Microbial Filter Research Articles

Dynamics and Controls of Methane Oxidation in the Aerobic Waters of Eastern China Marginal Seas

AbstractAerobic methane oxidation (MOx) mediated by methanotrophs is a crucial mechanism in controlling methane emissions from the surface ocean to the atmosphere. Coastal waters dominate global oceanic methane emissions, but the dynamics, controls and roles of MOx remain largely unconstrained in the marginal seas around China. Here, we conducted a variety of biogeochemical analyses to investigate the controls of methane cycling and the dynamics of methanotrophic activity in the East China Sea and Yellow Sea. Methane was supersaturated in the surface seawater and the concentrations ranged from 2.8 to 19.8 nM. The distribution of methane was regulated by the sources and sinks, which were influenced largely by hydrological and biogeochemical factors. Methane was turned over rapidly with high rates (k: 5 × 10−4–0.04 d−1), indicating the enzymatic capability of methanotrophic biomass to metabolize methane. Rates of MOx varied significantly between sites (1 × 10−3–0.60 nM d−1) and relatively high MOx rates were observed in shallow waters. MOx exhibited the Michaelis‐Menten kinetics with the V max of 0.30 nM d−1 and a K m of 78.3 nM. Methanotrophic activity was impacted by environmental factors such as methane availability, nutrient levels, bacterial production and temperature. Nutrient addition experiments demonstrated that phosphate elevated MOx rates, while the activity was largely inhibited by ammonium probably due to competitive inhibition of the methane monooxygenase by ammonia. Comparing the depth‐integrated MOx rates with the air‐sea fluxes at selected sites showed that methane consumed through microbial oxidation accounted for up to 78.1% of the total methane loss (=sum of MOx rates and air‐sea flux), highlighting the role of MOx as a microbial filter for methane emissions.

Characterization of heavy metal-associated bacteria from petroleum-contaminated soil and their resistogram and antibiogram analysis.

The aim of the current study was to screen and identify heavy metal (chromium, cadmium, and lead) associated bacteria from petroleum-contaminated soil of district Muzaffarabad, Azad Jammu and Kashmir, Pakistan to develop ecofriendly technology for contaminated soil remediation. The petroleum-contaminated soil was collected from 99 different localities of district Muzaffarabad and the detection of heavy metals via an atomic absorption spectrometer. The isolation and identification of heavy metals-associated bacteria were done via traditional and molecular methods. Resistogram and antibiogram analysis were also performed using agar well diffusion and agar disc diffusion methods. The isolated bacteria were classified into species, i.e., B. paramycoides, B. albus, B. thuringiensis, B. velezensis, B. anthracis, B. pacificus Burkholderia arboris, Burkholderia reimsis, Burkholderia aenigmatica, and Streptococcus agalactiae. All heavy metals-associated bacteria showed resistance against both high and low concentrations of chromium while sensitive towards high and low concentrations of lead in the range of 3.0 ± 0.0mm to 13.0 ± 0.0mm and maximum inhibition was recorded when cadmium was used. Results revealed that some bacteria showed sensitivity towards Sulphonamides, Norfloxacin, Erythromycin, and Tobramycin. It was concluded that chromium-resistant bacteria could be used as a favorable source for chromium remediation from contaminated areas and could be used as a potential microbial filter.

Near seafloor methane flux in the world's largest human-induced dead zone is regulated by sediment accumulation rate

The vast oxygen-depleted area of the central Baltic Sea is the largest human-induced dead zone in the world with 70,000 km2 or approximately three times the second largest one in the Gulf of Mexico. Methane occurs in high concentrations in bottom waters (3200 nM) and sediments (30 mM), and its dynamics is better constrained for the water column, but still poorly understood on sediments. Here we show that sediment accumulation rate plays a major role in regulating the quantity of organic matter and its residence time in the sulphate reduction and methanogenesis zones and, therefore, affects methane generation, consumption, and diffusive flux in sediments near the seafloor (< 1 m). High fluxes found in high sediment accumulation rate areas and competition for substrate (organoclastic sulphate reduction vs. anaerobic oxidation of methane with sulphate), compromise the ability of the thin microbial filter to consume and prevent methane diffusion through the seafloor.

