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PubMed1981

Isolation and characterization of thioredoxin from the cyanobacterium, Anabaena sp.

Thioredoxin from Anabaena sp. has been purified 800-fold with an assay based on the reduction of insulin disulfides by NADPH and the heterologous calf thymus thioredoxin reductase. The final material was homogeneous on polyacrylamide gel electrophoresis and had a molecular weight of 12,000; the NH2-terminal residue was serine and the COOH-terminal was leucine. Anabaena thioredoxin-(SH)2 is a hydrogen donor for the adenosylcobalamin-dependent anabaena ribonucleotide reductase and is equally active with the iron-containing ribonucleotide reductase from Escherichia coli. Anabaena thioredoxin-S2 is a good substrate for E. coli thioredoxin reductase. We have compared the structure of Anabaena and E. coli thioredoxins. Clear structural differences between the proteins, compatible with the large evolutionary distance between the organisms, were seen with respect to total amino acid composition, isoelectric point, tryptic peptide maps, and a low immunochemical cross-reactivity. However, both thioredoxins contain a single oxidation-reduction active disulfide bridge with the amino acid sequence: Cys-Gly-Pro-Cys-Lys. The tryptophan fluorescence emission of Anabaena thioredoxin-S2 increases more than 3-fold on reduction to thioredoxin-(SH)2. This behavior is identical with that of E. coli thioredoxin, suggesting a very similar overall folding of homologous molecules.

Amino Acid Sequence↗

PubMed1994

Protein HU from the cyanobacterium Anabaena.

Protein HU was purified from the cyanobacterium Anabaena 7120. Its complete amino acid sequence was determined by automated Edman degradation of the whole protein and of CNBr and chymotryptic peptides. The active DNA-binding protein is a homodimer of 94-amino acid subunits. Approximately half of the residues are identical to those of the two subunits of HU protein from E. coli. The protein binds to both supercoiled and relaxed double-stranded DNA, cooperatively. The contour lengths of circular DNAs were reduced up to six-fold by HU binding at low ratios of HU to DNA. At higher ratios, highly condensed aggregates were observed. Heterocysts are cells specialized for nitrogen fixation that differentiate at regular intervals along the filaments of Anabaena when they are transferred to a medium lacking combined nitrogen. Protein HU, labeled with 35S in cells growing on ammonia, disappears from developing heterocysts, although it is stably maintained in the intervening strings of vegetative cells. Following establishment of the heterocyst pattern, in which the differentiated cells are spaced about ten cells apart, HU is synthesized in the vegetative cells but not in the heterocysts. Several other vegetative cell DNA-binding proteins are also degraded during the differentiation. The major DNA-binding protein in heterocysts is a new one of subunit molecular mass around 12,000, whose relationship to other DNA-binding proteins is unknown. The gene encoding protein HU was cloned from Anabaena DNA and sequenced. The gene sequence is consistent with the amino acid sequence determined previously. Low stringency hybridization to Anabaena DNA digests suggest that there is a single gene for HU, consistent also with the unique amino acid sequence. S1 nuclease protection experiments suggest that the HU gene promoter differs from those of other Anabaena genes determined to date.

Amino Acid Sequence↗

PubMed1991

Promoter recognition by the RNA polymerase from vegetative cells of the cyanobacterium Anabaena 7120.

The transcription start points (tsp) of seven genes of Anabaena 7120 were previously identified by S1 nuclease protection and primer extension experiments using RNA extracted from cells. In the present work, these tsp were confirmed, with one exception, by in vitro transcription using purified RNA polymerases of Anabaena 7120 and Escherichia coli, and crude extracts of Anabaena 7120 active in transcription. In all cases, the template for transcription consisted of closed circular plasmid DNA in which the putative promoter-containing fragment was cloned in front of a strong terminator, which resulted in defined 'pseudo-runoff' transcripts whose sizes correspond (with one exception) to those expected on the basis of the tsp determined for in vivo RNA. These results, together with others obtained with templates containing bacteriophage T4 or cyanophage N1 promoters, led to the conclusion that the principal Anabaena 7120 RNA polymerase prefers promoters whose sequence and spacing approximate that of the E. coli consensus promoter, and that the Anabaena 7120 genes expressed in vegetative cells, characterized to date, have relatively weak promoters.

Anabaena↗

PubMedDate not supplied

Association of Vibrio cholerae O1 with the cyanobacterium, Anabaena sp., elucidated by polymerase chain reaction and transmission electron microscopy.

