L. pneumophila resists its self-harming metabolite HGA via secreted factors and collective peroxide scavenging.

IMPORTANCE: Before environmental opportunistic pathogens can infect humans, they must first successfully grow and compete with other microbes in nature, often via secreted antimicrobials. We previously discovered that the bacterium Legionella pneumophila, the causative agent of Legionnaires' disease, can compete with other microbes via a secreted molecule called HGA. Curiously, L. pneumophila strains that produce HGA is not wholly immune to its toxicity, making it a mystery how these bacteria can withstand the "friendly fire" of potentially self-targeting antimicrobials during inter-bacterial battles. Here, we identify several strategies that allow the high-density bacterial populations that secrete HGA to tolerate its effects. Our study clarifies how HGA works. It also points to some explanations of why it is difficult to disinfect L. pneumophila from the built environment and prevent disease outbreaks.

Ropa de un solo uso en un hospital terciario: La experiencia del complexo hospitalario universitario de Santiago / No disponible

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Analysis of the effect of pH on Cu2+-fulvic acid complexation using a simple electostatic model.

A simple electrostatic model was used to study the effect of pH on the binding of Cu2+ to fulvic acid in solutions containing similar amounts of dissolved organic carbon (DOC) as natural media, such as aquatic environments and soil solutions. Complexation behavior was affected by increased pH because of changes in the electrostatic interaction resulting from an increase in the negative charge on the fulvic acid molecule. Solutions of soil-extracted fulvic acid (FA), at concentrations of 25 and 35 mg L(-1), ionic strength 0.005 M, and pH 5.0, 5.5, 6.0, 6.5, 7.0, and 7.5, conditions that simulate those of natural freshwaters, were titrated with copper ion using differential pulse anodic stripping voltammetry. Assuming the formation of 1:1 complexes, the conditional binding parameters (stability constant and binding capacity) were calculated for each pH value. Use of a 1:1 electrostatic model allowed estimation of the contribution of the electrostatic effect to the ion binding reaction, at each pH value, as well as calculation of a binding constant that was not dependent on pH and which thus represented the contribution of the chemical heterogeneity. Furthermore, it was found that only a small proportion of the FA acid functional binding sites are involved in the formation of copper complexes.