Marine Actinomycetes in Biodiscovery 27.3 Ecological and Physiological Perspectives 667
Part E | 27.3
nomics. They observed relatedness between marine and
nonmarine actinobacteria through constructed phylogenic trees which might indicate recent introduction to
marine environments.
Sponga et al. [27.66] indicated that the presence of
a few antibacterial activities expressed when marinederived actinomycetes were incubated in a fermentation
medium diluted with sea water might be an indication
of adaptation of these isolates to the marine environment rather than originating from those environments.
The establishment of the marine affinity of organisms
isolated from the sea requires generation of scientific evidence beyond laboratory studies [27.67]. Initial
growth on complex laboratory media prepared with
sea water, or on media made isotonic with sea water by the addition of NaCl, may not be an absolute
criterion of marine adaptation as many terrestrial origin microorganisms also grow on such media [27.67].
True marine bacteria might be differentiated from their
land counterparts through their need for Na
C in the
medium for growth but not by having requirements for
sea water [27.67, 68]. Our knowledge is still poor about
specific, natural nutrients and growth factors required
for their cultivation. As stated by Fenical [27.8] common media constituents such as peptone, simple sugars
etc. are unrealistic marine nutrients. These are apparently replaced with complex carbon sources such as
chitin, sulfated polysaccharides, and marine proteins in
the marine environment. In addition, there is still little understanding of the effects of uncommon inorganic
elements, such as lithium, silicon, etc., which are also
abundant in marine sediments. All these factors are still
today greatly limiting our ability to isolate and culture
the majority of the interesting and new bacterial forms
present [27.8].
There is a need to develop a full understanding on
the survival and marine adaptations of bacteria which
can then be translated into development of effective
selective isolation protocols [27.69]. One successful
approach for the terrestrial ones has been the use of
data deriving from physiological and growth requirements of terrestrial streptomycetes to design targetspecific selective isolation methods [27.70]. Adaptation
of such an approach for marine-derived taxa would
result in effective recovery as well as generating information on the physiology and growth requirements
of marine bacteria. Imada et al. [27.71] investigated
the growth and antimicrobial compound production
of marine actinomycetes in the presence of seawater. While the optimal concentration of growth ranged
from 10 to 30 % .v=v/, the production of antibacterial substances was observed in the concentration
range 60110 % .v=v/ despite poor growth, indicating that the production of antibiotics is seawaterdependent.
27.3.3 Bacteriophage-Guided Route
to Detection and Recovery
of Marine Actinomycetes
When detection of rare actinomycetes is targeted, particularly the marine derived ones with low abundance
frequency unless highly selective pressures are used,
these taxa could not easily be isolated [27.69]. One approach has been the use of indicator phages specific
towards targeted taxa using their close relatives as propagation hosts, and provided clues whether such species
would be present in those environments [27.72–75].
An interesting finding was the occurrence of polyvalent Salinispora phages infecting members of Micromonsporacea including the type strains of terrestrial
origin in Germany [27.74].
Stadler et al. [27.76] isolated cinnabaramides A–G,
analogs of lactacystin and salinosporamide from a terrestrial streptomycete. These observations and findings
might be in agreement of the above mentioned fact by
Penn and Jensen [27.65] that a recent introduction of
genera like Salinispora occurred into the marine environments and terrestrial relatives of these genera might
also carry similar biosynthetic genes coding for the
production of similar bioactive compounds. Udwary
et al. [27.77] however, have indicated that due to the
current lack of information on the other Micromonsporacea genome sequences, it is unclear whether this
natural product diversity is common to this family or
whether the diversity in Salinispora derives from environmental pressures present in marine environments.
Once the presence of bioactive taxa is indicated by
bacteriophages in an environmental sample, they can
also be used to reduce the numbers of unwanted taxa
on isolation plates making the growth medium available
for consumption by targeted organisms without competition [27.73, 75, 78].
Bacteriophages can also indicate the relatedness
of unknown bacteria to their closest relatives [27.72].
In recent reviews Kurtböke [27.75, 79] provided insights into bacteriophage–host interactions. Examples
included multiple strategies evolved by bacteriophages
to interfere with bacterial growth. Such host conquering
strategies used by the bacteriophages can provide clues
towards detection of new bioactive compounds such as
turning phage endolysins to enzybiotics [27.80].
