title: The freshwater sponge Ephydatia fluviatilis harbours diverse Pseudomonas species (Gammaproteobacteria, Pseudomonadales) with broad-spectrum antimicrobial activity.
abstract: Bacteria are believed to play an important role in the fitness and biochemistry of sponges (Porifera). Pseudomonas species (Gammaproteobacteria, Pseudomonadales) are capable of colonizing a broad range of eukaryotic hosts, but knowledge of their diversity and function in freshwater invertebrates is rudimentary. We assessed the diversity, structure and antimicrobial activities of Pseudomonas spp. in the freshwater sponge Ephydatia fluviatilis. Polymerase Chain Reaction--Denaturing Gradient Gel Electrophoresis (PCR-DGGE) fingerprints of the global regulator gene gacA revealed distinct structures between sponge-associated and free-living Pseudomonas communities, unveiling previously unsuspected diversity of these assemblages in freshwater. Community structures varied across E. fluviatilis specimens, yet specific gacA phylotypes could be detected by PCR-DGGE in almost all sponge individuals sampled over two consecutive years. By means of whole-genome fingerprinting, 39 distinct genotypes were found within 90 fluorescent Pseudomonas isolates retrieved from E. fluviatilis. High frequency of in vitro antibacterial (49%), antiprotozoan (35%) and anti-oomycetal (32%) activities was found among these isolates, contrasting less-pronounced basidiomycetal (17%) and ascomycetal (8%) antagonism. Culture extracts of highly predation-resistant isolates rapidly caused complete immobility or lysis of cells of the protozoan Colpoda steinii. Isolates tentatively identified as P. jessenii, P. protegens and P. oryzihabitans showed conspicuous inhibitory traits and correspondence with dominant sponge-associated phylotypes registered by cultivation-independent analysis. Our findings suggest that E. fluviatilis hosts both transient and persistent Pseudomonas symbionts displaying antimicrobial activities of potential ecological and biotechnological value.
authors.affiliation: Centre of Marine Sciences (CCMAR), University of Algarve, Faro, Algarve, Portugal ; Department of Microbial Ecology, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands.
authors.forename: Tina
authors.initials: T
authors.lastname: Keller-Costa
authors.affiliation: Department of Ecology and Biodiversity, Utrecht University, Utrecht, The Netherlands.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Jousset
authors.affiliation: Plant Research International, Wageningen University and Research Centre, Wageningen, The Netherlands.
authors.forename: Leo
authors.initials: L
authors.lastname: van Overbeek
authors.affiliation: Department of Microbial Ecology, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands.
authors.forename: Jan Dirk
authors.initials: JD
authors.lastname: van Elsas
authors.affiliation: Department of Microbial Ecology, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands ; Microbial Ecology and Evolution Research Group, Centre of Marine Sciences (CCMAR), University of Algarve, Faro, Algarve, Portugal.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Costa
mesh_terms: D000818:Animals; D000898:Antibiosis; D018441:Biofilms; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D005838:Genotype; D016013:Likelihood Functions; D008826:Microbial Sensitivity Tests; D015999:Multivariate Analysis; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011161:Porifera / Q000382:microbiology*; D025341:Principal Component Analysis; D011549:Pseudomonas / Q000502:physiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013045:Species Specificity
chemical_list: D012336:RNA, Ribosomal, 16S