It has been hypothesized that Vibrio cholerae is an autochthonous flora of the estuarine and brackish water environment. Zooplankton and phytoplankton have been considered as possible reservoirs. The present study was carried out in microcosms to confirm the role of a cyanobacterium, Anabaena sp., as a reservoir of V. cholerae O1 using culture, polymerase chain reaction (PCR) and immunoelectron microscopy. Survival of culturable V. cholerae in microcosms was monitored by using tellurite taurocholate gelatin agar. Culturable V. cholerae were detected for up to 1 h in association with Anabaena sp. from a microcosm. However, viable but nonculturable (VBNC) V. cholerae O1 were detected for up to 25 months using PCR and immunoelectron microscopy. Results also showed that VBNC V. cholerae can multiply and maintain their progeny in the mucilaginous sheath of Anabaena sp. This is the first time that PCR and immunoelectron microscopy have been used to detect nonculturable V. cholerae in association with Anabaena sp. This study further clarifies the role of Anabaena sp. as a possible reservoir of cholera.

Anabaena↗

PubMed2002

Biotransformation of 2,4,6-trinitrotoluene in a continuous-flow Anabaena sp. system.

Reductive transformation of 2,4,6-trinitrotoluene (TNT) was observed in a continuous-flow system of Anabaena sp. operated for 33 d with a 5.7 d hydraulic retention time and a range of influent TNT concentrations of 1-58 mg/l. The TNT removal efficiency of the continuous-flow system at the highest influent TNT concentration of 58 mg/l was 96.7 +/- 1.7% (mean +/- 95% confidence interval). Culture chlorosis and growth inhibition were not observed during this study. The pseudo-first order TNT transformation rate constant values corresponding to the system performance range (0.14-0.46/h) were lower than the values previously recorded for batch Anabaena sp. cultures with less than 10 mg/l initial TNT concentrations, possibly due to an inhibition of the TNT transformation process by either TNT and/or TNT transformation products. Heterotrophic bacterial populations developed in the continuous-flow Anabaena sp. cultures also transformed TNT, but at a much lower rate than the Anabaena sp. Less than 1% of the overall TNT transformation observed in the continuous-flow system was attributed to the heterotrophic bacterial populations. The only TNT reduction products identified in both the culture media and in biomass extracts were azoxytetranitrotoluene isomers and low levels of aminodinitrotoluene isomers. TNT and TNT transformation products identified in the culture effluent and the biomass extract accounted for only about 24% of the TNT added to the system (on a molar basis). Production of soluble, polar metabolites, uptake, partial mineralization and/or sequestration of TNT and its transformation products by Anabaena may be responsible for the relatively low contaminant recovery and mass balance observed in this study.

Anabaena↗

PubMed2001

Assessment of the effect of azo dye RP2B on the growth of a nitrogen fixing cyanobacterium--Anabaena sp.

Certain nitrogen fixing cyanobacteria are diazotrophic, which profoundly impacts the aquatic ecosystem chemically and biologically. Although certain types are banned due to their carcinogenicity, azo dyes are commonly used in the dyeing or textile industry. This work investigates the effect of azo dye on the growth of cyanobacteria. Anabaena sp. isolated from the Da Jia Brook is an odor producing, nitrogen fixing cyanobacterium. The growth rates of Anabaena sp. in the media with or without nitrogen source were 3.56 x 10(-2) mg/ml day and 2.44 x 10(-2) mg/ml day, respectively. Anabaena sp. could not use azo dye RP2B as the nitrogen source. Experimental results indicated that the growth of Anabaena sp. was inhibited in the medium containing RP2B. The degree of inhibition increased from 50% to 81% with an increasing concentration of RP2B (0-50 mg/l). The IC-50 (inhibitory concentration) of RP2B on the growth of Anabaena sp. was 5 mg/l (as based on dry weight) or 7 mg/l (as measured by chlorophyll a).

Anabaena↗

PubMed2005

Chemotaxis between Vibrio cholerae O1 and a blue-green alga, Anabaena sp.

