Microbiota dispersion in the Uyuni salt flat (Bolivia) as determined by community structure analyses

Soil microbial communities are an important component of biological diversity and terrestrial ecosystems which is responsible for processes such as decomposition, mineralization of nutrients, and accumulation of organic matter. One of the factors that provide information on the mechanisms regulating biodiversity is spatial scaling. We characterized the microbial communities using 16S rRNA gene sequences from DNA isolated from halite at various locations and correlated these to geographic distance in the Uyuni salt flat (Bolivia). Sequences from each site were analyzed to determine any spatial patterns of diversity, as well as to describe the microbial communities. Results suggest that different taxa are able to disperse over Uyuni's surface crust regardless of distance. As expected, ubiquitous taxa included members of Halobacteriaceae such as Haloarcula, Halorubrum, Halorhabdus, Halolamina, and halophilic bacteria Salinibacter, Halorhodospira, and unclassified members of the Gammaproteobacteria. Archaeal communities were homogeneous across the salt flat. In contrast, bacterial communities present strong local variations which could be attributed to external factors. Likely sources for these variations are the Rio Grande river influent in the south shore and the Tunupa volcano influencing the northern area

No disponible

Microbiota dispersion in the Uyuni salt flat (Bolivia) as determined by community structure analyses.

Soil microbial communities are an important component of biological diversity and terrestrial ecosystems which is responsible for processes such as decomposition, mineralization of nutrients, and accumulation of organic matter. One of the factors that provide information on the mechanisms regulating biodiversity is spatial scaling. We characterized the microbial communities using 16S rRNA gene sequences from DNA isolated from halite at various locations and correlated these to geographic distance in the Uyuni salt flat (Bolivia). Sequences from each site were analyzed to determine any spatial patterns of diversity, as well as to describe the microbial communities. Results suggest that different taxa are able to disperse over Uyuni's surface crust regardless of distance. As expected, ubiquitous taxa included members of Halobacteriaceae such as Haloarcula, Halorubrum, Halorhabdus, Halolamina, and halophilic bacteria Salinibacter, Halorhodospira, and unclassified members of the Gammaproteobacteria. Archaeal communities were homogeneous across the salt flat. In contrast, bacterial communities present strong local variations which could be attributed to external factors. Likely sources for these variations are the Rio Grande river influent in the south shore and the Tunupa volcano influencing the northern area.

Stimulated Adsorption of Humic Acids on Capped Plasmonic Ag Nanoparticles Investigated by Surface-Enhanced Optical Techniques.

The adsorption of humic substances on Ag nanoparticles (AgNPs) is of crucial environmental importance and determines the toxicity of these NPs and the structure of adsorbed organic matter. In this work, the adsorption of two standard soil and leonardite International Humic Substances Society humic acids was studied on AgNPs of different sizes, shapes (spherical and star-like), and interfacial chemical compositions. Surface-enhanced optical (Raman and fluorescence) spectroscopies were used to follow the specific chemical groups involved in this adsorption. By means of the latter optical techniques, information regarding the binding mechanism and the macromolecular aggregation can be deduced. The influence of the surface chemical composition induced by the different functionalizations of the interfaces of these NPs is highly important regarding the chemical interactions of these complex organic macromolecules. The surface functionalization with positively charged alkyl diamines led to a large increase in the adsorption as well as a strong structural rearrangement of the macromolecule once adsorbed onto the surface.

Pathogens in crop production systems irrigated with low-quality water in Bolivia.

In dry areas, the need for irrigation to ensure agricultural production determines the use of all available water sources. However, the water sources used for irrigation are often contaminated by untreated or minimally treated wastewater. Microbial risks from reusing wastewater for vegetable irrigation can be addressed by installing environmental barriers that pathogens must cross to reach humans in the reuse system. Knowledge of pathogen flows inside the system and pathogen removal potential is the first step towards devising a risk management strategy. This study assessed microbe prevalence in farming systems in the Bolivian highlands that use wastewater-polluted sources for irrigation of lettuce. Samples of soil, lettuce and different water sources used in the farming systems were taken during one crop season and concentrations of coliphages, Escherichia coli and helminth eggs were measured. The results showed high spread of these microorganisms throughout the whole system. There was a significant correlation between microbial quality of water and of the harvested produce for several microorganisms. The microbial prevalence in protected shallow wells was found to be significantly lower than in other water sources. These findings can help formulate feasible risk management strategies in contexts where conventional technologies for microbial removal are not possible.

