Microbial functional genes associated with coral health and disease

Abstract

Both the incidence and prevalence of coral disease are rapidly increasing, and as a consequence, many studies involving coral microbial associates have been conducted. However, very few of these have considered microbial functional genes. This is an underutilized approach for studying coral disease etiology which is capable of revealing the molecular processes of the coral microbial community. This review presents a summary of the known microbial functional genes that have been linked to coral health and disease. Overall functional gene diversity tended to be lower in healthy corals than diseased or bleached corals, and respiration and photosynthesis functional genes appeared to be crucial to coral health. Genes associated with the nitrogen cycle were the most studied, were highly represented within the coral holobiont, and their expression often shifted in diseased or stressed individuals. Carbon metabolism, such as fatty acid and amino acid catabolism, also tended to shift in unhealthy corals. Genes associated with sulfite respiration as well as dimethylsulfoniopropionate degradation have been detected, although they have yet to be directly associated with coral disease. In addition, genes associated with xenobiotic degradation, antibiotic resistance, virulence, and oxidative stress may all be involved in maintaining coral health. However, the links between these functional genes and their roles in interacting with the coral host are not clear. Continuing identification of coral-associated microbial functional genes within the coral holobiont should facilitate advances in the field of coral health and disease. KEY WORDS: Etiology · Biogeochemical cycling · Holobiont · Functional diversity · Antibiotic resistance Resale or republication not permitted without written consent of the publisherDis Aquat Org 107: [161][162][163][164][165][166][167][168][169][170][171] 2013 diversity and the specific microbial habitat in which the bacteria were detected, as there was with functional gene diversity (Dinsdale et al. 2008). In most cases, the taxonomic identification of a microbe does not elucidate its functional role, giving little indication as to a microbe's importance. To complicate matters further, bacterial species with the same 16S rRNA gene sequence may play different roles in an ecosystem . On the other hand, bacterial species with different 16S rRNA gene sequences may be functionally redundant, with more than one taxonomic group satisfying a single niche (Allison & Martiny 2008). For these reasons, it is crucial that studies begin to examine the role that microbes play in coral health and disease, rather than focus on identification of the microbes present. As an example, 'Type A' Gammaproteobacteria have commonly been associated with healthy fragments of the coral Acropora, and it has been proposed that a disruption in this population may alter the entire microbial community (Kvennefors et al. 2010(Kvennefors et al. , 2012 and increase the coral's vulnerability to disease and bleaching. However, ...

Whole transcriptome analysis reveals changes in expression of immune-related genes during and after bleaching in a reef-building coral

“…and 'other-eukaryotes' transcriptomes represented a low percentage of the total number of reads obtained during sequencing. This observation suggests that the overall condition of the colony is a result of the physiological tolerance of each of the elements of the holobiont, but can also be a reflection of the different genetic composition of each portion across time [69][70][71][72][73].…”

Coral—the world's most diverse symbiotic ecosystem

“…), to pathogenesis/disease (Rosenberg et al . ; Richardson ; Pratte ), immunology (Work & Aeby ), host resilience (Raina et al . ), disease resistance (Krediet et al .…”

Coral-Associated Bacterial Diversity Is Conserved across Two Deep-Sea Anthothela Species

“…Understanding the metabolic pathways and biochemical processing of nutrients such as nitrogen, carbon, and sulfur are essential in coral health and development ( Zhang et al, 2015 ). Based on phylogenetic inference and functional gene data, nitrogen-cycling microbes appear to be common members of tropical stony coral microbiomes ( Wegley et al, 2007 ; Olson et al, 2009 ; Kimes et al, 2010 ; Lema et al, 2012 , 2014 ; Olson and Lesser, 2013 ; Pratte, 2013 ; Yang et al, 2013 , 2015 ) and have been suggested to be species-specific ( Wafar et al, 1990 ; Lema et al, 2012 ). The process of nitrogen fixation has been detected in a number of tropical stony corals ( Williams et al, 1987 ; Shashar et al, 1994 ; Grover et al, 2014 ; Rädecker et al, 2014 ), as has nitrification ( Wafar et al, 1990 ).…”