Part E | 27.3
nomics. They observed relatedness between marine and
nonmarine actinobacteria through constructed phylogenic trees which might indicate recent introduction to
marine environments.
Sponga et al. [27.66] indicated that the presence of
a few antibacterial activities expressed when marinederived actinomycetes were incubated in a fermentation
medium diluted with sea water might be an indication
of adaptation of these isolates to the marine environment rather than originating from those environments.
The establishment of the marine affinity of organisms
isolated from the sea requires generation of scientific evidence beyond laboratory studies [27.67]. Initial
growth on complex laboratory media prepared with
sea water, or on media made isotonic with sea water by the addition of NaCl, may not be an absolute
criterion of marine adaptation as many terrestrial origin microorganisms also grow on such media [27.67].
True marine bacteria might be differentiated from their
land counterparts through their need for Na
C in the
medium for growth but not by having requirements for
sea water [27.67, 68]. Our knowledge is still poor about
specific, natural nutrients and growth factors required
for their cultivation. As stated by Fenical [27.8] common media constituents such as peptone, simple sugars
etc. are unrealistic marine nutrients. These are apparently replaced with complex carbon sources such as
chitin, sulfated polysaccharides, and marine proteins in
the marine environment. In addition, there is still little understanding of the effects of uncommon inorganic
elements, such as lithium, silicon, etc., which are also
abundant in marine sediments. All these factors are still
today greatly limiting our ability to isolate and culture
the majority of the interesting and new bacterial forms
present [27.8].
There is a need to develop a full understanding on
the survival and marine adaptations of bacteria which
can then be translated into development of effective
selective isolation protocols [27.69]. One successful
approach for the terrestrial ones has been the use of
data deriving from physiological and growth requirements of terrestrial streptomycetes to design targetspecific selective isolation methods [27.70]. Adaptation
of such an approach for marine-derived taxa would
result in effective recovery as well as generating information on the physiology and growth requirements
of marine bacteria. Imada et al. [27.71] investigated
the growth and antimicrobial compound production
of marine actinomycetes in the presence of seawater. While the optimal concentration of growth ranged
from 10 to 30 % .v=v/, the production of antibacterial substances was observed in the concentration
range 60110 % .v=v/ despite poor growth, indicating that the production of antibiotics is seawaterdependent.
27.3.3 Bacteriophage-Guided Route
to Detection and Recovery
of Marine Actinomycetes
When detection of rare actinomycetes is targeted, particularly the marine derived ones with low abundance
frequency unless highly selective pressures are used,
these taxa could not easily be isolated [27.69]. One approach has been the use of indicator phages specific
towards targeted taxa using their close relatives as propagation hosts, and provided clues whether such species
would be present in those environments [27.72–75].
An interesting finding was the occurrence of polyvalent Salinispora phages infecting members of Micromonsporacea including the type strains of terrestrial
origin in Germany [27.74].
Stadler et al. [27.76] isolated cinnabaramides A–G,
analogs of lactacystin and salinosporamide from a terrestrial streptomycete. These observations and findings
might be in agreement of the above mentioned fact by
Penn and Jensen [27.65] that a recent introduction of
genera like Salinispora occurred into the marine environments and terrestrial relatives of these genera might
also carry similar biosynthetic genes coding for the
production of similar bioactive compounds. Udwary
et al. [27.77] however, have indicated that due to the
current lack of information on the other Micromonsporacea genome sequences, it is unclear whether this
natural product diversity is common to this family or
whether the diversity in Salinispora derives from environmental pressures present in marine environments.
Once the presence of bioactive taxa is indicated by
bacteriophages in an environmental sample, they can
also be used to reduce the numbers of unwanted taxa
on isolation plates making the growth medium available
for consumption by targeted organisms without competition [27.73, 75, 78].
Bacteriophages can also indicate the relatedness
of unknown bacteria to their closest relatives [27.72].
In recent reviews Kurtböke [27.75, 79] provided insights into bacteriophage–host interactions. Examples
included multiple strategies evolved by bacteriophages
to interfere with bacterial growth. Such host conquering
strategies used by the bacteriophages can provide clues
towards detection of new bioactive compounds such as
turning phage endolysins to enzybiotics [27.80].