Managing Microbial Risks from Indirect Wastewater Reuse for Irrigation in Urbanizing Watersheds.

Limited supply of clean water in urbanizing watersheds creates challenges for safely sustaining irrigated agriculture and global food security. On-farm interventions, such as riverbank filtration (RBF), are used in developing countries to treat irrigation water from rivers with extensive fecal contamination. Using a Bayesian approach incorporating ethnographic data and pathogen measurements, quantitative microbial risk assessment (QMRA) methods were employed to assess the impact of RBF on consumer health burdens for Giardia, Cryptosporidium, rotavirus, norovirus, and adenovirus infections resulting from indirect wastewater reuse, with lettuce irrigation in Bolivia as a model system. Concentrations of the microbial source tracking markers pepper mild mottle virus and HF183 Bacteroides were respectively 2.9 and 5.5 log10 units lower in RBF-treated water than in the river water. Consumption of lettuce irrigated with river water caused an estimated median health burden that represents 37% of Bolivia's overall diarrheal disease burden, but RBF resulted in an estimated health burden that is only 1.1% of this overall diarrheal disease burden. Variability and uncertainty associated with environmental and cultural factors affecting exposure correlated more with QMRA-predicted health outcomes than factors related to disease vulnerability. Policies governing simple on-farm interventions like RBF can be intermediary solutions for communities in urbanizing watersheds that currently lack wastewater treatment.

Taenia eggs in a stabilization pond system with poor hydraulics: concern for human cysticercosis?

The objective of this study is to compare the removal of Taenia eggs to the removal of Ascaris eggs in a wastewater stabilization pond system consisting of three ponds in series, where the hydraulic residence time distribution has been characterized via a tracer study supported by computational fluid dynamics modeling. Despite a theoretical hydraulic retention time of 30 days, the peak dye concentration was measured in the effluent of the first pond after only 26 hours. The smaller-sized Taenia eggs were detected in higher concentrations than Ascaris eggs in the raw wastewater. Ascaris eggs were not detected in the pond system effluent, but 45 Taenia eggs/L were detected in the system effluent. If some of these eggs were of the species Taenia solium, and if the treated wastewater were used for the irrigation of crops for human consumption, farmers and consumers could potentially be at risk for neurocysticercosis. Thus, limits for Taenia eggs in irrigation water should be established, and precautions should be taken in regions where pig taeniasis is endemic. The results of this study indicate that the theoretical hydraulic retention time (volume/flow) of a pond is not always a good surrogate for helminth egg removal.

Solar water disinfection (SODIS) of Escherichia coli, Enterococcus spp., and MS2 coliphage: effects of additives and alternative container materials.

The use of alternative container materials and added oxidants accelerated the inactivation of MS2 coliphage and Escherichia coli and Enterococcus spp. bacteria during solar water disinfection (SODIS) trials. Specifically, bottles made from polypropylene copolymer (PPCO), a partially UVB-transparent plastic, resulted in three-log inactivation of these organisms in approximately half the time required for disinfection in bottles made from PET, polycarbonate, or Tritan(®), which absorb most UVB light. Furthermore, the addition of 125 mg/L sodium percarbonate in combination with either citric acid or copper plus ascorbate tended to accelerate inactivation by factors of 1.4-19. Finally, it was observed that the inactivation of E. coli and enterococci derived from local wastewater was far slower than the inactivation of laboratory-cultured E. coli and Enterococcus spp., while the inactivation of MS2 was slowest of all. These results highlight the importance of UVB in SODIS under certain conditions, and also the greater sunlight resistance of some viruses and of bacteria of fecal origin, as compared to the laboratory-cultured bacteria commonly used to model their inactivation. Furthermore, this study illustrates promising new avenues for accelerating the inactivation of bacteria and viruses by solar disinfection.

Solar drinking water disinfection (SODIS) to reduce childhood diarrhoea in rural Bolivia: a cluster-randomized, controlled trial.

