The secretion of metabolites with antimicrobial activity is one of the strategies employed by bacteria to respond to negative stimuli promoted during interspecies competition. In a long -term stationary phase. Pseudomonas aeruginosa and Escherichia coli can synthesize diffusible exometabolites whose action is to mutually inhibit the exposed cells, guaranteeing the balance of both populations in a certain site. The P. aeruginosa may have an advantage in that it produces pyocyanin. Howeve r, the excretion of indole and acetate by E. coli may reduce this advantage. This work aims to detect the influence of different concentrations of these two exometabolites on the synthesis of pyocyanin in two wild isolates of P. aeruginosa. After incubatio n under shaking for 72 h at 29°C, reduction of up to 50% of the concentration of pyocyanin in the presence of indole was observed. On the other hand, no change was observed in the production of the pigment with the acetate, alone or when in combination with concentrations of less than 0.5 mM indole. It reduced the inhibitory effect of the compound, reflecting an increase in pyocyanin production of more than 20%. The results contribute to help understanding the ecological mechanisms of competition between t he two species.
Antimicrobial activity of pyocyanin against competing organisms of Pseudomonas aeruginosa is related to the oxidative stress that the compound promotes in susceptible cells. The objective of this work was to produce, extract and verify the activity of pyocyanin in planktonic and sessile forms from clinical strains, Staphylococcus aureus UFPEDA 02 and Escherichia coli UFPEDA 224. About 600 µg/mL of pyocyanin were obtained. The planktonic cells were highly sensitive. The MIC determined for S. aureus UFPEDA 02 and E. coli UFPEDA 224 were 18.75 and 37.5 µg/mL, respectively. The pyocyanin demonstrated biocidal effect against S. aureus UFPEDA 02. On the other hand, pyocyanin was not active in either sessile strain. The presence of the pigment allowed a greater adherence of the strains, forming more robust biofilms compared to the control. S. aureus UFPEDA 02 and E. coli UFPEDA 224 presented moderate and high hydrophobicity, respectively. Glass and dolomite surfaces were tested in the in vitro biofilm test. Both strains formed the biofilm better on the dolomite surface, obtaining a cell concentration (MPN/cm2) in the order of 3 log units after 48h of incubation.
Makeup is used by a large portion of humanity and often misused or stored incorrectly, leading to contamination by microbes. The water content in cosmetics influences susceptibility to microbial contamination, which can represent health risks, as well as deterioration. The aim of this work was to isolate and identify filamentous fungi in samples of face powder, foundation, blush, and lipstick of eight popular brands in Brazil. A study of their composition identified a total of 106 ingredients. Of the products, 75% of the samples showed contamination by filamentous fungi. Penicillium was the most prevalent, followed by Rhizopus and Scopulariopsis. The presence of these pathogens suggests misuse in the production and manipulation of these cosmetics as well as high risk to users' health.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.