Seasonal dynamics of aerobic anoxygenic phototrophs in freshwater lake Vlkov.

Aerobic anoxygenic phototrophic (AAP) bacteria are a common component of freshwater microbial communities. They harvest light energy using bacteriochlorophyll a-containing reaction centers to supplement their predominantly heterotrophic metabolism. We used epifluorescence microscopy, HPLC, and infrared fluorometry to examine the dynamics of AAP bacteria in the mesotrophic lake Vlkov during the seasonal cycle. The mortality of AAP bacteria was estimated from diel changes of bacteriochlorophyll a fluorescence. The AAP abundance correlated with water temperature and DOC concentration. Its maximum was registered during late summer, when AAP bacteria made up 20% of total bacteria. The novel element of this study is the seasonal measurements of AAP mortality rates. The rates ranged between 1.15 and 4.56 per day with the maxima registered in early summer coinciding with the peak of primary production, which documents that AAP bacteria are a highly active component of freshwater microbial loop.

Pulsed xenon ultraviolet and non-thermal atmospheric plasma treatments are effective for the disinfection of air in hospital blood sampling rooms.

BACKGROUND AND OBJECTIVES: Non-thermal atmospheric plasma treatment and pulsed xenon ultraviolet (PX-UV) treatment are widely used in disinfection of hospital environments. However, their effectiveness has not been evaluated against a comparator. The objective of this study is to evaluate their effectiveness in the disinfection of pathogens in the air in hospital blood sampling rooms. METHODS: Samples were taken from the air before and after disinfection with PX-UV and non-thermal atmospheric plasma. We counted bacterial colonies and identified the types of bacteria. RESULTS: Non-thermal plasma treatment significantly reduced bacterial counts in the air, the median reduced from 1 before treatment to zero afterwards (p = 0.03). PX-UV treatment also significantly reduced bacterial counts in the air (p = 0.01), the median reduced from 1.5 before treatment to zero afterwards. Pathogens identified in the current study include nosocomial bacteria, such as Staphylococcus aureus, Staphylococcus epidermidis, and yeast. CONCLUSION: Disinfection of blood sampling sites is essential in a health service department. The efficiency of PX-UV and non-thermal atmospheric plasma treatment are comparable in air disinfection.

Comparative effectiveness of rapid-cycle ultraviolet decontamination to chemical decontamination on high-touch communication devices.

BACKGROUND: This quantitative, comparative-descriptive study of inpatient units in a large military medical center was designed to compare the effectiveness of compact ultraviolet (UV-C) decontamination to standard chemical decontamination in reducing the microbial burden on Vocera (San Jose, CA) communication devices and to characterize changes in staff cleaning practices following UV-C device implementation. METHODS: Aerobic and anaerobic swabs were used to collect microbial samples from Vocera devices (n = 60) before and after chemical decontamination (first sampling) and before and after UV decontamination (second sampling). Cleaning behaviors were assessed by observation and oral inquiry during the baseline sampling and surveyed 8 weeks after UV-C device implementation. Outcomes included aerobic and anaerobic colony-forming units and prevalence of methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, or Clostridium difficile, as determined by standard microbiological methods. RESULTS: No differences were found between the two cleaning methods in their ability to reduce aerobic bacteria; however, UV-C was significantly more effective at reducing bacteria grown anaerobically (P < .01). This study elucidated an 8.3% prevalence of methicillin-resistant Staphylococcus aureus on Vocera devices in the inpatient environment. Initially, 42% of respondents reported deviations from manufacturer's cleaning guidelines, and 16.7% reported daily or more frequent cleaning of the Vocera devices. CONCLUSIONS: After implementation, UV-C decontamination reduced average cleaning time by 43% and increased the rate of daily Vocera cleaning to 86.5%. Respondents reported an overall 98% user satisfaction with the UV-C device.

Natural sunlight induced rapid formation of water-born algal-bacterial granules in an aerobic bacterial granular photo-sequencing batch reactor.

