A respiro-fermentative strategy to survive nanoxia in Acidobacterium capsulatum.

Microbial soil habitats are characterized by rapid shifts in substrate and nutrient availabilities, as well as chemical and physical parameters. One such parameter that can vary in soil is oxygen; thus, microbial survival is dependent on adaptation to this substrate. To better understand the metabolic abilities and adaptive strategies to oxygen-deprived environments, we combined genomics with transcriptomics of a model organism, Acidobacterium capsulatum, to explore the effect of decreasing, environmentally relevant oxygen concentrations.

Copper Catalysis-Based Amperometric Microsensors for Carbon Dioxide Monitoring.

A fast response microsensor that can detect the distribution of CO at the microscale level is essential for the observation of biophysiological activity, carbon flux, and carbon burial. Inspired by the previous success of Cu catalysis, we attempted to use this metal Cu material to develop an amperometric microsensor that can meet the requirements. Specifically, the ambient gases diffuse through a silicone membrane into a trap casing filled with an acidic CrCl solution, where the otherwise interfering O interferent is removed by a redox with Cr.

Microsensor for total dissolved sulfide (TDS).

Total Dissolved Sulfide (TDS) concentrations can either be derived from simultaneous measurement of pH and one of the sulfide species or determined indirectly in samples following an acidification step. Here we report a microsensor that allows for direct measurement of TDS in aquatic media without the need for pH monitoring. An acidic chamber placed in front of a commercial, amperometric HS microsensor allows for the in-situ conversion of dissolved ionic sulfide species to HS, which in turn is oxidized at the transducer anode.

Total Dissolved Inorganic Carbon Sensor Based on Amperometric CO Microsensor and Local Acidification.

We present a dipping probe total dissolved inorganic carbon (DIC) microsensor based on a localized acidic microenvironment in front of an amperometric CO microsensor. The acidic milieu facilitates conversion of bicarbonate and carbonate to CO, which in turn is reduced at a silver cathode. Interfering oxygen is removed by an acidic CrCl oxygen trap.

Microaerobic Lifestyle at Nanomolar O Concentrations Mediated by Low-Affinity Terminal Oxidases in Abundant Soil Bacteria.

High-affinity terminal oxidases (TOs) are believed to permit microbial respiration at low oxygen (O) levels. Genes encoding such oxidases are widespread, and their existence in microbial genomes is taken as an indicator for microaerobic respiration. We combined respiratory kinetics determined via highly sensitive optical trace O sensors, genomics, and transcriptomics to test the hypothesis that high-affinity TOs are a prerequisite to respire micro- and nanooxic concentrations of O in environmentally relevant model soil organisms: acidobacteria.

Urea Biosensor Based on a CO Microsensor.

Urea sensors based on electrodes in direct contact with the medium have limited long-term stability when exposed to complex media. Here, we present a urea biosensor based on urease immobilized in an alginate polymer, buffered at pH 6, and placed in front of a newly developed fast and sensitive CO microsensor, where the electrodes are shielded by a gas-permeable membrane. The CO produced by the urease in the presence of urea diffuses into the microsensor and is reduced at a Ag cathode.

Ion Selective Amperometric Biosensors for Environmental Analysis of Nitrate, Nitrite and Sulfate.

Inorganic ions that can be redox-transformed by living cells can be sensed by biosensors, where the redox transformation gives rise to a current in a measuring circuit. Such biosensors may be based on enzymes, or they may be based on application of whole cells. In this review focus will be on biosensors for the environmentally important ions NO, NO, and SO, and for comparison alternative sensor-based detection will also be mentioned.

Fast Responding Amperometric CO Microsensor with Ionic Liquid-Aprotic Solvent Electrolytes.

Knowledge about the microscale distribution of CO is essential in many environmental and technical settings, and electrochemical CO sensing may be optimized to yield such information. The performance of a Clark-type CO sensor was greatly improved by adding 20% dimethylformamide (DMF) to the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide (EMIM-DCA) previously used as an electrolyte. The addition of DMF resulted in a much faster response to increasing (95% response of about 100 s) or decreasing CO concentration, a negligible interference from low concentrations of NO, and a signal temperature dependence similar to that of O microsensors.

Microsensors in plant biology: in vivo visualization of inorganic analytes with high spatial and/or temporal resolution.

