308
communities belonging to Chloroflexi, Poribacteria and Acidobacteria were most
abundant and some of the functional characteristics of genes were identified that
were related to membrane transport, nitrification and related biological process
(Radax et al. 2012). Another study of Yang and Li (2012) demonstrated that nitrogen cycling genes (ammonia oxidizing) only present in the endosome tissue rather
than cortex region of the sponge (Astrosclera willeyana).
Microbiomes of macroalgae have not been as extensively investigated as compared to other hosts (sponges and human gut). However, few studies have used
metagenomic approach to identify composition and function of associated microbial communities (Burke et al. 2011a; de Oliveira et al. 2012; Dittami et al. 2014;
Martin et al. 2014; Campbell et al. 2015; Marzinelli et al. 2015). Martin et al. (2014)
studied functional metagenomics of bacterial communities associated with the
brown alga Ascophyllum nodosum and identified 13 novel putative esterase loci and
2 glycoside hydrolase loci. Marzinelli et al. (2015) studied bacterial and archaeal
communities associated with 260 samples of the kelp Ecklonia radiata from different biogeographical regions across the Australian continent and found extremely
stable microbial communities that were influenced by host state more than location.
Metagenomic studies of microbial communities of the Ulva australis indicate that
microbial communities on seaweeds are established based on a conservation of
functional traits rather than microbial species composition (Burke et al. 2011a).
Core groups of functional gene predicted to be important for algal association have
been repeatedly identified in microbial communities of U. australis including those
related to nitrate reduction, motility, QS systems, osmoregulation, cell differentiation, virulence and defence. Of particular relevance to microbial communities associated with macroalgae included stress responses relevant to protection against
oxidative stress, desiccation as well as degradation of host-secreted metabolites. de
Oliveira et al. (2012) have used transcriptomics analysis on the red macroalga
(Laurencia dendroidea) and their associated microbiome. Dominant bacterial
groups belonging to nitrogen-fixing Cyanobacteria and aerobic heterotrophic
Proteobacteria were identified. Comparative analysis of transcripts revealed an
abundance of transcripts related to glycolysis, polysaccharide and lipid breakdown.
Other features of the metatranscriptomics included the expression of genes related
to recognition of macroalgal surface, biofilm formation and mechanism for host
defence resistance and stress (biosynthesis of terpenoid backbone) (de Oliveira
et al. 2012). Transcripts related to bacterial QS signalling were also detected in the
meta-transcriptome analysis of L. dendroidea microbiome, including a high abundance for genes coding for the enzyme S-adenosylmethionine synthetases, an
important precursor for the synthesis of bacterial AHLs (Hanzelka and Greenberg
1996) among other biological reactions (Takusagawa et al. 1996). Whilst many
functional activities of the microbiome of L. dendroidea are congruent with those
associated with that of the U. australis (Burke et al. 2011a), the studies to date represent a snapshot of these complex communities. There is a need not only to further
validate these studies but to assess the stability of the microbial community and the
microbiome response to different environmental conditions commonly exposed to
the host. With the increased accessibility to next-generation sequencing (NGS)
R.P. Singh et al.
communities belonging to Chloroflexi, Poribacteria and Acidobacteria were most
abundant and some of the functional characteristics of genes were identified that
were related to membrane transport, nitrification and related biological process
(Radax et al. 2012). Another study of Yang and Li (2012) demonstrated that nitrogen cycling genes (ammonia oxidizing) only present in the endosome tissue rather
than cortex region of the sponge (Astrosclera willeyana).
Microbiomes of macroalgae have not been as extensively investigated as compared to other hosts (sponges and human gut). However, few studies have used
metagenomic approach to identify composition and function of associated microbial communities (Burke et al. 2011a; de Oliveira et al. 2012; Dittami et al. 2014;
Martin et al. 2014; Campbell et al. 2015; Marzinelli et al. 2015). Martin et al. (2014)
studied functional metagenomics of bacterial communities associated with the
brown alga Ascophyllum nodosum and identified 13 novel putative esterase loci and
2 glycoside hydrolase loci. Marzinelli et al. (2015) studied bacterial and archaeal
communities associated with 260 samples of the kelp Ecklonia radiata from different biogeographical regions across the Australian continent and found extremely
stable microbial communities that were influenced by host state more than location.
Metagenomic studies of microbial communities of the Ulva australis indicate that
microbial communities on seaweeds are established based on a conservation of
functional traits rather than microbial species composition (Burke et al. 2011a).
Core groups of functional gene predicted to be important for algal association have
been repeatedly identified in microbial communities of U. australis including those
related to nitrate reduction, motility, QS systems, osmoregulation, cell differentiation, virulence and defence. Of particular relevance to microbial communities associated with macroalgae included stress responses relevant to protection against
oxidative stress, desiccation as well as degradation of host-secreted metabolites. de
Oliveira et al. (2012) have used transcriptomics analysis on the red macroalga
(Laurencia dendroidea) and their associated microbiome. Dominant bacterial
groups belonging to nitrogen-fixing Cyanobacteria and aerobic heterotrophic
Proteobacteria were identified. Comparative analysis of transcripts revealed an
abundance of transcripts related to glycolysis, polysaccharide and lipid breakdown.
Other features of the metatranscriptomics included the expression of genes related
to recognition of macroalgal surface, biofilm formation and mechanism for host
defence resistance and stress (biosynthesis of terpenoid backbone) (de Oliveira
et al. 2012). Transcripts related to bacterial QS signalling were also detected in the
meta-transcriptome analysis of L. dendroidea microbiome, including a high abundance for genes coding for the enzyme S-adenosylmethionine synthetases, an
important precursor for the synthesis of bacterial AHLs (Hanzelka and Greenberg
1996) among other biological reactions (Takusagawa et al. 1996). Whilst many
functional activities of the microbiome of L. dendroidea are congruent with those
associated with that of the U. australis (Burke et al. 2011a), the studies to date represent a snapshot of these complex communities. There is a need not only to further
validate these studies but to assess the stability of the microbial community and the
microbiome response to different environmental conditions commonly exposed to
the host. With the increased accessibility to next-generation sequencing (NGS)
R.P. Singh et al.