title: Genome-derived insights into the biology of the hepatotoxic bloom-forming cyanobacterium Anabaena sp. strain 90.
abstract: BACKGROUND
  Cyanobacteria can form massive toxic blooms in fresh and brackish bodies of water and are frequently responsible for the poisoning of animals and pose a health risk for humans. Anabaena is a genus of filamentous diazotrophic cyanobacteria commonly implicated as a toxin producer in blooms in aquatic ecosystems throughout the world. The biology of bloom-forming cyanobacteria is poorly understood at the genome level.
  
  
  RESULTS
  Here, we report the complete sequence and comprehensive annotation of the bloom-forming Anabaena sp. strain 90 genome. It comprises two circular chromosomes and three plasmids with a total size of 5.3 Mb, encoding a total of 4,738 genes. The genome is replete with mobile genetic elements. Detailed manual annotation demonstrated that almost 5% of the gene repertoire consists of pseudogenes. A further 5% of the genome is dedicated to the synthesis of small peptides that are the products of both ribosomal and nonribosomal biosynthetic pathways. Inactivation of the hassallidin (an antifungal cyclic peptide) biosynthetic gene cluster through a deletion event and a natural mutation of the buoyancy-permitting gvpG gas vesicle gene were documented. The genome contains a large number of genes encoding restriction-modification systems. Two novel excision elements were found in the nifH gene that is required for nitrogen fixation.
  
  
  CONCLUSIONS
  Genome analysis demonstrated that this strain invests heavily in the production of bioactive compounds and restriction-modification systems. This well-annotated genome provides a platform for future studies on the ecology and biology of these important bloom-forming cyanobacteria.
authors.affiliation: Department of Food and Environmental Sciences, University of Helsinki, Helsinki, FIN-00014, Finland.
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.forename: Kaarina
authors.initials: K
authors.lastname: Sivonen
authors.forename: Leo
authors.initials: L
authors.lastname: Rouhiainen
authors.forename: David P
authors.initials: DP
authors.lastname: Fewer
authors.forename: Christina
authors.initials: C
authors.lastname: Lyra
authors.forename: Anne
authors.initials: A
authors.lastname: Rantala-Ylinen
authors.forename: Johanna
authors.initials: J
authors.lastname: Vestola
authors.forename: Jouni
authors.initials: J
authors.lastname: Jokela
authors.forename: Kaisa
authors.initials: K
authors.lastname: Rantasärkkä
authors.forename: Zhijie
authors.initials: Z
authors.lastname: Li
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
mesh_terms: D017033:Anabaena / Q000235:genetics* / Q000821:virology; D001483:Base Sequence; D053898:Biosynthetic Pathways / Q000235:genetics; D002874:Chromosome Mapping; D004251:DNA Transposable Elements / Q000235:genetics; D005786:Gene Expression Regulation / Q000235:genetics; D016680:Genome, Bacterial / Q000235:genetics*; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D039002:Prophages / Q000235:genetics; D011544:Pseudogenes / Q000235:genetics; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000235:genetics
chemical_list: D004251:DNA Transposable Elements