title: Commensal interactions in a dual-species biofilm exposed to mixed organic compounds.
abstract: There is limited knowledge of interspecies interactions in biofilm communities. In this study, Pseudomonas sp. strain GJ1, a 2-chloroethanol (2-CE)-degrading organism, and Pseudomonas putida DMP1, a p-cresol-degrading organism, produced distinct biofilms in response to model mixed waste streams composed of 2-CE and various p-cresol concentrations. The two organisms maintained a commensal relationship, with DMP1 mitigating the inhibitory effects of p-cresol on GJ1. A triple-labeling technique compatible with confocal microscopy was used to investigate the influence of toxicant concentrations on biofilm morphology, species distribution, and exopolysaccharide production. Single-species biofilms of GJ1 shifted from loosely associated cell clusters connected by exopolysaccharide to densely packed structures as the p-cresol concentrations increased, and biofilm formation was severely inhibited at high p-cresol concentrations. In contrast, GJ1 was abundant when associated with DMP1 in a dual-species biofilm at all p-cresol concentrations, although at high p-cresol concentrations it was present only in regions of the biofilm where it was surrounded by DMP1. Evidence in support of a commensal relationship between DMP1 and GJ1 was obtained by comparing GJ1-DMP1 biofilms with dual-species biofilms containing GJ1 and Escherichia coli ATCC 33456, an adhesive strain that does not mineralize p-cresol. Additionally, the data indicated that only tower-like cell structures in the GJ1-DMP1 biofilm produced exopolysaccharide, in contrast to the uniform distribution of EPS in the single-species GJ1 biofilm.
authors.affiliation: University of California Joint Bioengineering Graduate Program, Berkeley, California 94720, USA.
authors.forename: S E
authors.initials: SE
authors.lastname: Cowan
authors.forename: E
authors.initials: E
authors.lastname: Gilbert
authors.forename: D
authors.initials: D
authors.lastname: Liepmann
authors.forename: J D
authors.initials: JD
authors.lastname: Keasling
mesh_terms: D018441:Biofilms; D001711:Biotransformation; D018920:Coculture Techniques; D003408:Cresols / Q000378:metabolism*; D005018:Ethyl Chloride / Q000031:analogs & derivatives* / Q000378:metabolism*; D007700:Kinetics; D018613:Microscopy, Confocal; D011549:Pseudomonas / Q000254:growth & development* / Q000378:metabolism; D016958:Pseudomonas putida / Q000254:growth & development* / Q000378:metabolism; D013386:Succinates / Q000378:metabolism
chemical_list: D003408:Cresols; D013386:Succinates; C032538:4-cresol; D005018:Ethyl Chloride