Reference Organisms Research Articles

Ultraviolet filters differentially impact the expression of key endocrine and stress genes in embryos and larvae of Chironomus riparius

Several organic UV filters have hormonal activity in vertebrates, as demonstrated in fishes, rodents and human cells. Despite the accumulation of filter contaminants in aquatic systems, research on their effects on the endocrine systems of freshwaters invertebrates is scarce. In this work, the effects of five frequently used UV filters were investigated in embryos and larvae of Chironomus riparius, which is a reference organism in ecotoxicology. LC50 values for larvae as well as the percentage of eclosion of eggs were determined following exposures to: octyl-p-methoxycinnamate (OMC) also known as 2-ethylhexyl-4-methoxycinnamate (EHMC); 4-methylbenzylidene camphor (4MBC); 4-hydroxybenzophenone (4HB); octocrylene (OC); and octyldimethyl-p-aminobenzoate (OD-PABA). To assess sublethal effects, expression levels of the genes coding for the ecdysone receptor (EcR) and heat shock protein HSP70 were investigated as biomarkers for endocrine and stress effects at the cellular level. Life-stage-dependent sensitivity was found. In embryos, all of the UV filters provoked a significant overexpression of EcR at 24h after exposure. OC, 4MBC and OD-PABA also triggered transcriptional activation of the hsp70 stress gene in embryos. In contrast, in larvae, only 4MBC and OMC/EHMC increased EcR and hsp70 mRNA levels and OD-PABA upregulated only the EcR gene. These results revealed that embryos are particularly sensitive to UV filters, which affect endocrine regulation during development. Most UV filters also triggered the cellular stress response, and thus exhibit proteotoxic effects. The differences observed between embryos and larvae and the higher sensitivity of embryos highlight the importance of considering different life stages when evaluating the environmental risks of pollutants, particularly when analyzing endocrine effects.

137Cs distribution in the northern Adriatic Sea

Anthropogenic radioactivity in the northern Adriatic Sea was assessed by analyzing 137Cs activity concentrations in seawater, sediment, and marine organisms in the period from 2006 to 2010. The investigated locations were the Po River delta, Lim Bay and the Rovinj coastal area. At all locations 137Cs activity concentrations in seawater were lower than pre-Chernobyl values (<4 Bq m−3). The highest 137Cs activity concentrations in sediment were found in the Po River delta (8.70 Bq kg−1). The data indicate that some species, such as sardine Sardina pilchardus, red mullet Mullus barbatus and the brown alga Fucusvirsoides are better bioaccumulators of 137Cs than others. In addition, the ERICA Assessment Tool was used to calculate the total dose rates for reference organisms included in the software, as well as for specific sampled marine organisms.

Biomonitoring of the environmental genotoxic potential of emissions from a complex of ceramic industries in Monte Carmelo, Minas Gerais, Brazil, using Tradescantia pallida

ABSTRACTThe micronucleus (MN) test and analysis of heavy metal biological accumulation in Tradescantia pallida (T. pallida) were bioassays used to assess the genotoxic potential of emissions from a complex of ceramic industries into the atmosphere in a city in Brazil that is considered a national reference source for roof tile production. The ceramic industry emission-exposed T. pallida plants were biomonitored during the dry season, in June, July, and August 2013. In addition to the contaminated monitoring site, a reference site in a peri-urban area was utilized, for comparative purposes. Genotoxicity assessments were determined monthly, while heavy metal bioaccumulation was measured at the end of the total exposure period. The MN frequency was significantly greater in T. pallida plants exposed in the ceramic industry emission monitored area compared to the reference site, and highest MN rates were observed in July and August. With respect to heavy metal bioaccumulation in T. pallida leaves, cadmium (Cd) and chromium (Cr) concentrations were significantly higher in plants at the ceramic industry emission monitoring site. Thus, in relation to the parameters assessed, T. pallida was found to be sensitive to atmospheric contamination by heavy metals attributed to ceramic products emissions generated by the ceramic industry, confirming that this plant species may be employed as a reference organism in biomonitoring studies.

