title: Singlet oxygen, a neglected but important environmental factor: short-term and long-term effects on bacterioplankton composition in a humic lake.
abstract: Photolysis of dissolved organic matter (DOM) leads to contrasting effects on bacterioplankton dynamics, i.e. stimulation and inhibition of bacterial activity. In particular, the role of short-lived reactive oxygen species (ROS), e.g. singlet oxygen (¹O₂), in altering microbial activity and species composition has scarcely been investigated. Therefore, we have artificially increased the natural rate of ¹O₂ formation in short-term (∼4 h) in situ and long-term (72 h) laboratory incubations of surface water samples from a humic acid-rich lake. Denaturing gradient gel electrophoresis (DGGE) patterns revealed significant changes in occurrence of abundant bacterioplankton phylotypes upon ¹O₂ exposure. Cluster analysis of DGGE patterns showed that a moderate increase in ¹O₂ exposure leads to similar changes in different years indicating the establishment of bacterial communities adapted to ¹O₂ exposure. Bacterioplankton phylotypes favoured under these conditions belonged to Betaproteobacteria of the beta II cluster (e.g. Polynucleobacter necessarius) and the beta I cluster related to Limnohabitans (R-BT subcluster) as well as Alphaproteobacteria affiliated to Novosphingobium acidiphilum. In contrast, Actinobacteria of the freshwater acI-B cluster were sensitive even against moderate ¹O₂ exposure. We conclude that ¹O₂ exposure due to DOM photolysis represents an important natural selective factor affecting bacterial species dynamics in aquatic ecosystems in many ways.
authors.affiliation: Department of Microbiology and Molecular Biology, Justus-Liebig-University, Giessen, Germany.
authors.forename: Stefanie P
authors.initials: SP
authors.lastname: Glaeser
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Grossart
authors.forename: Jens
authors.initials: J
authors.lastname: Glaeser
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000254:growth & development*; D004269:DNA, Bacterial / Q000235:genetics; D058645:Denaturing Gradient Gel Electrophoresis; D017753:Ecosystem; D005618:Fresh Water / Q000737:chemistry* / Q000382:microbiology; D006812:Humic Substances; D008969:Molecular Sequence Data; D010802:Phylogeny; D011157:Population Dynamics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D026082:Singlet Oxygen / Q000737:chemistry*; D014871:Water Microbiology
chemical_list: D004269:DNA, Bacterial; D006812:Humic Substances; D012336:RNA, Ribosomal, 16S; D026082:Singlet Oxygen