Biological energy requirements as quantitative boundary conditions for life in the subsurface

All life requires energy, which must be extracted from the environment. For all known life, free energy must be available at finite minimum levels in order to be usefully harnessed and must be delivered at finite minimum rates in order to support basic biochemical integrity and function. While seldom tested in the high energy light‐ and oxygen‐based metabolisms of the surface biosphere, the magnitude of these requirements – the biological energy quantum (BEQ) and maintenance energy (ME) requirements, respectively – is considerable with respect to the potential metabolisms and energy sources that characterize the deep subsurface realm. As such, they constitute a fundamental constraint on the possible nature, distribution, and activity of microbial life in that environment. Because the energy released in a chemical transformation can be equated to the concentrations of substrates and products, both the BEQ and ME requirements define the minimum substrate concentration and minimum substrate production rate that must be sustained by a given environment for it to be capable of supporting life. The magnitudes of the BEQ and ME requirements are sensitive to a range of environmental parameters that may vary significantly in the subsurface. Temperature exerts a particularly strong control and is among the most important parameters to be considered in evaluating the energetic habitability of subsurface environments.     

Comparison between two methods of assaying relative microbial activity in marine environments.

Two methods for determining relative microbial activity in the marine environment were compared. In one method, a single concentration of a labeled substrate was used to calculate rates of substrate utilization; in the other, multiple concentrations of the same substrate (heterotrophic activity method) were used to calculate maximum potential substrate utilization rates. These studies were made on 232 seawater and 79 sediment samples taken from a variety of marine environments. The highest correlations between these two methods were seen in the sediment samples tested. The lowest correlation coerfficient seen in the sediment samples was 0.90, and the highest was 0.98. In seawater samples (six studies), the lowest correlation coefficient was 0.77 and the highest was 0.95. The correlation between these two methods was also substrate concentration dependent. Higher correlation coefficients were observed when higher substrate concentrations were used. Under certain conditions, these two methods appear to be comparable for estimating relative levels of microbial activity in the marine environment.     

Comparison between two methods of assaying relative microbial activity in marine environments.

Two methods for determining relative microbial activity in the marine environment were compared. In one method, a single concentration of a labeled substrate was used to calculate rates of substrate utilization; in the other, multiple concentrations of the same substrate (heterotrophic activity method) were used to calculate maximum potential substrate utilization rates. These studies were made on 232 seawater and 79 sediment samples taken from a variety of marine environments. The highest correlations between these two methods were seen in the sediment samples tested. The lowest correlation coerfficient seen in the sediment samples was 0.90, and the highest was 0.98. In seawater samples (six studies), the lowest correlation coefficient was 0.77 and the highest was 0.95. The correlation between these two methods was also substrate concentration dependent. Higher correlation coefficients were observed when higher substrate concentrations were used. Under certain conditions, these two methods appear to be comparable for estimating relative levels of microbial activity in the marine environment.     

Microbiologic air contamination and building-associated illness

Summary Microbiologic air contamination plays, among other factors, a role in building associated illnesses i.e., hypersensitivity diseases, bacterial and fungal infections, sick building syndrome. Airborne microorganisms are separated into obligate parasites, such as the viruses and a few bacteria, that must find a suitable host within a brief period, and facultative saprophytes that are usually found in living hosts an/or in the environment (primary and opportunistic pathogens). The etiology of hypersensitivity diseases is biological allergens such as those from fungi (moulds), bacteria,Amoebae and other protozoa. Humidifiers, cold air coils and porous material belonging to mechanical ventilation system can all be reservoirs/amplifiers/disseminators for living organisms, allergens or other microbial products. Legionella is an ubiquitous bacterium in the environment. Bioaerosols from potable water and air conditioning components appear to be the source of most human infections with this organism (Legionnaire's disease and Pontiac fever).Aspergillus fumigatus has a risk of penetration indoor but affects only people with seriously impaired immunity. Responsibility of airborne moulds, bacterial endotoxins or mycotoxins in sick building syndrome complaints is unclear. Design, operation and maintenance of ventilation systems are fundamental to assure well-being to building occupants.     

