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Coral Microbiology , Volume 2, a Quarterly 20, Number the O Journal of by Eugene Rosenberg, Christina A This article has This been published in or collective redistirbution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The approval portionthe ofwith any permitted articleonly photocopy by is of machine, reposting, this means or collective or other redistirbution A S E A O F M I cr OB E S > SecTION V. EX AMPLES OF DIverSITY > CHAPTer 10. MIcrOBIAL COmmUNITIES Oceanography > C. COR AL Reef MIcrOBIOLOGY Coral Microbiology journal of The 20, Number 2, a quarterly , Volume BY EUGene ROSenBerG, CHRISTINA A . KELLOGG, AND FOreST ROHWer In the last 30 years, there has been their effects by altering the microbial tains multiple “taxa” (Baker, 2003). A approximately a 30% loss of corals population and causing certain microbes single species of coral can host multiple O worldwide, largely due to emerging dis- to become pathogens. types of Symbiodinium, often contain- ceanography eases (Harvell et al., 2002, 2007; Hughes ing different clades at different depths et al., 2003). Coral microbiology is a new MIcrOORGANISMS ASSOCIATED (Rowan and Knowlton, 1995). Reviews S ociety. Copyright 2007 by The 2007 by Copyright ociety. field, driven largely by a desire to under- WITH HeALTHY CORALS of Symbiodinium diversity, systematics, stand the interactions between corals The coral holobiont (host organism plus and relationships to coral diseases are and their symbiotic microorganisms and all of its associated microorganisms) is presented by Baker (2003, 2004). to use this knowledge to eventually pre- a complex system containing microbial vent the spread of coral diseases. representatives of all three domains: Bacteria O ceanography ceanography The last decade has brought substan- Eucarya, Bacteria, and Archaea, as well Corals provide three general habitats for O ceanography ceanography tial progress in determining the abun- as numerous viruses (Figure 1). We dis- bacteria: the surface mucus layer, coral S dance and diversity of microorganisms cuss the microorganisms associated with tissue, and the calcium carbonate skel- ociety. S associated with healthy and diseased healthy coral communities in the next eton, each of which has a distinct bac- ociety. A ll rights reserved. corals. Much of this progress is the result few sections, and then turn to the coral terial population (Bourne and Munn, S end all correspondence to: [email protected] or Th e [email protected] to: correspondence all end of the introduction of culture-indepen- diseases related to microbes. 2005; Koren and Rosenberg, 2006). It is dent molecular techniques into coral likely that within each of these habitats P microbiology (Rohwer et al., 2001). Eucarya (Zooxanthellae) there are microniches. Initially, research reproduction, systemmatic Republication, article use for research. and this copy in teaching to granted is ermission Consideration of the data published to Corals contain endosymbiotic dino- in coral microbiology concentrated on date leads to the hypothesis that envi- flagellates (algae) of the genus the mucus fraction, using culturing tech- ronmental stress factors contributing Symbiodinium, commonly referred to niques. These studies demonstrated that to coral disease, such as climate change, as zooxanthellae. Zooxanthellae pro- the mucus harbors a diverse and abun- water pollution, and overfishing, exert vide a large part of their hosts’ energy dant bacterial community (Ducklow and O ceanography ceanography requirements by transferring photo- Mitchell, 1979; Ritchie and Smith, 1997), EUGene ROSenBerG ([email protected]) synthetically fixed carbon to the coral including nitrogen fixers (Shashar et al., S is Professor, Department of Microbiology, (Fallowski et al., 1984). The algae also 1994; Lesser et al., 2004). The concen- ociety, Tel Aviv University, Tel Aviv, Israel. produce large amounts of molecular tration of colony-forming bacteria in PO 5 6 B CHRISTINA A. KELLOGG is Microbiologist, oxygen, which allow for efficient respi- the mucus is 10 –10 per ml (Koren and 1931, Rockville,ox M U.S. Geological Survey Center for Coastal ration by the coral and associated pro- Rosenberg, 2006; Ducklow and Mitchell, and Watershed Studies, St. Petersburg, karyotes. We now know from molecular 1979), about 0.2% of the total counts FL, USA. FOreST ROHWer is Assistant evidence that the genus Symbiodinium determined microscopically using a D Professor, San Diego State University, San is diverse, containing more than seven common technique for detecting micro- 20849-1931, Diego, CA, USA. principal clades, each of which con- organisms called SYBR Gold Staining USA . 