Evaluation of polycyclic aromatic hydrocarbons in sediments of Balsas River Mouth, Pacific Coast, Mexico: Sources, risks, and genotoxicity.

Polycyclic aromatic hydrocarbons (PAHs) were assessed in sediments (n = 7) collected from the mouth of the Balsas River, Pacific Coast, Mexico. The total PAH levels ranged between 142.1 and 3944.07 µg kg-1 in the summer and 137.65-3967.38 µg kg-1 in the winter, probably reflecting the anthropogenic activities of the region. Calculation of the four analytical ratios of [Anthracene/(Anthracene + Phenanthrene)]: [Fluoranthene/(Fluoranthene + Pyrene)], [Fluoranthene/Pyrene: Fluoranthene/(Fluoranthene + Pyrene)], [Indeno [123-cd]Pyrene/(Indeno [123-cd]Pyrene + Benzo [ghi]Perylene)]: [Benzo [a]anthracene/(Benzo [a]Anthracene + Chrysene)], and [Anthracene/Phenanthrene]: [Fluoranthene/(Fluoranthene + Pyrene)] revealed a mixed PAH source, from petroleum and biomass combustion. Significant statistical correlations (r2 = 0.90) between the 4 and 5 ringed PAHs denote that adsorption is the principal mechanism for accumulation in sedimentary archives. Ecotoxicological indices (Mean Effect Range Medium Quotient and Mean Probable Effect Level Quotient) indicated moderate pollution with adverse biological impacts on ambient benthonic organisms. The calculations of Toxicity Equivalent Quotient and Mutagen Equivalent Quotient values proposed that the region is highly polluted by mutagenic and carcinogenic PAH compounds. The genotoxic evaluation of Lutjanus guttatus (Spotted rose snapper) presented significant DNA damage and discrepancies in Ethoxyresorufin-O-Deethylase activity. Based on the toxicological and genotoxicological evaluation of PAHs in sediments, the region was observed to be largely impacted from biological damage.

Targeting of Streptococcus mutans Biofilms by a Novel Small Molecule Prevents Dental Caries and Preserves the Oral Microbiome.

Dental caries is a costly and prevalent disease characterized by the demineralization of the tooth's enamel. Disease outcome is influenced by host factors, dietary intake, cariogenic bacteria, and other microbes. The cariogenic bacterial species Streptococcus mutans metabolizes sucrose to initiate biofilm formation on the tooth surface and consequently produces lactic acid to degrade the tooth's enamel. Persistence of S. mutans biofilms in the oral cavity can lead to tooth decay. To date, no anticaries therapies that specifically target S. mutans biofilms but do not disturb the overall oral microbiome are available. We screened a library of 2-aminoimidazole antibiofilm compounds with a biofilm dispersion assay and identified a small molecule that specifically targets S. mutans biofilms. At 5 µM, the small molecule annotated 3F1 dispersed 50% of the established S. mutans biofilm but did not disperse biofilms formed by the commensal species Streptococcus sanguinis or Streptococcus gordonii. 3F1 dispersed S. mutans biofilms independently of biofilm-related factors such as antigen I/II and glucosyltransferases. 3F1 treatment effectively prevented dental caries by controlling S. mutans in a rat caries model without perturbing the oral microbiota. Our study demonstrates that selective targeting of S. mutans biofilms by 3F1 was able to effectively reduce dental caries in vivo without affecting the overall oral microbiota shaped by the intake of dietary sugars, suggesting that the pathogenic biofilm-specific treatment is a viable strategy for disease prevention.

Metal concentrations in aquatic environments of Puebla River basin, Mexico: natural and industrial influences.

The rapid urban expansion and presence of volcanoes in the premises of Puebla River basin in central Mexico exert significant influences over its aquatic environments. Twenty surface sediment samples from Puebla River basin consisting of R. Alseseca, R. Atoyac, and Valsequillo dam were collected during September 2009 and analyzed for major (Al, Fe, Mg, Ba, Ca, and K) and trace elements (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, V, and Zn) in order to identify the metal concentrations and their enrichment. R. Atoyac sediments presented higher concentrations of Ba (1193.8 µg g-1) and Pb (27.1 µg g-1) in comparison with the local reference sample values. All the metal concentrations except Sr for R. Alseseca sediments were within the range of local reference sample values indicating no significant external influence, whereas Valsequillo dam sediments had elevated concentrations of all the metals suggesting both natural and external influences in the study region. The magnitude of metal contamination was assessed using several indices such as geoaccumulation index (I geo), enrichment factor (EF), degree of contamination (C d ), and pollution load index (PLI). The results suggest that As, Pb, and Zn were predominantly enriched in the Puebla River basin sediments. Comparing with sediment quality guidelines and ecotoxicological values, it is revealed that Cd, Cr, Cu, and Ni have possible harmful effects on the biological community. The present study provides an outlook of metal enrichment in Puebla River basin sediments, highlighting the necessity to conserve this river ecosystem for the near future.

Streptococcus mutans copper chaperone, CopZ, is critical for biofilm formation and competitiveness.