BACKGROUND: Solar drinking water disinfection (SODIS) is a low-cost, point-of-use water purification method that has been disseminated globally. Laboratory studies suggest that SODIS is highly efficacious in inactivating waterborne pathogens. Previous field studies provided limited evidence for its effectiveness in reducing diarrhoea. METHODS AND FINDINGS: We conducted a cluster-randomized controlled trial in 22 rural communities in Bolivia to evaluate the effect of SODIS in reducing diarrhoea among children under the age of 5 y. A local nongovernmental organisation conducted a standardised interactive SODIS-promotion campaign in 11 communities targeting households, communities, and primary schools. Mothers completed a daily child health diary for 1 y. Within the intervention arm 225 households (376 children) were trained to expose water-filled polyethyleneteraphtalate bottles to sunlight. Eleven communities (200 households, 349 children) served as a control. We recorded 166,971 person-days of observation during the trial representing 79.9% and 78.9% of the total possible person-days of child observation in intervention and control arms, respectively. Mean compliance with SODIS was 32.1%. The reported incidence rate of gastrointestinal illness in children in the intervention arm was 3.6 compared to 4.3 episodes/year at risk in the control arm. The relative rate of diarrhoea adjusted for intracluster correlation was 0.81 (95% confidence interval 0.59-1.12). The median length of diarrhoea was 3 d in both groups. CONCLUSIONS: Despite an extensive SODIS promotion campaign we found only moderate compliance with the intervention and no strong evidence for a substantive reduction in diarrhoea among children. These results suggest that there is a need for better evidence of how the well-established laboratory efficacy of this home-based water treatment method translates into field effectiveness under various cultural settings and intervention intensities. Further global promotion of SODIS for general use should be undertaken with care until such evidence is available. TRIAL REGISTRATION: www.ClinicalTrials.govNCT00731497 Please see later in the article for Editors' Summary.

Detección y diferenciación de entamoeba histolytica / entamoeba dispar mediante reacción en cadena de la polimerasa (pcr) usando dna extraído de quistes presentes en muestras de heces fecales humanas / Detection and differentiation of entamoeba histolytica / entamoeba dispar by polymerase chain reaction (pcr) using DNA extracted from cysts present in human stool samples

Está establecido que existen dos especies distintas de amebas que originalmente fueron conocidas como Entamoeba Histolytica. Ellas son E. dispar (forma no patogénica) y E. histolytica (forma patogénica). La diferencia entre estos dos organismos es de gran importancia clínica desde que son morfológicamente indistinguibles. El diagnóstico diferencial de estas dos especies es esencial para la decisión del tratamiento y la salud pública. Se puede usar un método rápido de extracción de DNA directamente de especímenes suspendidos en formalina éter. La extracción de ADN fue usada para la identificación de las especies existentes en las herramientas por reacción de cadena polimerasa (PCR). Un total de 75 muestras recolectadas aleatoriamente fueron analizadas. Despues de la confirmación por PCR: 7/75 muestras resultaron positivas para E. histolytica, 60/75 muestras resultaron positivas para E. dispar y 8/75 resultaron negativas porque no amplificaron, pudiendo tratarse de otras amebas como E. hartmani. E. iodoamoeba, E. coli, etc. Con estos resultados podemos darnos cuenta de la magnitud de falsos positivos que se generan con los exámenes microscópicos. Estas observaciones implican que el uso del DNA extraído directamente a partir de concentración de quistes para amplificación por PCR, es una herramienta útil para obtener un diagnóstico sensitivo y preciso que puede ser aplicado incluso en epidemiología.

It has been established that two distinct species exist within what was originally known as Entamoeba histolytica. These are E. dispar (nonpathogenic form) and E. histolytica (pathogenic form). Differentiation of these two organisms is of great clinical importance since they are morphologically indistinguishable. Differential diagnosis of this two species is essential for treatment decision and public health knowledge. A simple and rapid DNA-extraction method that can be used directly on formalin-ether stool specimens. The extracted DNA was used for the identification of the species existing in the stools by polymerase chain reaction (PCR). A total of 75 randomly collected stool sample were analyzed. The samples analyzed by microscopic were 75, after confirmation by PCR: 7/75 samples resulting positive for E. histolytica, 60/75 samples resulting positive for E. dispar and 8/75 resulting negative because didn't amplify be able to be other amoebas like E. hartmani, E. iodoamoeba, E. coli, etc. With these results we can realize the magnitude of false positive that are generated with the microscopic exams. These observations imply that the use of the DNA extracted directly of the concentrate of cysts for PCR amplification is a useful tool for obtaining a sensitive and accurate diagnosis that can be applied even in epidemiology.