306
the ability of AHLs to modulate multiple aspects of green algal reproduction and
early growth.
The effect of AHL is not only restricted to green algae but has also been observed
in red algal species such as Gracilaria and Acrochaetium species. In these macroalgae, C 4 - and C 6 -HSLs have been shown to control carpospore liberation (Weinberger
et al. 2007; Singh et al. 2015). Furthermore, sodium dodecyl sulphate- polyacrylamide
gel electrophoresis analysis of total protein of C 4 - and C 6 -HSL-treated cystocarps of
G. dura revealed the induction of specific polypeptide bands of approximate molecular weights 50 and 60 kDa (Singh et al. 2015). The finding suggested that these
unidentified proteins may have a role in carpospores releasing from cystocarp.
Nevertheless, identifying interconnection of these proteins and their expression
under AHL treatment would enhance knowledge about carpospore liberation from
G. dura.
15.3 Host-Associated Bacterial Diversity and NextGeneration Sequencing
There are a growing number of studies that have assessed the diversity of the epiphytic bacterial communities associated with macroalgal hosts (Staufenberger et al.
2008; Goecke et al. 2010; Burke et al. 2011a; Hollants et al. 2013). These studies
highlight that bacterial communities associated with macroalgal whilst distinct
from the bacteria found in the surrounding seawater vary across different seasons
(Tujula et al. 2010; Burke et al. 2011b), geographical locations (Tait et al. 2009;
Lachnit et al. 2011; Bondoso et al. 2014), different parts of the thallus (Staufenberger
et al. 2008) and different pools based on host trait (Campbell et al. 2015).
Several studies have suggested that bacteria within the phyla Proteobacteria and
Firmicutes are among the most abundant taxa associated with the surface of macroalgal hosts as summarized previously (Goecke et al. 2010; Singh and Reddy
2014). Therefore one might predict that these bacterial groups have particular characteristics that have enabled their adaptation to marine hosts, including but not limited to (1) the ability to cope with multiple stress parameters such as ionic, osmotic,
chaotropic, hydrophobic and other activities of solutes, (2) providing direct benefit
to the host (see below) and (3) having high-efficiency energy-generation systems
(Burke et al. 2011b; Wahl et al. 2012; Cray et al. 2013). With respect to host benefits, many of these bacterial communities are reported to possess various biological
activities such as antibacterial, antisettlement, antilarval and antifungal activities
(Egan et al. 2008; Penesyan et al. 2009) that also secure their abundance over the
host surface.
Early studies of bacterial communities associated with macroalgae employed
culture-dependent or microscopy methods with fewer studies employing cultureindependent molecular methods such as restriction fragment length polymorphism
and terminal restriction fragment length polymorphism of DNA for identifying bacR.P. Singh et al.
the ability of AHLs to modulate multiple aspects of green algal reproduction and
early growth.
The effect of AHL is not only restricted to green algae but has also been observed
in red algal species such as Gracilaria and Acrochaetium species. In these macroalgae, C 4 - and C 6 -HSLs have been shown to control carpospore liberation (Weinberger
et al. 2007; Singh et al. 2015). Furthermore, sodium dodecyl sulphate- polyacrylamide
gel electrophoresis analysis of total protein of C 4 - and C 6 -HSL-treated cystocarps of
G. dura revealed the induction of specific polypeptide bands of approximate molecular weights 50 and 60 kDa (Singh et al. 2015). The finding suggested that these
unidentified proteins may have a role in carpospores releasing from cystocarp.
Nevertheless, identifying interconnection of these proteins and their expression
under AHL treatment would enhance knowledge about carpospore liberation from
G. dura.
15.3 Host-Associated Bacterial Diversity and NextGeneration Sequencing
There are a growing number of studies that have assessed the diversity of the epiphytic bacterial communities associated with macroalgal hosts (Staufenberger et al.
2008; Goecke et al. 2010; Burke et al. 2011a; Hollants et al. 2013). These studies
highlight that bacterial communities associated with macroalgal whilst distinct
from the bacteria found in the surrounding seawater vary across different seasons
(Tujula et al. 2010; Burke et al. 2011b), geographical locations (Tait et al. 2009;
Lachnit et al. 2011; Bondoso et al. 2014), different parts of the thallus (Staufenberger
et al. 2008) and different pools based on host trait (Campbell et al. 2015).
Several studies have suggested that bacteria within the phyla Proteobacteria and
Firmicutes are among the most abundant taxa associated with the surface of macroalgal hosts as summarized previously (Goecke et al. 2010; Singh and Reddy
2014). Therefore one might predict that these bacterial groups have particular characteristics that have enabled their adaptation to marine hosts, including but not limited to (1) the ability to cope with multiple stress parameters such as ionic, osmotic,
chaotropic, hydrophobic and other activities of solutes, (2) providing direct benefit
to the host (see below) and (3) having high-efficiency energy-generation systems
(Burke et al. 2011b; Wahl et al. 2012; Cray et al. 2013). With respect to host benefits, many of these bacterial communities are reported to possess various biological
activities such as antibacterial, antisettlement, antilarval and antifungal activities
(Egan et al. 2008; Penesyan et al. 2009) that also secure their abundance over the
host surface.
Early studies of bacterial communities associated with macroalgae employed
culture-dependent or microscopy methods with fewer studies employing cultureindependent molecular methods such as restriction fragment length polymorphism
and terminal restriction fragment length polymorphism of DNA for identifying bacR.P. Singh et al.