Path2PPI: an R package to predict protein-protein interaction networks for a set of proteins.

Summary: We introduce Path2PPI, a new R package to identify protein–protein interaction (PPI) networks for fully sequenced organisms for which nearly none PPI are known. Path2PPI predicts PPI networks based on sets of proteins from well-established model organisms, providing an intuitive visualization and usability. It can be used to combine and transfer information of a certain pathway or biological process from several reference organisms to one target organism.Availability and implementation: Path2PPI is an open-source tool implemented in R. It can be obtained from the Bioconductor project: http://bioconductor.org/packages/Path2PPI/Contact: ina.koch@bioinformatik.uni-frankfurt.deSupplementary information: Supplementary data are available at Bioinformatics online.

Diversity of &lt;em&gt;Micromonospora&lt;/em&gt; strains from the deep Mediterranean Sea and their potential to produce bioactive compounds

During studies on bacteria from the Eastern Mediterranean deep-sea, incubation under in situ conditions (salinity, temperature and pressure) and heat treatment were used to selectively enrich representatives of Micromonospora. From sediments of the Ierapetra Basin (4400 m depth) and the Herodotos Plain (2800 m depth), 21 isolates were identified as members of the genus Micromonospora. According to phylogenetic analysis of 16S rRNA gene sequences, the Micromonospora isolates could be assigned to 14 different phylotypes with an exclusion limit of ≥ 99.5% sequence similarity. They formed 7 phylogenetic clusters. Two of these clusters, which contain isolates obtained after enrichment under pressure incubation and phylogenetically are distinct from representative reference organism, could represent bacteria specifically adapted to the conditions in situ and to life in these deep-sea sediments. The majority of the Micromonospora isolates (90%) contained at least one gene cluster for biosynthesis of secondary metabolites for non-ribosomal polypeptides and polyketides (polyketide synthases type I and type II). The determination of biological activities of culture extracts revealed that almost half of the strains produced substances inhibitory to the growth of Gram-positive bacteria. Chemical analyses of culture extracts demonstrated the presence of different metabolite profiles also in closely related strains. Therefore, deep-sea Micromonospora isolates are considered to have a large potential for the production of new antibiotic compounds.

Enhanced Radiation Resistance of Methanosarcina soligelidi SMA-21, a New Methanogenic Archaeon Isolated from a Siberian Permafrost-Affected Soil in Direct Comparison to Methanosarcina barkeri.

Permafrost-affected soils are characterized by a high abundance and diversity of methanogenic communities, which are considered suitable model organisms for potential life on Mars. Methanogens from Siberian permafrost have been proven to be highly resistant against divers stress conditions such as subzero temperatures, desiccation, and simulated thermophysical martian conditions. Here, we studied the radiation resistance of the currently described new species Methanosarcina soligelidi SMA-21, which was isolated from a Siberian permafrost-affected soil, in comparison to Methanosarcina barkeri, which is used as a reference organism from a nonpermafrost soil environment. Both strains were exposed to solar UV and ionizing radiation to assess their limits of survival. Methanosarcina soligelidi exhibit an increase in radiation resistance to UV (2.5- to 13.8-fold) and ionizing radiation (46.6-fold) compared to M. barkeri. The F10 (UVC) and D10 (X-rays) values of M. soligelidi are comparable to values for the well-known, highly radioresistant species Deinococcus radiodurans. In contrast, the radiation response of M. barkeri was highly sensitive to UV and ionizing radiation comparably to Escherichia coli and other radiosensitive microorganisms. This study showed that species of the same genus respond differently to UV and ionizing radiation, which might reflect the adaptation of Methanosarcina soligelidi SMA-21 to the harsh environmental conditions of the permafrost habitat. Methanogenic archaea-Environmental UV-Ionizing radiation-Permafrost-Radiation resistance-Mars.