Follow the Metaplasia: Characteristics and Oncogenic Implications of Metaplasia's Pattern of Spread Throughout the Stomach.

The human stomach functions as both a digestive and innate immune organ. Its main product, acid, rapidly breaks down ingested products and equally serves as a highly effective microbial filter. The gastric epithelium has evolved mechanisms to appropriately handle the myriad of injurious substances, both exogenous and endogenous, to maintain the epithelial barrier and restore homeostasis. The most significant chronic insult that the stomach must face is Helicobacter pylori (Hp), a stomach-adapted bacterium that can colonize the stomach and induce chronic inflammatory and pre-neoplastic changes. The progression from chronic inflammation to dysplasia relies on the decades-long interplay between this oncobacterium and its gastric host. This review summarizes the functional and molecular regionalization of the stomach at homeostasis and details how chronic inflammation can lead to characteristic alterations in these developmental demarcations, both at the topographic and glandular levels. More importantly, this review illustrates our current understanding of the epithelial mechanisms that underlie the pre-malignant gastric landscape, how Hp adapts to and exploits these changes, and the clinical implications of identifying these changes in order to stratify patients at risk of developing gastric cancer, a leading cause of cancer-related deaths worldwide.

The water column of the Yamal tundra lakes as a microbial filter preventing methane emission

Abstract. Microbiological, molecular ecological, biogeochemical, and isotope geochemical research was carried out in four lakes of the central part of the Yamal Peninsula in the area of continuous permafrost. Two of them were large (73.6 and 118.6 ha) and deep (up to 10.6 and 12.3 m) mature lakes embedded into all geomorphological levels of the peninsula, and two others were smaller (3.2 and 4.2 ha) shallow (2.3 and 1.8 m) lakes which were formed as a result of thermokarst on constitutional (segregated) ground ice. Samples were collected in August 2019. The Yamal tundra lakes were found to exhibit high phytoplankton production (340–1200 mg C m−2 d−1) during the short summer season. Allochthonous and autochthonous, particulate and dissolved organic matter was deposited onto the bottom sediments, where methane was the main product of anaerobic degradation, and its content was 33–990 µmol CH4 dm−3. The rates of hydrogenotrophic methanogenesis appeared to be higher in the sediments of deep lakes than in those of the shallow ones. In the sediments of all lakes, Methanoregula and Methanosaeta were predominant components of the archaeal methanogenic community. Methane oxidation (1.4–9.9 µmol dm−3 d−1) occurred in the upper sediment layers simultaneously with methanogenesis. Methylobacter tundripaludum (family Methylococcaceae) predominated in the methanotrophic community of the sediments and the water column. The activity of methanotrophic bacteria in deep mature lakes resulted in a decrease in the dissolved methane concentration in lake water from 0.8–4.1 to 0.4 µmol CH4 L−1 d−1, while in shallow thermokarst lakes the geochemical effect of methanotrophs was much less pronounced. Thus, only small, shallow Yamal lakes may contribute significantly to the overall diffusive methane emissions from the water surface during the warm summer season. The water column of large, deep lakes on Yamal acts, however, as a microbial filter preventing methane emission into the atmosphere. It can be assumed that climate warming will lead to an increase in the total area of thermokarst lakes, which will enhance the effect of methane release into the atmosphere.

Formicine ants swallow their highly acidic poison for gut microbial selection and control.

