Antibacterial chemical defenses in Hawaiian corals provide possible protection from disease

Abstract

Diseases of marine organisms, and corals in particular, have been reported with increasing frequency over the past 3 decades. Although little is known about resistance to disease in corals, a potential mechanism of defense is the production of antimicrobial compounds that protect corals from microbial pathogens. We assessed the antibacterial activity of crude aqueous extracts from 3 common Hawaiian reef corals, Montipora capitata, Porites lobata, and Pocillopora meandrina, against 9 strains of bacteria. The bacteria selected included known coral pathogens, potential marine pathogens found in human waste, and bacteria previously identified from the surfaces of Hawaiian corals. Extracts from all 3 coral species exhibited high levels of antibacterial activity. Overall, 54.3% of assays resulted in bacterial growth inhibition. In addition, 9.9% of extracts stimulated the growth of certain bacteria. Although levels of overall antibacterial activity did not differ significantly among coral species (ranging from 40.7% of assays for P. meandrina to 63.0% of assays for M. capitata), the 3 species exhibited a high degree of selectivity as demonstrated by significant variability in their effects toward specific bacteria. Extracts also exhibited intraspecific variability, both within and between sites, and significant site-by-species interactions were observed against 6 of 9 bacterial strains. In M. capitata, healthy corals had significantly higher levels of antibacterial activity than those affected by Montipora White Syndrome, and affected tissues had significantly higher levels of antibacterial activity than unaffected tissues. Variability in antibacterial activity of Hawaiian corals may, in part, explain differential susceptibility to disease at the colony, species, or population level.

Patterns of coral ecological immunology: variation in the responses of Caribbean corals to elevated temperature and a pathogen elicitor

“…Geffen and Rosenberg, 2005;Xian et al, 2009), thus killing potentially harmful bacteria within the immediate surroundings. Conversely, there is also evidence that within-tissue bactericidal activity is increased in corals naturally infected with yellow band disease (Mydlarz et al, 2009) and white syndrome relative to unaffected parts of the same colony (Gochfeld and Aeby, 2008). These studies of within-tissue bactericidal activity of naturally infected corals may not accurately compare with our study because the effects of the infecting bacteria themselves and the coral mucus may play a large role in observed antimicrobial activity (Ritchie, 2006).…”

“…In fact, only the ambient temperature controls of S. intersepta extracts actually demonstrated any bactericidal activity; the rest of the treatments promoted growth of V. alginolyticus, which has been reported previously for another coral species (Gochfeld and Aeby, 2008). Although the significant decrease in bactericidal activity by both M. faveolata and S. intersepta in response to the LPS and elevated temperature treatments appear counter-productive to an effective immune response, antibacterial compounds may be released upon recognition of an immune challenge (e.g.…”

“…However, antimicrobial, or bactericidal, activity of secondary metabolites (Slattery et al, 1995;Mydlarz and Jacobs, 2006;Dunn, 2009) of the mucus layer (Brown and Bythell, 2005) and of symbiotic bacteria (Ritchie, 2006) has been established for several coral species. Furthermore, the release of bactericidal activity has been demonstrated in response to mechanical agitation of corals (Geffen and Rosenberg, 2005;Geffen et al, 2009) and tissue bactericidal activity has been shown to increase in infected corals (Gochfeld and Aeby, 2008;Mydlarz et al, 2009). These studies indicate that bactericidal activity is a key component of coral defense and therefore is a useful measurement for ascertaining levels of immunity.…”

Fourier-transformed infrared spectroscopy: a tool to identify gross chemical changes from healthy to yellow band disease tissues

“…Each of these habitats provide numerous carbon sources for different microbial guilds that play an important role in nutrient cycling and/or the biogeochemistry of corals (Ferrier-Pagès et al 1998, 2000, Lesser et al 2007, Chimetto et al 2008, Olson et al 2009, Raina et al 2009, Kimes et al 2010. Coral microbial associations are also important for the synthesis and metabolism of a myriad of organic compounds, such as lipids, carbohydrates, organic acids, glycoproteins and more complex polymers, such as enzymes and antibiotic-like compounds (Rohwer & Kelley 2004, Kelman et al 2006, Ritchie 2006, Nis simov et al 2009, Shnit-Orland & Kushmaro 2009, Kvennefors et al 2010, that are essential either for metabolism (Ritchie & Smith 1995, 2004 and/or for various mechanisms of defense (Gochfeld & Aeby 2008).…”

“…Each of these habitats provide numerous carbon sources for different microbial guilds that play an important role in nutrient cycling and/or the biogeochemistry of corals (Ferrier-Pagès et al 1998, 2000, Lesser et al 2007, Chimetto et al 2008, Olson et al 2009, Raina et al 2009, Kimes et al 2010. Coral microbial associations are also important for the synthesis and metabolism of a myriad of organic compounds, such as lipids, carbohydrates, organic acids, glycoproteins and more complex polymers, such as enzymes and antibiotic-like compounds (Rohwer & Kelley 2004, Kelman et al 2006, Ritchie 2006, Nis simov et al 2009, Shnit-Orland & Kushmaro 2009, Kvennefors et al 2010, that are essential either for metabolism (Ritchie & Smith 1995, 2004 and/or for various mechanisms of defense (Gochfeld & Aeby 2008).The chemical composition of the SML and the coral tissues are both susceptible to rapid change due to variations in the contribution of photoassimilates of zooxanthellae, the metabolism of microbial partners and/or the coral host (Rowan et al 1997, Ritchie & Smith 1995, 2004), for such a physi cally close assemblage typically shows a high degree of syntropy or co-metabolism. Because the structure and function of the coral-associated microbiota shift from healthy to YBD states (Kimes et al 2010, Cróquer et al 2012, it should not be surprising that the chemical properties of the SML and the coral tissues change accordingly with the status of the coral host because the organic by-products of particular metabolic groups of bacteria are often the organic substrates for another (Ritchie & Smith 2004).…”