Plasmids in toxic and nontoxic strains of the cyanobacteriumMicrocystis aeruginosa

Schwabe, Wolfgang; Weihe, Andreas; Börner, Thomas; Henning, Manfred; Kohl, Johannes-Günther

doi:10.1007/bf01573468

Cited by 33 publications

(18 citation statements)

References 20 publications

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“…The genes rhiA and rhiB, together with rhiC, form an operon which is located on the sym plasmid and is flanked by nifH and the nod gene cluster (Cubo et al, 1992). Several plasmids of different sizes exist in M. aeruginosa (Schwabe et al, 1988 ;E. Dittmann & G. Christiansen, unpublished data).…”

Section: Discussionmentioning

confidence: 97%

Altered expression of two light-dependent genes in a microcystin-lacking mutant of Microcystis aeruginosa PCC 7806

Erhard²,

et al. 2001

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Microcystin is a potent inhibitor of eukaryotic protein phosphatases and has been implicated in causing hepatotoxicity to humans and animals worldwide. It is produced primarily by the bloom-forming cyanobacterium Microcystis aeruginosa, although the function of the peptide in this micro-organism is unknown. In this study, a microcystin-related protein, MrpA, was identified using a microcystin-lacking mutant of M. aeruginosa, PCC 7806. Comparative two-dimensional protein electrophoresis showed that MrpA was strongly expressed in wild-type PCC 7806, but was not detectable in the mcyB mutant. MrpA showed similarity to the RhiA protein from Rhizobium leguminosarum, which is encoded by the rhiABC operon and controlled by quorum-sensing mediators. Sequencing of mrpA flanking regions in M. aeruginosa PCC 7806 revealed the presence of a rhiB homologue, mrpB, directly downstream of mrpA. Northern blot analyses of mrpA expression in cells exposed to different light conditions revealed a rapid decline of transcription under high light conditions. Most striking was a strong increase in transcript levels from cultures irradiated with blue light. The mrpA transcription level was strongly reduced in two independent microcystin-lacking mutants under all light conditions investigated.

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Section: Discussionmentioning

confidence: 97%

Altered expression of two light-dependent genes in a microcystin-lacking mutant of Microcystis aeruginosa PCC 7806

Erhard²,

et al. 2001

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“…However, although strain V145 contained all five C i uptake systems, strain V163 lacked a complete bicA (Table 1). Similarly, strains HUB 5-2-4 and HUB 5-3 were isolated from the same Microcystis bloom in Lake Pehlitzsee, Germany (Schwabe et al, 1988), but strain HUB 5-3 contained all five C i uptake systems, whereas strain HUB 5-2-4 lacked bicA.…”

Section: Growth Under Different C I Conditionsmentioning

confidence: 99%

Genetic diversity of inorganic carbon uptake systems causes variation in CO2 response of the cyanobacterium Microcystis

et al. 2013

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Rising CO 2 levels may act as an important selective factor on the CO 2 -concentrating mechanism (CCM) of cyanobacteria. We investigated genetic diversity in the CCM of Microcystis aeruginosa, a species producing harmful cyanobacterial blooms in many lakes worldwide. All 20 investigated Microcystis strains contained complete genes for two CO 2 uptake systems, the ATP-dependent bicarbonate uptake system BCT1 and several carbonic anhydrases (CAs). However, 12 strains lacked either the high-flux bicarbonate transporter BicA or the high-affinity bicarbonate transporter SbtA. Both genes, bicA and sbtA, were located on the same operon, and the expression of this operon is most likely regulated by an additional LysR-type transcriptional regulator (CcmR2). Strains with only a small bicA fragment clustered together in the phylogenetic tree of sbtAB, and the bicA fragments were similar in strains isolated from different continents. This indicates that a common ancestor may first have lost most of its bicA gene and subsequently spread over the world. Growth experiments showed that strains with sbtA performed better at low inorganic carbon (C i ) conditions, whereas strains with bicA performed better at high C i conditions. This offers an alternative explanation of previous competition experiments, as our results reveal that the competition at low CO 2 levels was won by a specialist with only sbtA, whereas a generalist with both bicA and sbtA won at high CO 2 levels. Hence, genetic and phenotypic variation in C i uptake systems provide Microcystis with the potential for microevolutionary adaptation to changing CO 2 conditions, with a selective advantage for bicA-containing strains in a high-CO 2 world.

