phytoplankton communities under natural or in situ-like conditions [33, 68]. In
summary, the natural functions of microcystins need further consideration in future
research.
Cylindrospermopsin (CYN) produced by genus Cylindrospermopsis and other
strains are cytotoxic and hepatotoxic [63, 69]. To date, five different CYNs have
been isolated with different shares of the total CYN concentration, but their
physiological function is not clear [70]. Several studies support the role of CYNs
as allelochemicals. CYNs inhibited the growth and caused cell necrosis in the
target strain M. aeruginosa, and the production of CYNs increased under environmental stress [71, 72]. CYNs may thus support the dominance and expansion of
CYNs-producing strains [70]. Another toxin produced by cyanobacteria is saxitoxin [70, 73], but its neurotoxic property has led to a research focus on mammal
poisoning.
Overall, most studies on these well-known cyanobacterial toxins have focused on
their toxic abilities against humans or animals, while research on their potential role
in controlling phytoplankton communities and their succession are still rare.
Apart from those widely studied toxins, other toxic chemicals have also been
separated from several cyanobacterial strains from the genus Microcystis,
Fischerella, Anabaena, Aphanizomenon, Cylindrospermopsis, Nostoc, etc. The
most common effective secondary metabolites include cyclic peptides, alkaloids,
terpenoids, ketone/ester, and member of the phenyl family (Table 1). The potential
role of these secondary metabolites as allelochemicals or pharmaceutical or for
agricultural applications has been reviewed in several studies [16, 18, 74]. In this
chapter, we describe selected bioactive chemicals, their source species, modes of
actions, and target species.
Peptides produced by cyanobacteria are the best studied type of secondary and
bioactive metabolites. The most famous example are microcystins (see above), while
other cyclic peptides detected in cyanobacteria include fischerellin, hassallidin, and
portoamide. These peptides have shown toxicity against cyanobacteria, green algae,
bacteria, yeast, and crustaceans (Table 1).
Bio-alkaloids are commonly considered to be potent toxins [75, 76] and are also
found in the cells of cyanobacteria (Table 1). They showed inhibitory effects on
cyanobacteria, bacteria (model), green algae, and zebrafish embryos. The majority of
these chemicals are indole moiety contained. Most of the studies relevant for aquatic
ecosystems indicate that alkaloids are more likely to interact with the environment of
cyanobacteria than peptides. However, the pathways of their synthesis have rarely
been explained and need cross-disciplinary research.
Terpenoids are compounds existing in all living organisms and consist of diverse
structural variants. Their synthesis in cyanobacterial cells via the methylerythritolphosphate (MEP) pathway has been identified, and present knowledge has led to the
manipulation of their synthesis [77]. Documented natural terpenoids from
cyanobacterial sources are inhibitors of bacteria, cyanobacteria, eukaryotic algae,
invertebrates, and vertebrates (Table 1). They are mostly low molecular weight
compounds and their toxicity can be weakened by shaking or “disturbing” the
cultures [78].
14 Effects of Cyanobacterial Secondary Metabolites on Phytoplankton Community. . . 329
summary, the natural functions of microcystins need further consideration in future
research.
Cylindrospermopsin (CYN) produced by genus Cylindrospermopsis and other
strains are cytotoxic and hepatotoxic [63, 69]. To date, five different CYNs have
been isolated with different shares of the total CYN concentration, but their
physiological function is not clear [70]. Several studies support the role of CYNs
as allelochemicals. CYNs inhibited the growth and caused cell necrosis in the
target strain M. aeruginosa, and the production of CYNs increased under environmental stress [71, 72]. CYNs may thus support the dominance and expansion of
CYNs-producing strains [70]. Another toxin produced by cyanobacteria is saxitoxin [70, 73], but its neurotoxic property has led to a research focus on mammal
poisoning.
Overall, most studies on these well-known cyanobacterial toxins have focused on
their toxic abilities against humans or animals, while research on their potential role
in controlling phytoplankton communities and their succession are still rare.
Apart from those widely studied toxins, other toxic chemicals have also been
separated from several cyanobacterial strains from the genus Microcystis,
Fischerella, Anabaena, Aphanizomenon, Cylindrospermopsis, Nostoc, etc. The
most common effective secondary metabolites include cyclic peptides, alkaloids,
terpenoids, ketone/ester, and member of the phenyl family (Table 1). The potential
role of these secondary metabolites as allelochemicals or pharmaceutical or for
agricultural applications has been reviewed in several studies [16, 18, 74]. In this
chapter, we describe selected bioactive chemicals, their source species, modes of
actions, and target species.
Peptides produced by cyanobacteria are the best studied type of secondary and
bioactive metabolites. The most famous example are microcystins (see above), while
other cyclic peptides detected in cyanobacteria include fischerellin, hassallidin, and
portoamide. These peptides have shown toxicity against cyanobacteria, green algae,
bacteria, yeast, and crustaceans (Table 1).
Bio-alkaloids are commonly considered to be potent toxins [75, 76] and are also
found in the cells of cyanobacteria (Table 1). They showed inhibitory effects on
cyanobacteria, bacteria (model), green algae, and zebrafish embryos. The majority of
these chemicals are indole moiety contained. Most of the studies relevant for aquatic
ecosystems indicate that alkaloids are more likely to interact with the environment of
cyanobacteria than peptides. However, the pathways of their synthesis have rarely
been explained and need cross-disciplinary research.
Terpenoids are compounds existing in all living organisms and consist of diverse
structural variants. Their synthesis in cyanobacterial cells via the methylerythritolphosphate (MEP) pathway has been identified, and present knowledge has led to the
manipulation of their synthesis [77]. Documented natural terpenoids from
cyanobacterial sources are inhibitors of bacteria, cyanobacteria, eukaryotic algae,
invertebrates, and vertebrates (Table 1). They are mostly low molecular weight
compounds and their toxicity can be weakened by shaking or “disturbing” the
cultures [78].
14 Effects of Cyanobacterial Secondary Metabolites on Phytoplankton Community. . . 329