor is equipped with a Au-coated Pt working electrode (WE) and a Pt guard electrode (GE) positioned in an outer glass casing. The WE and GE are polarized at a fixed value of +150 mV with respect to a pseudo-reference electrode. The outer casing is filled with an acid electrolyte solution, and the tip is sealed using a thin silicone membrane. Mixed gases from the environment diffuse through the first layer of the silicone membrane, and the major H2S disruptor is eliminated by a ZnCl2-propylene carbonate trap positioned in the front of the microsensor. Later, the gases diffuse into an electrolytic solution through the second layer of the silicone membrane, and PH3 is selectively oxidized into H3PO4 on the Au-coated Pt WE. This electrochemical oxidation thereby creates a current that is proportional to the concentration of PH3 (>2 nmol·L-1). With the aid of the H2S trap casing and selective catalysis, the effects of other gases on the microsensor can be ignored in terms of environmental monitoring. An example from the sedimentary profile shows that high PH3 accumulations are found 13 mm below the sediment surface.

Bacterial community of sediments under the Eastern Boundary Current System shows high microdiversity and a latitudinal spatial pattern.

The sediments under the Oxygen Minimum Zone of the Eastern Boundary Current System (EBCS) along Central-South Peru and North-Central Chile, known as Humboldt Sulfuretum (HS), is an organic-matter-rich benthic habitat, where bacteria process a variety of sulfur compounds under low dissolved-oxygen concentrations, and high sulfide and nitrate levels. This study addressed the structure, diversity and spatial distribution patterns of the HS bacterial community along Northern and South-Central Chile using 16S rRNA gene amplicon sequencing. The results show that during the field study period, the community was dominated by sulfur-associated bacteria. Indeed, the most abundant phylum was Desulfobacterota, while Sva0081 sedimentary group, of the family Desulfosarcinaceae (the most abundant family), which includes sulfate-reducer and H2 scavenger bacteria, was the most abundant genus. Furthermore, a spatial pattern was unveiled along the study area to which the family Desulfobulbaceae contributed the most to the spatial variance, which encompasses 42 uncharacterized amplicon sequence variants (ASVs), three assigned to Ca. Electrothrix and two to Desulfobulbus. Moreover, a very high microdiversity was found, since only 3.7% of the ASVs were shared among localities, reflecting a highly diverse and mature community.

[Smoking cessation and drug interactions].

Tobacco smoke can cause drug interactions by induction of CYP1A2, which metabolizes drugs like clozapine, olanzapine and theophylline. This means that smokers need higher doses to achieve the same plasma concentrations as non-smokers. Furthermore, smoking cessation can cause an increase in plasma concentrations of drugs metabolised by CYP1A2, which in turn may lead to adverse effects. Of the drugs used for smoking cessation only bupropione has clinically relevant interactions. All of these situations may be handled by dose adjustment.

Acute drug poisonings leading to hospitalization.

Knowledge about current trends and epidemiology in poisonings is important to maintain quality in diagnostics, treatment and prevention. We performed a cross-sectional study of all cases (n = 261) admitted with drug poisoning to Aalborg University Hospital during 1 year in 2017-2018. Median age was 30 (22-49) years, and 58% were female. Fifty percent were suicide attempts. In most cases, involved drugs were identified by history taking; blood analysis barely revealed any additional paracetamol and salicylicate poisonings. Drugs prescribed to the patient or available over the counter were involved in nearly two thirds of cases. Weak analgesics dominated by paracetamol (n = 91, 35%) was the most frequently involved group of drugs followed by opioids and benzodiazepines. Gender differences were observed with respect to involvement of weak analgesics and central stimulants. A higher prevalence of unidentified involved drugs was observed in 26 cases (10%) in which the length of admission exceeded 2 days and/or intensive care was needed. No deaths, cardiac arrhythmias or physical complications occurred. Thus, current handling of the acute poisoning seems effective in most cases. However, a more tailored use of blood analyses including a toxicological screen in selected cases may represent an opportunity for improvement.

[Management of antipsychotic-induced metabolic side effects].

Antipsychotics are associated with significant weight gain and other metabolic side effects. There are, however, substantial differences in their propensity for causing metabolic side effects as summarised in this review. These differences are important to consider when deciding which antipsychotic to use. Given the risk of metabolic side effects, patients should be closely monitored regarding anthropometric measures and metabolic parameters. Moreover, both non-pharmacological and pharmacological interventions should be considered for treatment of antipsychotic-induced weight gain.

External validation of the Medication Risk Score in polypharmacy patients in general practice: A tool for prioritizing patients at greatest risk of potential drug-related problems.

