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Front. Microbiol. | doi: 10.3389/fmicb.2018.00021

Synergistic interactions in microbial biofilms facilitate the establishment of opportunistic pathogenic fungi in household dishwashers

  • 1Biotechnical Faculty, University of Ljubljana, Slovenia
  • 2University of Copenhagen, Denmark
  • 3Ghent University, Belgium

Biofilms formed on rubber seals in dishwashers harbour diverse microbiota. In this study, we focussed on the microbial composition of bacteria and fungi, isolated from a defined area of one square centimetre of rubber from four domestic dishwashers and assessed their abilities to in-vitro multispecies biofilm formation. A total of 80 isolates (64 bacterial and 16 fungal) were analysed. Multiple combinations of bacterial isolates from each dishwasher were screened for synergistic interactions. 32 out of 140 tested (23%) four-species bacterial combinations displayed consistent synergism leading to an overall increase in biomass, in all experimental trails. Bacterial isolates from two of the four dishwashers generated a high number of synergistically interacting four-species consortia. Network based correlation analyses also showed higher co-occurrence patterns observed between bacterial members in the same two dishwasher samples, indicating cooperative effects. Furthermore, two synergistic 4-species bacterial consortia were tested for their abilities to incorporate an opportunistic fungal pathogen, Exophiala dermatitidis and their establishment as biofilms on sterile ethylene propylene diene monomer M-class (EPDM) rubber and polypropylene (PP) surfaces. When the bacterial consortia included E. dermatitidis, the overall cell numbers of both bacteria and fungi increased and a substantial increase in biofilm biomass was observed. These results indicate a novel phenomenon of cross kingdom synergy in biofilm formation and these observations could have potential implications for human health.

Keywords: Synergism, Biofilm formation, EPDM, Exophiala dermatitidis, Dishwashers, Multispecies biofilm

Received: 07 Nov 2017; Accepted: 05 Jan 2018.

Edited by:

Satoshi Tsuneda, Waseda University, Japan

Reviewed by:

Dong Li, University of California, Santa Barbara, United States
Dieter M. Tourlousse, National Institute of Advanced Industrial Science and Technology, Japan  

Copyright: © 2018 Zupančič, Raghupathi, Houf, Burmølle, Sørensen and Gunde - Cimerman. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Mr. Prem K. Raghupathi, University of Copenhagen, Copenhagen, Denmark, prem.raghupathi@bio.ku.dk
Prof. Nina Gunde - Cimerman, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia, nina.gunde-cimerman@bf.uni-lj.si