Animals continuously encounter microorganisms that are essential for health or cause disease. They are thus challenged to control harmful microbes while allowing the acquisition of beneficial microbes. This challenge is likely especially important for social insects with respect to microbes in food, as they often store food and exchange food among colony members. Here we show that formicine ants actively swallow their antimicrobial, highly acidic poison gland secretion. The ensuing acidic environment in the stomach, the crop, can limit the establishment of pathogenic and opportunistic microbes ingested with food and improve the survival of ants when faced with pathogen contaminated food. At the same time, crop acidity selectively allows acquisition and colonization by Acetobacteraceae, known bacterial gut associates of formicine ants. This suggests that swallowing of the poison in formicine ants acts as a microbial filter and that antimicrobials have a potentially widespread but so far underappreciated dual role in host-microbe interactions.

Acid and the basis for cellular plasticity and reprogramming in gastric repair and cancer.

Subjected to countless daily injuries, the stomach still functions as a remarkably efficient digestive organ and microbial filter. In this Review, we follow the lead of the earliest gastroenterologists who were fascinated by the antiseptic and digestive powers of gastric secretions. We propose that it is easiest to understand how the stomach responds to injury by stressing the central role of the most important gastric secretion, acid. The stomach follows two basic patterns of adaptation. The superficial response is a pattern whereby the surface epithelial cells migrate and rapidly proliferate to repair erosions induced by acid or other irritants. The stomach can also adapt through a glandular response when the source of acid is lost or compromised (that is, the process of oxyntic atrophy). We primarily review the mechanisms governing the glandular response, which is characterized by a metaplastic change in cellular differentiation known as spasmolytic polypeptide-expressing metaplasia (SPEM). We propose that the stomach, like other organs, exhibits marked cellular plasticity: the glandular response involves reprogramming mature cells to serve as auxiliary stem cells that replace lost cells. Unfortunately, such plasticity might mean that the gastric epithelium undergoes cycles of differentiation and de-differentiation that increase the risk of accumulating cancer-predisposing mutations.

Hydrodynamics of microbial filter feeding

Microbial filter feeders are an important group of grazers, significant to the microbial loop, aquatic food webs, and biogeochemical cycling. Our understanding of microbial filter feeding is poor, and, importantly, it is unknown what force microbial filter feeders must generate to process adequate amounts of water. Also, the trade-off in the filter spacing remains unexplored, despite its simple formulation: A filter too coarse will allow suitably sized prey to pass unintercepted, whereas a filter too fine will cause strong flow resistance. We quantify the feeding flow of the filter-feeding choanoflagellate Diaphanoeca grandis using particle tracking, and demonstrate that the current understanding of microbial filter feeding is inconsistent with computational fluid dynamics (CFD) and analytical estimates. Both approaches underestimate observed filtration rates by more than an order of magnitude; the beating flagellum is simply unable to draw enough water through the fine filter. We find similar discrepancies for other choanoflagellate species, highlighting an apparent paradox. Our observations motivate us to suggest a radically different filtration mechanism that requires a flagellar vane (sheet), something notoriously difficult to visualize but sporadically observed in the related choanocytes (sponges). A CFD model with a flagellar vane correctly predicts the filtration rate of D. grandis, and using a simple model we can account for the filtration rates of other microbial filter feeders. We finally predict how optimum filter mesh size increases with cell size in microbial filter feeders, a prediction that accords very well with observations. We expect our results to be of significance for small-scale biophysics and trait-based ecological modeling.

Protozoa graze on the 2,6-dichlorobenzamide (BAM)-degrading bacterium Aminobacter sp. MSH1 introduced into waterworks sand filters.