Wastewater treatment by means of algal-bacterial granules has become a hot topic worldwide recently. Rapid granulation of algal-bacterial granules was achieved in an aerobic bacterial granular sequencing batch reactor (SBR) under natural sunlight exposure. Occurrence of abundant filamentous bacteria bridging the water-born algae, and overproduction of extracellular polymeric substances (EPS) (especially polysaccharides (PS), tryptophan & protein-like, and humic acid-like substances) were observed on the first 3 days, while the algae grew into the inner side of the granules and mature granules were obtained on day 7. The growth of the water-born algae slightly decreased the settleability, mean sizes of the granules, but stimulated the bioactivity significantly. Whereas, the biomass retention decreased before day 3, and got stable soon with the maturation period with symbiotic growth of algal-bacterial biomass. Illumina results revealed that the introduction of algae reduced the richness and diversity of bacterial community. Besides, few changes in structure and some compositions shifts in bacterial communities were found, while the predominant algae shifted from Diatomea to green algae Chlorophyceae. The possible mechanism for natural sunlight induced granulation of algal-bacterial granules was thus proposed based on the interactions between algae and bacteria.

Effect of pulsed xenon ultraviolet room disinfection devices on microbial counts for methicillin-resistant Staphylococcus aureus and aerobic bacterial colonies.

BACKGROUND: Inadequate environmental disinfection represents a serious risk for health care-associated infections. Technologic advancements in disinfection practices, including no-touch devices, offer significant promise to improve infection control. We evaluated one such device, portable pulsed xenon ultraviolet (PX-UV) units, on microbial burden during an implementation trial across 4 Veterans Affairs hospitals. METHODS: Environmental samples were collected before and after terminal room cleaning: 2 facilities incorporated PX-UV disinfection into their cleaning protocols and 2 practiced manual disinfection only. Specimens from 5 high-touch surfaces were collected from rooms harboring methicillin-resistant Staphylococcus aureus (MRSA) or aerobic bacteria colonies (ABC). Unadjusted pre-post count reductions and negative binomial regression modeled PX-UV versus manual cleaning alone. RESULTS: Seventy samples were collected. Overall, PX-UV reduced MRSA and ABC counts by 75.3% and 84.1%, respectively, versus only 25%-30% at control sites. Adjusting for baseline counts, manually cleaned rooms had significantly higher residual levels than PX-UV sites. Combined analyses revealed an incident rate ratio of 5.32 (P = .0024), with bedrails, tray tables, and toilet handrails also showing statistically superior PX-UV disinfection. CONCLUSIONS: This multicenter study demonstrates significantly reduced disinfection across several common pathogens in facilities using PX-UV devices. Clinical impact of laboratory reductions on infection rates was not assessed, representing a critical future research question. However, such approaches to routine cleaning suggest a practical strategy when integrated into daily hospital operations.

Light enhances the growth rates of natural populations of aerobic anoxygenic phototrophic bacteria.

Aerobic anoxygenic phototrophic (AAP) bacteria are microorganisms that can harvest light energy using bacteriochlorophyll a to supplement their predominantly organotrophic metabolism. Growth enhancement by light has repeatedly been demonstrated in laboratory experiments with AAP isolates. However, the ecological advantage of light utilization is unclear, as it has never been proven in the natural environment. Here, we conducted manipulation experiments in the NW Mediterranean and found that AAP bacteria display high growth rates which are controlled to a large extent by intense grazing pressure and phosphorous availability. Foremost, we found that, contrarily to the bulk bacterioplakton, AAP bacteria display higher growth rates when incubated under light-dark cycles than in complete darkness. These results represent the first direct evidence that natural populations of marine AAP bacteria can be stimulated by light.

E-Beam Irradiation for Improving the Microbiological Quality of Smoked Duck Meat with Minimum Effects on Physicochemical Properties During Storage.