Developing a sentinel mollusc species for toxicity assessment: metal exposure, dose and response – laboratory v. field exposures and resident organisms

Environmental contextMetal contamination in estuarine sediments can affect ecosystem health. Molluscs are commonly used as environmental indicators because they accumulate contaminants that cause adverse health effects. We investigated metal uptake and effects in the Sydney cockle, comparing exposure to contaminated lake sediments in situ and in laboratory aquariums. Although differences were observed between the different exposure types, all approaches were found to be valid for investigating metal health effects in this organism. AbstractRelationships between exposure, tissue dose and biological responses of the benthic marine bivalve Anadara trapezia to an estuarine sediment zinc, copper, lead, cadmium and selenium contamination gradient in Lake Macquarie, NSW, were evaluated using three approaches. Organisms were exposed to sediments in laboratory aquaria, caged in situ in the lake and lake resident organisms collected. Dose included total metal tissue burden and subcellular metal distribution to determine metabolically available metal. Response indices were total antioxidant capacity, lipid peroxidation, lysosomal stability and condition index. Bioaccumulation of total metals was higher in the laboratory and resident organisms than in those transplanted in the field but the contribution of individual metals to the total differed. Laboratory-exposed organisms had increased concentrations of cadmium and lead in their biologically active and detoxified metal fractions but not of the essential elements zinc and copper. Subcellular metal distribution patterns were the same in resident organisms but cadmium and lead burdens were higher in both fractions. Biomarker responses were similar in laboratory, transplanted and resident organisms. Total antioxidant capacity was significantly reduced and lipid peroxidation and lysosomal destabilisation significantly increased in all metal-exposed organisms compared with the reference A. trapezia. Condition index of laboratory-exposed organisms was significantly lower than in situ, resident and reference organisms. Clear metal exposure–dose–response relationships have been demonstrated for A. trapezia in laboratory and in situ experiments. Non-resident organisms, in both exposure scenarios, gave similar responses to resident metal-exposed organisms, showing all approaches are valid when investigating effects in this species.

The assessment of ionising radiation impact on the cooling pond freshwater ecosystem non-human biota from the Ignalina NPP operation beginning to shut down and initial decommissioning

The radiological doses to non-human biota of freshwater ecosystem in the Ignalina NPP cooling pond – Lake Druksiai were evaluated for several cases including the plant's operation period and initial decommissioning activities, using the ERICA 1.2 code with IAEA SRS-19 models integrated approach and tool.Among the Lake Druksiai freshwater ecosystem reference organisms investigated the highest exposure dose rate was determined for bottom fauna – benthic organisms (mollusc-bivalves, crustaceans, mollusc-gastropods, insect larvae), and among the other reference organisms – for vascular plants. The mean and maximum total dose rate values due to anthropogenic radionuclide ionising radiation impact in all investigated cases were lower than the ERICA screening dose rate value of 10 μGy/h. The main exposure of reference organisms as a result of Ignalina NPP former effluent to Lake Druksiai is due to ionizing radiation of radionuclides 60Co and 137Cs, of predicted releases to Lake Druksiai during initial decommissioning period – due to radionuclides 60Co, 134Cs and 137Cs, and as a result of predicted releases to Lake Druksiai from low- and intermediate-level short-lived radioactive waste disposal site in 30–100 year period – due to radionuclides 99Tc and 3H.The risk quotient expected values in all investigated cases were <1, and therefore the risk to non-human biota can be considered negligible with the exception of a conservative risk quotient for insect larvae. Radiological protection of non-human biota in Lake Druksiai, the Ignalina NPP cooling pond, is both feasible and acceptable.

Chlamydomonas Genome Resource for Laboratory Strains Reveals a Mosaic of Sequence Variation, Identifies True Strain Histories, and Enables Strain-Specific Studies.

