title: Interspecific diversity reduces and functionally substitutes for intraspecific variation in biofilm communities.
abstract: Diversity has a key role in the dynamics and resilience of communities and both interspecific (species) and intraspecific (genotypic) diversity can have important effects on community structure and function. However, a critical and unresolved question for understanding the ecology of a community is to what extent these two levels of diversity are functionally substitutable? Here we show, for a mixed-species biofilm community composed of Pseudomonas aeruginosa, P. protegens and Klebsiella pneumoniae, that increased interspecific diversity reduces and functionally substitutes for intraspecific diversity in mediating tolerance to stress. Biofilm populations generated high percentages of genotypic variants, which were largely absent in biofilm communities. Biofilms with either high intra- or interspecific diversity were more tolerant to SDS stress than biofilms with no or low diversity. Unexpectedly, genotypic variants decreased the tolerance of biofilm communities when experimentally introduced into the communities. For example, substituting P. protegens wild type with its genotypic variant within biofilm communities decreased SDS tolerance by twofold, apparently due to perturbation of interspecific interactions. A decrease in variant frequency was also observed when biofilm populations were exposed to cell-free effluents from another species, suggesting that extracellular factors have a role in selection against the appearance of intraspecific variants. This work demonstrates the functional substitution of inter- and intraspecific diversity for an emergent property of biofilms. It also provides a potential explanation for a long-standing paradox in microbiology, in which morphotypic variants are common in laboratory grown biofilm populations, but are rare in diverse, environmental biofilm communities.
authors.affiliation: Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore.|School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
authors.forename: Kai Wei
authors.initials: KW
authors.lastname: Kelvin Lee
authors.affiliation: Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore.|Interdisciplinary Graduate School, Nanyang Technological University, Singapore, Singapore.
authors.forename: Joey Kuok
authors.initials: JK
authors.lastname: Hoong Yam
authors.affiliation: Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore.|School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
authors.forename: Manisha
authors.initials: M
authors.lastname: Mukherjee
authors.affiliation: Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore.
authors.forename: Saravanan
authors.initials: S
authors.lastname: Periasamy
authors.affiliation: Advanced Environmental Biotechnology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, Singapore, Singapore.|Centre for Marine Bio-Innovation, University of New South Wales, Sydney, NSW, Australia.|School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia.|Sydney Institute of Marine Science, Mosman, NSW, Australia.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Steinberg
authors.affiliation: Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore.|School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.|Centre for Marine Bio-Innovation, University of New South Wales, Sydney, NSW, Australia.|School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia.
authors.forename: Staffan
authors.initials: S
authors.lastname: Kjelleberg
authors.affiliation: Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore.|School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.|Centre for Marine Bio-Innovation, University of New South Wales, Sydney, NSW, Australia.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Rice
mesh_terms: D000220:Adaptation, Biological; D044822:Biodiversity; D018441:Biofilms; D018432:Drug Resistance, Multiple; D005838:Genotype; D007711:Klebsiella pneumoniae / Q000502:physiology*; D011549:Pseudomonas / Q000145:classification / Q000502:physiology*; D011550:Pseudomonas aeruginosa / Q000502:physiology*