This study was performed to evaluate the effect of different doses (0, 1.5, 3, and 4.5 kGy) of e-beam irradiation on the quality parameters (pH, Hunter's parameter, and heme pigment) and stability qualifiers (peroxide value [POV], thiobarbituric acid reactive substances [TBARSs], and total volatile basic nitrogen [TVBN]) of smoked duck meat during 40 d of storage under vacuum packaging at 4 °C. The initial populations of total bacteria (7.81 log CFU/g) and coliforms (5.68 log CFU/g) were reduced by approximately 2 to 5 log cycles with respect to irradiation doses. The results showed that pH, myoglobin, met-myoglobin, L* , a* , and b* showed significant differences with respect to different doses and storage intervals; a* and b* did not vary significantly because of storage. Higher pH was found in samples treated with 4.5 kGy at 40 d, while the minimum was observed in nonirradiated samples at day 0 of storage. Higher POV (2.31 ± 0.03 meq peroxide/kg) and TBARS (5.24 ± 0.03 mg MDA/kg) values were found in 4.5 kGy-treated smoked meat at 40 d and the lowest was reported in 0 kGy-treated meat at initiation of storage (0 d). However, irradiation suppressed TVBN during storage and higher TVBN (7.09 ± 0.32 mg/100 mL) was found in duck meat treated with 0 kGy at 40 d. The electronic nose (e-nose) effectively distinguished flavor profiles during the different storage intervals. The results showed that different sensory attributes did not vary significantly with respect to the dose of irradiation. We conclude that low dose of e-beam irradiation and vacuum packaging is beneficial for safety and shelf life extension without affecting the sensory characteristics of smoked duck meat.

Single-cell activity of freshwater aerobic anoxygenic phototrophic bacteria and their contribution to biomass production.

Aerobic anoxygenic phototrophic (AAP) bacteria are photoheterotrophs that despite their low abundances have been hypothesized to play an ecologically and biogeochemically important role in aquatic systems. Characterizing this role requires a better understanding of the in situ dynamics and activity of AAP bacteria. Here we provide the first assessment of the single-cell activity of freshwater AAP bacteria and their contribution to total bacterial production across lakes spanning a wide trophic gradient, and explore the role of light in regulating AAP activity. The proportion of cells that were active in leucine incorporation and the level of activity per cell were consistently higher for AAP than for bulk bacteria across lakes. As a result, AAP bacteria contributed disproportionately more to total bacterial production than to total bacterial abundance. Interestingly, although environmentally driven patterns in activity did not seem to differ largely between AAP and bulk bacteria, their response to light did, and exposure to light resulted in increases in the proportion of active AAP bacteria with no clear effect on their cell-specific activity. This suggests that light may play a role in the activation of AAP bacteria, enabling these photoheterotrophs to contribute more to the carbon cycle than suggested by their abundance.

Aerobic cervical bacteriology and antibiotic sensitivity patterns in patients with advanced cervical cancer before and after radiotherapy at a national referral hospital in Uganda.

OBJECTIVE: To determine prevalent aerobic cervical bacteria and sensitivity to commonly used antibiotics in patients with advanced cervical cancer before and after 4 weeks of external beam radiotherapy (EBRT). METHODS: Cervical swabs were collected prior to the initial radiation dose and after 4 weeks of radiotherapy at Mulago Hospital. Aerobic culture was performed on blood agar, chocolate agar, and MacConkey agar, and incubated at 35-37 ° for 24-48 hours. Isolates were identified using colonial morphology, Gram staining, and biochemical analysis. Sensitivity testing was performed via Kirby-Bauer disk diffusion and dilution. Differences in the proportions of bacteria isolated before and after radiotherapy were compared. Paired t test was used to obtain differences in sensitivity before and after radiotherapy. RESULTS: Normal flora increased significantly after EBRT (P=0.02). There was no significant change in overall proportion of positive cultures. Sensitivity to commonly used antibiotics improved (P=0.05) and resistance significantly decreased (P=0.005). Significant differences were seen mainly with ciprofloxacin, ceftriaxone, and gentamicin. CONCLUSION: Four weeks of EBRT did not sterilize the cervix but resulted in an increase in normal flora. Radiotherapy appeared to reduce resistance to commonly used antibiotics. Sensitivity to chloramphenicol was higher than for the more commonly used antibiotics.

Curcumin as a potential non-steroidal contraceptive with spermicidal and microbicidal properties.

