Biology Reference
In-Depth Information
IV. CYANOBACTERIAL LIPOPOLYSACCHARIDES (LPS)
Cyanobacterial LPS are reported to be responsible for an outbreak of gastro-enteritis in Sewickley,
Pennsylvania (Lippy and Erb, 1976; Keleti et al ., 1979). These are considered to be 10-times less
toxic than LPS of Salmonella (Keleti and Sykora, 1982; Raziuddin et al ., 1983; Bell and Codd, 1996).
LPS molecules consist of O antigens, core polysaccharides and lipid A moieties. Lipid A region is
responsible for its activity leading to symptoms such as fever, diarrhoea, vomiting and hypotension
(Metcalf and Codd, 2004). The toxicity caused by LPS endotoxins remains largely unknown (Duy
et al ., 2000). Stewart et al . (2006) reviewed the current knowledge on cyanobacterial LPS. These are
weakly toxic when compared to LPS from the Enterobacteriaceae. Moreover, the toxic moiety of LPS,
lipid A has not so far been detected in any cyanobacterial wall component. So it is highly improper
to assign the above symptoms to the cyanobacterial LPS without any scientifi c basis.
V. OTHER MISCELLANEOUS TOXINS
Cyanobacterin has been isolated from Scytonema hofmanii (UTEX1581) that is reported to inhibit
growth of various algae by exerting its action on cell membrane and thylakoids (Mason et al ., 1982).
Fischerellin A is produced by Fischerella muscicola and has a minimum inhibitory concentration of
14 nM against Synechococcus PCC 6911 and inhibits photosystem II (Hagmann and Juettner, 1996).
These two substances are suggested to be responsible for chemical defence. Kasumigamide, an
antialgal tetrapeptide has been detected in cells of M . aeruginosa NIES-87. This peptide has a molecular
formula of C 40 H 50 N 8 O 9 and is a linear tetrapeptide containing N-terminal-α-hydroxyacid. Erythro-
β-phenyl-D-serine, D-arginine, β-alanine and D-Pla are the four sub-units. It inhibited the growth
of Chlamydomonas neglecta NIES-439 (Ishida and Murakami, 2000).
Anabaenopeptilide 90A and 90B are seven residue depsipeptides isolated from Anabaena
strain 90, besides three six-residue peptides called anabaenopeptins. As yet their function has not
been clearly understood, although four genes governing anabaenopeptilide synthetase domains apdA ,
apdB and apdD containing two, four and one module, respectively have been identifi ed. The fourth
gene apdC , present between modules six and seven, is similar to halogenase genes (Rouhiainen et al .,
2000). Besides the production of anabaenopeptilide 90A and 90B, Anabaena strain 90 also produces
anabaenopeptins and both of these are serine protease inhibitors (Namikoshi and Rinehart, 1996;
Weckesser et al. , 1996). Mutation of anabaenopeptilide gene in Anabaena strain 90 resulted in the
enhanced production of anabaenopeptins (Repka et al ., 2004). Spiroidesin, a D-amino acid-containing
lipopeptide was isolated and characterized from Anabaena spiroides that inhibited cell growth of M .
aeruginosa at 1.6 µM (IC 50 ) (Kaya et al. , 2002). Lobocyclamide B, a cyclododecapeptide containing fi ve
β-hydroxy-α-amino acid residues was isolated from L . confervoides . This report constitutes fi rst such
occurrence of χ-hydroxythreonine in a natural peptide (MacMillan and Molinski, 2002). Aeruginosin
98-B from M . aeruginosa as the lead molecule, Radau et al . (2003) designed, synthesized and conducted
inhibition tests selective against serine proteases. Cyanostatin A and B have been isolated from
Microcystis sp. at Loch Rescobic in Scotland. These two are lipopeptides that contain 3-amino-2-
hydroxydecadonic acid and weakly inhibit PP2A. However, these strongly inhibited the activity
of leucine aminopeptidase M with IC 50 values of 40 and 12 nM ml -1 , respectively (Sano et al ., 2005).
Nostopeptolides ( nos ) A1 and A2, isolated from Nostoc sp. GSV224, are cyclic peptides containing
nine amino acid residues, a butyric acid group and an internal acetate-derived unit linked by peptide
and ester bonds. A gene cluster of eight ORFs encoding the biosynthesis and transport of this group
of nonapeptides has also been characterized (Hoffmann et al ., 2003). A mixed NRPS-PKS seems to
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