Gloeobacter violaceus

The phycobilisome core is the site of attachment to the thylakoid membrane. Hemidiscoidal phycobilisomes, shown earlier in Fig. 2, are present in both cyanobacteria and some red algae, while hemiellipsoidal phycobilisomes are found only in certain other red algae. The phycobilisome in the thylakoid-less cyanobacterium Gloeobacter violaceus is present as a bundle of six rods in the phycobilisome of Synechococcus 6301, the core (attached to the thylakoid) has only two short rods attached. 

Phycobilisomes (PBsomes) constitute the light-harvesting antennae of cyanobacteria. Most of them are made up of a central three-cylinder core from which six rods radiate (1). However, exceptions have been described i) Synechococcus sp. PCC 6301 and 7942 have hemidiscoidal PBsomes, but the six rods radiate from a core made up of only two cylinders (2) ii) according to the observed ratio of rod phycobiliproteins (PB) versus core PBs, as well as to electron microscopy studies, Phormidium sp. PCC 7376 seems to have PBsomes resembling more closely the hemi-ellipsoidal tyjpt described for most of the rhodophytes (3) iii) finally, Gloeobacter violaceus, which does not have classical thylakoid membranes, harbors very peculiar rod-shaped PBsomes directly attached to the cytoplasmic membrane (4). 

In contrast, eubacteria (including purple bacteria, green filamentous bacteria, and heliobacteria), archaea, and fungi use only one enzyme phytoene desaturase (CrtI) to convert phytoene 3 to lycopene 7. Exceptionally, the primitive cyanobacterium Gloeobacter violaceus PCC 7421 uses this CrtI [29, 30]. G. violaceus is the first oxygenic phototroph that has been shown to use this enzyme (Table 106.3), whereas green sulfur bacteria use CrtP, CrtQ, and CrtH [14, 31]. 

Tsuchiya T, Takaichi S, Misawa N, Maoka T, Miyashita H, Mimuro M (2005) The cyanobacterium Gloeobacter violaceus PCC 7421 uses bacterial-type phytoene desaturase in carotenoid biosynthesis. FEES Lett 579 2125-2129... 

THE CYANOBACTERIUM GLOEOBACTER VIOLACEUS l.ACKS> SULFOQUINOVOSYL DIACYLGLYCEROL... 

Gloeobacter violaceus is a unicellular cyanobacteria that besides the outer wall layer only has one membrane the cell membrane. It performs oxygenic photosynthesis and the photosynthetic complexes are localised in the cell membrane (Rippka et al, 1974). Long phycobilisomes are oriented perpendicular to the cell membrane and the phycobiliproteins carry phycoerythrobilin, phycourobilin, phycocyanin and allophycocyanin (Guglielmi et al, 1981, Bryant era/., 1981)... 

Gloeobacter violaceus sp. PCC 7421 was grown under illumination of white fluorescent tubes (10 jiimol photons m s ) at 26 X in inorganic BG 11 media (Rippka et al, 1979), buffered to pH 7.5 with 10 mM Mops. The cells were harvested by centrifugation and cell lipids were extracted and analysed according to Wingsle et al. (1992). 

The acyl groups esterified to the membrane lipids are presented in Table 2. The major fatty acids are 16 0,18 0,18 1,18 2 and a-18 3. Trace amounts of 14 0 and 16 1 was also found. The presence of 32 % 16-carbon fatty acids and 63 % 18-carbon fatty acids place Gloeobacter violaceus outside any of the typical cyanobacterial fatty acid groupings (Murata et al., 1992, Murata and Wada, 1995). 

Table 2. Acyl groups (mol %) esterified to membrane lipids of Gloeobacter violaceus.

Bryant, D.A., Cohen-Bazire, G. and Glazer, A.N. (1981) Characterization of the biliproteins of Gloeobacter violaceus. Chromophore content of a cyanobacterial phycoerythrin carrying phycouorbilin chromophore. Arch Microbiol 129, 190-198. 

The Cyanobacterium Gloeobacter violaceus Lacks Sulfoquinovosyl Diacylglycerol. E. Selstam and D. Campbell... 

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