Part A | 8.2
222 Part A Marine Flora and Fauna
kinase cascades are all present [8.8], and compounds
with antimicrobial and anti-inflammatory properties
have been extracted from sponge tissues. The primary
producer of sponge-derived secondary metabolites is,
however, still quite unclear although many of the
sponge-derived compounds identified to date strongly
resemble compounds that are known to be produced by
microbes [8.9].
8.2 Sponge-Associated Microorganisms
Marine sponges play host to microbes from all domains
of life; Eukarya [8.10, 11], Archaea [8.12, 13], and Bacteria [8.7]. Viruses and bacteriophages have also been
detected in sponge tissues [8.14, 15]. These close and
consistent associations are thought to be based on various symbiotic relationships including commensalist
and mutualist [8.16], as well as parasitic. Microbes are
also a significant food source for marine sponges [8.17]
which, as sessile animals, must derive their nutrition by
active filter-feeding from ambient seawater. This water
filtering activity results in a remarkable enrichment of
microbes in sponge tissues where 10
8
10
10 bacteria=g
wet weight have been recorded [8.18], with microorganisms constituting up to 35% of the total sponge
biomass and densities exceeding 10
9 microbial cells/cm
of sponge tissue; which is three to four orders of
magnitude greater than the density of bacteria in the
surrounding seawater (10
6 mL
1 ).
8.2.1 Sponge-Associated Bacteria
Bacterial associates of sponges have been investigated
through the use of both culture-dependent and cultureindependent methods. Culture isolation from sponges
is, like all other environmental sources, hampered by
the great plate anomaly where less than 1% of taxa observed through other methods have proven amenable to
culture under laboratory conditions through traditional
or, indeed, more novel innovative approaches [8.9].
Researchers have used a wide range of culture
conditions (including various growth media and different incubation temperatures) in attempts to access as
wide a variety of bacterial diversity as possible [8.19–
25]. Others have targeted the isolation of particular
taxa of interest [8.26–40]. In addition, a number of
innovative culture isolation methods have been employed, including the manipulation of bacterial communities through antibiotic administration prior to isolation [8.41], or other quite imaginative approaches such
as liquid culturing and floating-filter culturing methodologies [8.42].
Despite these efforts the same bacterial phyla repeatedly appear following culture isolations, with members of only seven bacterial phyla (Proteobacteria, Firmicutes, Actinobacteria, Planctomycetes, Verrucomicrobia, Cyanobacteria, and Bacteroidetes) [8.7] to date
being isolated in culture from sponge tissues; despite
the observation that > 30 phyla or candidate phyla can
be found in close association with sponges through
molecular methods [8.9]. Notwithstanding this, diverse
novel bacterial taxa are regularly isolated from sponge
species worldwide (Table 8.1).
Culture-Independent Analyses
Microscopy. The presence of bacteria in the mesohyl
of sponges was first confirmed in the early 1960s [8.69]
by use of electron microscopy (EM). Subsequently,
EM studies reported various cell types, including
Cyanobacteria, in sponge tissues [8.70], and later still
dense bacterial cell populations in sponge mesohyl tissues [8.71] were estimated to comprise 30% of the
sponge biomass. Scanning electron microscopy (SEM)
was subsequently employed to report the presence of
unicellular cyanobacteria and non-photosynthetic filamentous cyanobacteria in the tissues of Theonella swinhoei [8.72]. The development of fluorescence in situ
hybridization (FISH) allowed subsequent investigators
to identify particular bacterial taxa and their spatial distribution within sponge tissues by designing probes to
target particular 16S ribosomal ribonucleic acid (rRNA)
genes. This allowed for the identification of Cyanobacteria [8.73, 74], Actinobacteria, Bacteroidetes, Planctomycetes as well as - and ˇ-Proteobacteria [8.38] in
sponges, and also demonstrated the vertical transmission of eubacteria and archaea in sponge larvae [8.75].
