323
recruiting the bacteria within the holobiont. Whereas some other studies have
revealed that coral-associated microbial species display site specificity with community composition that differs in location rather than coral species (Littman et al.
2009; Barott et al. 2011) which suggests that ecological factors have some role in
influencing the coral-associated-bacterial communities. It is not clear how bacteria
are associated with corals—whether corals recruit their own microbiota or microbes
choose to colonize the host. But in either case, the hypothetical mechanism behind
coral-bacterial association involves motility/chemotaxis (Tout et al. 2014) and quorum sensing (Ransome et al. 2014a).
Now, scientists are also focusing on microbial functioning rather than phylogeny
to define the diversity of microbial communities on the different coral host. Functional
studies based on metagenomics, transcriptomics, proteomics, and metabolomics will
provide us the knowledge related to the diversity and functionality of symbiotically
associated bacteria rather than opportunistic bacteria on the coral surface (Burke
et al. 2011). For example, Tout et al. (2014) studied microbial community composition and function within a coral reef ecosystem. They observed substantially different microbial compositions and metabolic functions between the four niches across
Heron Island Reef, within the Great Barrier Reef. The microbial composition of
seawater and sandy substrate is dominated by the genes associated with core housekeeping processes such as lipid, carbohydrate, protein, and nucleic acid metabolism,
whereas the metagenome from the coral surface had an enhanced occurrence of
genes associated with dynamic processes such as motility and chemotaxis. These
studies suggest that metabolic pathways and functional capabilities define the “core”
microbiota more accurately than the phylogenic diversity on the coral host (Krediet
et al. 2013). Thus, a scientist should combine both functional- based and phylogenetic-based studies to define the diversity of coral-associated bacteria.
16.4 Role of Coral-Associated Bacteria
Bacteria have a beneficial as well as a detrimental role in coral holobiont.
Understanding this role and mechanism behind them will probably help us in protecting the reef ecosystem, for instance, by the application of probiotic bacteria on
diseased corals. Moreover, we could find promising bacteria having commercial
application in the medical fields such as high antibiotic resistance and ROS scavenging properties. Maybe in the future, these bacteria can be taken as probiotic by
health-compromised patients.
16.4.1 Coral-Associated Bacteria as a Companion of Coral
Holobiont
The beneficial role of coral-associated bacteria involves nutrient supplying and
cycling such as carbon, nitrogen, and sulfur, larval metamorphosis and settlement,
host resilience, and disease resistance, by providing antibiotic defense against
16 Role of Bacteria in Coral Ecosystem
recruiting the bacteria within the holobiont. Whereas some other studies have
revealed that coral-associated microbial species display site specificity with community composition that differs in location rather than coral species (Littman et al.
2009; Barott et al. 2011) which suggests that ecological factors have some role in
influencing the coral-associated-bacterial communities. It is not clear how bacteria
are associated with corals—whether corals recruit their own microbiota or microbes
choose to colonize the host. But in either case, the hypothetical mechanism behind
coral-bacterial association involves motility/chemotaxis (Tout et al. 2014) and quorum sensing (Ransome et al. 2014a).
Now, scientists are also focusing on microbial functioning rather than phylogeny
to define the diversity of microbial communities on the different coral host. Functional
studies based on metagenomics, transcriptomics, proteomics, and metabolomics will
provide us the knowledge related to the diversity and functionality of symbiotically
associated bacteria rather than opportunistic bacteria on the coral surface (Burke
et al. 2011). For example, Tout et al. (2014) studied microbial community composition and function within a coral reef ecosystem. They observed substantially different microbial compositions and metabolic functions between the four niches across
Heron Island Reef, within the Great Barrier Reef. The microbial composition of
seawater and sandy substrate is dominated by the genes associated with core housekeeping processes such as lipid, carbohydrate, protein, and nucleic acid metabolism,
whereas the metagenome from the coral surface had an enhanced occurrence of
genes associated with dynamic processes such as motility and chemotaxis. These
studies suggest that metabolic pathways and functional capabilities define the “core”
microbiota more accurately than the phylogenic diversity on the coral host (Krediet
et al. 2013). Thus, a scientist should combine both functional- based and phylogenetic-based studies to define the diversity of coral-associated bacteria.
16.4 Role of Coral-Associated Bacteria
Bacteria have a beneficial as well as a detrimental role in coral holobiont.
Understanding this role and mechanism behind them will probably help us in protecting the reef ecosystem, for instance, by the application of probiotic bacteria on
diseased corals. Moreover, we could find promising bacteria having commercial
application in the medical fields such as high antibiotic resistance and ROS scavenging properties. Maybe in the future, these bacteria can be taken as probiotic by
health-compromised patients.
16.4.1 Coral-Associated Bacteria as a Companion of Coral
Holobiont
The beneficial role of coral-associated bacteria involves nutrient supplying and
cycling such as carbon, nitrogen, and sulfur, larval metamorphosis and settlement,
host resilience, and disease resistance, by providing antibiotic defense against
16 Role of Bacteria in Coral Ecosystem