Chlamydomonas reinhardtii is a widely used reference organism in studies of photosynthesis, cilia, and biofuels. Most research in this field uses a few dozen standard laboratory strains that are reported to share a common ancestry, but exhibit substantial phenotypic differences. In order to facilitate ongoing Chlamydomonas research and explain the phenotypic variation, we mapped the genetic diversity within these strains using whole-genome resequencing. We identified 524,640 single nucleotide variants and 4812 structural variants among 39 commonly used laboratory strains. Nearly all (98.2%) of the total observed genetic diversity was attributable to the presence of two, previously unrecognized, alternate haplotypes that are distributed in a mosaic pattern among the extant laboratory strains. We propose that these two haplotypes are the remnants of an ancestral cross between two strains with ∼2% relative divergence. These haplotype patterns create a fingerprint for each strain that facilitates the positive identification of that strain and reveals its relatedness to other strains. The presence of these alternate haplotype regions affects phenotype scoring and gene expression measurements. Here, we present a rich set of genetic differences as a community resource to allow researchers to more accurately conduct and interpret their experiments with Chlamydomonas.

Quest for Orthologs Entails Quest for Tree of Life: In Search of the Gene Stream.

Quest for Orthologs (QfO) is a community effort with the goal to improve and benchmark orthology predictions. As quality assessment assumes prior knowledge on species phylogenies, we investigated the congruency between existing species trees by comparing the relationships of 147 QfO reference organisms from six Tree of Life (ToL)/species tree projects: The National Center for Biotechnology Information (NCBI) taxonomy, Opentree of Life, the sequenced species/species ToL, the 16S ribosomal RNA (rRNA) database, and trees published by Ciccarelli et al. (Ciccarelli FD, et al. 2006. Toward automatic reconstruction of a highly resolved tree of life. Science 311:1283–1287) and by Huerta-Cepas et al. (Huerta-Cepas J, Marcet-Houben M, Gabaldon T. 2014. A nested phylogenetic reconstruction approach provides scalable resolution in the eukaryotic Tree Of Life. PeerJ PrePrints 2:223) Our study reveals that each species tree suggests a different phylogeny: 87 of the 146 (60%) possible splits of a dichotomous and rooted tree are congruent, while all other splits are incongruent in at least one of the species trees. Topological differences are observed not only at deep speciation events, but also within younger clades, such as Hominidae, Rodentia, Laurasiatheria, or rosids. The evolutionary relationships of 27 archaea and bacteria are highly inconsistent. By assessing 458,108 gene trees from 65 genomes, we show that consistent species topologies are more often supported by gene phylogenies than contradicting ones. The largest concordant species tree includes 77 of the QfO reference organisms at the most. Results are summarized in the form of a consensus ToL (http://swisstree.vital-it.ch/species_tree) that can serve different benchmarking purposes.

Health and ecological hazards due to natural radioactivity in soil from mining areas of Nasarawa State, Nigeria

Nasarawa State is located in north central Nigeria and it is known as Nigeria's home of solid minerals. It is endowed with barite, copper, zinc, tantalite and granite. Continuous releases of mining waste and tailings into the biosphere may result in a build-up of radionuclides in air, water and soil. This work therefore aims to measure the activity concentration levels of primordial radionuclides in the soil/sediment samples collected from selected mines of the mining areas of Nasarawa State. The paper also assesses the radiological and radio ecological impacts of mining activities on the residents of mining areas and their environment. The activity concentrations of primordial radionuclides (226Ra, 232Th and 40K) in the surface soils/sediment samples were determined using sodium iodide-thallium gamma spectroscopy. Seven major mines were considered with 21 samples taken from each of the mines for radiochemistry analysis. The human health hazard assessment was conducted using regulatory methodologies set by the United Nations Scientific Committee on the Effects of Atomic Radiation, while the radio ecological impact assessment was conducted using the ERICA tool v. 1.2. The result shows that the activity concentrations of 40K in the water ways of the Akiri copper and the Azara barite mines are 60 and 67 % higher than the world average value for 40K, respectively. In all mines, the annual effective dose rates (mSv y−1) were less than unity, and a maximum annual gonadal dose of 0.58 mSv y−1 is received at the Akiri copper mine, which is almost twice the world average value for gonadal dose. The external hazard indices for all the mines were less than unity. Our results also show that mollusc-gastropod, insect larvae, mollusc-bivalve and zooplankton are the freshwater biotas with the highest dose rates ranging from 5 to 7 µGy h−1. These higher dose rates could be associated with zinc and copper mining at Abuni and Akiri, respectively. The most exposed terrestrial reference organisms are lichen and bryophytes. In all cases, the radio ecological risks are not likely to be discernible. This paper presents a pioneer data for ecological risk from ionizing contaminants due to mining activity in Nasarawa State, Nigeria. Its methodology could be adopted for future work on radioecology of mining.

