Ana M. García

Isolation and identification of bacteria from spent nuclear fuel pools

The aim of the present research was to isolate and identify bacteria from spent nuclear fuel pools of a Spanish nuclear power plant. Water samples were collected and inoculated onto different culture media to isolate the highest number of species. 16S rDNA fragments from colonies growing on solid media were amplified and analysed by denaturing gradient gel electrophoresis. Sequencing revealed the presence of 21 different bacteria belonging to several phylogenetic groups (α, β, and γ-Proteobacteria, Actinomycetales, Flavobacterium, and the Bacillus/Staphylococcus group). The isolation of these microorganisms in this particular environment (oligotrophic and radioactive) is highly interesting because of the possibility of their being used for the bioremediation of radionuclide-contaminated waters.

Biofouling on the Walls of a Spent Nuclear Fuel Pool with Radioactive Ultrapure Water

Microbial activity in spent nuclear fuel pools which contain ultrapure and radioactive water has been previously observed. The aim of the present research was to isolate and identify the microorganisms attached to the nuclear pool wall of a Spanish nuclear power plant. Amplification of 16S rDNA fragments from the culturable microorganisms by PCR using universal primers for the domain ‘Bacteria’, followed by Denaturing Gradient Gel Electrophoresis analysis revealed the presence of six different bacteria. The complete gene for 16S rDNA of each one was sequenced and identified as belonging to three different phylogenetic groups, viz. β-Proteobacteria, Actinomycetales and the Bacillus/Staphylococcus group. A fungus was also found and identified as Aspergillus fumigatus by sequencing the D2 region of the large subunit rDNA gene. The isolation of these microorganisms in oligotrophic and radioactive conditions is of great interest due to the possibility of their use in bioremediation processes of radionuclide-contaminated environments.

Development and characterization of biofilms on stainless steel and titanium in spent nuclear fuel pools

The aim of the present research was to study the biofilms developed in a Spanish nuclear power plant and their ability to entrap radionuclides. In order to carry this out, a bioreactor, which was then submerged in a spent nuclear fuel pool, was designed. To characterise the biofilm on two different metallic materials (stainless steel and titanium), standard culture microbiological methods and molecular biology tools, as well as epifluorescence and scanning electron microscopy were used. The bacterial composition of the biofilm belongs to several phylogenetic groups (α, β, and γ-Proteobacteria, Actinobacteridae, and Firmicutes). The radioactivity of the biofilms was measured by gamma-ray spectrometry. Biofilms were able to retain radionuclides from radioactive water, especially 60Co. The potential use of these biofilms in bioremediation of radioactive water is discussed.

Corrosión por picaduras en depósitos de agua de acero inoxidable austenítico en trenes hotel

The water storage tanks of hotel trains suffered pitting corrosion. To identify the cause, the tanks were subjected to a detailed metallographic study and the chemical composition of the austenitic stainless steels used in their construction was determined. Both the tank water and the corrosion products were further examined by physicochemical and microbiological testing. Corrosion was shown to be related to an incompatibility between the chloride content of the water and the base and filler metals of the tanks. These findings formed the basis of recommendations aimed at the prevention and control of corrosion in such tanks. Se han detectado problemas de corrosion por picaduras en los depositos de agua de trenes hotel. Para identificar las causas se llevo a cabo un detallado estudio metalografico asi como de la composicion quimica de los aceros inoxidables austeniticos utilizados en su construccion. Tambien se realizaron estudios fisicoquimicos y microbiologicos de los productos de corrosion. Se ha encontrado que los problemas de corrosion estan relacionados con la incompatibilidad entre el contenido en cloruros del agua y los metales base y de aporte de la soldadura de los tanques. En base a estos hallazgos se proponen una serie de recomendaciones encaminadas a la prevencion y control de la corrosion de dichos depositos.

Validation of the Hirst-Type Spore Trap for Simultaneous Monitoring of Prokaryotic and Eukaryotic Biodiversities in Urban Air Samples by Next-Generation Sequencing

ABSTRACT Pollen, fungi, and bacteria are the main microscopic biological entities present in outdoor air, causing allergy symptoms and disease transmission and having a significant role in atmosphere dynamics. Despite their relevance, a method for monitoring simultaneously these biological particles in metropolitan environments has not yet been developed. Here, we assessed the use of the Hirst-type spore trap to characterize the global airborne biota by high-throughput DNA sequencing, selecting regions of the 16S rRNA gene and internal transcribed spacer for the taxonomic assignment. We showed that aerobiological communities are well represented by this approach. The operational taxonomic units (OTUs) of two traps working synchronically compiled >87% of the total relative abundance for bacterial diversity collected in each sampler, >89% for fungi, and >97% for pollen. We found a good correspondence between traditional characterization by microscopy and genetic identification, obtaining more-accurate taxonomic assignments and detecting a greater diversity using the latter. We also demonstrated that DNA sequencing accurately detects differences in biodiversity between samples. We concluded that high-throughput DNA sequencing applied to aerobiological samples obtained with Hirst spore traps provides reliable results and can be easily implemented for monitoring prokaryotic and eukaryotic entities present in the air of urban areas. IMPORTANCE Detection, monitoring, and characterization of the wide diversity of biological entities present in the air are difficult tasks that require time and expertise in different disciplines. We have evaluated the use of the Hirst spore trap (an instrument broadly employed in aerobiological studies) to detect and identify these organisms by DNA-based analyses. Our results showed a consistent collection of DNA and a good concordance with traditional methods for identification, suggesting that these devices can be used as a tool for continuous monitoring of the airborne biodiversity, improving taxonomic resolution and characterization together. They are also suitable for acquiring novel DNA amplicon-based information in order to gain a better understanding of the biological particles present in a scarcely known environment such as the air.

Monitoring of airborne biological particles in outdoor atmosphere. Part 2: Metagenomics applied to urban environments

The air we breathe contains microscopic biological particles such as viruses, bacteria, fungi and pollen, some of them with relevant clinic importance. These organisms and/or their propagules have been traditionally studied by different disciplines and diverse methodologies like culture and microscopy. These techniques require time, expertise and also have some important biases. As a consequence, our knowledge on the total diversity and the relationships between the different biological entities present in the air is far from being complete. Currently, metagenomics and next-generation sequencing (NGS) may resolve this shortage of information and have been recently applied to metropolitan areas. Although the procedures and methods are not totally standardized yet, the first studies from urban air samples confirm the previous results obtained by culture and microscopy regarding abundance and variation of these biological particles. However, DNA-sequence analyses call into question some preceding ideas and also provide new interesting insights into diversity and their spatial distribution inside the cities. Here, we review the procedures, results and perspectives of the recent works that apply NGS to study the main biological particles present in the air of urban environments. [Int Microbiol 19(2):69-80(2016)].