OBJECTIVE: Curcumin, a component of the curry powder turmeric, has immense biological properties, including anticancer effects. The objective of this study was to determine if curcumin can provide a novel non-steroidal contraceptive having both spermicidal and microbicidal properties. STUDY DESIGN: The effect of curcumin, with and without photosensitization, was examined on human sperm forward motility and growth of several aerobic (n=8) and anaerobic bacteria (n=4) and yeast (n=7) strains implicated in vaginosis, vaginitis, and vaginal infections in women. The effect of various concentrations of curcumin on human sperm and microbes (aerobic and anaerobic bacteria and yeast) was tested. The effect on sperm was examined by counting the sperm forward motility, and on microbes by agar and broth dilutions and colony counting. Each experiment was repeated using different semen specimens, and bacteria and yeast stocks. RESULTS: Curcumin caused a concentration-dependent inhibition of sperm forward motility with a total block at ≥250µM concentration. After photosensitization, the effective concentration to completely block sperm forward motility decreased 25-fold, now requiring only 10µM concentration for total inhibition. Curcumin concentrations between 100 and 500µM completely blocked the growth of all the bacteria and yeast strains tested. After photosensitization, the effective concentration to completely inhibit microbial growth decreased 10-fold for aerobic bacteria and yeast, and 5-fold for anaerobic bacteria. CONCLUSIONS: These findings suggest that curcumin can block sperm function and bacteria/yeast growth. It can potentially provide an ideal non-steroidal contraceptive having both spermicidal and microbicidal properties against vaginal infections.

Enhancement in mesophilic aerobic digestion of waste activated sludge by chemically assisted thermal pretreatment method.

The effects of hybrid microwave (MW)-alkali pretreatment methods on the efficiency of mesophilic aerobic digestion were studied. The MW-alkali pretreatment (95°C-pH 12) was observed to enhance the sludge solubilization synergistically from 0.5% (raw) to 52.5% (MW-NaOH) and 48.7% (MW-KOH), which are 20% greater than the additive value of MW only and alkali only (16%(MW)+28.4%(NaOH)=44.4% and 16%(MW)+25.5(KOH)=41.5). The higher VSS solubilization was observed for hybrid MW-NaOH (53.9%) and MW-KOH (47.4%) methods. The batch mesophilic (35°C) aerobic digestion system led to 81.1% TCOD degradation and 72.4% VSS degradation at 20 days of retention time, with 35% higher TCOD and VSS reduction in comparison with the control system. The filterability of microwave-alkali pretreated sludge was improved remarkably after aerobic digestion. Moreover, the proposed method is capable of effectively sanitize the sewage sludge and produce Class A biosolids.

A pilot study on the regeneration of ferrous chelate complex in NOx scrubber solution by a biofilm electrode reactor.

A chemical absorption-biological reduction integrated process has been proposed for the removal of nitrogen oxides (NO(x)) from flue gases. In this study, we report a new approach using biofilm electrode reactor (BER) to regenerate Fe(II)EDTA via simultaneously reducing Fe(II)EDTA-NO and Fe(III)EDTA in NO(x) scrubber solution. Biofilm formed on the surface of the cathode was confirmed by Environmental Scan Electro-Microscope. Experimental results demonstrated that it was effective and feasible to utilize the BER to promote the reduction of Fe(II)EDTA-NO and Fe(III)EDTA simultaneously. The reduction efficiency of Fe(II)EDTA-NO and Fe(III)EDTA was up to 85% and 78%, respectively when the BER was continuously operated with electricity current at 30 mA. The absence of electricity induced an immediate decrease in reduction efficiency, indicating that the bio-regeneration of ferrous chelate complex was electrochemically accelerated. The present approach is considered advantageous for the enhanced bio-reduction in the NO(x) scrubber solution.

[Deep-sea research ground for the study of living matter properties in extreme conditions].

The Black Sea hollow bottom is a promising research ground in the field of deep-sea radiochemoecology and exobiology. It has turned out to be at the intersection of the earth and cosmic scientific interests such as deep-sea marine radiochemoecology from the perspective of the study of extreme biogeocenological properties of the Earth biosphere and exobiology from the standpoint of the study of life phenomena (living matter) outside the Earth biosphere, i.e. on other planets and during hypothetical transfer of spores in the outer space. The potential of this ground is substantiated with the data published by the author and co-workers on accumulation of 90Sr, 137Cs and Pu isotopes with silts of bathyal pelo-contour, on the quality of deep-sea hydrogen sulphide waters (after their contact with air) for vital functions of planktonic and benthic aerobes, as well as the species composition of marine, freshwater and terrestrial plants grown from the spores collected from the bottom sediments of the Black Sea bathyal. Discussion was based on V.I. Vernadsky's ideas about the living matter and biosphere, which allowed conclusions about the biospheric and outer space role of the described phenomena.

