Calothrix

In 1999, Rickards et al. reported the isolation of calothrixins A (377) and B (378) from photoautrophic cultures of Calothrix cyanobacteria (345). These two, novel, pentacyclic carbazole alkaloids contain a quinolino[4,3-fc]carbazole-l,4-quinone framework. Calothrixins A and B inhibit the growth of a chloroquin-resistant strain of the malaria parasite P. falciparum and human HeLa cancer cells (345). 

The main framework is made up of five key modules for chemical library editing, enumeration, conversion, visualization, and analysis. The operations of these functionalities are accomplished by the various applications at the resource layer. For the purpose of illustration, the compound calothrixin B, a secondary metabolite isolated from the Calothrix cyanobacteria (11-13), is used as the scaffold molecule with the variable functional groups Rw] attached (Fig. 18.1). The calothrixins are redox-active natural products which display potent antimalarial and anticancer properties and thus there is interest in probing the physical as well as biological profiles of their derivatives (14). In this exercise, six functional groups have been selected as the building blocks (Table 18.1). 

Rickards, R. W., Rothschild, J. M., Willis, A. C., de Chazal, N. M., Kirk, J., Kirk, K., Sal-iba, K. J., Smith, G. D. (1999) Calothrixins A and B, novel pentacyclic metabolites from Calothrix Cyanobacteria with potent activity against malaria parasites and human cancer cells. Tetrahedron Lett 55, 13513-13520. 

Brenowitz, S. and Castenholz, R. W., Long-term effects of UV and visible irradiance on natural populations of a scytonemin-containing cyanobacterium (Calothrix sp.), FEMS Microbiol. Ecol., 24, 343, 1997. 

Savela, K. (1983) Nitrogen fixation by the blue-green alga Calothrix scopulorum in coastal waters of the Baltic. Ann. Bot. Fenn. 20, 399-405. 

Fig. 12. Amino acid sequence of the three biliproteins from the phycobilisome of the cyanobacterium M. laminosus (Fischerella PCC 7603) a/3-APC, a/3-C-PC, a/3-PEC and of C-PE from the cyanobacterium Fremyella diplosiphon (Calothrix UTEX 481). [PEB] is the phycoerythrobilin chromophore of C-PE the PCB-chromophores of a/8-APC, a/3-C-PC and -PEC and the PXB-chromophore of a-PEC are bound at homologous positions (to Cys and to Cys" ) and are not shown. The names of the amino acids are abbreviated according to the one-letter code (Eur. J. Biochem. (1983) 183, 9-33).

Fig, 13. Three-dimensional structure of C-phycocyanin (C-PC) o-subunit and j8-subunit (A and B) and o/3-trimer (C) derived from X-ray diffraction analysis of crystals of C-PC isolated from the cyanobacterium Mastigocladus laminosus (Fischerella PCC 7603) (101,145]. The possible positions of the additional PEB chromophores in C-PE from Fremyella diplosiphon (Calothrix UTEX 481) are adapted to the models of C-PC, using data from the amino acid sequence of C-PE [115]. Positions of the PEB chromophores at cysteine 50/61 X-X and 143a X. The beginning of the insertion 141a-o in J-C-PE is indicated by an arrow (— ). 

Photic zone I Cyanobacteria E Endosymbiont/ diatom Calothrix rhizosoleniae Janson et al., 1999a,b Foster and Zehr, 2006... 

Lemmerman (1905) was one of the first to depict the unique association of another heterocystous cyanobacterium, Calothrix rhizosoleniae, attached to the spines of a Chaetocoeros compressus diatom. Norris (1961) noted that the cyanobionts only attach transversely to the intercellular spaces of the diatom with the heterocyst closest to the host diatom. Others report the same symbiont as R. intracellularis (G6mez et al., 2005 Janson et ai, 1999 Karsten, 1907 Norris, 1961), thus there is... 

In Fall 2004, several chains of Chaetoceros compressus chains were hand-picked from the subtropical Pacific (station ALOHA) that had several symbiotic Calothrix cells attached to the host diatoms spines (Foster and Zehr unpubl.). We were... 

