Unravelling the interactions among microbial populations found in activated sludge during biofilm formation.
Microorganisms colonize surfaces and develop biofilms through interactions that are not yet thoroughly understood, with important implications for water and wastewater systems. This study investigated the interactions between N-acyl homoserine lactone (AHL)-producing bacteria, yeasts and protists, and their contribution to biofilm development. Sixty-one bacterial strains were isolated from activated sludge and screened for AHL production, with Aeromonas sp. found to be the dominant AHL producer. Shewanella xiamenensis, Aeromonas allosaccharophila, Acinetobacter junii and Pseudomonas aeruginosa recorded the highest adherence capabilities, with S. xiamenensis being the most effective in surface colonization. Additionally, highly significant interactions (i.e. synergic or antagonistic) were described for dual and multistrain mixtures of bacterial strains (P. aeruginosa, S. xiamenensis, A. junii and Pseudomonas stutzeri), as well as for strongly adherent bacteria co-cultured with yeasts. In this last case, the adhered biomass in co-cultures was lower than the monospecific biofilms of bacteria and yeast, with biofilm observations by microscopy suggesting that bacteria had an antagonist effect on the whole or part of the yeast population. Finally, protist predation by Euplotes sp. and Paramecium sp. on Aeromonas hydrophila biofilms not only failed to reduce biofilm formation, but also recorded unexpected results leading to the development of aggregates of high density and complexity.
Department of Microbiology III, Faculty of Biology, Complutense University of Madrid, José Antonio Novais 12, 28040 Madrid, Spain Division of Water Environment Technology, Department of Civil and Environmental Engineering, Chalmers University of Technology, Sven Hultins gata 8, 412 96 Gothenburg, Sweden raquel.liebana@chalmers.se.
Raquel
R
Liébana
Department of Microbiology III, Faculty of Biology, Complutense University of Madrid, José Antonio Novais 12, 28040 Madrid, Spain.
Lucía
L
Arregui
Department of Microbiology III, Faculty of Biology, Complutense University of Madrid, José Antonio Novais 12, 28040 Madrid, Spain.
Antonio
A
Santos
Department of Applied Mathematics (Biomathematics), Faculty of Biology, Complutense University of Madrid, José Antonio Novais 12, 28040 Madrid, Spain.
Antonio
A
Murciano
Department of Microbiology III, Faculty of Biology, Complutense University of Madrid, José Antonio Novais 12, 28040 Madrid, Spain.
Domingo
D
Marquina
Department of Microbiology III, Faculty of Biology, Complutense University of Madrid, José Antonio Novais 12, 28040 Madrid, Spain.
Susana
S
Serrano
D054742:Acyl-Butyrolactones / Q000378:metabolism*; D001419:Bacteria / Q000302:isolation & purification / Q000378:metabolism; D001422:Bacterial Adhesion; D018407:Bacterial Physiological Phenomena; D018441:Biofilms / Q000254:growth & development*; D056265:Microbial Interactions; D012722:Sewage / Q000382:microbiology*; D015003:Yeasts / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology
D054742:Acyl-Butyrolactones; D012722:Sewage
AHL-producing bacteria; biofilms; predation; protist; quorum sensing; yeast