Part E | 27.4
668 Part E Marine Microbiology and Biotechnology
27.4 An Australian Example: Exploring the Biosynthetic Potential
of a Marine-Derived Streptomycete
Through systematic screening of marine environments
in the Sunshine Coast Region of Australia using the
information derived from indicator phages, a novel marine streptomycete species USC-633 was isolated from
near shore marine waters [27.81] with an optimum
growth temperature at 28
ı C. Growing very slowly
(over 34 weeks) in both salt dependent and independent media this near shore marine actinomycete was
highly susceptible to low temperatures and lost viability immediately in cold storage temperatures (e.g.
4
ı C) indicating it was an organism truly deriving
from subtropical marine waters. Following the 16S
rRNA sequencing investigation it occupied a distinct
position on the phylogenetic tree (Fig. 27.1) and displayed only 68% similarity to other previously described bioactive marine streptomycete species such as
the DQ448742 [27.82].
27.4.1 Morphology, Physiology,
and Secondary Metabolite Production
The isolate displayed a range of growth characteristics when grown on different media. Only on oatmeal
agar (3% yeast extract, 20% oats, and 20% agar) scarce
aerial mycelium formation and sporulation were observed both visually and through electron microscopy
studies (Fig. 27.2, 27.3a,b). On all other growth media
including the Marine agar (Difco) used to grow the microorganism, extensive aerial mycelium development
and subsequent sporulation were absent even after 46
weeks of incubation (Fig. 27.4).
However, well-defined chemical profiles were obtained on bold cultures of the isolate such as when it was
grown on glucose yeast extract and malt extract agar
(GYM; medium 65, www.dsmz.de) (Figs. 27.5, 27.6).
These observations might correlate with the findings of
Ng et al. [27.83] where increased rifamycin production
was recorded after 31 days of growth with darkened
color colony with S. arenicola.
In most actinomycetes including the streptomycetes
the vegetative mycelia directly develops by germinated
spores in a parallel disposition of the mycelium [27.83].
Such growth structure allows for the efficient utilization of the nutrients in the agar due to the hydrolytic
enzymes secreted by the microorganisms allowing theefficient use of polymers [27.83–85].
Production of hydrolytic enzymes has also been
linked to bioactivity. Of 116 chitinolytic actinomycetes
isolated from marine sediments, 85 were found to possess antimicrobial activity by Pisano et al. [27.86].
They noted a high correlation between chitinolysis and
bioactivity. Furthermore, addition of CaCO 3 by Macedo
et al. [27.87] resulted in higher values of maximum
lignin peroxidase activity. GYM agar contained CaCO 3
which might be triggering increased enzyme activity
and in turn bioactivity. Deep dark green color produced
on the GYM agar by the USC-633 might be related to
the presence of such hydrolytic ability resulting in increased bioactivity.
Dark coloration was also evident with co-culture inoculations with other bacteria and fungi on the same
solid state fermentation environment. Perhaps a wide
array of characteristic demonstrated by the isolate making it adaptable to different substrates including marine
ones highlights the fact that occurrence and adaptation is an ecological factor perhaps in response to
environmental stresses rather than a true taxonomical
separation [27.66, 67]. As soon as the culture was given
the marine conditions a brominated compound was produced as a response to its new environment.
A large variety of aromatic and aliphatic carbon
centers have been reported to be halogenated during
natural product biosynthesis, with over 95% of the cases
involving chlorine or bromine. In the marine environment where bromine is in higher concentration than in
fresh water a comparable bromination of aromatic and
heteroaromatic molecules as well as bromination of isoprenoid metabolites have been reported [27.88].
Magarvey et al. [27.89] investigated the obligate
growth requirements of the PNG1 and UMM518 clades
and concluded that they do not have an obligate requirement for salt like the true marine clade MAR1, but do
complete a full developmental cycle in submerged cultures (liquid saltwater growth medium containing 3%
NaCl). Both of these slowly growing actinomycetes
were capable of sporulating under submerged conditions in the presence of a salt concentration of 3%,
typical of seawater, consistent with their ability to grow
and divide in the marine environment.