This Expert View provides an update on the recent development of new microsensors, and briefly summarizes some novel applications of existing microsensors, in plant biology research. Two major topics are covered: (i) sensors for gaseous analytes (O2, CO2, and H2S); and (ii) those for measuring concentrations and fluxes of ions (macro- and micronutrients and environmental pollutants such as heavy metals). We show that application of such microsensors may significantly advance understanding of mechanisms of plant-environmental interaction and regulation of plant developmental and adaptive responses under adverse environmental conditions via non-destructive visualization of key analytes with high spatial and/or temporal resolution.

Amperometric sensor for nanomolar nitrous oxide analysis.

Nitrous oxide is an important greenhouse gas and there is a need for sensitive techniques to study its distribution in the environment at concentrations near equilibrium with the atmosphere (9.6 nM in water at 20 °C). Here we present an electrochemical sensor that can quantify NO in the nanomolar range.

Root O consumption, CO production and tissue concentration profiles in chickpea, as influenced by environmental hypoxia.

Roots in flooded soils experience hypoxia, with the least O in the vascular cylinder. Gradients in CO across roots had not previously been measured. The respiratory quotient (RQ; CO produced : O consumed) is expected to increase as O availability declines.

Strong leaf surface basification and CO limitation of seagrass induced by epiphytic biofilm microenvironments.

Coastal eutrophication is a growing problem worldwide, leading to increased epiphyte overgrowth of seagrass leaves. Yet little is known about how epiphytes affect key biogeochemical conditions and processes in the seagrass phyllosphere. We used electrochemical microsensors to measure microgradients of O , pH, and CO at the bare and epiphyte-covered leaf surface of seagrass (Zostera marina L.

Anammox and partial nitritation in the mainstream of a wastewater treatment plant in a temperate region (Denmark).

The Marselisborg WWTP (Aarhus, Denmark) fed the mainstream nitrification/denitrification tanks with excess sludge from a sidestream DEMON tank for more than three years to investigate if anammox can supplement conventional nitrification/denitrification in a mainstream of a temperate region. To evaluate this long-term attempt, anammox and also denitrification rates were measured in activated sludge from the main- and sidestream at 10, 20 and 30 °C using N-labelling (stable isotope) experiments. The results show that anammox contributes by approximately 1% of the total nitrogen removal in the mainstream tanks and that anammox conversion rates there are approximately 800-900 times lower than in the DEMON.

Biogas upgrading with hydrogenotrophic methanogenic biofilms.

Hydrogen produced from periodic excess of electrical energy may be added to biogas reactors where it is converted to CH that can be utilized in the existing energy grid. The major challenge with this technology is gas-to-liquid mass transfer limitation. The microbial conversions in reactors designed for hydrogenotrophic methanogenesis were studied with microsensors for H, pH, and CO.

CO2 and O2 dynamics in leaves of aquatic plants with C3 or CAM photosynthesis - application of a novel CO2 microsensor.

Background And Aims: Leaf tissue CO2 partial pressure (pCO2) shows contrasting dynamics over a diurnal cycle in C3 and Crassulacean Acid Metabolism (CAM) plants. However, simultaneous and continuous monitoring of pCO2 and pO2 in C3 and CAM plants under the same conditions was lacking. Our aim was to use a new CO2 microsensor and an existing O2 microsensor for non-destructive measurements of leaf pCO2 and pO2 dynamics to compare a C3 and a CAM plant in an aquatic environment.

Gene expression of terminal oxidases in two marine bacterial strains exposed to nanomolar oxygen concentrations.

The final step of aerobic respiration is carried out by a terminal oxidase transporting electrons to oxygen (O2). Prokaryotes harbor diverse terminal oxidases that differ in phylogenetic origin, structure, biochemical function, and affinity for O2. Here we report on the expression of high-affinity (cytochrome cbb3 oxidase), low-affinity (cytochrome aa3 oxidase), and putative low-affinity (cyanide-insensitive oxidase (CIO)) terminal oxidases in the marine bacteria Idiomarina loihiensis L2-TR and Marinobacter daepoensis SW-156 upon transition to very low O2 concentrations (<200 nM), measured by RT-qPCR.

Hydrogen Dynamics in Cyanobacteria Dominated Microbial Mats Measured by Novel Combined H/HS and H/O Microsensors.

