Persister cells in Pseudomonas fluorescens biofilms treated with a biocide

• Author(s): Simões, M. ; Vieira, M. J.
• Date: 2009
• Persistent ID: http://hdl.handle.net/1822/9711
• Origin: RepositóriUM - Universidade do Minho
• Subject(s): Biofilm control; Ortho-phtalaldehyde; Persistence; Phenotypic changes; Recovery
• Document Type: Conference Object
• Language: English

Description

This study investigates the physiology and the behavior, after treatment with ortho-phtalaldehyde (OPA), of Pseudomonas fluorescens in both planktonic and sessile states. Steady-state biofilms and planktonic cells were collected from a bioreactor rotating system and their extracelular polymeric substances (EPS) were extracted using a non-invasive method. The cell physiology was compared in terms of respiratory activity, morphology, amount of cell proteins and polysaccharides and outer membrane proteins expression. Significant differences were found when comparing the physiological parameters analysed. Planktonic cells were more metabolically active, and were composed by a higher amount of proteins and polysaccharides than biofilm cells. Moreover, the biofilm formation process promoted the expression of distinct OMP. Additional experiments were performed in order to compare the susceptibility of planktonic and biofilm cells to OPA. That cells were completely inactivated after biocide exposure (minimum bactericidal concentration - MBC = 0.65 ± 0.20 mM – planktonic cells; MBC = 1.5 ± 0.25 mM – biofilm cells). After treatment, the potential of inactivated cells to recover from antimicrobial exposure was evaluated. Planktonic cells remained inactivated while cells from biofilms recovered (from an initial population of log 9.0 ± 0.21 cells/mL of inactivated bacteria it was verified a final population of log 3.3 ± 0.35 cells/mL of viable bacteria). This result indicates the possibility of existence of persister cells in the biofilm population and the extreme ability of biofilm bacteria to recover from inauspicious situations, even in the absence of EPS.