RESUMO
Under specific environmental conditions, Pseudomonas aeruginosa produces a biodegradable surfactant rhamnolipid. Evidences suggest that this biosurfactant is involved in protecting cells against oxidative stress; however, the effects of oxidative stress on its production and other virulence factors are still unclear. Here we show that rhamnolipid production is dependent on the aeration surface when P. aeruginosa is cultured in shaken flasks, as well as in production of elastases and alkaline proteases. The production of alginate, lipase, and pyocyanin was not detected in our shaken-flask experiments. P. aeruginosa was treated with hydrogen peroxide to trigger its oxidative stress response, and the proteome profile was analyzed. We identified 14 proteins that were expressed differently between samples that were treated and not treated with peroxide; these proteins are potentially involved in the rhamnolipid production/secretion pathway and oxidative stress.
Assuntos
Proteínas de Bactérias/metabolismo , Glicolipídeos/biossíntese , Estresse Oxidativo , Proteoma/metabolismo , Pseudomonas aeruginosa/metabolismo , Fatores de Virulência/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Eletroforese em Gel Bidimensional , Endopeptidases/química , Endopeptidases/genética , Endopeptidases/metabolismo , Regulação Bacteriana da Expressão Gênica , Elastase Pancreática/química , Elastase Pancreática/genética , Elastase Pancreática/metabolismo , Proteoma/química , Proteoma/genética , Pseudomonas aeruginosa/química , Pseudomonas aeruginosa/enzimologia , Pseudomonas aeruginosa/genética , Fatores de Virulência/química , Fatores de Virulência/genéticaRESUMO
Rhamnolipids have been pointed out as promising biosurfactants. The most studied microorganisms for the aerobic production of these molecules are the bacteria of the genus Pseudomonas. The aim of this work was to produce a rhamnolipid-type biosurfactant in a bench-scale bioreactor by one strain of Pseudomonas aeruginosa isolated from oil environments. To study the microorganism growth and production dependency on oxygen, a nondispersive oxygenation device was developed, and a programmable logic controller (PLC) was used to set the dissolved oxygen (DO) concentration. Using the data stored in a computer and the predetermined characteristics of the oxygenation device, it was possible to evaluate the oxygen uptake rate (OUR) and the specific OUR (SOUR) of this microorganism. These rates, obtained for some different DO concentrations, were then compared to the bacterial growth, to the carbon source consumption, and to the rhamnolipid and other virulence factors production. The SOUR presented an initial value of about 60.0 mgO(2)/g(DW) h. Then, when the exponential growth phase begins, there is a rise in this rate. After that, the SOUR reduces to about 20.0 mgO(2)/g(DW) h. The carbon source consumption is linear during the whole process.