It has frequently been reported that small changes
in culture conditions can have a major influence in the
spectrum of secondary metabolites [27.50]. In-depth
information gained from physiological studies can further be used to manipulate secondary metabolite production in conjunction with the reflected information
deriving from secondary metabolism. Co-culture exper-
668 Part E Marine Microbiology and Biotechnology
27.4 An Australian Example: Exploring the Biosynthetic Potential
of a Marine-Derived Streptomycete
Through systematic screening of marine environments
in the Sunshine Coast Region of Australia using the
information derived from indicator phages, a novel marine streptomycete species USC-633 was isolated from
near shore marine waters [27.81] with an optimum
growth temperature at 28
ı C. Growing very slowly
(over 34 weeks) in both salt dependent and independent media this near shore marine actinomycete was
highly susceptible to low temperatures and lost viability immediately in cold storage temperatures (e.g.
4
ı C) indicating it was an organism truly deriving
from subtropical marine waters. Following the 16S
rRNA sequencing investigation it occupied a distinct
position on the phylogenetic tree (Fig. 27.1) and displayed only 68% similarity to other previously described bioactive marine streptomycete species such as
the DQ448742 [27.82].
27.4.1 Morphology, Physiology,
and Secondary Metabolite Production
The isolate displayed a range of growth characteristics when grown on different media. Only on oatmeal
agar (3% yeast extract, 20% oats, and 20% agar) scarce
aerial mycelium formation and sporulation were observed both visually and through electron microscopy
studies (Fig. 27.2, 27.3a,b). On all other growth media
including the Marine agar (Difco) used to grow the microorganism, extensive aerial mycelium development
and subsequent sporulation were absent even after 46
weeks of incubation (Fig. 27.4).
However, well-defined chemical profiles were obtained on bold cultures of the isolate such as when it was
grown on glucose yeast extract and malt extract agar
(GYM; medium 65, www.dsmz.de) (Figs. 27.5, 27.6).
These observations might correlate with the findings of
Ng et al. [27.83] where increased rifamycin production
was recorded after 31 days of growth with darkened
color colony with S. arenicola.
In most actinomycetes including the streptomycetes
the vegetative mycelia directly develops by germinated
spores in a parallel disposition of the mycelium [27.83].
Such growth structure allows for the efficient utilization of the nutrients in the agar due to the hydrolytic
enzymes secreted by the microorganisms allowing theefficient use of polymers [27.83–85].
Production of hydrolytic enzymes has also been
linked to bioactivity. Of 116 chitinolytic actinomycetes
isolated from marine sediments, 85 were found to possess antimicrobial activity by Pisano et al. [27.86].
They noted a high correlation between chitinolysis and
bioactivity. Furthermore, addition of CaCO 3 by Macedo
et al. [27.87] resulted in higher values of maximum
lignin peroxidase activity. GYM agar contained CaCO 3
which might be triggering increased enzyme activity
and in turn bioactivity. Deep dark green color produced
on the GYM agar by the USC-633 might be related to
the presence of such hydrolytic ability resulting in increased bioactivity.
Dark coloration was also evident with co-culture inoculations with other bacteria and fungi on the same
solid state fermentation environment. Perhaps a wide
array of characteristic demonstrated by the isolate making it adaptable to different substrates including marine
ones highlights the fact that occurrence and adaptation is an ecological factor perhaps in response to
environmental stresses rather than a true taxonomical
separation [27.66, 67]. As soon as the culture was given
the marine conditions a brominated compound was produced as a response to its new environment.
A large variety of aromatic and aliphatic carbon
centers have been reported to be halogenated during
natural product biosynthesis, with over 95% of the cases
involving chlorine or bromine. In the marine environment where bromine is in higher concentration than in
fresh water a comparable bromination of aromatic and
heteroaromatic molecules as well as bromination of isoprenoid metabolites have been reported [27.88].
Magarvey et al. [27.89] investigated the obligate
growth requirements of the PNG1 and UMM518 clades
and concluded that they do not have an obligate requirement for salt like the true marine clade MAR1, but do
complete a full developmental cycle in submerged cultures (liquid saltwater growth medium containing 3%
NaCl). Both of these slowly growing actinomycetes
were capable of sporulating under submerged conditions in the presence of a salt concentration of 3%,
typical of seawater, consistent with their ability to grow
and divide in the marine environment.
It has frequently been reported that small changes
in culture conditions can have a major influence in the
spectrum of secondary metabolites [27.50]. In-depth
information gained from physiological studies can further be used to manipulate secondary metabolite production in conjunction with the reflected information
deriving from secondary metabolism. Co-culture exper-