Interpretation of the Genome in Synchronized Chlamydomonas Cells

Chlamydomonas has served for over half a century as a reference organism for fundamental discoveries in photosynthesis. Cultures of Chlamydomonas are readily synchronized by alternating light‐dark cycles. We sampled synchronized cultures of Chlamydomonas over a 24 h period to reveal highly coordinated expression of sets of genes encoding individual complexes or pathways. The density of sampling permits us to resolve closely spaced events to reveal that the expression of the nucleus‐encoded subunits of the proton pumping complexes precedes the expression of the photosynthetic reaction centers and their associated light harvesting complexes, which are themselves very tightly coordinated. The separation of expression of genes encoding photosynthetic metabolism from those encoding respiratory metabolism allows us to assign function in the Calvin‐Benson vs. oxidative pentose phosphate pathway to genes encoding isoforms of the same enzyme. The expression profile shows evidence for transient photo‐oxidative stress at the transition from dark to light and more sustained stress towards the end of the light cycle. Candidate regulatory RNAs have been identified as well.

Planting molecular functions in an ecological context with Arabidopsis thaliana.

The vascular plant Arabidopsis thaliana is a central genetic model and universal reference organism in plant and crop science. The successful integration of different fields of research in the study of A. thaliana has made a large contribution to our molecular understanding of key concepts in biology. The availability and active development of experimental tools and resources, in combination with the accessibility of a wealth of cumulatively acquired knowledge about this plant, support the most advanced systems biology approaches among all land plants. Research in molecular ecology and evolution has also brought the natural history of A. thaliana into the limelight. This article showcases our current knowledge of the natural history of A. thaliana from the perspective of the most closely related plant species, providing an evolutionary framework for interpreting novel findings and for developing new hypotheses based on our knowledge of this plant.DOI: http://dx.doi.org/10.7554/eLife.06100.001

Previous physicochemical stress exposures influence subsequent resistance of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes to ultraviolet-C in coconut liquid endosperm beverage

This study investigated the influences of prior exposures to common physicochemical stresses encountered by microorganisms in food and food processing ecologies such as acidity, desiccation, and their combinations, on their subsequent susceptibility towards UV-C treatment in coconut liquid endosperm beverage. Cocktails of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes were separately subjected to gradually acidifying environment (final pH4.46), exposed to abrupt desiccation by suspension in saturated NaCl solution (aw=0.85) for 4, 8, and 24h, and sequential acidic and desiccated stresses before suspending in the coconut beverage for UV-C challenge. The exposure times (D) and UV-C energy dose values (DUV-C) necessary to reduce 90% of the population of the different test organisms varied with previous exposures to different sublethal stresses, indicating possible influence of implicit microbial factors towards resistance to UV-C. All tested individual and combined stresses resulted in increased resistance, albeit some were not statistically significant. Non-stressed cells had D values of 3.2–3.5s, and corresponding DUV-C values of 8.4–9.1mJ/cm2. Cells exposed to previous acid stress had D values of 4.1–4.8s and corresponding DUV-C values of 10.7–12.5mJ/cm2. Prior exposure to desiccation resulted in D values of 5.6–7.9s and DUV-C values of 14.7–20.6mJ/cm2, while exposure to combined acid and desiccation stresses resulted in D values of 6.1–8.1s and DUV-C values of 15.9–21.0mJ/cm2. The D and DUV-C values of S. enterica after previous exposure to sequential acid (24h) and desiccation (24h) stresses were found significantly greatest, making the organism and physiological state an appropriate reference organism for the establishment of UV-C pasteurization process for the beverage.

