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Open Access Highly Accessed Research article

Genome-derived insights into the biology of the hepatotoxic bloom-forming cyanobacterium Anabaena sp. strain 90

Hao Wang1, Kaarina Sivonen1*, Leo Rouhiainen1, David P Fewer1, Christina Lyra1, Anne Rantala-Ylinen1, Johanna Vestola1, Jouni Jokela1, Kaisa Rantasärkkä1, Zhijie Li2 and Bin Liu3

Author affiliations

1 Department of Food and Environmental Sciences, University of Helsinki, Helsinki, FIN-00014, Finland

2 BGI LifeTech Co., Ltd., Beijing, China

3 Center of Systematic Genomics, Xinjiang Institute of Ecology and Geography/Institute of Oceanology, Chinese Academy of Sciences, 818 South Beijing Road Urumqi, 830011, Xinjiang, China

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Citation and License

BMC Genomics 2012, 13:613  doi:10.1186/1471-2164-13-613

Published: 13 November 2012

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.

Keywords:
Cyanobacteria; Anabaena; Mobile genetic elements; Insertion sequences; Biosynthetic gene clusters; Restriction-modification system; nifH excision element