Drug-related problems are important causes of patient harm and increased healthcare costs. To assist general practitioners in prioritizing patients in need of a critical medication review, we aimed to assess the ability of the Medication Risk Score (MERIS) to stratify patients with polypharmacy in general practice according to their risk of drug-related problems. We conducted a cross-sectional multi-centre external validation study. Patients receiving more than five concomitant medications (polypharmacy) were eligible. The outcome was potentially serious drug-related problems as evaluated by expert consensus. Performance was assessed in terms of calibration and discrimination indices. Of 497 patients, 489 were included in the main analysis. The median age (interquartile range) was 70.5 years (60-79). In total, 372 potentially serious drug-related problems were observed in 253 patients (52%). The MERIS was well calibrated above a score level of 10. The area under the receiver operating characteristic curve was 0.70 (95% confidence interval: 0.65-0.74). The performance of the MERIS was fair in patients with polypharmacy in general practice. Given the scale of drug-related problems and the lack of efficient prioritization tools in this setting, the MERIS could be a useful risk indicator to complement usual practice.

How to grow your cable bacteria: Establishment of a stable single-strain culture in sediment and proposal of Candidatus Electronema aureum GS.

Cable bacteria are multicellular filamentous bacteria within the Desulfobulbaceae that couple the oxidation of sulfide to the reduction of oxygen over centimeter distances via long distance electron transport (LDET). So far, none of the freshwater or marine cable bacteria species have been isolated into pure culture. Here we describe a method for establishing a stable single-strain cable bacterium culture in partially sterilized sediment. By repeated transfers of a single cable bacterium filament from freshwater pond sediment into autoclaved sediment, we obtained strain GS, identified by its 16S rRNA gene as a member of Ca. Electronema. This strain was further propagated by transferring sediment clumps, and has now been stable within its semi-natural microbial community for several years. Its metagenome-assembled genome was 93% complete, had a size of 2.76 Mbp, and a DNA G + C content of 52%. Average Nucleotide Identity (ANI) and Average Amino Acid Identity (AAI) suggest the affiliation of strain GS to Ca. Electronema as a novel species. Cell size, number of outer ridges, and detection of LDET in the GS culture are likewise consistent with Ca. Electronema. Based on these combined features, we therefore describe strain GS as a new cable bacterium species of the candidate genus Electronema, for which we propose the name Candidatus Electronema aureum sp.nov. Although not a pure culture, this stable single-strain culture will be useful for physiological and omics-based studies; similar approaches with single-cell or single-filament transfers into natural medium may also aid the characterization of other difficult-to-culture microbes.

Efficient long-range conduction in cable bacteria through nickel protein wires.

Filamentous cable bacteria display long-range electron transport, generating electrical currents over centimeter distances through a highly ordered network of fibers embedded in their cell envelope. The conductivity of these periplasmic wires is exceptionally high for a biological material, but their chemical structure and underlying electron transport mechanism remain unresolved. Here, we combine high-resolution microscopy, spectroscopy, and chemical imaging on individual cable bacterium filaments to demonstrate that the periplasmic wires consist of a conductive protein core surrounded by an insulating protein shell layer. The core proteins contain a sulfur-ligated nickel cofactor, and conductivity decreases when nickel is oxidized or selectively removed. The involvement of nickel as the active metal in biological conduction is remarkable, and suggests a hitherto unknown form of electron transport that enables efficient conduction in centimeter-long protein structures.

Cable bacteria at oxygen-releasing roots of aquatic plants: a widespread and diverse plant-microbe association.

Cable bacteria are sulfide-oxidising, filamentous bacteria that reduce toxic sulfide levels, suppress methane emissions and drive nutrient and carbon cycling in sediments. Recently, cable bacteria have been found associated with roots of aquatic plants and rice (Oryza sativa). However, the extent to which cable bacteria are associated with aquatic plants in nature remains unexplored. Using newly generated and public 16S rRNA gene sequence datasets combined with fluorescence in situ hybridisation, we investigated the distribution of cable bacteria around the roots of aquatic plants, encompassing seagrass (including seagrass seedlings), rice, freshwater and saltmarsh plants. Diverse cable bacteria were found associated with roots of 16 out of 28 plant species and at 36 out of 55 investigated sites, across four continents. Plant-associated cable bacteria were confirmed across a variety of ecosystems, including marine coastal environments, estuaries, freshwater streams, isolated pristine lakes and intensive agricultural systems. This pattern indicates that this plant-microbe relationship is globally widespread and neither obligate nor species specific. The occurrence of cable bacteria in plant rhizospheres may be of general importance to vegetation vitality, primary productivity, coastal restoration practices and greenhouse gas balance of rice fields and wetlands.

Long-distance electron transfer in a filamentous Gram-positive bacterium.

Long-distance extracellular electron transfer has been observed in Gram-negative bacteria and plays roles in both natural and engineering processes. The electron transfer can be mediated by conductive protein appendages (in short unicellular bacteria such as Geobacter species) or by conductive cell envelopes (in filamentous multicellular cable bacteria). Here we show that Lysinibacillus varians GY32, a filamentous unicellular Gram-positive bacterium, is capable of bidirectional extracellular electron transfer. In microbial fuel cells, L. varians can form centimetre-range conductive cellular networks and, when grown on graphite electrodes, the cells can reach a remarkable length of 1.08 mm. Atomic force microscopy and microelectrode analyses suggest that the conductivity is linked to pili-like protein appendages. Our results show that long-distance electron transfer is not limited to Gram-negative bacteria.