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