Deoxyribonucleic Acid Base Composition of Cyanobacteria

Abstract

The DNA base compositions of 176 strains of cyanobacteria were determined by thermal denaturation or by CsCl density gradient centrifugation. A summary of all data now available for this prokaryotic group is presented and the taxonomic and evolutionary implications are discussed. et al. (1967) reported mean DNA base compositions for a limited number of strains of cyanobacteria, representative of many different sub-groups. More extensive data were published by Stanier et al. (1971) for one sub-group, the unicellular cyanobacteria. In this paper we present data for a large number of additional strains, broadly representative of this major prokaryotic taxon. I N T R O D U C T I O N Edelman METHODS Strains.The strains examined are all maintained in the Pasteur Culture Collection (PCC) and havenow been deposited in the American Type Culture Collection (ATCC). They are identified here by both PCC and ATCC strain numbers. Full strain histories, media employed for cultivation and the explanation of generic terminology are given by Rippka et al. (1979). An additional strain (Oscillatoria agardhii) was isolated by Dr F. I. Kappers from the Veluwemeer, The Netherlands, and is now in pure culture as strain PCC 7805.Extraction of DNA. DNA for use in thermal denaturation experiments was purified by a method modified from that of Britten et al. (1968). Harvested cells (approximately 5 g wet wt) were suspended in 20 ml lysis mixture containing 8 M-urea, 1 M-NaClO,, 0.01 M-EDTA (disodium salt) and 1 % (w/v) sodium dodecyl sulphate (SDS) in 0.24 M-phosphate buffer (pH 7-0), disrupted by passage through a French press at 76 MPa, and partially deproteinized by shaking with an equal volume of chloroform/3-methylbutan-l-ol (24: 1, v/v) at room temperature for 30 min. Following centrifugation at 3000 g for 15 min the upper (aqueous) phase, containing DNA, was retained. DNA-grade hydroxyapatite (HAP; 2 g; Bio-Rad) was suspended in 20 ml 0.24 M-phosphate buffer (pH 7.0), boiled for 30 min, centrifuged at low speed, and washed twice with 15 ml MUP (Britten et al., 1968) containing 8 M-urea in 0.24 M-phosphate buffer (pH 7.0), being sedimented after each wash by brief low-speed centrifugation. The deproteinized nucleic acid solution was mixed with the washed HAP and stirred (5 min) to permit binding of DNA. The bound DNA was purified by washing the mixture (by centrifugation) seven times with 15 ml MUP, to remove RNA and residual protein, and then four times with 15 ml 0.014 M-phosphate buffer (pH 7.0), to remove urea. The purified DNA was eluted Present address :

Magnetovibrio blakemorei gen. nov., sp. nov., a magnetotactic bacterium ( Alphaproteobacteria : Rhodospirillaceae ) isolated from a salt marsh

“…plasmids) were not detected (Dean & Bazylinski, 1999). The G+C content of the genomic DNA of strain MV-1 T was determined by HPLC by the DSMZ, according to the method of Mesbah et al (1989) and by the thermal denaturation technique (Herdman et al, 1979) after purification of genomic DNA using the method described by Kimble et al (1995). The G+C content of the genome as determined by HPLC was 52.9±0.1 mol% (three measurements); that determined by thermal denaturation was 53.5±0.1 mol% (three measurements).…”

Comparison of conserved structural and regulatory domains within divergent 16S rRNA–23S rRNA spacer sequences of cyanobacteria The GenBank accession numbers for the sequences reported in this paper are AF180968 and AF180969 for ITS-L and ITS-S, respectively.

“…Under conditions of combined nitrogen limitation, many filamentous strains such as Nostoc PCC 7120 are able to differentiate heterocysts, specialized cells responsible for the aerobic fixation of molecular N # (Wolk, 1996). This morphological and physiological diversity is mirrored by extensive genetic variability, cyanobacterial genomes ranging in mean DNA base composition from 32 to 71 mol % GjC (Herdman et al, 1979b ;M. Herdman & R. Rippka, unpublished) and in complexity from 2n0 to 13n2 Mbp (Herdman et al, 1979a ;M.…”

DNA base composition of planktonic species of Anabaena (Cyanobacteria) and its taxonomic value.

“…In the bacteriological view, the DNA base composition of strains of a species shows a narrow range within 1 to 3 mol% GC (Mandel, 1966;Tamaoka, 1994). In the planktonic strains of Anabaena, DNA base composition ranged from 35.9 to 56.4 mol%, which is a wider range than that determined for non-planktonic strains of Anabaena, 38.3-44 mol% (Herdman et al, 1979). However, about 80% of the planktonic strains of Anabaena fell in the range of 37-42 mol% (Table 1).…”

“…Previous studies of the DNA base composition of cyanobacteria (Herdman et al, 1979;Paula et al, 1992) have been conducted using indirect methods, such as thermal denaturation of DNA (the T m method) and buoyant density measurements in caesium chloride (the B d method). The HPLC method for measuring DNA base composition is popular in microbial taxonomy, because it allows a direct, rapid and precise determination of base composition (Mebash et al, 1989;Tamaoka and Komagata, 1984).…”