Chamber Bioaerosol Study: Outdoor Air and Human Occupants as Sources of Indoor Airborne Microbes

Human occupants are an important source of microbes in indoor environments. In this study, we used DNA sequencing of filter samples to assess the fungal and bacterial composition of air in an environmental chamber under different levels of occupancy, activity, and exposed or covered carpeting. In this office-like, mechanically ventilated environment, results showed a strong influence of outdoor-derived particles, with the indoor microbial composition tracking that of outdoor air for the 2-hour sampling periods. The number of occupants and their activity played a significant but smaller role influencing the composition of indoor bioaerosols. Human-associated taxa were observed but were not particularly abundant, except in the case of one fungus that appeared to be transported into the chamber on the clothing of a study participant. Overall, this study revealed a smaller signature of human body-associated taxa than had been expected based on recent studies of indoor microbiomes, suggesting that occupants may not exert a strong influence on bioaerosol microbial composition in a space that, like many offices, is well ventilated with air that is moderately filtered and moderately occupied.     

Metagenomic Insights into the Bioaerosols in the Indoor and Outdoor Environments of Childcare Facilities

Airborne microorganisms have significant effects on human health, and children are more vulnerable to pathogens and allergens than adults. However, little is known about the microbial communities in the air of childcare facilities. Here, we analyzed the bacterial and fungal communities in 50 air samples collected from five daycare centers and five elementary schools located in Seoul, Korea using culture-independent high-throughput pyrosequencing. The microbial communities contained a wide variety of taxa not previously identified in child daycare centers and schools. Moreover, the dominant species differed from those reported in previous studies using culture-dependent methods. The well-known fungi detected in previous culture-based studies (Alternaria, Aspergillus, Penicillium, and Cladosporium) represented less than 12% of the total sequence reads. The composition of the fungal and bacterial communities in the indoor air differed greatly with regard to the source of the microorganisms. The bacterial community in the indoor air appeared to contain diverse bacteria associated with both humans and the outside environment. In contrast, the fungal community was largely derived from the surrounding outdoor environment and not from human activity. The profile of the microorganisms in bioaerosols identified in this study provides the fundamental knowledge needed to develop public health policies regarding the monitoring and management of indoor air quality.     

Airborne bacteria, fungi, and endotoxin levels in residential microenvironments: a case study

Limited data are currently available on the concentrations of airborne bacteria, fungi, and endotoxins in indoor environments. The levels of aerial bacteria and fungi were measured at several microenvironments within a well-ventilated residential apartment in Singapore including the living room, kitchen, bedroom, toilet, and at a workplace environment by sampling indoor air onto culture medium plates using the 6-stage Andersen sampler. Total microbial counts were determined by collecting the air samples in water with the Andersen sampler, staining the resultant extracts with a fluorescent dye, acridine orange, and counting the microbes using a fluorescent microscope. The levels of airborne endotoxins were also determined by sampling the airborne microorganisms onto 0.4?μm polycarbonate membrane filter using the MiniVol sampler at 5?l/min for 20?h with a PM_2.5 cut-off device. The aerial bacterial and fungal concentrations were found to be in the ranges of 117–2,873?CFU/m³ and 160–1,897?CFU/m³, respectively. The total microbial levels ranged from 49,000 to 218,000?microbes/m³. The predominant fungi occurring in the apartment were Aspergillus and Penicillium while the predominant bacterial strains appeared to be Staphylococcus and Micrococcus. The average indoor endotoxin level was detectable in the range of 6–39?EU/m³. The amount of ventilation and the types of human activities carried out in the indoor environment appeared to be important factors affecting the level of these airborne biological contaminants.     