Enhancement of biological treatment of wastewater by magnetic field.

In this study, effect of magnetic field on the activity of activated sludge in wastewater treatment was investigated. During the experiment, biodegradation duration, magnetic density, operating temperature and medium pH value were changed within the ranges from 0 to 60h, 0 to 500.0mT, 10.0 to 50.0 degrees C and 3.0 to 12.0, respectively. These results revealed that activated sludge acclimatization and organic pollutant biodegradation processes under magnetic field were stimulated, resulting in a higher efficiency of wastewater treatment. Biodegradation of organic compounds under magnetic field could reach stable states after 48h. The organic compounds removal rate first roared up and then fell down with the increase of magnetic density of the field, turning at 20.0mT. On account of application of magnetic field, the range of temperature and pH, which is suitable for the growth of microbe, were 20.0-40.0 degrees C and 6.0-10.0, respectively, which were expanded compared with those without the magnetic field.

Electroactive mixed culture biofilms in microbial bioelectrochemical systems: the role of temperature for biofilm formation and performance.

In this paper we investigate the temperature dependence and temperature limits of waste water derived anodic microbial biofilms. We demonstrate that these biofilms are active in a temperature range between 5°C and 45°C. Elevated temperatures during initial biofilm growth not only accelerate the biofilm formation process, they also influence the bioelectrocatalytic performance of these biofilms when measured at identical operation temperatures. For example, the time required for biofilm formation decreases from above 40 days at 15°C to 3.5 days at 35°C. Biofilms grown at elevated temperatures are more electrochemically active at these temperatures than those grown at lower incubation temperature. Thus, at 30°C current densities of 520 µA cm(-2) and 881 µA cm(-2) are achieved by biofilms grown at 22°C and 35°C, respectively. Vice versa, and of great practical relevance for waste water treatment plants in areas of moderate climate, at low operation temperatures, biofilms grown at lower temperatures outperform those grown at higher temperatures. We further demonstrate that all biofilms possess similar lower (0°C) and upper (50°C) temperature limits--defining the operational limits of a respective microbial fuel cell or microbial biosensor--as well as similar electrochemical electron transfer characteristics.

Effects of gamma irradiation and electron beam irradiation on quality, sensory, and bacterial populations in beef sausage patties.

This study compared effects of gamma ray (GR) and electron beam (EB) irradiation on quality (TBARS value, hardness, color), sensory characteristics, and total bacterial populations in beef sausage patties during accelerated storage at 30 degrees C for 10days. Beef sausage patties were vacuum-packaged and irradiated by GR and EB at 0, 5, 10, 15, and 20kGy at room temperature. The results of quality evaluation showed that the effects of GR irradiation were similar (p0.05) to EB irradiation on lipid oxidation, hardness, color and sensory scores of the beef sausage patties. However, GR-irradiated samples had lower (p<0.05) total bacterial counts than EB-irradiated samples after irradiation, and during storage regardless of irradiation dose. The results indicate that use of GR irradiation up to 10kGy on patties should be useful in reducing bacterial populations with no adverse effect on quality and most of sensory characteristics (color, chewiness, and taste).

Germicidal activity of antimicrobials and VIOlight Personal Travel Toothbrush sanitizer: an in vitro study.

OBJECTIVES: The study evaluated the antibacterial effect of VIOlight (VL) Personal Travel Toothbrush Sanitizer on biofilms after toothbrush exposure to human saliva compared to Listerine Antiseptic (LA), 3% hydrogen peroxide (3%HP) and water. METHODS: Twenty toothbrush heads (n=5/Gp) were immersed in saliva and to allow for bacterial growth and biofilm formation for 24h. VL sanitizer and antiseptic(s) were used for 7 min; after treatment, brush heads were rinsed and placed into 10 mL of 2x AOAC Letheen Broth, sonicated and vortexed for 10s. Tenfold serial dilutions were prepared and plated and incubated aerobically and anaerobically. Log(10)CFU/mL data were compared utilizing ANOVA (p<0.05). RESULTS: Results showed 3%HP with significantly lower counts than LA, VL and control for aerobic and anaerobic bacteria. LA had significantly lower counts than VL and control for both types of bacteria and VIOlight had significantly lower counts than the control for aerobic bacteria. 3%HP and LA were most effective in rapidly killing bacteria when compared to VIOlight. CONCLUSIONS: Results showed that 3% hydrogen peroxide was most effective in reducing the numbers of both aerobic and anaerobic bacteria present on the toothbrush heads. Under the same test conditions, Listerine Antiseptic was shown to be secondarily effective for the same bacteria while the VIOlight unit was the least effective when compared to the other treatment groups.