Identification of Putative Drug Targets and Vaccine Candidates for Pathogens Causing Atherosclerosis

Atherosclerosis is a chronic inflammatory artery disease, responsible for both cardiovascular (heart) and cerebrovascular (brain) stroke with high morbidity and mortality worldwide. Infectious pathogens such as Chlamydophila pneumoniae, Porphyromonas gingivalis and Helicobacter pylori are shown to be associated with the disease in recent epidemiological studies. Therefore, identification of common drug targets and vaccine candidates against these three pathogens would be vital towards therapy and management of atherosclerosis. Chlamydophila pneumonia was selected as a reference organism due to its predominant role in atherosclerosis. Implementing comparative genomic approach, subtractive genomic approach, metabolic pathway analysis, non-homologous gut flora analysis and domain search analysis, 35 common putative drug targets were identified against pathogens of atherosclerosis. Subcellular localization studies were performed and identified UvrABC protein as vaccine candidate. Metabolic pathway analysis has showed that, out of 35 drug targets, 14 enzymes were participating in key pathways linked to pathogen’s survival, proliferation and pathogenesis without any alternative mechanism to synthesize the product. The gut microbiota analysis was performed to identify the drug targets which do not affect the microbiota in the humans. Domain search was performed for the identified 14 drug targets using Pfam and SMART databases and protein network analysis was carried out using STRING and Cytoscape v3.2.0. The drug targets and vaccine candidates proposed in the present study would serve as basis to design potent inhibitors and subunit vaccines through in silico approach for combating atherosclerosis caused by infectious pathogens.

Molecular Identification of Bacterial Species Present on Toothbrushes

Toothbrushes play an essential role in oral hygiene. However, they can be significant in microbial transmission and can increase the risk of infection, since they can serve as a reservoir for microorganisms in healthy, oral-diseased and medically ill adults. This study was conducted to evaluate toothbrush contamination in six toothbrushes donated from four people. Two participants each supplied two toothbrushes - one used in the bathroom and one used in the workplace. The other two people each donated two toothbrushes used in the workplace. Polymerase chain reaction was used to construct a 16S rRNA clone library. Sequences of cloned DNA were compared with those from the reference organisms provided by GenBank. A total 120 clones, representing 20 clones for each toothbrush, were analyzed. They are composed of six pylum, 46 genera and 79 species. The most dominant species were Streptococcus oralis, Streptococcus parasanguinis and Haemophilus parainfluenzae. Enterobacter and Escherichia were recovered from toothbrushes used domestically. Toothbrushes used in the workplace did not contain Enterobacteria.

Microscopic and spectroscopic techniques to investigate lipid droplet formation and turnover in yeast.

In spite of some progress in understanding the molecular basis of lipid-associated disorders, major questions about the regulation of synthesis and degradation of lipids and the interaction of these processes with other aspects of cellular physiology are still unresolved. Studies in reference organisms such as various yeast species, the fruit fly Drosophila melanogaster, or the nematode Caenorhabditis elegans complement efforts in mouse models as well as clinical studies in humans to address these questions. Imaging techniques play a pivotal role in understanding lipid droplet biology, and the implementation of imaging-based high-content screens of mutant collections has led to the identification of novel molecular players. This study focuses on novel fluorescent probes as well as spectroscopic imaging techniques to investigate lipid droplet formation and turnover in yeast. The application and limitations of such techniques in understanding lipid storage and turnover are discussed.

