title: Interactions of Freshwater Cyanobacteria with Bacterial Antagonists.
abstract: Cyanobacterial and algal mass development, or blooms, have severe effects on freshwater and marine systems around the world. Many of these phototrophs produce a variety of potent toxins, contribute to oxygen depletion, and affect water quality in several ways. Coexisting antagonists, such as cyanolytic bacteria, hold the potential to suppress, or even terminate, such blooms, yet the nature of this interaction is not well studied. We isolated 31 cyanolytic bacteria affiliated with the generaPseudomonas,Stenotrophomonas,Acinetobacter, andDelftiafrom three eutrophic freshwater lakes in Sweden and selected four phylogenetically diverse bacterial strains with strong-to-moderate lytic activity. To characterize their functional responses to the presence of cyanobacteria, we performed RNA sequencing (RNA-Seq) experiments on coculture incubations, with an initial predator-prey ratio of 1:1. Genes involved in central cellular pathways, stress-related heat or cold shock proteins, and antitoxin genes were highly expressed in both heterotrophs and cyanobacteria. Heterotrophs in coculture expressed genes involved in cell motility, signal transduction, and putative lytic activity. l,d-Transpeptidase was the only significantly upregulated lytic gene inStenotrophomonas rhizophilaEK20. Heterotrophs also shifted their central metabolism from the tricarboxylic acid cycle to the glyoxylate shunt. Concurrently, cyanobacteria clearly show contrasting antagonistic interactions with the four tested heterotrophic strains, which is also reflected in the physical attachment to their cells. In conclusion, antagonistic interactions with cyanobacteria were initiated within 24 h, and expression profiles suggest varied responses for the different cyanobacteria and studied cyanolytes.IMPORTANCEHere, we present how gene expression profiles can be used to reveal interactions between bloom-forming freshwater cyanobacteria and antagonistic heterotrophic bacteria. Species-specific responses in both heterotrophs and cyanobacteria were identified. The study contributes to a better understanding of the interspecies cellular interactions underpinning the persistence and collapse of cyanobacterial blooms.
authors.affiliation: Department of Ecology and Genetics, Limnology, and Science for Life Laboratory, Uppsala University, Uppsala, Sweden omnabdel@gmail.com Stebe@ebc.uu.se.
authors.forename: Omneya Ahmed
authors.initials: OA
authors.lastname: Osman
authors.affiliation: Leibniz Institute for Baltic Sea Research, Warnemünde, Germany.
authors.forename: Sara
authors.initials: S
authors.lastname: Beier
authors.affiliation: Department of Medical Microbiology and Biochemistry, Bioinformatics Infrastructure for Life Sciences, and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Manfred
authors.initials: M
authors.lastname: Grabherr
authors.affiliation: Department of Ecology and Genetics, Limnology, and Science for Life Laboratory, Uppsala University, Uppsala, Sweden omnabdel@gmail.com Stebe@ebc.uu.se.
authors.forename: Stefan
authors.initials: S
authors.lastname: Bertilsson
mesh_terms: D000150:Acinetobacter / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D000898:Antibiosis; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D018407:Bacterial Physiological Phenomena; D001427:Bacterial Toxins / Q000378:metabolism; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005068:Eutrophication; D005618:Fresh Water / Q000382:microbiology*; D020869:Gene Expression Profiling; D006360:Heat-Shock Proteins / Q000235:genetics; D060106:Lakes / Q000382:microbiology; D010802:Phylogeny; D011549:Pseudomonas / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012336:RNA, Ribosomal, 16S; D017423:Sequence Analysis, RNA; D013548:Sweden; D014871:Water Microbiology
chemical_list: D001427:Bacterial Toxins; D006360:Heat-Shock Proteins; D012336:RNA, Ribosomal, 16S
keywords: coculture interaction; cyanobacteria; metatranscriptome