Hydrogen may accumulate to micromolar concentrations in cyanobacterial mat communities from various environments, but the governing factors for this accumulation are poorly described. We used newly developed sensors allowing for simultaneous measurement of HS and H or O and H within the same point to elucidate the interactions between oxygen, sulfate reducing bacteria, and H producing microbes. After onset of darkness and subsequent change from oxic to anoxic conditions within the uppermost ∼1 mm of the mat, H accumulated to concentrations of up to 40 μmol L in the formerly oxic layer, but with high variability among sites and sampling dates.

Cryptic oxygen cycling in anoxic marine zones.

Oxygen availability drives changes in microbial diversity and biogeochemical cycling between the aerobic surface layer and the anaerobic core in nitrite-rich anoxic marine zones (AMZs), which constitute huge oxygen-depleted regions in the tropical oceans. The current paradigm is that primary production and nitrification within the oxic surface layer fuel anaerobic processes in the anoxic core of AMZs, where 30-50% of global marine nitrogen loss takes place. Here we demonstrate that oxygenic photosynthesis in the secondary chlorophyll maximum (SCM) releases significant amounts of O to the otherwise anoxic environment.

Ammonium and nitrite oxidation at nanomolar oxygen concentrations in oxygen minimum zone waters.

A major percentage of fixed nitrogen (N) loss in the oceans occurs within nitrite-rich oxygen minimum zones (OMZs) via denitrification and anammox. It remains unclear to what extent ammonium and nitrite oxidation co-occur, either supplying or competing for substrates involved in nitrogen loss in the OMZ core. Assessment of the oxygen (O2) sensitivity of these processes down to the O2 concentrations present in the OMZ core (<10 nmol⋅L(-1)) is therefore essential for understanding and modeling nitrogen loss in OMZs.

Micro-scale H2-CO2 Dynamics in a Hydrogenotrophic Methanogenic Membrane Reactor.

Biogas production is a key factor in a sustainable energy supply. It is possible to get biogas with very high methane content if the biogas reactors are supplied with exogenous hydrogen, and one of the technologies for supplying hydrogen is through gas permeable membranes. In this study the activity and stratification of hydrogen consumption above such a membrane was investigated by use of microsensors for hydrogen and pH.

Effects of Bacterial Community Members on the Proteome of the Ammonia-Oxidizing Bacterium Nitrosomonas sp. Strain Is79.

Unlabelled: Microorganisms in the environment do not exist as the often-studied pure cultures but as members of complex microbial communities. Characterizing the interactions within microbial communities is essential to understand their function in both natural and engineered environments. In this study, we investigated how the presence of a nitrite-oxidizing bacterium (NOB) and heterotrophic bacteria affect the growth and proteome of the chemolithoautotrophic ammonia-oxidizing bacterium (AOB) Nitrosomonas sp.

In Situ Hydrogen Dynamics in a Hot Spring Microbial Mat during a Diel Cycle.

Unlabelled: Microbes can produce molecular hydrogen (H2) via fermentation, dinitrogen fixation, or direct photolysis, yet the H2 dynamics in cyanobacterial communities has only been explored in a few natural systems and mostly in the laboratory. In this study, we investigated the diel in situ H2 dynamics in a hot spring microbial mat, where various ecotypes of unicellular cyanobacteria (Synechococcus sp.) are the only oxygenic phototrophs.

Respiratory Kinetics of Marine Bacteria Exposed to Decreasing Oxygen Concentrations.

During aerobic respiration, microorganisms consume oxygen (O2) through the use of different types of terminal oxidases which have a wide range of affinities for O2. The Km values for O2 of these enzymes have been determined to be in the range of 3 to 200 nmol liter(-1). In this study, we examined the time course of development of aerobic respiratory kinetics of four marine bacterial species (Dinoroseobacter shibae, Roseobacter denitrificans, Idiomarina loihiensis, and Marinobacter daepoensis) during exposure to decreasing O2 concentrations.

Microsensor measurements of hydrogen gas dynamics in cyanobacterial microbial mats.

We used a novel amperometric microsensor for measuring hydrogen gas production and consumption at high spatio-temporal resolution in cyanobacterial biofilms and mats dominated by non-heterocystous filamentous cyanobacteria (Microcoleus chtonoplastes and Oscillatoria sp.). The new microsensor is based on the use of an organic electrolyte and a stable internal reference system and can be equipped with a chemical sulfide trap in the measuring tip; it exhibits very stable and sulfide-insensitive measuring signals and a high sensitivity (1.