Characterization of genes for an alternative nitrogenase in the cyanobacterium Anabaena variabilis.

摘要: Abstract Anabaena variabilis ATCC 29413 is a heterotrophic, nitrogen-fixing cyanobacterium that has been reported to fix nitrogen and reduce acetylene ethane in the absence of molybdenum. DNA from this strain hybridized well at low stringency nitrogenase 2 (vnfDGK) genes Azotobacter vinelandii. The hybridizing region was cloned lambda EMBL3 genomic library A. variabilis, mapped, sequenced. deduced amino acid sequences vnfD vnfK showed only about 56% similarity nifDK Anabaena sp. PCC 7120 but were 76 86% similar anfDK or vnfDK organization vnf gene cluster However, vnfG fused vnfD; hence, designated vnfDG. A vnfH not contiguous with vnfDG yet identified. mutant strain, which neomycin resistance cassette inserted into cluster, grew medium lacking source fixed presence molybdenum poorly when vanadium replaced In contrast, parent equally media containing either vanadium. transcribed molybdenum, without did hybridize chromosomal heterotrophic strains, Nostoc Mac 29150. ClaI fragment very size present isolated several independent, cultured isolates Azolla symbiosis.