Metabolic turnover and catalase activity of biofilm of P. fluorescens (ATCC 17552) as related to copper corrosion

NERCESSIAN, DÉBORA; DUVILE, FRANCISCO BERNARDO; DESIMONE, MARIELA; SIMISON, SILVIA; BUSALMEN, JUAN PABLO

WATER RESEARCH

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2010 vol. 44 p. 2592 - 2600

0043-1354

In this work we report the results of a combined biochemical and electrochemical studyaimed to analyze both the growth of biofilms of Pseudomonas fluorescens on copper samplesand its possible role in the instability of the metal/electrolyte interface.DNA and RNA were quantified along the time for biofilms grown on copper and glass toestimate both the growth of the bacterial population and its metabolic state (through theRNA/DNA ratio). The expression and specific activity of catalase were also determined togain insight into their possible role in corrosion acceleration. The electrochemical behaviorof the biofilm/copper interface was monitored by Linear Polarization Resistance (Rp) andelectrochemical impedance spectroscopy (EIS) along the experiments.Results showed a longer lag phase for biofilms developing on copper that includeda period of high metabolic activity (as measured by the RNA/DNA ratio) without biomassgrowth. Biological activity introduced a new time constant at intermediate frequencies inEIS spectra whose capacitive behavior increased with the biofilm development. Theincrement in this biofilm-related signal was accompanied by a strong limitation to chargetransfer through a diffusion controlled process probably due to oxygen exhaustion by cellsrespiration, while the resistance of the interface decreased presumably due to oxidedissolution by local acidification under the colonies. In addition, catalase activity wasfound to be high in mature copper-tolerant biofilms, which differentially express a catalaseisoform not present in biofilms growing on glass.