EFFECT OF POLY(3-HYDROXYBUTYRATE) ON BIOFILM FORMATION UNDER COLD CONDITIONS IN THE NOVEL ANTARCTIC SPECIES PSEUDOMONAS EXTREMAUSTRALIS

PAULA M. TRIBELLI; LAURA J. RAIGER IUSTMAN; NANCY I. LOPEZ

Seattle

Simposio; 13th International Symposium on Microbial Ecology; 2010

ISME

P. extremaustralis is an Antarctic strain, capable of synthesizing polyhydroxyalkanoates (PHAs) in the form of polyhydroxybutyrate (PHB). Previous studies have shown that PHA is essential to grow under cold conditions and to cope with the oxidative stress. In this study we hypothesized that PHB producing strains can be found in cold environments in both planktonic and biofilms, while mutant strains unable to synthesize it can only withstand with oxidative stress derived from cold in the biofilm state. P. extremaustralis and its PHB minus (phaC) mutant were used to asses the effect of PHB accumulation on biofilm formation capability under low temperature (10°C). We also analyzed cold survival in a planktonic reducing environment (low oxygen content). Surface attachment of the strains was evaluated using a microtiter assay. Number of viable cells of wild type strain was similar in both biofilm and planktonic state. By contrast, the mutant was able to survive in the sessile form in cold. We performed liquid cultures under 3 different aeration conditions using Erlenmeyer flasks and hermetically sealed bottles in order to analyze the effect of the oxygen level on growth under cold conditions. Both strains showed similar growth at room temperature but at 10°C, while the wild type grew in all oxygen conditions, the mutant only grew in microaerobiosis, showing that in reducing environments mutant strain was able to solve the PHB deficiency. Complementation of the mutant strain with phaC restored the wild-type phenotype in all the experiments. Under biofilm life style, cells are protected against many environmental stressors and our results suggest that in this state the PHB mutant could avoid the redox imbalance, alleviating the oxidative stress. PHB allowed the survival of the wild type strain in both planktonic and biofilm states increasing its capability to colonize different habitats. Other advantages related with biofilm life style could also be involved.