Genes coding for hepatotoxic heptapeptides (microcystins) in the cyanobacterium Anabaena strain 90.

The cluster of microcystin synthetase genes from Anabaena strain 90 was sequenced and characterized. The total size of the region is 55.4 kb, and the genes are organized in three putative operons.

Heterocyst-specific expression of patB, a gene required for nitrogen fixation in Anabaena sp. strain PCC 7120.

The patB gene product is required for growth and survival of the filamentous cyanobacterium Anabaena sp. strain PCC 7120 in the absence of combined nitrogen. A patB::gfp fusion demonstrated that this gene is expressed exclusively in heterocysts.

The role of HetN in maintenance of the heterocyst pattern in Anabaena sp. PCC 7120.

The gene hetN encodes a putative oxidoreductase that is known to suppress heterocyst differentiation when present on a multicopy plasmid in Anabaena sp. PCC 7120. To mimic the hetN null phenotype and to examine where HetN acts in the regulatory cascade that controls heterocyst differentiation, we replaced the native chromosomal hetN promoter with the copper-inducible petE promoter.

Expression of the Anabaena hetR gene from a copper-regulated promoter leads to heterocyst differentiation under repressing conditions.

Heterocyst differentiation in the filamentous cyanobacterium Anabaena PCC 7120 requires a functional hetR gene. Increased expression of the hetR gene is seen in developing and mature heterocysts in response to fixed nitrogen limitation. We mapped four likely transcriptional start sites for hetR and identified a specific transcript that is positively autoregulated.

Genes encoding synthetases of cyclic depsipeptides, anabaenopeptilides, in Anabaena strain 90.

Anabaena strain 90 produces three hepatotoxic heptapeptides (microcystins), two seven-residue depsipeptides called anabaenopeptilide 90A and 90B, and three six-residue peptides called anabaenopeptins. The anabaenopeptilides belong to a group of cyanobacterial depsipeptides that share the structure of a six-amino-acid ring with a side-chain. Despite their similarity to known cyclic peptide toxins, no function has been assigned to the anabaenopeptilides.

The hglK gene is required for localization of heterocyst-specific glycolipids in the cyanobacterium Anabaena sp. strain PCC 7120.

Mutant strain 543 of the cyanobacterium Anabaena sp. strain PCC 7120 was originally isolated as a Fox- mutant following chemical mutagenesis. Ultrastructural analysis shows that in nitrogen-replete media the vegetative cells of the mutant are more cylindrical and have thicker septa than those of the wild type, while in nitrogen-free media the mutant heterocysts lack the normal glycolipid layer external to the cell wall.

Characterization of toxin-producing cyanobacteria by using an oligonucleotide probe containing a tandemly repeated heptamer.

Cyanobacteria produce toxins that kill animals. The two main classes of cyanobacterial toxins are cyclic peptides that cause liver damage and alkaloids that block nerve transmission. Many toxin-producing strains from Finnish lakes were brought into axenic culture, and their toxins were characterized.

A short-filament mutant of Anabaena sp. strain PCC 7120 that fragments in nitrogen-deficient medium.

Strain 129 is a fragmentation mutant of the filamentous cyanobacterium Anabaena sp. strain PCC 7120. Growing with fixed nitrogen, this mutant forms filaments that are much shorter than wild-type filaments.

Molecular cloning and expression of the gene encoding ADP-glucose pyrophosphorylase from the cyanobacterium Anabaena sp. strain PCC 7120.

Previous studies have indicated that ADP-glucose pyrophosphorylase (ADPGlc PPase) from the cyanobacterium Anabaena sp. strain PCC 7120 is more similar to higher-plant than to enteric bacterial enzymes in antigenicity and allosteric properties. In this paper, we report the isolation of the Anabaena ADPGlc PPase gene and its expression in Escherichia coli.

Isolation and complementation of nitrogen fixation mutants of the cyanobacterium Anabaena sp. strain PCC 7120.

Approximately 140 mutants of Anabaena sp. strain PCC 7120 unable to grow aerobically on media lacking fixed nitrogen (Fix-) were isolated after mutagenesis with diethyl sulfate and penicillin enrichment. A large cosmid library of wild-type Anabaena sp.

Characterization of a gene controlling heterocyst differentiation in the cyanobacterium Anabaena 7120.

Anabaena 7120 mutant 216 fails to differentiate heterocyst. We previously identified a 2.4-kb wild-type DNA fragment able to complement this mutant.

Expression, nucleotide sequence and mutational analysis of two open reading frames in the nif gene region of Anabaena sp. strain PCC7120.

A 1.8 kb transcript corresponding to a region of the Anabaena 7120 chromosome 4 kb downstream of the nifHDK operon appears 12-18 h after heterocyst induction. The DNA corresponding to this transcript was sequenced and found to contain two open reading frames, designated ORF 1 and ORF 2.

Bacterial-type ferredoxin genes in the nitrogen fixation regions of the cyanobacterium Anabaena sp. strain PCC 7120 and Rhizobium meliloti.

The nucleotide sequence of a region located downstream of the nifB gene, both in the cyanobacterium Anabaena sp. strain PCC 7120 and in Rhizobium meliloti, has been determined. This region contains a gene (fdxN) whose predicted polypeptide product strongly resembles typical bacterial ferredoxins.

Conservation of structure and location of Rhizobium meliloti and Klebsiella pneumoniae nifB genes.

Using transposon Tn5-mediated mutagenesis, an essential Rhizobium meliloti nitrogen fixation (nif) gene was identified and located directly downstream of the regulatory gene nifA. Maxicell and DNA sequence analysis demonstrated that the new gene is transcribed in the same direction as nifA and codes for a 54-kilodalton protein. In Klebsiella pneumoniae, the nifBQ operon is located directly downstream of a gene which is structurally and functionally homologous to the R.

Nitrogen fixation specific regulatory genes of Klebsiella pneumoniae and Rhizobium meliloti share homology with the general nitrogen regulatory gene ntrC of K. pneumoniae.

We have determined the complete nucleotide sequences of three functionally related nitrogen assimilation regulatory genes from Klebsiella pneumoniae and Rhizobium meliloti. These genes are: 1) The K. pneumoniae general nitrogen assimilation regulatory gene ntrC (formerly called glnG), 2) the K.

Construction of a broad host range cosmid cloning vector and its use in the genetic analysis of Rhizobium mutants.

We have constructed a cosmid derivative of the low copy-number broad host-range cloning vector pRK290 (Ditta et al., 1980) by inserting a 1.6-kb Bg/II fragment containing lambda cos into the unique Bg/II site in pRK290.