Although the Calothrix cyanobionts of Chaetoceros are attached to the diatom spines, the cyanobionts are only located at the interceUular spaces and attached transversely at the heterocyst (Norris, 1961), which could be seen as a morphological adaptation for nitrogen transfer. Others (e.g., ViUareal, 1990) have suggested that the extraceUular location of the Richelia symbionts with Rhizosolenia clevei is mechanistic for nitrogen transfer. 

After several months in isolation without the Chaetoceros host, our cultured isolate, Calothrix SCOl, started to change its ceU character. For example, the trichome length extended, intercalary heterocysts were observed, and several trichomes appeared to branch. We interpreted such changes in the symbiont trichome and ceU integrity as due to loss of control by the diatom host over the symbiont since the symbiont is in a free-Uving state. These latter observations also suggest that the free-living trichome potentiaUy looks different than that which is observed when it lives symbioticaUy, and thus could be easily misidentified/overlooked in the field. 

Others (Foster et al., 2007 Kimor et al., 1978 ViUareal, 1989) have reported that vegetative ceUs degrade first, and often the heterocysts are the last part of the Richelia trichome to remain in a host diatom, which could also suggest host control or some sort of ceU signaUng between host and symbiont. Gomez et al. (2005) observed Calothrix symbionts associated with Chaetoceros diatoms which lacked chloroplasts suggesting that the host diatoms were senescent quite possibly though the symbiotic... 

Calothrix act as a source of iaxed carbon to their hosts. Transfer of iaxed nitrogen and/or carbon remains undocumented in all the DDAs it has only been inferred from growth of the Rhizosoknia-Richelia symbioses in N-free media in culture (Villareal, 1989). 

Most heterocystous cyanobacteria dominate brackish and freshwater environments where they occur in the plankton and the benthos as free-Hving cells and are seldom found in the open ocean. Few report Richelia and Calothrix as free-living (Gomez et al., 2005 White et al., 2007), thus both are the exception and have made their successful transition to the open ocean as symbionts. 

Koster J., Volkman J. K., Rullkotter J., Scholz-Bottcher B. M., Rethmeier J., and Fischer U. (1999) Mono-, di- and trimethyl-branched alkanes in cultures of the filamentous cyanobacterium Calothrix scopulorum. Org. Geochem. 30, 1367-1379. 

Reports on the anti-influenza virus effects of extracts from marine algae from all over the world have been found in the literature [115]. These results show that the blue-green algae (cyanobacterium) are able to produce compounds with anti-influenza activity that may be of potential clinical interest. For example, aqueous and methanolic extracts of cultured cyanobacteria of several genera. Microcystis, Nodularia, Oscillatoria, Scytonema, Lyngbya and Calothrix were evaluated for their in vitro antiviral activity against the influenza A virus in Madin Darby kidney cells [116,117]. The further analysis of methanolic extracts of cultured strains of genus Microcystis revealed a remarkable antiviral... 

Calothrix is a genus of cyanobacteria that produces what is known as the black zone, a line of black, tarlike blobs, in the high intertidal zone. Each globule is a colony of cyanobacterial cells. These colonies can endure extended periods without water because they are contained in gel-like sheaths that keep them moist. Calothrix also grows like a crust on rocks and on other types of algae in many intertidal regions. 

Fig. 4.8. Characteristic cyanobacteria 1 — Chroococcus, 2 — Aphanothece, 3 — Chamaeaiphon, 4 — Oscillatoria, 5 — Spirulina, 6 — Lyngbya, 7 — Anabaena, 8 — Cylindrospermum, 9 — Calothrix, 10 — Tolypothrix, 11 — Richelia inside a cell of the diatom Rhizosolenia (modified from ref. [13])...

The aggregation of cells and filaments often yields macroscopic colonies which lie on lake sediments, float freely in the water, rest on soil or form blackish clusters on rock faces. Colonies of Calothrix (Fig. 4.8) often form a conspicuous zone on rocks in the upper inter-tidal zone, in some areas associated with other cyanobacteria which actively bore into the rock. 

Pedersen, M. and DaSilva, E.J., 1973. Simple brominated phenols in the bluegreen alga Calothrix brevissima West. Plants, 115 83—86. 

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