A fosmid cloning strategy for detecting the widest possible spectrum of microbes from the international space station drinking water system

In this study, fosmid cloning strategies were used to assess the microbial populations in water from the International Space Station (ISS) drinking water system (henceforth referred to as Prebiocide and Tank A water samples). The goals of this study were: to compare the sensitivity of the fosmid cloning strategy with that of traditional culture-based and 16S rRNA-based approaches and to detect the widest possible spectrum of microbial populations during the water purification process. Initially, microbes could not be cultivated, and conventional PCR failed to amplify 16S rDNA fragments from these low biomass samples. Therefore, randomly primed rolling-circle amplification was used to amplify any DNA that might be present in the samples, followed by size selection by using pulsed-field gel electrophoresis. The amplified high-molecular-weight DNA from both samples was cloned into fosmid vectors. Several hundred clones were randomly selected for sequencing, followed by Blastn/Blastx searches. Sequences encoding specific genes from Burkholderia, a species abundant in the soil and groundwater, were found in both samples. Bradyrhizobium and Mesorhizobium, which belong to rhizobia, a large community of nitrogen fixers often found in association with plant roots, were present in the Prebiocide samples. Ralstonia, which is prevalent in soils with a high heavy metal content, was detected in the Tank A samples. The detection of many unidentified sequences suggests the presence of potentially novel microbial fingerprints. The bacterial diversity detected in this pilot study using a fosmid vector approach was higher than that detected by conventional 16S rRNA gene sequencing.

Ag colloids and Ag clusters over EDAPTMS-coated silica nanoparticles: synthesis, characterization, and antibacterial activity against Escherichia coli

To produce better antibacterial water-insoluble nanocomposites of silver (Ag), silver-silicon dioxide (Ag-SiO(2)) hybrid and silver colloid (Ag-c) nanoparticles (NPs) were studied. Ag-c NPs were synthesized using reduction of AgNO(3), and Ag-SiO(2) composites were prepared on a core of silica NPs functionalized with ethylenediamino-propyltrimethoxysilane, where Ag clusters were fabricated on amino groups using seed-mediated growth and characterized by transmission electron microscopy and ultraviolet-visible absorption spectroscopy. Antibacterial effectiveness of the Ag-SiO(2) NPs was tested against general Escherichia coli (E. coli ATCC 25922) and E. coli O157:H7 by measuring the growth based on optical density and digital counting of live-dead cells using a fluorescent microscope, and a field emission scanning electron microscope. Minimum inhibitory concentration values were studied against four representative bacteria along with E. coli O157:H7. Results showed that Ag NPs of 6.6 ± 4.5 nm were attached to the surface of SiO(2) NPs (74 ± 13.5 nm), and the Ag-c NPs (3.5 ± 2 nm) showed excellent antibacterial properties.

FROM THE CLINICAL EDITOR

In this paper, the synthesis of Ag colloids and Ag clusters over EDAPTMS-coated silica nanoparticles is reported. Both NPs were examined for antibacterial effectiveness against representative bacteria including E. coli O157:H7 and found to have excellent antibacterial properties.

Microbial diversity of Indian Ocean hydrothermal vent plumes: microbes tolerant of desiccation, peroxide exposure, and ultraviolet and gamma-irradiation

The microbial diversity of Kali chimney plumes, part of a hydrothermal vent field in the Rodriguez Triple Junction, Indian Ocean (depth approximately 2,240 m), was examined in an attempt to discover "extremotolerant" microorganisms that have evolved unique resistance capabilities to this harsh environment. Water and sediment samples were collected from the vent and from sediments located at various distances (2-20 m) away from and surrounding the chimney. Samples were screened for hypertolerant microbes that are able to withstand multiple stresses. A total of 46 isolates were selected for exposure to a number of perturbations, such as heat shock, desiccation, H(2)O(2), and ultraviolet (UV) and gamma-irradiation. The survival of Psychrobacter sp. L0S3S-03b following exposure to >1,000 J/m(2) UV(254) radiation was particularly intriguing amid a background of varying levels of resistance. Vegetative cells of this non-spore-forming microbe not only survived all of the treatments, but also exhibited a 90% lethal dose of 30 s when exposed to simulated martian UV radiation and a 100% lethal dose of 2 min when exposed to full spectrum UV, which is comparable to findings for bacterial endospores.

Transformation and fate of 2,4,6-trinitrotoluene (TNT) in anaerobic bioslurry reactors under various aeration schemes: implications for the decontamination of soils

Energetic compounds have been used in a variety of industrial and military applications worldwide leading to widespread environmental contamination. Many of these compounds are toxic and resist degradation by oxidative enzymes resulting in a need for alternative remediation methods. It has been shown that trinitrotoluene (TNT)-contaminated soil subjected to treatment in strictly anaerobic bioreactors results in tight binding of TNT transformation products to soil organic matter. The research presented here examined the fate of TNT and its metabolites in bioreactors under three different aeration regimes. In all treatment regimes, the typical metabolites of aminodinitrotoluenes and diaminonitrotoluenes were observed prior to irreversible binding into the soil fraction of the slurry. Significant transformation of TNT into organic acids or simple diols, as others report in prior work, was not observed in any of the treatments and is an unlikely fate of TNT in anaerobic soil slurries. These results indicate that aeration does not dramatically affect transformation or fate of TNT in reactor systems that receive a rich carbon source but does affect the rate at which metabolites become tightly bound to the soil. The most rapid transformations and lowest redox potentials were observed in reactors in which an aerobic headspace was maintained suggesting that aerobes play a role in establishing conditions that are most conducive to TNT reduction.

