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Journal of Bacteriology, December 2001, p. 6841-6851, Vol. 183, No. 23
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.23.6841-6851.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

HcwA, an Autolysin, Is Required for Heterocyst Maturation in Anabaena sp. Strain PCC 7120

Jinsong Zhu,dagger Karin Jäger, Todd Black,Dagger Kelly Zarka,§ Olga Koksharova,|| and C. Peter Wolk*

MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824

Received 6 June 2001/Accepted 12 September 2001

In many filamentous cyanobacteria, vegetative cells can differentiate into heterocysts, cells that are specialized for aerobic fixation of N2. Synthesis of the heterocyst envelope polysaccharide is dependent on the gene hepA in Anabaena sp. strain PCC 7120. In search of genes that are involved in the regulation of hepA, we transposon mutagenized strain DR1069, which bears a chromosomal hepA::luxAB fusion. One resulting mutant, designated HNL3, grows normally in medium with nitrate and shows poor induction of hepA in response to nitrogen deprivation. In HNL3, transposon Tn5-1058 is inserted within gene hcwA, a constitutively expressed open reading frame whose predicted product resembles N-acetylmuramoyl-L-alanine amidases. Reconstruction of the mutation confirmed that the mutant phenotype resulted from the insertion of the transposon. The induction of hepA in HNL3 is partially restored upon recombination of HNL3 with plasmid-borne, wild-type hcwA. Moreover, HcwA expressed in Escherichia coli exhibits wall-lytic activity. These results suggest that the degradation, or possibly reconstruction, of the cell peptidoglycan layer is a prerequisite for heterocyst maturation.

* Corresponding author. Mailing address: MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824. Phone: (517) 353-2049. Fax: (517) 353-9168. E-mail: wolk{at}msu.edu.

dagger Present address: Department of Entomology, Michigan State University, East Lansing, MI 48824.

Dagger Present address: Schering-Plough Research Institute, Kenilworth, NJ 07033-0539.

§ Present address: Department of Crop and Soil Sciences, Michigan State University, East Lansing, MI 48824.

|| Permanent address: N. Vavilov Institute of General Genetics, Moscow 117809, Russia.

Journal of Bacteriology, December 2001, p. 6841-6851, Vol. 183, No. 23
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.23.6841-6851.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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