16S rRNA Clone Libraries. Polymerase chain reaction (PCR)-based approaches involving the amplification of 16S ribosomal deoxyribonucleic acid (rDNA)
molecules and their subsequent cloning and analysis
have been successfully employed to allow the species’
composition of unculturable sponge-associated bacte-
222 Part A Marine Flora and Fauna
kinase cascades are all present [8.8], and compounds
with antimicrobial and anti-inflammatory properties
have been extracted from sponge tissues. The primary
producer of sponge-derived secondary metabolites is,
however, still quite unclear although many of the
sponge-derived compounds identified to date strongly
resemble compounds that are known to be produced by
microbes [8.9].
8.2 Sponge-Associated Microorganisms
Marine sponges play host to microbes from all domains
of life; Eukarya [8.10, 11], Archaea [8.12, 13], and Bacteria [8.7]. Viruses and bacteriophages have also been
detected in sponge tissues [8.14, 15]. These close and
consistent associations are thought to be based on various symbiotic relationships including commensalist
and mutualist [8.16], as well as parasitic. Microbes are
also a significant food source for marine sponges [8.17]
which, as sessile animals, must derive their nutrition by
active filter-feeding from ambient seawater. This water
filtering activity results in a remarkable enrichment of
microbes in sponge tissues where 10
8
10
10 bacteria=g
wet weight have been recorded [8.18], with microorganisms constituting up to 35% of the total sponge
biomass and densities exceeding 10
9 microbial cells/cm
of sponge tissue; which is three to four orders of
magnitude greater than the density of bacteria in the
surrounding seawater (10
6 mL
1 ).
8.2.1 Sponge-Associated Bacteria
Bacterial associates of sponges have been investigated
through the use of both culture-dependent and cultureindependent methods. Culture isolation from sponges
is, like all other environmental sources, hampered by
the great plate anomaly where less than 1% of taxa observed through other methods have proven amenable to
culture under laboratory conditions through traditional
or, indeed, more novel innovative approaches [8.9].
Researchers have used a wide range of culture
conditions (including various growth media and different incubation temperatures) in attempts to access as
wide a variety of bacterial diversity as possible [8.19–
25]. Others have targeted the isolation of particular
taxa of interest [8.26–40]. In addition, a number of
innovative culture isolation methods have been employed, including the manipulation of bacterial communities through antibiotic administration prior to isolation [8.41], or other quite imaginative approaches such
as liquid culturing and floating-filter culturing methodologies [8.42].
Despite these efforts the same bacterial phyla repeatedly appear following culture isolations, with members of only seven bacterial phyla (Proteobacteria, Firmicutes, Actinobacteria, Planctomycetes, Verrucomicrobia, Cyanobacteria, and Bacteroidetes) [8.7] to date
being isolated in culture from sponge tissues; despite
the observation that > 30 phyla or candidate phyla can
be found in close association with sponges through
molecular methods [8.9]. Notwithstanding this, diverse
novel bacterial taxa are regularly isolated from sponge
species worldwide (Table 8.1).
Culture-Independent Analyses
Microscopy. The presence of bacteria in the mesohyl
of sponges was first confirmed in the early 1960s [8.69]
by use of electron microscopy (EM). Subsequently,
EM studies reported various cell types, including
Cyanobacteria, in sponge tissues [8.70], and later still
dense bacterial cell populations in sponge mesohyl tissues [8.71] were estimated to comprise 30% of the
sponge biomass. Scanning electron microscopy (SEM)
was subsequently employed to report the presence of
unicellular cyanobacteria and non-photosynthetic filamentous cyanobacteria in the tissues of Theonella swinhoei [8.72]. The development of fluorescence in situ
hybridization (FISH) allowed subsequent investigators
to identify particular bacterial taxa and their spatial distribution within sponge tissues by designing probes to
target particular 16S ribosomal ribonucleic acid (rRNA)
genes. This allowed for the identification of Cyanobacteria [8.73, 74], Actinobacteria, Bacteroidetes, Planctomycetes as well as - and ˇ-Proteobacteria [8.38] in
sponges, and also demonstrated the vertical transmission of eubacteria and archaea in sponge larvae [8.75].
16S rRNA Clone Libraries. Polymerase chain reaction (PCR)-based approaches involving the amplification of 16S ribosomal deoxyribonucleic acid (rDNA)
molecules and their subsequent cloning and analysis
have been successfully employed to allow the species’
composition of unculturable sponge-associated bacte-