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“…These similarities and their prokaryotic nature make cyanobacteria good model systems for molecular genetic studies of chloroplasts. Many cyanobacterial strains contain endogenous plasmids of various sizes (2,6,8,28,29,31,39,40,43,(46)(47)(48)52), but thus far all of these plasmids have proven to be cryptic.Central to the genetic study of cyanobacteria has been the development of efficient cloning vectors that can transform cyanobacteria. However, the construction of these cloning and expression vectors is greatly dependent upon an understanding of DNA replication of cyanobacterial plasmids.…”

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A small plasmid, pCA2.4, from the cyanobacterium Synechocystis sp. strain PCC 6803 encodes a rep protein and replicates by a rolling circle mechanism

Yang

McFadden

1993

J Bacteriol

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Cyanobacteria are gram-negative prokaryotes that carry out oxygenic photosynthesis. In their function and ultrastructure, they have numerous similarities to chloroplasts in higher plants (19). These similarities and their prokaryotic nature make cyanobacteria good model systems for molecular genetic studies of chloroplasts. Many cyanobacterial strains contain endogenous plasmids of various sizes (2,6,8,28,29,31,39,40,43,(46)(47)(48)52), but thus far all of these plasmids have proven to be cryptic.Central to the genetic study of cyanobacteria has been the development of efficient cloning vectors that can transform cyanobacteria. However, the construction of these cloning and expression vectors is greatly dependent upon an understanding of DNA replication of cyanobacterial plasmids. At present, no cyanobacterial plasmids are found to replicate in Escherichia coli (27, 53), and no E. coli plasmids except a promiscuous IncQ plasmid (24) are known to replicate within cyanobacteria (26,45,58). Therefore, many shuttle vectors comprising E. coli plasmid and cyanobacterial DNA have been constructed (4, 9-13, 16, 22, 27, 30). However, these chimeric plasmids usually do not replicate efficiently in cyanobacteria (6, 45, 55), leading to difficulties in identifying these plasmids directly and employing them as efficient expression vectors in cyanobacteria. It appears that the copy numbers of the plasmids in cyanobacteria are stringently controlled. Furthermore, in many cases, shuttle vectors tend to integrate into chromosomal DNA and recombine with resident plasmids (26,49,55,57 been established that most plasmids from gram-negative bacteria (for example, F, pSC101, R6K, R1, and ColEl-type plasmids) replicate by a theta-form mechanism. In contrast, plasmids of less than 10 kbp from gram-positive bacteria, such as the pT181 and pUB110 families, replicate by a rolling circle mechanism via a single-stranded (ss) intermediate (17,25) and therefore are referred to as ssDNA plasmids (17). One exception is the recent discovery that plasmid pKYM from the gram-negative bacterium Shigella sonnei replicates by a rolling circle instead of a theta-form mechanism (59).With the exception of ColEl-type plasmids (23), most of the characterized plasmids encode a specific replication (Rep) protein which, in addition to the host proteins, is necessary for their replication (17,44). In contrast to the situation with E. coli, studies of the replication of cyanobacterial plasmids at the molecular level have never been performed. To enhance the understanding of the replication, genomic organization, and function of cyanobacterial plasmids, we report here the complete nucleotide sequence of a small plasmid, pCA2.4, isolated from the unicellular cyanobacterium Synechocystis strain PCC 6803. This plasmid contains an open reading frame (ORF) which, on the basis of the homology studies, probably encodes a replication protein (RepA). This putative RepA protein has been expressed in E. coli, and the gene product has been characterized. We also report the ...

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Plasmids in toxic and nontoxic strains of the cyanobacteriumMicrocystis aeruginosa

Cited by 33 publications

References 20 publications

Altered expression of two light-dependent genes in a microcystin-lacking mutant of Microcystis aeruginosa PCC 7806

Altered expression of two light-dependent genes in a microcystin-lacking mutant of Microcystis aeruginosa PCC 7806

Genetic diversity of inorganic carbon uptake systems causes variation in CO2 response of the cyanobacterium Microcystis

A small plasmid, pCA2.4, from the cyanobacterium Synechocystis sp. strain PCC 6803 encodes a rep protein and replicates by a rolling circle mechanism

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