Synechococcus elongatus

From MicrobeWiki, the student-edited microbiology resource

A Microbial Biorealm page on the genus Synechococcus elongatus

Classification

Higher order taxa

Bacteria; Cyanobacteria; Chroococcales; Synechococcus

Species

Synechococcus elongatus

NCBI: Taxonomy Genome

Description and significance

The genus Synechococcus encompasses cyanobacteria in both freshwater and marine environments. In the typical marine environment, they are approximately responsible for 25% of the primary production, making them one of the most significant photosynthetic bacteria (6). In eutrophic habitats or habitats with high nutrients, blooms of cyanobacteria can occur, producing harmful neurotoxins that effect the nerve cells of other organisms (4). Synechococcus elongatus is a freshwater unicellular cyanobacterium. Cyanobacteria, sometimes referred to as blue-green algae, are prokaryotes that are able to obtain their energy through photosynthesis. Synechococcus elongatus has a rod-shaped appearance and is oligotrophic, having the ability to survive in freshwater environments with low nutrients. Living habitats include freshwater hot springs and other freshwater habitats preferably with a mesophilic or moderate temperature range (9). Geitler first identified Synechococcus elongatus in Germany during the year 1925. Later, Frenkel et. al. in 1950 discovered Synechococcus elongatus in small rain-filled pools on Angelica Rock, located in Massachusetts. Frenkel and his colleagues took a suspension of the water and identified the blue-green algae as Synechococcus elongatus. They cultured Synechococcus elongatus and ran tests to confirm its ability to photosynthesize (1). Currently, two complete Synechococcus elongatus (previously known as Anacystis nidulans) genomes have been sequenced, Synechococcus elongatus PCC 6301 and Synechococcus elongatus PCC 7942.

Genome structure

Synechococcus elongatus has one circular chromosome with two plasmids. Two genomic strains of these cyanobacteria have been sequenced: Synechococcus elongatus PCC 6301 and Synechococcus elongatus PCC 7942. Both strains are closely related to each other. Synechococcus elongatus PCC 6301 contains a circular chromosome 2,696,255 bp long with a GC content of 55.5 percent. The Synechococcus elongatus PCC 6301 chromosome contains the genes for 2,527 proteins and 55 RNAs (7). Synechococcus elongatus PCC 7942 also contains a circular chromosome approximately 2,700,000 bp long with a GC content of 55.5 percent. The Synechococcus elongatus PCC 7942 chromosome contains the genes for 2,612 proteins and 53 RNAs. One plasmid of Synechococcus elongatus PCC 7942 is currently being sequenced by Dr. Golden’s lab at Texas A&M University in conjunction with the DOE Joint Genome Institute.

Cell structure and metabolism

Synechococcus elongatus is unicellular, rod-shaped, and may appear in the environment as isolated, paired, linearly connected, or in small clusters. Synechococcus elongatus is a Gram-negative bacterium with an inner and outer cell membrane enveloping a cell wall (3). This cyanobacterium is able to swim or glide despite lacking flagella or cilia. It moves in a wave-like manner and this movement is possibly accomplished via projections from the cell surface (9). Also, its movement is not influenced by light stimulation. Synechococcus elongatus is a photoautotroph, due to its ability to undergo photosynthesis using energy from sunlight, carbon dioxide, and water (9). Through photosynthesis, Synechococcus elongatus may perform biosynthesis and respiration. A very significant by-product of Synechococcus elongatus photosynthesis is oxygen. Synechococcus elongatus uses carbon dioxide (CO2) as its carbon source through the Calvin cycle. During photosynthesis, Synechococcus elongatus uses water (H2O) for the electron donor, which produces oxygen (O2) as the by-product. Carbon dioxide is then converted to glucose through the Calvin cycle and is used for biosynthesis or other energetic needs. Photosynthesis occurs at the cell membrane inside thylakoids, which are compartments containing the photosynthetic pigments. The coupling of photosystems I and II in the thylakoid membrane drives photosynthesis and the oxidation of H2O, providing energy for carbon fixation (12). Chlorophyll a is the primary pigment required for photosynthesis in Synechococcus elongatus. Chlorophyll a is also extremely common in eukaryotic organisms such as plants. Other accessory pigments include phycobiliproteins, which give the blue-green coloration or pigmentation of Synechococcus elongatus as well as other cyanobacteria (2).

Ecology

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Pathology

Synechococcus elongatus is currently not known to cause any diseases.

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

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References

Beissinger, Martina et al. 1998. Solution structure of cytochrome c6 from the thermophilic cyanobacterium Synechococcus elongatus. The EMBO Journal, Vol. 17: 27-36.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=17211581&dopt=Abstract