Groundwater contamination by pesticide residues often leads to the closure of drinking water wells, making the development of new techniques to remediate drinking water resources of considerable interest. Pesticide-degrading bacteria were recently added to a waterworks sand filter in an attempt to remediate pesticide-polluted drinking water. The density of the introduced bacteria, however, decreased rapidly, which was partly attributed to predation by protozoa in the sand filter. This study investigated the effects of indigenous sand filter protozoa on the population density and degradation efficiency of degrader bacteria introduced into sand from a waterworks sand filter. The 2,6-dichlorobenzamide (BAM)-degrading bacterium Aminobacter sp. MSH1 was used as a model organism. The introduction of MSH1 at high cell densities was followed by a >1000-fold increase in the protozoan population size and at the same time a 29% reduction in Aminobacter cell numbers. The protozoan population in the systems that had MSH1 added at a lower density only increased 50-fold, and a decrease in Aminobacter numbers was not detectable. Furthermore, a reduction in the number of Aminobacter and in BAM degradation efficiency was seen in flow-through sand filter columns inoculated with MSH1 and fed BAM-contaminated water, when comparing sand columns containing the indigenous microbial filter community, i.e. containing protozoa, to columns with sterilised sand. These results suggest that degrader bacteria introduced into waterworks sand filters are adversely affected by grazing from the indigenous protozoa, reducing the size of the degrader population and the sand filter degradation efficiency.

Styrene Removal from Polluted Air in Biotrickling Filter with Pyrocarbon-Sawdust and Ceramic-Raschig-Rings-Sawdust Packings

In this paper, a mixed microbial population biotrickling filter (BTF) was investigated for styrene removal with two different packings at different empty bed residence times and gas-liquid ratio(GLR). The two biotrickling filters inoculated with a Pyrocarbon-sawdust and ceramic-raschig-rings-sawdust mixed packings were filled respectively in two identical laboratory-scale biotrickling filters which were operated in parallel. The results showed that the BTF filling with pyrocarbon-sawdust packings had higher rate of bio-film formation and removal efficiency of styrene than that of ceramic-raschig-rings-sawdust packings. When an inlet gas concentration of 50 to 450 mg/m³, an Empty Bed Residence Time (EBRT) of 21.6 to 43.2 s, and a gas-liquid ratio (GLR) of 110.7 to 55.3, a maximum styrene removal load is up to 153.1 g/(m³·h). During shock-load experiments with shutdown, the styrene removal efficiency of the BTF could gradually reach 92 % to 100 % by 14 h.

INFLUENCE OF ANTIBIOTICS, SEALING SYSTEM AND GENOTYPE ON SHOOT REGENERATION VIA ORGANOGENESIS IN PASSION FLOWERS

In this work we evaluated the influence of three antibiotics (A) [Meropenem (MER), Cefotaxime (CEF) and Timentin (TIM)], three sealing systems-SS (PVPM, Petri dish, and PVC) and two genotypes (G) (Passiflora edulis ‘FB’ 100 and P. cincinnata) on shoot regeneration from in vitro cultured leaf explants. Explants were grown on MS medium supplemented with 2.0 mg.L-1 6-benzyladenine (BA) plus different concentrations of MER (0, 12.5 and 25.0 mg.L-1), CEF (0, 250 and 500 mg. L-1) or TIM (0, 150 and 300 mg.L-1), for five days in the dark. The flasks were sealed with three types of material (SS): polypropylene folding bag with microbial filter (ESPM), Petri dish with hypoallergenic tape (PDH), and a single layer of polyvinyl chlorine film (PVC). After explant inoculation and sealing of the flasks, these were transferred to a growth room at temperature 27±2°C. The flasks were transferred to a 16/8 h (light/dark) photoperiod, under irradiance of 36 μmol.m-2.s-1, for 30 days. The experimental design was completely randomized in triple factorial scheme. Each treatment was replicated four times, and each replicate consisted of ten leaf explants. Shoot regeneration was evaluated 30 days after inoculation. Data were subjected to variance analysis and means were compared by Tukey’s test at 5% probability. Percentage data were transformed in arcsin before analysis. Significant differences were observed for G, SS, A, and double (G x SS and G x A) and triple (G x SS x A) interactions on the shoot regeneration. In general, the best response with respect to G was obtained with P. edulis ‘FB-100’. For SS ESPM is more indicated, whereas TIM presented the better results among antibiotics evaluated. Regarding to the triple interactions the best responses achieved were P. cincinnata x PDH x R (12.5 mg.L-1), and P. edulis x ESPM x TIM (150 mg.L-1). Based on these results we suggest the use of different protocols for the two species.