Electrochemical activity and bacterial diversity of natural marine biofilm in laboratory closed-systems.

Even if a widely shared mechanism actually does not exist, it is now generally accepted that, in aerobic conditions, marine electrochemically active biofilms (MEABs) induce faster oxygen reduction on stainless steel immersed in seawater. This phenomenon has been widely studied, but nearly all the experiments found in literature have been conducted in open-systems (i.e. experimental environments where seawater is constantly renewed). In this work we tried to obtain, in open circuit and potentiostatic conditions, MEABs in different laboratory closed-systems without water renewal (mesocosms), in order to verify the relationship between electrochemical activity and biofilm composition. The diversity of the microbial populations of biofilms obtained by our new kind of approach was examined by the DGGE technique (denaturing gradient gel electrophoresis). MEABs were obtained in all the mesocosms from 2000 to 2 L, showing in some cases electrochemical performances comparable to those of open-systems, and a very high genetic variability. Our DGGE results underline the difficulty in finding a correlation between electrochemical activity and composition of microbial populations.

Impact of microparticles on UV disinfection of indigenous aerobic spores.

Numerous studies have shown that the efficacy of ultraviolet (UV) disinfection can be hindered by the presence of particles that can shield microorganisms. The main objective of this study was to determine to what extent natural particulate matter can shield indigenous spores of aerobic spore-forming bacteria (ASFB) from UV rays. The extent of the protective shielding was assessed by comparing the inactivation rates in three water fractions (untreated, dispersed and filtered on an 8 microm membrane) using a collimated beam apparatus with a low-pressure lamp emitting at 254 nm. Levels of inactivation were then related to the distribution and abundance of particles as measured by microflow imaging. Disinfection assays were completed on two source waters of different quality and particle content. A protocol was developed to break down particles and disperse aggregates (addition of 100mg/L of Zwittergent 3-12 and blending at 8000 rpm for 4 min). Particle size distribution (PSD) analysis confirmed a statistically significant decrease in the number of particles for diameter ranges above 5 microm following the dispersion protocol and 8 microm filtration. The fluence required to reach 1-log inactivation of ASFB spores was independent of particle concentration, while that required to reach 2-log inactivation or more was correlated with the concentration of particles larger than 8 microm (R(2)>0.61). Results suggest that natural particulate matter can protect indigenous organisms from UV radiation in waters with elevated particle content, while source water with low particle counts may not be subject to this interference.

Kinetic modeling of phototrophic biofilms: the PHOBIA model.

A kinetic model for mixed phototrophic biofilms is introduced, which focuses on the interactions between photoautotrophic, heterotrophic, and chemoautotrophic (nitrifying) functional microbial groups. Biofilm-specific phenomena are taken into account, such as extracellular polymeric substances (EPS) production by phototrophs as well as gradients of substrates and light in the biofilm. Acid-base equilibria, in particular carbon speciation, are explicitly accounted for, allowing for the determination of pH profiles across the biofilm. Further to previous models reported in literature, the PHOBIA model combines a number of kinetic mechanisms specific to phototrophic microbial communities, such as internal polyglucose storage under dynamic light conditions, phototrophic growth in the darkness using internally stored reserves, photoadaptation and photoinhibition, preference for ammonia over nitrate as N-source and the ability to utilize bicarbonate as a carbon source in the absence of CO(2). The sensitivity of the PHOBIA model to a number of key parameters is analyzed. An example on the potential use of phototrophic biofilms in wastewater polishing is discussed, where their performance is compared with conventional algal ponds. The PHOBIA model is presented in a manner that is compatible with other reference models in the area of water treatment. Its current version forms a theoretical base which is readily extendable once further experimental observations become available.