title: Betaproteobacteria Limnohabitans strains increase fecundity in the crustacean Daphnia magna: symbiotic relationship between major bacterioplankton and zooplankton in freshwater ecosystem.
abstract: How symbioses between bacteria and aquatic animals influence food webs in freshwater ecosystems is a fundamental question in ecology. We investigated symbiosis between a crustacean zooplankton Daphnia magna and its dominant bacterial symbiont Limnohabitans, an abundant and globally distributed freshwater Betaproteobacteria. Aposymbiotic juvenile Daphnia were prepared and exposed to any of four Limnohabitans sp. - Limnohabitans strains DM1, 2KL-3, 2KL-7 and Limnohabitans planktonicus strain II-D5, all previously found in D. magna digestive tract or culture. Re-infected Daphnia were cultured until they produced the first clutch of juveniles. Limnohabitans strain DM1 and L. planktonicus strain II-D5 successfully re-infected Daphnia through single exposure at the first instar juvenile stage. In contrast to aposymbiotic Daphnia that produced non-viable juveniles, re-infected Daphnia produced viable juveniles and increased fecundity to levels of that of symbiotic Daphnia. Re-infected Daphnia did not increase their number of eggs nor growth rates. Limnohabitans strains 2KL-7 and 2KL-3 could not recover fecundity even in multiple exposures during culture. This study shows the functional evidence demonstrating that a single bacterium Limnohabitans regulates fecundity of the consumer Daphnia through symbiosis. Our results indicated that symbiotic relationship between major bacterioplankton and zooplankton is important for maintaining the population of zooplankton in freshwater ecosystems.
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565 0871, Japan.
authors.forename: Saranya
authors.initials: S
authors.lastname: Peerakietkhajorn
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565 0871, Japan.|Frontier Research Base for Global Young Researchers, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565 0871, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Kato
authors.affiliation: Biology Centre CAS, Institute of Hydrobiology, České Budějovice, Czech Republic.
authors.forename: Vojtěch
authors.identifier: 0000-0002-9132-8321
authors.initials: V
authors.lastname: Kasalický
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565 0871, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Matsuura
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565 0871, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D020562:Betaproteobacteria / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology*; D003621:Daphnia / Q000382:microbiology* / Q000502:physiology*; D017753:Ecosystem; D005298:Fertility; D020387:Food Chain; D005618:Fresh Water / Q000382:microbiology; D013559:Symbiosis; D015048:Zooplankton / Q000382:microbiology* / Q000502:physiology*