Research on the Biofilm Accretion of Flotation Bio-Filter

Removal the pollutants of the polluted water through flotation bio-film are reached by the cooperation work of microbial degradation and sand filter. This paper through dosing the bacterial suspension and nutrition did the research on biofilm accretion. Results showed that the biomass on quartz sand had greatly increased, and the removal rates of organic and ammonia nitrogen also had a huge increase. At the end of biofilm accretion, the removal rates of pollutants keep at a stable value.

Transformation of particulate organic matter at the water-bottom boundary in the Russian Arctic seas: Evidence from isotope and radioisotope data

Complex biogeochemical studies including the determination of isotopic composition of Corg in both suspended particulate matter and surface horizon (0–1 cm) of sediments (more than 260 determinations of δ13C-Corg) were carried out for five Arctic shelf seas: White, Barents, Kara, East Siberian, and Chukchi. The aim of this study is to elucidate causes that change the isotopic composition of particulate organic carbon at the water-sediment boundary. It is shown that the isotopic composition of Corg in sediments from seas with a high river runoff (White, Kara, and East Siberian) does not inherit the isotopic composition of Corg in particles precipitating from the water column, but is enriched in heavy 13C. Seas with a low river runoff (Barents and Chukchi) show insignificant difference between the value of δ13C-Corg in both suspended load and sediment because of a low content of the isotopically light allochthonous organic matter (OM) in particulates. Complex biogeochemical studies with radioisotope tracers (14CO2, 35S, and 14CH4) revealed the existence of specific microbial filter formed from heterotrophic and autotrophic organisms at the water-sediment boundary. This filter prevents the mass influx of products of OM decomposition into water column, as well as reduces the influx of a part of OM contained in the suspended particulate matter from water into sediment.

생물벽체를 이용한 PCE로 오염된 지하수의 환원성 탐염소화: 칼럼 실험

The applicability of in situ biobarrier or microbial filter technology for the remediation of groundwater contaminated with chlorinated solvent was investigated through column study. In this study, the effect of packing materials on the reductive dechlorination of PCE was investigated using Canadian peat, Pahokee peat, peat moss and vermicompost (or worm casting) as a biobarrier medium. Optimal conditions previously determined from a batch microcosm study was applied in this column study. Lactate/benzoate was amended as electron donors to stimulate reductive dechlorination of PCE. Hydraulic conductivity was approximately and no difference was found among the packing materials. The transport and dispersion coefficients determined from the curve-fitting of the breakthrough curves of using CXTFIT 2.1 showed no difference between single-region and two-region models. The reductive dechlorination of PCE was efficiently occurred in all columns. Among the columns, especially the column packed with vermicompost exhibited the highest reductive dechlorination efficiency. The results of this study showed the promising potential of in situ biobarrier technology using peat and vermicompost for the remediation of groundwater contaminated with chlorinated solvents.

Spatial distribution of mud flows, chemoautotrophic communities, and biogeochemical habitats at Håkon Mosby Mud Volcano