The oral cavity is a dynamic environment characterized by hundreds of bacterial species, saliva, and an influx of nutrients and metal ions such as copper. Although there is a physiologic level of copper in the saliva, the oral cavity is often challenged with an influx of copper ions. At high concentrations copper is toxic and must therefore be strictly regulated by pathogens for them to persist and cause disease. The cariogenic pathogen Streptococcus mutans manages excess copper using the copYAZ operon that encodes a negative DNA-binding repressor (CopY), the P1-ATPase copper exporter (CopA), and the copper chaperone (CopZ). These hypothetical roles of the copYAZ operon in regulation and copper transport to receptors led us to investigate their contribution to S. mutans virulence. Mutants defective in the copper chaperone CopZ, but not CopY or CopA, were impaired in biofilm formation and competitiveness against commensal streptococci. Characterization of the CopZ mutant biofilm revealed a decreased secretion of glucosyltransferases and reduced expression of mutacin genes. These data suggest that the function of copZ on biofilm and competitiveness is independent of copper resistance and CopZ is a global regulator for biofilm and other virulence factors. Further characterization of CopZ may lead to the identification of new biofilm pathways.

Metal enrichment of soils following the April 2012-2013 eruptive activity of the Popocatépetl volcano, Puebla, Mexico.

We analyzed the total (Zn, Pb, Ni, Hg, Cr, Cd, Cu, As) and partially leachable metals (PLMs) in 25 ash and soil samples from recent (2012-2013) eruptions of the Popocatépetl Volcano in Central Mexico. More recent ash and soil samples from volcanic activity in 2012-2013 had higher metal concentrations than older samples from eruptions in 1997 suggesting that the naturally highly volatile and mobile metals leach into nearby fresh water sources. The higher proportions of As (74.72%), Zn (44.64%), Cu (42.50%), and Hg (32.86%) reflect not only their considerable mobility but also the fact that they are dissolved and accumulated quickly following an eruption. Comparison of our concentration patterns with sediment quality guidelines indicates that the Cu, Cd, Cr, Hg, Ni, and Pb concentrations are higher than permissible limits; this situation must be monitored closely as these concentrations may reach lethal levels in the future.

Characterization of As and trace metals embedded in PM10 particles in Puebla City, México.

Forty-eight air-filter samples (PM10) were analysed to identify the concentration level of partially leached metals (PLMs; As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and V) from Puebla City, México. Samples were collected during 2008 from four monitoring sites: (1) Tecnológico (TEC), (2) Ninfas (NIN), (3) Hermanos Serdán (HS) and (4) Agua Santa (AS). The results indicate that in TEC, As (avg. 424 ng m(-3)), V (avg. 19.2 ng m(-3)), Fe (avg. 1,202 ng m(-3)), Cu (avg. 86.6 ng m(-3)), Cr (41.9 ng m(-3)) and Ni (18.6 ng m(-3)) are on the higher side than other populated regions around the world. The enrichment of PLMs is due to the industrial complexes generating huge dust particles involving various operations. The results are supported by the correlation of metals (Mn, Cd and Co) with Fe indicating its anthropogenic origin and likewise, As with Cd, Co, Fe, Mn, Pb and V. The separate cluster of As, Fe and Mn clearly signifies that it is due to continuous eruption of fumaroles from the active volcano Popocatépetl in the region.

Initial results of environmental monitoring in the Texas Rio Grande Valley.

Previous studies have suggested that a segment of human disease may be attributable to environmental exposures. These may include exposure to chemicals released from a broad range of natural and man-made sources. The purpose of this study was to develop the sampling methodology and prepare a preliminary database on the presence of various organic chemicals in environmental media in two South Texas counties bordered by the Rio Grande River. A third county, located approximately 150 miles north of the Rio Grande River, was also sampled. The South Texas counties were the focus of study due to an increased incidence of anencephalic births in recent years. The environmental media that was sampled included surface water and sediment from the Rio Grande River and irrigation canals, as well as soil from adjacent cropland and pastures. Samples were collected using United States Geological Survey (USGS) quadrangle maps (7.5'; 1:24,000 scale) to identify the area of interest. At least one sampling location was established in each quadrangle. A pond sampler was used for the collection of surface water samples, while soil was collected with a stainless steel trowel. Sediment samples were collected directly in a glass jar. Solid samples were extracted in a soxhlet extractor using methylene chloride. Organic chemicals were concentrated from water samples on a Sep-Pak cartridge and the organics eluted with methanol/acetonitrile. Extracts were analyzed using GC-MS. All of the surface water samples contained aliphatic hydrocarbons and plasticizers, while soil samples contained aliphatics, plasticizers, pesticides, and industrial estrogens. Specific chemicals detected in environmental samples included atrazine and benzene dicarboxylic acid. Contaminant levels in sediments were generally higher than were detected in other media. The results demonstrate the broad variability of contaminant types and concentrations in environmental samples. Although this study presents only a very preliminary characterization of a large area of South Texas, the data indicate a number of pesticides and xenobiotic estrogens that were identified in environmental samples. Additional data providing more details of spatial and temporal distribution of contaminants as well as wildlife studies are needed.