The chemotactic response of Vibrio cholerae O1 towards the mucilaginous sheath of Anabaena sp. was investigated by capillary tube method using a virulent strain of V. cholerae O1, El Tor, Ogawa (3083-T) and its isogenic mutant (HAP-1-T) that lacks the hap gene, which codes for mucinase (HA/protease). Homogenates of Anabaena sp. and purified mucin were used in this study as chemoattractants. Results showed 5.7% bacterial accumulation of wild-type V. cholerae O1 towards 4% homogenates of Anabaena sp. whereas, its mutant (hap-) showed 2.9% accumulation after 90 min. The higher percentage of attraction of wild-type V. cholerae O1 than the mutant (hap-) towards mucin and the homogenates of Anabaena sp. might be due to the activity of mucinase. These results indicate the role of mucinase in the chemotactic motility of V. cholerae O1 towards Anabaena sp.

Anabaena↗

PubMed1996

A comparative thermodynamic analysis by laser-flash absorption spectroscopy of photosystem I reduction by plastocyanin and cytochrome c6 in Anabaena PCC 7119, Synechocystis PCC 6803 and Spinach.

A comparative thermodynamic analysis of photosystem I (PSI) reduction by plastocyanin (Pc) and cytochrome c6 (Cyt) has been carried out by laser-flash absorption spectroscopy in the cyanobacteria Anabaena PCC 7119 and Synechocystis PCC 6803 as well as in spinach. These three organisms have been reported to exhibit different reaction mechanisms [Hervas, M., Navarro, J. A.. Díaz, A., Bottin, H., & De la Rosa, M. A. (1995) Biochemistry, 34, 11321-11326]. Whereas the activation free energy for the overall reaction is mainly enthalpic in nature, long-range electrostatic interactions appear to be attractive in Anabaena, but repulsive in Synechocystis and spinach. The net interaction between PSI and its two donor proteins in Anabaena is similarly affected by ionic strength (the rate constant decreases with increasing salt concentration), but the activation parameters delta H+/+ delta S+/+ show different dependencies on ionic strength. A compensation effect between entropy and enthalpy at varying ionic strength is found in all these Pc/PSI and Cyt/PSI systems, except with Cyt and PSI from Anabaena. Such a compensation effect is proposed to be mainly due to stabilization of the intermediate electrostatic complex by hydrophobic forces. The electron transfer step seems to be well optimized in the Anabaena Cyt/PSI couple, which exhibits a temperature-independent fast kinetic phase and, therefore, a low activation energy barrier. Short-distance forces appear to have gained relevancy in the reaction mechanism of PSI reduction by Cyt and Pc throughout evolution, whereas long-range interactions are prevalent in less evolved organisms.

Anabaena↗

PubMed1992

Purification, characterization and function of dihydrolipoamide dehydrogenase from the cyanobacterium Anabaena sp. strain P.C.C. 7119.

A dihydrolipoamide dehydrogenase (dihydrolipoamide: NAD+ oxidoreductase, EC 1.8.1.4) (DLD) has been found in the soluble fraction of cells of both unicellular (Synechococcus sp. strain P.C.C. 6301) and filamentous (Calothrix sp. strain P.C.C. 7601 and Anabaena sp. strain P.C.C. 7119) cyanobacteria. DLD from Anabaena sp. was purified 3000-fold to electrophoretic homogeneity. The purified enzyme exhibited a specific activity of 190 units/mg and was characterized as a dimeric FAD-containing protein with a native molecular mass of 104 kDa, a Stokes' radius of 4.28 nm and a very acidic pI value of about 3.7. As is the case with the same enzyme from other sources, cyanobacterial DLD showed specificity for NADH and lipoamide, or lipoic acid, as substrates. Nevertheless, the strong acidic character of the Anabaena DLD is a distinctive feature with respect to the same enzyme from other organisms. The presence of essential thiol groups was suggested by the inactivation produced by thiol-group-reactive reagents and heavy-metal ions, with lipoamide, but not NAD+, behaving as a protective agent. The function and physiological significance of Anabaena DLD are discussed in relation to the fact that 2-oxoacid dehydrogenase complexes have not been detected so far in filamentous cyanobacteria. Glycine decarboxylase activity, which might be involved in photorespiratory metabolism, has been found, however, in cell extracts of Anabaena sp. strain P.C.C. 7119 as the present study demonstrates.

Amino Acid Oxidoreductases↗

PubMed2002

Cellular fatty acids as chemotaxonomic markers of the genera Anabaena, Aphanizomenon, Microcystis, Nostoc and Planktothrix (cyanobacteria).