146 Oceanography Vol. 20, No. 2 Protist Figure 1. The coral holobiont consists of Zooxanthellae the coral animal and associated viruses, microbes (both bacteria and archaea), zooxanthellae, and endolithic organisms. Most of the viruses are phages, which attack the microbes. The endolithic organisms include algae, fungi, sponges, and microbes that bore into the coral skeleton. The holobiont likely occupies different coral reef niches by mixing and matching different components (i.e., the Probiotic Hypothesis). Zooxanthellae and protist micrographs by Linda Wegley and Ian Hewson, respectively Endolithic Algae Viruses, Bacteria, & Archaea (Koren and Rosenberg, 2006). Culture-free, DNA-based techniques found on the same coral species that are Bacteria can also be found in coral first applied by Rohwer et al. (2001) geographically separated, while different tissue after removal of the mucus and to the study of coral bacteria provide populations are found on different coral skeleton. The numbers of culturable and useful data on the bacterial commu- species; and (5) different populations total tissue bacteria are similar to those nity associated with different corals are found in mucus and tissue from the found in mucus. However, the abundant (Bourne and Munn, 2005; Koren and same coral fragment. bacterial species associated with coral tis- Rosenberg, 2006; Pantos et al., 2003; sue is very different from those found in Rohwer et al., 2001, 2002; Frias-Lopez Archaea mucus (Bourne and Munn, 2005; Koren et al., 2002; Cooney et al., 2002; Sekar Previously pigeonholed as extremo- and Rosenberg, 2006). et al., 2006; Casas et al., 2004). Certain philes, archaea have been found in a Coral skeletons are porous struc- generalizations are beginning to emerge: number of mesophilic marine niches: tures inhabited by a variety of bacteria. (1) the diversity of bacterial species asso- coastal waters (DeLong 1992; Fuhrman This endolithic community may sat- ciated with a particular coral species is et al., 1992), marsh sediments (Munson isfy 50% of the nitrogen required by high, including a majority of novel spe- et al., 1997), fishes (van der Maarel et the coral (Ferrer and Szmant, 1988). cies; (2) bacteria in a particular coral al., 1998, 1999), sponges (Preston et al., Cyanobacteria in the skeleton of Oculina community are different from those 1996; Margot et al., 2002; Webster et al., patagonica provide photoassimilates to in the seawater surrounding the coral, 2001), a sea cucumber (McInerney et the coral tissue (Fine and Loya, 2002). suggesting the association is specific; al., 1995), and several species of corals These may be critical for the survival of (3) the species composition of the uncul- (Kellogg, 2004; Wegley et al., 2004). Like the coral during times when it loses its tured bacterial population is completely coral-associated bacterial communities, endosymbiotic algae, a disease referred different from the cultured population; these archaeal communities are distinct to as coral bleaching. (4) similar bacterial populations are from those in surrounding seawater, Oceanography June 2007 147 they consist of undescribed species, and particles (VLP) in the water above corals. nism by which viruses might be involved different populations appear to inhabit Microscale profiles show that VLP abun- in coral bleaching. However, the field of the mucus and the tissue. The mucus dance is significantly higher closest to coral virology is still extremely under- samples were dominated by euryar- the coral surface. It also appears that studied and a major effort to uncover chaeotes (Kellogg, 2004) and the tissue VLP concentrations are highest above the diversity and identity of coral viruses samples by crenarchaeotes (Wegley et al., healthy and diseased corals, in compari- present in healthy versus stressed corals 2004). Unlike zooxanthellae and bacteria, son to coral rubble (Patten et al., 2006). is desperately needed (Davy et al., 2006). however, there is no evidence of species- The authors suggest that there are fun- specific associations between particular damental shifts in the VLP and bacterial InfecTIOUS DISEASES OF CORALS archaea and individual corals. In fact, community in the water associated with Of more than twenty coral diseases there appear to be archaeal generalists; diseased corals. Most of the coral reef- described by coral biologists, the caus- two independent studies found major associated VLPs are phages—viruses that ative agent for only six of the diseases archaeal ribotypes present in multiple infect bacteria (recent work of author has been isolated and characterized species of coral (Kellogg, 2004; Wegley Rohwer and Rebecca Thurber, San Diego (Table 1, Figure 2). et al., 2004). Although both studies State University). However, the effects of included the coral Diploria strigosa, they phages on the food-web structure of the Coral Bleaching had no archaea in common.
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