Human occupancy as a source of indoor airborne bacteria

Exposure to specific airborne bacteria indoors is linked to infectious and noninfectious adverse health outcomes. However, the sources and origins of bacteria suspended in indoor air are not well understood. This study presents evidence for elevated concentrations of indoor airborne bacteria due to human occupancy, and investigates the sources of these bacteria. Samples were collected in a university classroom while occupied and when vacant. The total particle mass concentration, bacterial genome concentration, and bacterial phylogenetic populations were characterized in indoor, outdoor, and ventilation duct supply air, as well as in the dust of ventilation system filters and in floor dust. Occupancy increased the total aerosol mass and bacterial genome concentration in indoor air PM(10) and PM(2.5) size fractions, with an increase of nearly two orders of magnitude in airborne bacterial genome concentration in PM(10). On a per mass basis, floor dust was enriched in bacterial genomes compared to airborne particles. Quantitative comparisons between bacterial populations in indoor air and potential sources suggest that resuspended floor dust is an important contributor to bacterial aerosol populations during occupancy. Experiments that controlled for resuspension from the floor implies that direct human shedding may also significantly impact the concentration of indoor airborne particles. The high content of bacteria specific to the skin, nostrils, and hair of humans found in indoor air and in floor dust indicates that floors are an important reservoir of human-associated bacteria, and that the direct particle shedding of desquamated skin cells and their subsequent resuspension strongly influenced the airborne bacteria population structure in this human-occupied environment. Inhalation exposure to microbes shed by other current or previous human occupants may occur in communal indoor environments.     

Airborne bacteria and fungal spores in the indoor environment. A case study in Singapore

The concentration of airborne fungal spores and bacteria as related to room temperature, humidity and occupancy levels within a library building in Singapore was determined. Measurement of indoor air quality with respect to microorganisms is of particular importance in tropical environments due to the extensive use of air‐conditioning systems and the potential implications for human health. This study has revealed a number of interesting relationships between the concentrations of fungal spores and bacteria in relation to both environmental and human factors. The levels of fungal spores measured in the indoor environment were approximately fifty times lower than those measured outside, probably because of the lowered humidity caused by air‐conditioning in the indoor environment. The variation in fungal spore concentration in the outdoor environment is likely to be due to the diurnal periodicity of spore release and the response to environmental factors such as light temperature and humidity. The indoor concentration of fungal spores in air was not clearly correlated to concentrations measured in air outside of the library building and remained relatively constant, unaffected by the difference in the numbers of occupants in the library. In contrast, the indoor concentrations of bacteria in air were approximately ten times higher than those measured outdoors, indicating a signficant internal source of bacteria. The elevated levels of indoor bacteria were primarily attributed to the number of library occupants. Increased human shedding of skin cells, ejection of microorganisms and particulates from the respiratory tract, and the transport of bacteria on suspended dust particles from floor surfaces probably accounts for the strong positive correlation between occupancy levels and the concentration of bacteria in internal air.     

Microbial contamination of storerooms at the Auschwitz-Birkenau Museum

Biodeterioration of heritage collections caused by microorganisms is a worldwide problem. To avoid degradation caused by biological contaminants transported into the indoor environment by air, proper bioaerosol protection is required. The aim of this study was to assess the level of microbial contamination of the Auschwitz-Birkenau Museum collection based on qualitative and quantitative analyses of bacteria and fungi isolated from the atmosphere and settled dust of museum storerooms. The obtained results demonstrated that a correctly operated air-conditioning system and limiting the number of visitors in the studied storerooms can significantly inhibit microbial contamination of the air and decrease deposition of bacterial and fungal particulates on exhibit surfaces. The performed analyses confirm that an aerobiological assessment of museum premises is a useful tool in their hygienic evaluation and, if necessary, in decision-making regarding interventions to minimize biological decay of collections.     