The cellular fatty acid content of 22 cyanobacterial strains belonging to the genera Anabaena, Aphanizomenon, Calothrix, Cylindrospermum, Nostoc, Microcystis and Planktothrix were analysed. The identities of the major peaks were confirmed by MS. Correspondence analysis of the data revealed three distinct groups formed by the Microcystis strains, the Nostoc/Planktothrix strains and the Anabaena/Aphanizomenon/Cylindrospermum strains. The Calothrix strain did not cluster with the other heterocystous cyanobacteria, supporting its morphological classification separate from the Nostocaceae family. The presence of large amounts of the fatty acids 18:30omega6,9,12c and 18:0 iso distinguished the Microcystis strains from the other cyanobacteria studied. The high content of 16:1omega7c grouped the Nostoc strains with the Planktothrix strains. A free-living strain of Nostoc contained 16:1omegao5c and 16: 1omega7c (about 1: 1), separating it from the symbiotic Nostoc strain and the Planktothrix strains. the strains of Anabaena, Aphanizomenon and Cylindrospermum grouped tightly and were characterized by the presence of 16:1omega9c and 16:0 anteiso fatty acids. Correspondence analysis of Anabaena, Aphanizomenon and Cylindrospermum showed that all hepatotoxic Anabaena strains grouped together, whereas the non-toxic and neurotoxic Anabaena strains grouped with the non-toxic Aphanizomenon strains.

Anabaena↗

PubMed1995

Characterization of a nitrogen-fixation (nif) gene cluster from Anabaena azollae 1a shows that closely related cyanobacteria have highly variable but structured intergenic regions.

The exact identity of cyanobacteria that have been cultured from symbiotic associations with the water fern Azolla spp., whether they are required in the symbiotic process, and their relationship to the symbiotic species, is a matter of some debate. We have characterized a 6 kb region containing the nifB operon and the nifH gene from cyanobacterium Anabaena azollae 1a, a putative symbiont of Azolla caroliniana. Five complete open reading frames have been sequenced. All are very highly conserved when compared with the corresponding regions of Anabaena sp. PCC 7120, with 93% to 97% identity at the nucleotide level and 93% to almost 100% at the amino-acid level. The intergenic regions, however, are not highly conserved (53-89% identity) when compared to the corresponding regions of Anabaena 7120: the A. azollae genome contains both more copies and more types of short tandemly repeated repetitive sequences than Anabaena 7120. The start points of transcription for both the nifB and nifH operons were mapped and found to be the same as those in Anabaena 7120. It was not possible to discern an improved consensus nif promoter sequence, but it was possible to define the likely extent of the promoter to within 40 bases upstream of the transcription start-point.

Amino Acid Sequence↗

PubMed1996

Isolation, characterization and electron microscopy analysis of a hemidiscoidal phycobilisome type from the cyanobacterium Anabaena sp. PCC 7120.

In this work we present the characterization of a hemidiscoidal phycobilisome type of the heterocyst-forming cyanobacterium Anabaena sp. PCC 7120. The phycobilisome of this organism contains allophycocyanin, phycocyanin and phycoerythrocyanin, similar to the closely related thermophilic cyanobacterium Mastigocladus laminosus. Intact phycobilisomes exhibit an absorption maximum at 619 nm and two fluorescence maxima at 664 nm and 680 nm, corroborating the presence of a complete energy pathyway along the antenna. Upon dissociation, the phycobiliproteins were released from the phycobilisome. One phycoerythrocyanin, one phycocyanin and three allophycocyanin complexes were isolated by ion-exchange chromatography and characterized by absorption and fluorescence spectroscopy and by SDS/PAGE. The amino-terminal sequences of the polypeptides belonging to the phycoerythrocyanin and phycocyanin families were identical with the derived sequences of their corresponding genes. Partial amino-terminal sequences of the polypeptides belonging to the allophycocyanin family are presented here. Our results show that the phycobiliproteins and linker polypeptides from Anabaena sp. PCC 7120 are similar to the phycobilisome components characterized in other cyanobacteria. The phycobilisome of Anabaena sp. PCC 7120 was extensively analyzed by electron microscopy. It differs from the common hemidiscoidal tricylindrical, six-rod phycobilisome type by a core domain consisting of five core cylinders surrounded by up to eight rods radiating in a hemidiscoidal manner. One rod is linked to each basal core cylinder, whereas the remaining core cylinders bind two rods each. On the basis of the data presented in this work, a revised model for the hemidiscoidal pentacylindrical phycobilisome of Anabaena sp. PCC 7120, M. laminosus and Anabaena variabilis is proposed. This model accounts more accurately for the 'grape' pattern typically exhibited by these phycobilisomes in electron micrographs.