Marine mud volcanoes are significant source locations contributing to the marine methane cycle. Enhanced heat flow, unique chemoautotrophic communities, occurrence of massive gas hydrates and large gas plumes are direct evidences of elevated methane concentrations and the dynamic environment of mud volcanoes. Related to the high concentrations and large inventories of CH 4 in surface sediments only a fraction of the methane is exported to the bottom water. This is mainly due to chemoautotrophic communities oxidizing methane and proving a “microbial filter” reducing CH 4 fluxes. Although these processes were studied for several mud volcanoes still little is known about the spatial pattern and the areas covered by chemoautotrophic communities or by present mud flows. For this purposes the Håkon Mosby Mud Volcano (HMMV), which is located at the continental slope of the Barents Sea, was studied by several dives with the Remotely Operated Vehicle Victor6000. During these dives a high resolution microbathymetric map, with a footprint of 25 × 25 cm and a vertical resolution of better than 10 cm was derived. Furthermore, video streams of the bottom camera were converted into georeferenced mosaics, providing a detailed image about the spatial distribution of seafloor features as bacterial mats, pogonophorans, both indicating methane oxidation, or mud flows. Based on visual inspection of 2310 georeferenced mosaics covering an area of 46,160 m 2, different biogeochemical habitats were identified and quantified on a m 2-basis. By application of geostatistic techniques as indicator kriging the distribution of different biogeochemical habitats was quantified and mapped for the entire HMMV. Considering the flat and hummocky area of HMMV, approximately 16% (115,165 m 2) of the flat centre is nearly void of any benthic communities. This area is considered as a region of high methane discharge into bottom water. An area of 5% (38,244 m 2), located in the south-eastern part, is densely inhabited by Beggiatoa. The hummocky outer part is colonised dominantly by pogonophoran tube worms (37.3%; 276,121 m 2) and only occasional by Beggiatoa. Source locations and drainage directions for current mud flows were identified by computation of trend surfaces and consideration of temperature data. This suggests that present mud flow ascend close to the northern edge of the flat unit of HMMV, and that the drainage pattern of mud flows shifted from a westward to a south-south-eastern direction.

Attachment/detachment and trichloroethylene degradation-longevity of a resting cell Methylosinus trichosporium OB3b filter

We are investigating a methanotrophic filter strategy for the in situ bioremediation of low levels of chlorinated aliphatic, volatile organic chemicals (VOCs). It is based on the use of pregrown, resting cells, instead of growth-nutrient stimulations. The economic feasibility of such a filter is dependent on its operational longevity at ground-water temperatures. The latter, in turn, is dependent on several key parameters, such as the bacterial attachment densities reached during the injection of the microbial suspension and the subsequent detachment-removal of cells from the filter over time. Scaled attachment/detachment experiments were carried out using a representative quartzitic sand in glass 1-cm x 10-cm columns to simulate a filter. A rosette-dominated form of Methylosinus trichosporium OB3b was isolated and used in these and the subsequent catalytic longevity experiments. Its initial attachment, employing Higgins' medium phosphate buffer, pH 7.0 (HPB), was 7.0 to 8.0 x 10(8) bacteria/g of dry sand. This was elevated to approximately 1.5 x 10(9) cells/g by including 1.0 mM MgCl(2), 100 muM FeSO(4), and 0.025% agar in the cell-suspension loading buffer. These loading additives also increased the time required to reach 50% cell detachment with HPB alone from 5 days to approximately 45 days. The functional longevity of a column biofilter, formed with resting-state rosette-enriched cells in the presence of the aforementioned additives, was determined at 21 degrees C by challenging it with weekly 12 h, approximately 250 ppb pulses of trichloroethylene (TCE). The column results indicate that for our attached-cell filter to biodegrade TCE levels of several hundred ppb sufficiently, to <5 ppb, it will likely need replenishment at approximately 8 week intervals, due to the instability of the endogenous whole-cell soluble methane monooxygenase specific activity beyond that time period. This study represents the first time that anyone has shown that a rosette-enriched substrain can be isolated from a well-known methanotrophic strain and then stably cultured and utilized advantageously for a specific application-namely its improved attachment-slowed detachment characteristics in a microbial filter.

