Contrasting Antibacterial Capabilities of the Surface Mucus Layer From Three Symbiotic Cnidarians

Abstract

Rivera-Ortega and Thomé Antibacterial Capabilities of SML in Symbiotic Cnidarians In this work, we show that the surface mucus layer itself has antibacterial properties not associated with the bacteria this layer houses; such properties diminished due to disease or bleaching, while immunological responses increased in the mucus of diseased animals.

Local dynamics of a white syndrome outbreak and changes in the microbial community associated with colonies of the scleractinian brain coral Pseudodiploria strigosa

“…Changes in the bacterial community of coral holobionts in response to environmental stress, may affect the defense mechanisms contributing to the sensitivity of the host to bleaching and disease ( Bourne, Morrow & Webster, 2016 ). According to our observations, the antibacterial activity of the mucus layer effectively inhibited the growth of two potential pathogens of corals, regardless of the health status of the coral or the location into the colony (close or away from the lesion), as has been reported for this coral species with black band disease ( Rivera-Ortega & Thomé, 2018 ) and also for other diseased corals ( Palmer, Bythell & Willis, 2010 ; Ocampo et al, 2015 ). Phenoloxidase activity in P. strigosa behaved similarly to that reported in colonies affected by black band disease ( Rivera-Ortega & Thomé, 2018 ), although the overall values measured for this activity in the mucus of healthy and WS affected colonies (close and away to the lesion) were several orders of magnitude higher.…”

“…According to our observations, the antibacterial activity of the mucus layer effectively inhibited the growth of two potential pathogens of corals, regardless of the health status of the coral or the location into the colony (close or away from the lesion), as has been reported for this coral species with black band disease ( Rivera-Ortega & Thomé, 2018 ) and also for other diseased corals ( Palmer, Bythell & Willis, 2010 ; Ocampo et al, 2015 ). Phenoloxidase activity in P. strigosa behaved similarly to that reported in colonies affected by black band disease ( Rivera-Ortega & Thomé, 2018 ), although the overall values measured for this activity in the mucus of healthy and WS affected colonies (close and away to the lesion) were several orders of magnitude higher. These results suggest that the immunological response in P. strigosa was enhanced as reported in compromised, infected, and thermally stressed tissues of many coral species ( Palmer & Traylor-Knowles, 2012 ).…”

“…For the SML treatment, the mucus was sterilized for 20 min under UV light (254 nm) and its effect corroborated by incubating an irradiated sample on marine agar (Sobel Marine Agar, Difco) at 27 °C overnight and checking for the absence of bacterial growth. For antibacterial activity assessments, we employed a swarming assay combined with a double agar overlay assay, as previously described ( Rivera-Ortega & Thomé, 2018 ), challenging the SML and MC samples against two potential coral pathogens, Aurantimonas sp. (strain BAA-667, ATCC) and Serratia marcescens (strain BAA-632, ATCC) ( Patterson et al, 2001 ; Denner et al, 2003 ).…”

“…The synthesis of melanin is activated by pathways associated with invertebrate immune responses and is mainly used to entrap potential pathogens (reviewed in Palmer & Traylor-Knowles, 2018 ). In addition, phenoloxidase is an enzyme involved in the synthesis of melanin ( Palmer, Mydlarz & Willis, 2008 ; Mydlarz et al, 2009 ) whose activity can also be detected in the Surface Mucus Layer (SML) ( Rivera-Ortega & Thomé, 2018 ). This enzyme produces toxic intermediates, such as cytokines and reactive oxygen species, and its activity increases in corals challenged by pathogens, bleaching, and injuries ( Palmer, Mydlarz & Willis, 2008 ; Mydlarz et al, 2009 ; Palmer, Bythell & Willis, 2010 ; Van der Water et al, 2018 ).…”

A trade-off between mucocytes and bacteriocytes in Loripes orbiculatus gills (Bivalvia, Lucinidae): a mixotrophic adaptation to seasonality and reproductive status in a symbiotic species?

“…Beyond the role of mucus in particle capture for host nutrition, it also represents the first line of defence to fight harmful microbes in marine invertebrates. The structure and composition of the mucus covering the body surface in invertebrates influence its effectiveness in immunity; mucin matrices contain a large variety of bioactive molecules such as lysozymes, antimicrobial peptides (Vidal-Dupiol et al 2011, Destoumieux-Garzon et al 2016, Rivera-Ortega and Thomé 2018, and adhesion molecules such as lectins and agglutinins (Xing et al 2011;Pales-Espinosa et al 2016). The diversity of immune effectors found in mucus allows a tailored immune response (Allam and Pales-Espinosa, 2016) according to the type of hostmicrobe association.…”