Amino Acid Sequence↗

PubMed1996

Cloning, analysis and inactivation of the ndhK gene encoding a subunit of NADH quinone oxidoreductase from Anabaena PCC 7120.

The function of the type-1 pyridine nucleotide dehydrogenase (NDH-1) in the cyanobacterium Anabaena PCC 7120 was investigated. Immunological analysis with antibodies raised against NdhK from Synechocystis PCC 6803, a subunit of NDH-1, showed that NdhK in Anabaena PCC 7120 is only present on the plasma membrane, which confirms the results of previous studies [Howitt, C.A., Smith, G.D. & Day, D. A. (1993) Biochim. Biophys. Acta 114], 313-320]. Southern analysis with probes from the operon encoding ndhC-K-J from Synechocystis PCC 6803 showed that this operon is also conserved in Anabaena PCC 7120. Part of the operon was amplified using PCR with degenerate primers designed against two sequences encoding regions of NdhC and NdhJ that are conserved between cyanobacteria and chloroplasts. The nucleotide sequence of ndhK encodes a protein of 245 amino acids with a predicted molecular mass of 27.5 kDa. The coding regions of ndhC and ndhK overlap by 7 bp, as found in the chloroplasts of liverwort, maize, and rice. This is markedly different from the case in Synechocystis PCC 6803 where a 71-bp non-coding, intergenic spacer region lies between ndhC and ndhK. The ndhK clone was interrupted by the insertion of a kanamycin-resistance gene and used to transform Anabaena PCC 7120.20 unsegregated transformants were produced, all of which died during attempts to segregate them. This indicates that under the selection conditions used, ndhK is an essential gene in Anabaena PCC 7120.

Amino Acid Sequence↗

PubMed2002

Transcript levels of rbcR1, ntcA, and rbcL/S genes in cyanobacterium Anabaena sp. PCC 7120 are downregulated in response to cold and osmotic stress.

Using differential display, we identified the Anabaena sp. PCC 7120 ribulose 1,5-bisphosphate carboxylase transcriptional regulator (rbcR1) gene, a member of the LysR family of positive transcription factors. The rbcR1 transcript and its putative target gene ribulose 1,5-bisphosphate carboxylase/oxygenase (rbcL/S) were repressed by cold (20 degrees C) and osmotic (sucrose and salt) stress. Cold stress also induced a transient downregulation of the Anabaena 7120 ntcA transcriptional regulator. Expression of the ntcA gene, however, returned to normal levels 2 h after initiation of cold stress and increased significantly above normal levels 24 h after growth at 20 degrees C. The early decline in the expression of the ntcA, rbcR1, and rbcL/S transcripts appears to be part of the Anabaena 7120 global adaptation response to stress. The substantial increase in the ntcA gene expression 24 h following cold stress suggests that Anabaena 7120 experiences substantial nitrogen limitation under these conditions. These data suggest that in response to stress, Anabaena 7120 decreases its metabolic activity through regulation of the CO(2) fixation machinery while enhancing its nitrogen assimilation by inducing the expression of the nitrogen global transcriptional regulator, NtcA.

Amino Acid Sequence↗

PubMed2003

Quantitative real-time PCR for determination of microcystin synthetase e copy numbers for microcystis and anabaena in lakes.

Cyanobacterial mass occurrences in freshwater lakes are generally formed by Anabaena, Microcystis, and Planktothrix, which may produce cyclic heptapeptide hepatotoxins, microcystins. Thus far, identification of the most potent microcystin producer in a lake has not been possible due to a lack of quantitative methods. The aim of this study was to identify the microcystin-producing genera and to determine the copy numbers of microcystin synthetase gene E (mcyE) in Lake Tuusulanjärvi and Lake Hiidenvesi in Finland by quantitative real-time PCR. The microcystin concentrations and cyanobacterial cell densities of these lakes were also determined. The microcystin concentrations correlated positively with the sum of Microcystis and Anabaena mcyE copy numbers from both Lake Tuusulanjärvi and Lake Hiidenvesi, indicating that mcyE gene copy numbers can be used as surrogates for hepatotoxic Microcystis and ANABAENA: The main microcystin producer in Lake Tuusulanjärvi was Microcystis spp., since average Microcystis mcyE copy numbers were >30 times more abundant than those of ANABAENA: Lake Hiidenvesi seemed to contain both nontoxic and toxic Anabaena as well as toxic Microcystis strains. Identifying the most potent microcystin producer in a lake could be valuable for designing lake restoration strategies, among other uses.