A report on Penicillium in the intramural and extramural air of residential areas of Nagpur city (India)

Prevalence of different species of Penicillium and their concentrations per cubic meter of air were evaluated with the use of Hi-Air sampler system Mark II (Hi-Media Laboratories Ltd., India) in the air of homes (bed-rooms) at four different sites in Nagpur. At each of these sites, air sampling was done fortnightly in triplicate for 2 years duration from June 2000 to May 2002. The sampling was also done in triplicate for the outdoor air in the vicinity of each home on the same day immediately after the indoor sampling was over. The mean concentration of Penicillium colony forming units at four different sites in the indoor air was 32, 46.9, 35 and 35.4 CFU/m³, respectively, whereas in the outdoor air at these same four sites, the mean concentration was 24, 28, 25 and 25.8 CFU/m³ respectively. The Penicillium concentration in the indoor air was found to be higher in winter than in other seasons (ANOVA, p < 0.05). Concentration of Penicillium spp. in intramural environment was always higher than that in extramural environment. Statistically significant difference existed between intramural and extramural environments at all the sites, with maximum difference at a site, which is old crowded area of the city. During the 2-years investigations, 11 species of Penicillium were isolated from the indoor air while nine species were isolated from the air outside the homes. The dominant species of Penicillium in indoor as well as outdoor air were P. citrinum (33.78 and 32.81), P. oxalicum (19.70 and 22.60), and P. chrysogenum (17.64 and 14.50). The percentage of the Penicillium in the indoor air was 10.70 while it was 8.36 in outdoor air. Indoor air showed the presence of P. glaber and P. sclerotiorum, which were absent in the outdoor air.     

Controlled gas environments in industrial fermentations

The gas environment is of major importance in controlling aerobic fermentation processes for the manufacture of microbial products. Oxygen and carbon dioxide levels in gas-liquid equilibria affect productivity and energy consumption in such processes and appear to be implicated in the regulation of microbial metabolism. Gas-liquid transfer has been intensively studied by many investigators for Newtonian and non-Newtonian fluids, primarily in terms of oxygen-limitation in biomass and product formation. More recentreports show that microbial growth and product formation are affected by levels of oxygen and carbon dioxide in the gas environment, suggesting that microbial metabolism may be directed towards specific products by the control of such environments. High product concentrations may also be obtained by solid substrate fermentations with mycelial organisms cultured on semi-solid agricultural products at low moisture contents. Such methods are commonly used in the Orient for the manufacture of enzymes and traditional fermented foods and could probably be extended to other microbial products. This review covers fundamental aspects of engineering research in microbial processes that suggest applications for controlled gas environments in submerged culture and solid substrate fermentations of potential industrial interest.     

Kinetics and Yields of Pesticide Biodegradation at Low Substrate Concentrations and under Conditions Restricting Assimilable Organic Carbon

The fundamentals of growth-linked biodegradation occurring at low substrate concentrations are poorly understood. Substrate utilization kinetics and microbial growth yields are two critically important process parameters that can be influenced by low substrate concentrations. Standard biodegradation tests aimed at measuring these parameters generally ignore the ubiquitous occurrence of assimilable organic carbon (AOC) in experimental systems which can be present at concentrations exceeding the concentration of the target substrate. The occurrence of AOC effectively makes biodegradation assays conducted at low substrate concentrations mixed-substrate assays, which can have profound effects on observed substrate utilization kinetics and microbial growth yields. In this work, we introduce a novel methodology for investigating biodegradation at low concentrations by restricting AOC in our experiments. We modified an existing method designed to measure trace concentrations of AOC in water samples and applied it to systems in which pure bacterial strains were growing on pesticide substrates between 0.01 and 50 mg liter⁻¹. We simultaneously measured substrate concentrations by means of high-performance liquid chromatography with UV detection (HPLC-UV) or mass spectrometry (MS) and cell densities by means of flow cytometry. Our data demonstrate that substrate utilization kinetic parameters estimated from high-concentration experiments can be used to predict substrate utilization at low concentrations under AOC-restricted conditions. Further, restricting AOC in our experiments enabled accurate and direct measurement of microbial growth yields at environmentally relevant concentrations for the first time. These are critical measurements for evaluating the degradation potential of natural or engineered remediation systems. Our work provides novel insights into the kinetics of biodegradation processes and growth yields at low substrate concentrations.     

