Extracellular polymeric substances diversity of biofilms grown under contrasted environmental conditions

Extracellular Polymeric Substances (EPS) analysis was undertaken on three biofilms grown under different feeding conditions and offering diverging microbial activities and structural characteristics. EPS were extracted by a multi-method protocol including sonication, Tween and EDTA treatments and were characterized by size exclusion chromatography (SEC). Tween and sonication extracts presented higher EPS size diversity compared to EDTA extracts. EPS size diversity also increased with microbial functions within the biofilms and a specific 25–50 kDa cluster was identified only in extracts from biofilms presenting autotrophic activity. Another specific size cluster (180 kDa) occurred in Tween extracts provided from the mechanically stable biofilms. Such specific EPS appear as potential indicators for describing microbial and structural properties of biofilms.This study brings new elements for designing EPS fractionation and shows that size distribution analysis is an interesting tool to relate EPS diversity with macro-scale characteristics of biofilms.

Research highlights
► This study investigated molecular aspects of mature thick biofilms performing heterotrophic and heterotrophic–autotrophic activities.
► EPS size characteristics seemed to be related to biological activities measured inside the biofilm.
► Results highlight the importance of extraction methods in qualitative investigations of EPS.
► Tween extraction provided the less EPS but brought interesting qualitative information.
► A particular EPS size fraction, potentially hydrophobic, could be associated to biofilm cohesiveness.