Anabaena↗

PubMed2005

Differential expression of the two kdp operons in the nitrogen-fixing cyanobacterium Anabaena sp. strain L-31.

In several types of bacteria, the Kdp ATPase (comprising of the KdpABC complex) is an inducible, high-affinity potassium transporter that scavenges K+ from the environment. The cyanobacterium Anabaena sp. strain L-31 showed the presence of not one but two distinct kdp operons in its genome. The kdp1 consisted of kdpA1B1G1C1D genes, whereas the kdp2 contained the kdpA2B2G2C2 genes. Among the regulatory genes, the kdpD open reading frame of Anabaena sp. strain L-31 was truncated compared to the kdpD of other bacteria, whereas a kdpE-like gene was absent in the vicinity of the two kdp operons. In response to K+ limitation (<0.05 mM external K+), only kdp2 (and not kdp1) expression could be detected as a 5.3-kb transcript on Northern blots, indicating that kdpA2B2G2C2 genes constitute a polycystronic operon. Unlike E. coli, addition of osmolytes like NaCl, or a change in pH of the medium did not enhance the kdp expression in Anabaena sp. strain L-31. Interestingly, the Anabaena sp. strain L-31 kdp2 operon was strongly induced in response to desiccation stress. The addition of K+ to K+ -starved cultures resulted in repression and degradation of kdp2 transcripts. Our results clearly show that kdp2 is the major kdp operon expressed in Anabaena sp. strain L-31 and may play an important role in adaptation to K+ limitation and desiccation stress.

Adenosine Triphosphatases↗

PubMed1992

Activities of two dissimilar thioredoxins from the cyanobacterium Anabaena sp. strain PCC 7120.

Thioredoxin is a small redox protein that functions as a reducing agent and modulator of enzyme activity. A gene for an unusual thioredoxin was previously isolated from the cyanobacterium Anabaena sp. strain PCC 7120 and cloned and expressed in Escherichia coli. However, the protein could not be detected in Anabaena cells (J. Alam, S. Curtis, F. K. Gleason, M. Gerami-Nejad, and J. A. Fuchs, J. Bacteriol. 171:162-171, 1989). Polyclonal antibodies to the atypical thioredoxin were prepared, and the protein was detected by Western immunoblotting. It occurs at very low levels in extracts of Anabaena sp. and other cyanobacteria. No antibody cross-reaction was observed in extracts of eukaryotic algae, plants, or eubacteria. The anti-Anabaena thioredoxin antibodies did react with another unusual thioredoxin-glutaredoxin produced by bacteriophage T4. Like the T4 protein and other glutaredoxins, the unusual cyanobacterial thioredoxin can be reduced by glutathione. The Anabaena protein can also activate enzymes of carbon metabolism and has some functional similarity to spinach chloroplast thioredoxin f. However, it shows only 23% amino acid sequence identity to the spinach chloroplast protein and appears to be distantly related to other thioredoxins. The data indicate that cyanobacteria, like plant chloroplasts, have two dissimilar thioredoxins. One is related to the more common protein found in other prokaryotes, and the other is an unusual thioredoxin that can be reduced by glutathione and may function in glucose catabolism.

Anabaena↗

PubMed1986

Differences in mRNA levels in Anabaena living freely or in symbiotic association with Azolla.

Azolla is a small water fern in whose leaf cavities the filamentous nitrogen-fixing cyanobacterium Anabaena azollae is symbiotically associated. Using cloned genes from Anabaena 7120 for glutamine synthetase (GS), ribulose-1,5-bisphosphate (RuBP) carboxylase, nitrogenase and the 32-kd protein of photosystem II, mRNA levels of the corresponding genes in the Anabaena endosymbiont were studied by Northern hybridization. In RNA isolated from the endosymbiont there is a 10-fold reduction of GS transcript levels, a greater than 5-fold increase in 32-kd transcript levels and a greater than 5-fold decrease in RuBP carboxylase transcript levels, compared with levels in the free-living Anabaena azollae. In the endosymbiont and in heterocysts of the free-living Anabaena azollae the nif H, nif D, and nif K genes are transcribed from a single nif HDK operon.

Chlorophyll↗