Survival of spacecraft-associated microorganisms under simulated martian UV irradiation

Spore-forming microbes recovered from spacecraft surfaces and assembly facilities were exposed to simulated Martian UV irradiation. The effects of UVA (315 to 400 nm), UVA+B (280 to 400 nm), and the full UV spectrum (200 to 400 nm) on the survival of microorganisms were studied at UV intensities expected to strike the surfaces of Mars. Microbial species isolated from the surfaces of several spacecraft, including Mars Odyssey, X-2000 (avionics), and the International Space Station, and their assembly facilities were identified using 16S rRNA gene sequencing. Forty-three Bacillus spore lines were screened, and 19 isolates showed resistance to UVC irradiation (200 to 280 nm) after exposure to 1,000 J m(-2) of UVC irradiation at 254 nm using a low-pressure mercury lamp. Spores of Bacillus species isolated from spacecraft-associated surfaces were more resistant than a standard dosimetric strain, Bacillus subtilis 168. In addition, the exposure time required for UVA+B irradiation to reduce the viable spore numbers by 90% was 35-fold longer than the exposure time required for the full UV spectrum to do this, confirming that UVC is the primary biocidal bandwidth. Among the Bacillus species tested, spores of a Bacillus pumilus strain showed the greatest resistance to all three UV bandwidths, as well as the total spectrum. The resistance to simulated Mars UV irradiation was strain specific; B. pumilus SAFR-032 exhibited greater resistance than all other strains tested. The isolation of organisms like B. pumilus SAFR-032 and the greater survival of this organism (sixfold) than of the standard dosimetric strains should be considered when the sanitation capabilities of UV irradiation are determined.

Bioremediation of soils contaminated with explosives

The large-scale industrial production and processing of munitions such as 2,4,6-trinitrotoluene (TNT) over the past 100 years led to the disposal of wastes containing explosives and nitrated organic by-products into the environment. In the US, the Army alone has estimated that over 1.2 million tons of soil have been contaminated with explosives, and the impact of explosives contamination in other countries is of similar magnitude. In recent years, growing concern about the health and ecological threats posed by man-made chemicals have led to studies of the toxicology of explosives, which have identified toxic and mutagenic effects of the common military explosives and their transformation products (Bruns-Nagel et al., 1999a; Fuchs et al., 2001; Homma-Takeda et al., 2002; Honeycutt et al., 1996; Rosenblatt et al., 1991; Spanggord et al., 1982; Tan et al., 1992 and Won et al., 1976). Because the cleanup of areas contaminated by explosives is now mandated because of public health concerns, considerable effort has been invested in finding economical remediation technologies. Biological treatment processes are often considered, since these are usually the least expensive means of destroying organic pollution. This review examines the most important groups of chemicals that must be treated at sites contaminated by explosives processing, the chemical and biological transformations they undergo, and commercial processes developed to exploit these transformations for treatment of contaminated soil. We critically examine about 150 papers on the topic, including approximately 60 published within the past 5 years.

Detection and Decontamination of Residual Energetics from Ordnance and Explosives Scrap

Extensive manufacturing of explosives in the last century has resulted in widespread contamination of soils and waters. Decommissioning and cleanup of these materials has also led to concerns about the explosive hazards associated with residual energetics still present on the surfaces of ordnance and explosives scrap. Typically, open burning or detonation is used to decontaminate ordinance and explosive scrap. Here the use of an anaerobic microbiological system applied as a bioslurry to decontaminate energetics from the surfaces of metal scrap is described. Decontamination of model metal scrap artificially contaminated with 2,4,6-trinitrotoluene and of decommissioned mortar rounds still containing explosives residue was examined. A portable ion mobility spectrometer was employed for the detection of residual explosives residues on the surfaces of the scrap. The mixed microbial populations of the bioslurries effectively decontaminated both the scrap and the mortar rounds. Use of the ion mobility spectrometer was an extremely sensitive field screening method for assessing decontamination and is a method by which minimally trained personnel can declare scrap clean with a high level of certainty.

Bioremediation of atrazine-contaminated soil by repeated applications of atrazine-degrading bacteria

Bioaugmentation has previously been unreliable for the in situ clean-up of contaminated soils because of problems with poor survival and the rapid decline in activity of the bacterial inoculum. In an attempt to solve these problems, a 500-l batch fermenter was investigated for its ability to deliver inoculum repeatedly to contaminated soils via irrigation lines. In a field experiment, mesocosms were filled with 350 kg soil containing 100 mg kg-1 atrazine, and inoculated one, four or eight times with an atrazine-degrading bacterial consortium that was produced in the fermenter. After 12 weeks, no significant degradation of atrazine had occurred in soil that was inoculated only once; whereas, mesocosms inoculated four and eight times mineralized 38% and 72% of the atrazine respectively. Similar results were obtained in a laboratory experiment using soil contaminated with 100 mg kg-1 [14C]atrazine. After 35 days, soil that was inoculated once with 10(8) cfu ml-1 of the consortium or with the atrazine-degrading bacterium, Pseudomonas sp. strain ADP, mineralized 17% and 35% of the atrazine respectively. In comparison, microcosms inoculated every 3 days with the consortium or with Pseudomonas sp. (ADP) mineralized 64% or 90% of the atrazine over this same period. Results of these experiments suggest that repeated inoculation from an automated fermenter may provide a strategy for bioaugmentation of contaminated soil with xenobiotic-degrading bacteria.