THE GENOME OF THE FILAMENTOUS NITROGEN‐FIXING, SYMBIOTIC CYANOBACTERIUM NOSTOC PUNCTIFORME

Abstract

Meeks, J.Section of Microbiology, University of California, Davis, CA 95616 USANostoc punctiforme is a terrestrial oxygenic photo‐auto‐ trophic cyanobacterium with a complex life style as exemplified by multiple developmental alternatives of its vegetative cells, its ability to establish a symbiosis with plants, its capacity for facultative heterotrophic growth, and it is amenable to genetic analysis. These multiple phenotypic characteristics are indicative of the breadth of genetic information that is likely to be present in its genome. The shot gun sequencing phase of the more than 9.76 Mb genome of N. punctiforme ATCC 29133 was completed in July, 2000 by the Joint Genome Institute with support of the DOE (http://www.jgi.doe.gov/). Preliminary annotation of a 9.13 Mb database identified 7,432 putative protein encoding ORFs. Seventy‐one percent (5,324) of the putative genes have sequence similarity to previously recognized genes in the current database of all organisms, while twenty‐nine percent (2,164) are unique to N. punctiforme. Forty‐five percent (3,328) of the genes putatively encode proteins with known or probable known function. This latter value is two‐three times the number of known genes in the unicellular cyanobacteria Synechocystis PCC6803 and Synechococcus WH8102. Some of the excess coding capacity in N. punctiforme is seen in multiple members of gene families encoding sensory transduction systems, putative transcriptional regulatory proteins, transporters, transposases and very large multidomain proteins with peptide synthetase and polyketide synthase domains. The genetic potential detectable in the currently unfinished genome of N. punctiforme encompasses nearly all characteristics that define cyanobacteria as a phylogenetic group and the data will be presented in that context.