Design of in-situ microbial filter for the remediation of naphthalene

The in-situ microbial filter (ISMF) is a specific application of in-situ bioremediation (ISB) for the treatment of groundwater contaminated plumes. The ISMF filter consists of an in-situ reactor, composed of sand mixed with non-indigenous microorganisms, that is placed ahead of migrating contaminant plumes and removes contaminants by biological and abiological processes. This paper presents the results of an experimental study investigating the remediation of naphthalene contaminated water through a lab scale ISMF. Mathematical modeling was performed to determine the optimum dimensions and configuration of the ISMF, and to stimulate the migration of naphthalene through the ISMF. Soil column tests were carried out to determine the biomass concentration and hydraulic conductivity to attain effective biodegradation within an ISMF. The optimum biomass concentration was determined to be 1.4 mg VSS/g sand and the optimum hydraulic conductivity was determined to be approximately 1×10 −5 m/s. FLOTRANS, a two-dimensional finite element hydrogeological model based on the advection-dispersion equation, was used to illustrate the effect of different filter and barrier configurations on the discharge through the filter and to stimulate naphthalene migration through an ISMF. Experimental results and the mean simulation values obtained through Crystal Ball ®, a forecasting and risk analysis program, were used as the input parameters for the FLOTRANS model. Optimum dimensions and configurations of the filter were determined for effective remediation of naphthalene. Modeling results indicated that an ISMF, with the flow and transport properties determined in this study, has the capacity to substantially attenuate naphthalene contaminated groundwater. A sensitivity analysis was performed using Crystal Ball ® to determine the relative influence of the basic parameters from the advection–dispersion equation on the contaminant concentration.

Convection warmers--not just hot air.

We sought to determine whether the forced air convection warmers (nine Bair Huggers, Augustine Medical, and one Warm Touch, Mallinkrodt Medical) used in our operating theatres could be a source of microbial pathogens. Agar plates were placed directly in the air stream of the warmers. Four of these grew potentially pathogenic organisms. When the warmers were set to blow through perforated blankets, no growth occurred. Three of the warmers were swabbed and sites of colonisation were found in their hoses. After fixing a microbial filter to the end of the hose, organisms were no longer detectable. We conclude that these warming devices are a potential source of nosocomial infection. They should only be used in conjunction with perforated blankets, should have their microbial filters changed regularly and their hoses sterilised. The inclusion of a microbial filter into the nozzle of the hose could be incorporated into the design of the warmer.

In situbioremediation of trichloroethylene-contaminated water by a resting-cell methanotrophic microbial filter

Abstract An in situ microbial filter technology is being tested and developed for remediating migrating subsurface plumes contaminated with low concentrations of trichloroethylene (TCE). The current focus is the establishment of a replenishable bioactive zone (catalytic filter) along expanding plume boundaries by the injection of a representative methanotrophic bacterium, Methylosinus trichosporium OB3b. This microbial filter strategy has been successfully demonstrated using emplaced, attached resting cells (no methane additions) in a 1.1 m flow-through test bed loaded with water-saturated sand. Two separate 24 h pulses of TCE (109 ppb and 85 ppb), one week apart, were pumped through the system at a flow velocity of 15 mm h−1; no TCE (< 0.5 ppb) was detected on the downstream side of the microbial filter. Subsequent excavation of the wet sand confirmed the existence of a TCE-bioactive zone 21 days after it had been created. An enhanced longevity of the cellular, soluble-form methane monooxygenase produced...

An Alternative Strategy for Infection Control of Anesthesia Breathing Circuits

Contaminated breathing systems have been responsible for nosocomial upper respiratory tract and pulmonary infections in patients undergoing general anesthesia. The current infection control guidelines for anesthesia breathing circuits require single-patient use or high-level disinfection of breathing tubes, y-connector, and reservoir bag. An alternative infection control strategy has been suggested that incorporates placement of a microbial filter downstream from the y-connector between the circuit and the patient. This laboratory study assessed the capacity of the Pall HME Filter as a bidirectional barrier to transmission of bacteria between the y-connector of an anesthesia circle breathing system and a test lung. The investigators modified a sterile circle system to allow aerosolization of a suspension of 10(9) Micrococcus luteus over 5 h into the inspiratory limb proximal to the y-connector or downstream from the filter into the test lung. Cultures indicated that the Pall HME Filter placed between the y-connector and the test lung completely prevented transmission of bacteria in both directions. The results of this study suggest that the Pall HME Filter could be used as an effective microbial barrier between the anesthesia circle breathing system and the patient as part of an alternative strategy for infection control.