Influence of the adherent population level on biofilm population, structure and resistance to chlorination

Abstract

The aim of this work was to study the influence of adherent population level on biofilm development, either on biofilm population, or on its structure. Our results, obtained from 13 strains isolated from dairy industries environments, demonstrated that, on the whole, Gram-negative bacteria were, although not significantly, globally more adherent to glass than Gram-positive ones (total mean of 6·1 and 5·7 log cfu cm−2respectively for an inoculum of 8 log cfu ml−1). Gram-negative bacteria also exhibited a significantly higher biofilm population after 2 days of culture than Gram-positives (7·0 and 6·3 log cfu cm−2respectively) and a significant correlation between adhesion ability and biofilm population was seen. Elsewhere, we demonstrated that the level of adherent population did not influence biofilm biomass after 2 days of culture, although it strikingly influenced the biofilm structure. Biofilm resistance to chlorine was significantly increased with age of biofilm (2 log order after 1 day of culture and less than 1 log order after 3 days), but not by its structure.