Application of ultraviolet-C radiation to inactivate acid-and-desiccation stressed Salmonella enterica in young and mature coconut liquid endosperm mix beverage

The occurrences of outbreaks of infections due to consumption of unpasteurized fruit beverages, and the negative effects of heat treatment towards quality are features of the consumer demand paradox on safety and quality that the industry has to address. This study established the efficacy of ultraviolet-C (UV-C) treatment against acid-and-desiccation stressed Salmonella enterica; and applied and evaluated a process schedule with a recommended lethal rate of 99.999% against the target pathogen. Determinations of decimal reduction times revealed that suspension volume and flow property significantly affected inactivation of the test organism, which exhibited the greatest resistance to UV-C when suspended in 500 ml, non-agitated coconut beverage. A UV-C process schedule with a level of lethality of 5-log cycle reduction against the reference organism was then applied to the beverage. Quality evaluations showed that the pasteurization process resulted in significant color changes in the beverage. The process also significantly affected the microbiology of the beverage, but the population of spoilage microorganisms continuously increased during storage; surpassing microbial limits by the 2nd d of refrigerated storage. The sensory quality scores of the processed beverage were not significantly different from the non-processed control, and were higher than an established commercial brand.

Potential radiological impact of the phosphate industry on wildlife

The activities of the phosphate industry may lead to enhanced levels of naturally occurring radioactivity in terrestrial and aquatic ecosystems. We performed a preliminary environmental risk assessment (ERA) of environmental contamination resulting from the activities of 5 phosphate fertiliser plants (located in Belgium, Spain, Syria, Egypt, Brazil), a phosphate-mine and a phosphate-export platform in a harbour (both located in Syria). These sites were selected because of the availability of information on concentrations of naturally occurring radionuclides in the surrounding environments. Assessments were generally performed considering highest environmental concentrations reported in the studies. The ERICA Tool, operating in a Tier 2 assessment mode, was used to predict radiation dose rates and associated risk to the selected reference organisms using the ERICA default parameter setting. Reference organisms were those assigned as default by the ERICA Tool. Potential impact is expressed as a best estimate risk quotient (RQ) based on a radiation screening value of 10 μGy h−1. If RQ ≤ 1, the environment is considered unlikely to be at risk and further radiological assessment is not deemed necessary. Except for one of the cases assessed, the best estimate RQ exceeded 1 for at least one of the reference organisms. Internal exposure covered for 90–100 % of the total dose. 226Ra or 210Po were generally the highest contributors to the dose. The aquatic ecosystems in the vicinity of the phosphate fertiliser plants in Tessenderlo (Belgium), Huelva (Spain), Goiás (Brazil) and the terrestrial environment around the phosphate mine in Palmyra (Syria) are the ecosystems predicted to be potentially most at risk.

Identification of non-streptococcal organisms from human dental plaque grown on the Streptococcus-selective medium mitis-salivarius agar

ObjectiveMitis-salivarius (MS) agar has been used widely in microbial epidemiological studies because oral viridans streptococci can be selectively grown on this medium. Even though the previous findings reported the limited selecting power of MS agar for streptococcus strains, the identities of non-streptococcal strains from human oral samples which can grow on this medium are not clear yet. In this study, we identified non-streptococcal organisms grown on MS agar plates by polymerase chain reaction (PCR) amplification and sequencing of the 16S ribosomal RNA (rRNA) gene. DesignEighty bacterial colonies on MS plates were isolated from plaque samples, and bacterial identification was achieved with the rapid ID 32 Strep system and mini API reader. The bacterial colonies identified as non-streptococci by the API system were selected for further identification. The 16S rRNA gene was amplified by PCR and verified using DNA sequencing analysis for identification. Sequences were compared with those of reference organisms in the genome database of the National Center for Biotechnology Information using the Basic Local Alignment Search Tool (BLAST). ResultsAmong the 11 isolated non-streptococcal strains on MS plates, 3 strains were identified as Actinomyces naeslundii, 7 strains were identified as Actinomyces oris and 1 strain were identified as Actinomyces sp. using Blastn. ConclusionsIn this study, we showed that some oral Actinomyces species can grow on Streptococcus-selective MS agar plates.