Utilization of Mucus from the Coral Acropora palmata by the Pathogen Serratia marcescens and by Environmental and Coral Commensal Bacteria

Abstract

In recent years, diseases of corals caused by opportunistic pathogens have become widespread. How opportunistic pathogens establish on coral surfaces, interact with native microbiota, and cause disease is not yet clear. This study compared the utilization of coral mucus by coral-associated commensal bacteria ("Photobacterium mandapamensis" and Halomonas meridiana) and by opportunistic Serratia marcescens pathogens. S. marcescens PDL100 (a pathogen associated with white pox disease of Acroporid corals) grew to higher population densities on components of mucus from the host coral. In an in vitro coculture on mucus from Acropora palmata, S. marcescens PDL100 isolates outgrew coral isolates. The white pox pathogen did not differ from other bacteria in growth on mucus from a nonhost coral, Montastraea faveolata. The ability of S. marcescens to cause disease in acroporid corals may be due, at least in part, to the ability of strain PDL100 to build to higher population numbers within the mucus surface layer of its acroporid host. During growth on mucus from A. palmata, similar glycosidase activities were present in coral commensal bacteria, in S. marcescens PDL100, and in environmental and human isolates of S. marcescens. The temporal regulation of these activities during growth on mucus, however, was distinct in the isolates. During early stages of growth on mucus, enzymatic activities in S. marcescens PDL100 were most similar to those in coral commensals. After overnight incubation on mucus, enzymatic activities in a white pox pathogen were most similar to those in pathogenic Serratia strains isolated from human mucosal surfaces.

Catabolite regulation of enzymatic activities in a white pox pathogen and commensal bacteria during growth on mucus polymers from the coral Acropora palmata

“…Consistent with this hypothesis, of all the tested coral and environmental bacteria, Serratia marcescens PDL100 reached the highest final population density when grown in vitro on mucus of Acropora palmata (Krediet et al 2009). This strain of S. marcescens was originally isolated as a cause of white pox, a rapidly progressing coral tissue necrosis of the threatened Caribbean coral A. palmata (Patterson et al 2002).…”

“…This strain of S. marcescens was originally isolated as a cause of white pox, a rapidly progressing coral tissue necrosis of the threatened Caribbean coral A. palmata (Patterson et al 2002). The observations that the white pox strain was more efficient at utilizing mucus of the host coral in vitro suggested that this ability to efficiently degrade mucus may be linked to its pathogenicity (Krediet et al 2009).…”

“…The ability to utilize coral mucus as a growth substrate involves glycosidases, proteases and esterases (Vacelet & Thomassin 1991, Krediet et al 2009). These enzymatic activities are generally consistent with the composition of coral mucus.…”

Signaling-mediated cross-talk modulates swarming and biofilm formation in a coral pathogen Serratia marcescens

“…Bacterial receptors can bind to mucus (Rosenberg and Falkovitz, 2004;Kvennefors et al, 2008), and this directly controls the composition of the associated microbiota. The mucus polymer itself and small molecular weight compounds within it serve as both nutrient sources for the microbes and signals that modulate behavior and gene expression in the associated microbial communities (Vacelet and Thomassin, 1991;Wild et al, 2004;Ritchie, 2006;Sharon and Rosenberg, 2008;Krediet et al, 2009aKrediet et al, , 2009b. Although the fate of coral mucus in the reef environment and its role in coral-associated microbial communities are becoming more clear, significantly less is known about the microbe-microbe interactions within the coral surface mucus layer.…”

Members of native coral microbiota inhibit glycosidases and thwart colonization of coral mucus by an opportunistic pathogen

“…Coral mucus supports growth of bacteria up to 10 6 -10 8 cfu ml À 1 (Sharon and Rosenberg, 2008;Krediet et al, 2009b;Garren and Azam, 2010). Nutrients and chemicals from the host excreted with the mucus determine the composition and structure of the associated microbial communities (Ritchie, 2006;Garren and Azam, 2012).…”