Affiliation:
1. Department of Plant and Environmental Sciences, Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem 91904, Israel
2. Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, Massachusetts 02543
Abstract
ABSTRACT
Cyanobacteria of the genera
Synechococcus
and
Prochlorococcus
are the most abundant photosynthetic organisms on earth, occupying a key position at the base of marine food webs. The
cynS
gene that encodes cyanase was identified among bacterial, fungal, and plant sequences in public databases, and the gene was particularly prevalent among cyanobacteria, including numerous
Prochlorococcus
and
Synechococcus
strains. Phylogenetic analysis of
cynS
sequences retrieved from the Global Ocean Survey database identified >60% as belonging to unicellular marine cyanobacteria, suggesting an important role for cyanase in their nitrogen metabolism. We demonstrate here that marine cyanobacteria have a functionally active cyanase, the transcriptional regulation of which varies among strains and reflects the genomic context of
cynS
. In
Prochlorococcus
sp. strain MED4,
cynS
was presumably transcribed as part of the
cynABDS
operon, implying cyanase involvement in cyanate utilization. In
Synechococcus
sp. strain WH8102, expression was not related to nitrogen stress responses and here cyanase presumably serves in the detoxification of cyanate resulting from intracellular urea and/or carbamoyl phosphate decomposition. Lastly, we report on a cyanase activity encoded by
cynH
, a novel gene found in marine cyanobacteria only. The presence of dual cyanase genes in the genomes of seven marine
Synechococcus
strains and their respective roles in nitrogen metabolism remain to be clarified.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
43 articles.
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