A single-container procedure for multiple genomic DNA samples preparation for pulsed field gel electrophoresis.

Genomic DNA preparation is a critical step for successful fingerprinting analysis by Pulsed Field Gel Electrophoresis (PFGE). This paper presents a simple and rapid protocol to prepare DNA samples from up to 24 bacterial isolates simultaneously. It involves performing the conventional PFGE sample preparation steps (cell growth and harvest, agarose-immobilization of intact cells, and DNA release and purification) into a 24-wells culture plate, without subjecting the biological material to repeated transference of containers. The single-container protocol rendered high quality genomic DNA from E. coli clinical isolates. The DNA yields obtained from samples prepared with the single-container protocol showed no differences to those obtained using the conventional DNA sample preparation for PFGE. This procedure is a cost-effective alternative that provides a larger capacity of analysis to the PFGE technique, which could be advantageous in a context of infectious disease outbreaks for pathogens molecular subtyping.

How to stay together? Habitat use by three sympatric sharks in the western coast of Baja California Sur, Mexico.

Sharks are top predators and play an important role in the regulation of marine ecosystems at lower trophic position. Mustelus californicus, Sphyrna zygaena, and Isurus oxyrinchus prove to be important fishery resources along the western coast of Baja California Sur and cohabit the same coastal areas, probably sharing resources. However, our knowledge about ecological dynamics of multiple species coexisting and sharing similar habitat resources is still limited, particularly for predators such as sharks. Therefore, this study focuses on the analysis of trophic ecology of the sharks species, using carbon (13C) and nitrogen (15N) stable isotope values in muscle tissues coupled with trace element concentration (Hg, Se, and Cd) in muscle and hepatic tissues of sharks. The values of δ13C (M. californicus -17.3 ± 1.1‰, S. zygaena -17.9 ± 0.5‰, and I. oxyrinchus -18.3 ± 0.3‰) and δ15N (M. californicus 18.2 ± 1.1‰, S. zygaena 18.4 ± 0.9‰, and I. oxyrinchus 17.8 ± 1.1‰) indicated that these species feed in the Gulf of Ulloa all throughout the year, and for extended periods with similar habitat use and trophic niche. The above-mentioned statement is also a conclusion supported by the significant correlation between isotopic and trace element concentrations in the muscular tissues in all studied species. Thus, the results of the present study emphasize the habitat and niche characteristics of three sympatric sharks off the coast of Baja California Sur, Mexico.

Mercury, selenium and cadmium in juvenile blue (Prionace glauca) and smooth hammerhead (Sphyrna zygaena) sharks from the Northwest Mexican Pacific coast.

Cadmium, selenium, and mercury concentrations were measured in muscle and liver of juvenile blue (Prionace glauca) and smooth hammerhead (Sphyrna zygaena) sharks caught on the west coast of Baja California Sur, Mexico, to evaluate the human health risk associated with its consumption. Cd and Hg were lower than the maximum allowable limit for human consumption established by the Mexican government (Hg = 1.0 µg g-1 and Cd = 0.50 µg g-1). Interspecific differences in trace elements accumulation denoted diet variations and physiological requirements of each shark species. Calculated biomagnification factor (BMF) values confirmed a prey-predator trophic transfer of elements. Not significant results of Selenium health benefit Index value (P. glauca = -0.46; S. zygaena = -0.02) signify no potential risks for human health. However, calculated Hazard Index values displayed possible health hazards to the children who consume blue shark meat regularly. The local population is advised regarding the ingestion rates of shark.

Mercury and selenium concentrations in different tissues of brown smooth-hound shark (Mustelus henlei) from the western coast of Baja California Sur, Mexico.

A study on mercury (Hg) and selenium (Se) concentrations in the liver and muscle of brown smooth-hound shark Mustelus henlei and its principal prey items, was conducted in the western coast of Baja California Sur, Mexico. Average Hg concentrations were found to be high in the muscle than in the liver; however, Hg concentrations were below the maximum permissible limits, and hence, the consumption of this species does not constitute a risk to human health. The mean Se concentrations were higher in the liver than in the muscle. The results of Hg: Se molar ratio revealed that Se counteracts the toxicity of Hg in hepatic tissues, whereas the contrary occurs in the muscle. Significant differences in Hg and Se accumulation were observed between females and males. Biomagnification factor values >1 demonstrate a biomagnification process from its principal prey species (i.e., red crab, Pleuroncodes planipes and Pacific mackerel, Scomber japonicus).

Bioaccumulation and trophic transfer of Cd in commercially sought brown smoothhound Mustelus henlei in the western coast of Baja California Sur, Mexico.

A study on cadmium concentration in Mustelus henlei (liver and muscle) was carried out in an area influenced by natural phosphorite deposits and coastal upwelling. Our results indicate that liver (0.96 µg/g) concentrations were higher compared to the muscle (0.040 µg/g) suggesting it is on the safer level for human consumption. The male/female ratio indicates higher values (based on liver & muscle) in males (0.899 µg/g), which contributes to these differences in concentration. Higher values in the liver (0.96 µg/g) is due to the influence of phosphorite deposits in the region as well as the high metabolic activity. The other important factor responsible for these high Cd values are the prey, which also poses high values and is well supported by the biomagnification (1.08 & 4.57) of this element. The study also benefited in evaluating the environmental conditions for this particular species and elemental concentration in relation to human health.