Characterization of an airborne microbial community: A case study in the archive of the University of Coimbra,Portugal

Understanding the structure of indoor airborne microbial communities could be useful in optimizing conservation and disinfection procedures in archive repositories, preventing the biodeterioration of stored collections. In this study we characterized the microbial air community inside the Archive of the University of Coimbra, by identifying different fungal and bacterial organisms retrieved from air samples. The microbial contamination was determined using conventional culture methods, and the isolates were typified using morphological techniques. Results indicated a low microbial air contamination (107 ± 12 CFU/m³), particularly regarding fungal propagules (6 ± 1 CFU/m³). Fungal isolates were identified using ITS-DNA sequencing. Among fungal isolates, Penicillium was the most frequent genus, and Penicillium griseofulvum was the predominant species. Simpson diversity index (1-D) was applied to phenotypic and genotypic results. Total phenotypic diversity varied from 0.4 to 0.8 and regarding fungal species, the diversity was higher than 0.5. These results were compared with previous analyses of the Archive's air, suggesting that short-term changes in atmospheric conditions may influence the indoor air microbial community structure.     

A report on <Emphasis Type="Italic">Penicillium</Emphasis> in the intramural and extramural air of residential areas of Nagpur city (India)

Prevalence of different species of Penicillium and their concentrations per cubic meter of air were evaluated with the use of Hi-Air sampler system Mark II (Hi-Media Laboratories Ltd., India) in the air of homes (bed-rooms) at four different sites in Nagpur. At each of these sites, air sampling was done fortnightly in triplicate for 2 years duration from June 2000 to May 2002. The sampling was also done in triplicate for the outdoor air in the vicinity of each home on the same day immediately after the indoor sampling was over. The mean concentration of Penicillium colony forming units at four different sites in the indoor air was 32, 46.9, 35 and 35.4 CFU/m³, respectively, whereas in the outdoor air at these same four sites, the mean concentration was 24, 28, 25 and 25.8 CFU/m³ respectively. The Penicillium concentration in the indoor air was found to be higher in winter than in other seasons (ANOVA, p < 0.05). Concentration of Penicillium spp. in intramural environment was always higher than that in extramural environment. Statistically significant difference existed between intramural and extramural environments at all the sites, with maximum difference at a site, which is old crowded area of the city. During the 2-years investigations, 11 species of Penicillium were isolated from the indoor air while nine species were isolated from the air outside the homes. The dominant species of Penicillium in indoor as well as outdoor air were P. citrinum (33.78 and 32.81), P. oxalicum (19.70 and 22.60), and P. chrysogenum (17.64 and 14.50). The percentage of the Penicillium in the indoor air was 10.70 while it was 8.36 in outdoor air. Indoor air showed the presence of P. glaber and P. sclerotiorum, which were absent in the outdoor air.     

Imaging and speciation of trace elements in biological environment

Mineral elements, often at the trace level, play a considerable role in physiology and pathology of biological systems. Metallogenomics, metalloproteomics, and metallomics are among the emerging disciplines which are critically dependent on spatially resolved concentration maps of trace elements in a cell or tissue, on information on chemical speciation, and on that on metal-binding coordination sites. The mini-review discusses recent progress in analytical techniques for element profiling on the genome scale, biological trace element imaging, and probing, identification and quantification of chemical species in the biological environment. Imaging of the element distribution in cells and tissue sections is becoming possible with sub-micrometer spatial resolution and picogram-level sensitivity owing to advances in laser ablation MS, ion beam and synchrotron radiation X-ray fluorescence microprobes. Progress in nanoflow chromatography and capillary electrophoresis coupled with element specific ICP MS and molecule-specific electrospray MS/MS and MALDI enables speciation of elements in microsamples in a complex biological environment. Laser ablation ICP MS, micro-SXRF, and micro-PIXE allow mapping of trace element distribution in 1D and 2D proteomics gels. The increasing sensitivity of EXAFS and XANES owing to the use of more intense synchrotron beams and efficient focusing optics provide information about oxidation state, fingerprint speciation of metal sites and metal-site structures.     

