The Calyptogena magnifica chemoautotrophic symbiont genome.

Chemoautotrophic endosymbionts are the metabolic cornerstone of hydrothermal vent communities, providing invertebrate hosts with nearly all of their nutrition. The Calyptogena magnifica (Bivalvia: Vesicomyidae) symbiont, Candidatus Ruthia magnifica, is the first intracellular sulfur-oxidizing endosymbiont to have its genome sequenced, revealing a suite of metabolic capabilities. The genome encodes major chemoautotrophic pathways as well as pathways for biosynthesis of vitamins, cofactors, and all 20 amino acids required by the clam.

Mercury poisoning associated with a Mexican beauty cream.

OBJECTIVES: To describe demographic characteristics, patterns of use, and symptoms associated with mercury poisoning among persons who used a Mexican beauty cream containing mercurous chloride and to estimate the prevalence of cream use in Texas near the Mexico border. DESIGN: Case series and cross-sectional survey. SETTING: Border communities of Arizona, California, New Mexico, and Texas. PARTICIPANTS: Persons who used the cream and contacted a health department in response to announcements about the cream and households that participated in the Survey of Health and Environmental Conditions in Texas Border Counties and Colonias, 1997. MAIN OUTCOME MEASURES: Urine mercury concentrations, self-reported symptoms, and prevalence of cream use among households. RESULTS: Of 330 cream users who contacted their health department, 96% were women, and 95% were Hispanic. The mean urine mercury concentration was 146.7 microg/L (reference range : 0-20 microg/L). In 5% of 2,194 randomly selected Texas households near the Mexico border, at least 1 person had used "Crema de Belleza-Manning" (Laboratorios Vida Natural, S.A., Tampico, Tamaulipas, Mexico) in the previous year. CONCLUSIONS: Most cream users had increased urine mercury concentrations. Cream use was common in Texas near the Mexico border. Physicians should consider toxicity in patients with neurologic symptoms of unclear cause and use public health departments when investigating unusual illnesses.

Effect of environmental toxicants on enzyme biosynthesis: a comparison of beta-galactosidase, alpha-glucosidase and tryptophanase.

Except for beta-galactosidase, little is known about the effect of environmental toxicants on enzyme induction. The information could be potentially useful for the development of low-cost and rapid ecotoxicity assays. The effect of toxicants on the de novo biosynthesis of three inducible enzymes, beta-galactosidase and tryptophanase in E. coli and alpha-glucosidase in B. subtilis was investigated. Biosynthesis of alpha-glucosidase was the most sensitive to environmental toxicants, particularly pentachlorophenol and sodium dodecyl sulfate. The sensitivity of B. subtilis to toxicants was further increased when Tween 80 was incorporated in the growth medium.

Malachite green-INT (MINT) method for determining active bacteria in sewage.

A membrane filtration method was developed to determine the proportion of active (respiring) bacteria at various stages of sewage treatment. Samples were incubated in the presence of 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride (INT) and, after fixation, passed through membrane filters. Filters were counterstained with malachite green and then were examined by bright-field microscopy. The contrast between bacteria and the filter background was greatly improved by drying and then clearing the filter before counterstaining. By this method, it was found that active bacterial fractions in raw sewage, settled sewage, and secondary effluent were 40, 29, and 58%, respectively, whereas the proportion of respiring bacteria in chlorinated secondary effluent was 6.1%. The active bacterial fraction of activated sludge was found to be 16%. The proposed method represents a significant improvement in speed and simplicity over existing methods for determining active bacteria in sewage.

New rapid technique for counting microorganisms directly on membrane filters.

The proposed technique is a modification of classical procedures for counting micoorganisms directly on membrane filters. The technique consists of clearing the filter with immersion oil, paraffin oil or cedar oil prior to staining with crystal violet, carbol fuchsin or malachite green. Millipore filters (0.1 micron pore size, VC type) were found to be superior to other filters with regard to the contrast between microorganisms and filter surface.