A comprehensive review on application of bioreactor for industrial wastewater treatment

In the recent past, wastewater treatment processes performed a pivotal role in accordance with maintaining the sustainable environment and health of mankind at a proper hygiene level. It has been proved indispensable by government regulations throughout the world on account of the importance of preserving freshwater bodies. Human activities, predominantly from industrial sectors, generate an immeasurable amount of industrial wastewater loaded with toxic chemicals, which not only cause dreadful environmental problems, but also leave harmful impacts on public health. Hence, industrial wastewater effluent must be treated before being released into the environment to restrain the problems related to industrial wastewater discharged to the environment. Nowadays, biological wastewater treatment methods have been considered an excellent approach for industrial wastewater treatment process because of their cost-effectiveness in the treatment, high efficiency and their potential to counteract the drawbacks of conventional wastewater treatment methods. Recently, the treatment of industrial effluent through bioreactor has been proved as one of the best methods from the presently available methods. Reactors are the principal part of any biotechnology-based method for microbial or enzymatic biodegradation, biotransformation and bioremediation. This review aims to explore and compile the assessment of the most appropriate reactors such as packed bed reactor, membrane bioreactor, rotating biological contactor, up-flow anaerobic sludge blanket reactor, photobioreactor, biological fluidized bed reactor and continuous stirred tank bioreactor that are extensively used for distinct industrial wastewater treatment.     

Viable airborne microbial counts from air-cooling units with and without complaints of urine and body odors

Viable airborne microbial counts are commonly used in indoor air quality (IAQ) assessment, but studies linking the microbial counts to a specific type of indoor microbial contamination are limited. We hypothesize that the airborne microbial counts can differentiate air-cooling units with and without complaints of urine and body odors. The keratinolytic property of some isolated bacteria prompts to the hypothesis that keratinase is present in the units to break down keratins, structural proteins that form human skin scales, as sources of amino acids and ammonium to produce the odors. Seven bacterial species and four fungal species were identified in the units and room air. Airborne Staphylococcus haemolyticus and Methylobacterium organophilum counts contributed the most to the microbial dissimilarities of units with and without odor complaints. Keratinolytic bacteria and a methylotrophic bacterium were abundant in the units. All the units contained ammonium, and keratinase activity was higher in the units with odor complaints. Extracellular keratinase activity was more effective at 20 °C than at 30 or 4 °C. Keratinolytic bacteria produced high levels of ammonium in the culture with skin cells. Viable airborne microbial counts can help IAQ inspectors to identify potential odor-causing air-cooling units. Keratins may be broken down in the units and associated with the odor complaints.     

Fungal pollution of indoor environments and its management

Indoor environments play important roles in human health. The health hazards posed by polluted indoor environments include allergy, infections and toxicity. Life style changes have resulted in a shift from open air environments to air tight, energy efficient, environments, in which people spend a substantial portion of their time. Most indoor air pollution comes from the hazardous non biological agents and biological agents. Fungi are ubiquitous in distribution and are a serious threat to public health in indoor environments. In this communication, we have reviewed the current status on biotic indoor air pollution, role of fungi as biological contaminants and their impact on human health.     

Microbial growth inside insulated external walls as an indoor air biocontamination source

The association between moisture-related microbial growth (mesophilic fungi and bacteria) within insulated exterior walls and microbial concentrations in the indoor air was studied. The studied apartment buildings with precast concrete external walls were situated in a subarctic zone. Actinomycetes in the insulation layer were found to have increased concentrations in the indoor air. The moisture content of the indoor air significantly affected all measurable airborne concentrations.