11th ICRS Abstract book - Nova Southeastern University

8-1
From Bacterial Bleaching To The Hologenome Theory Of Evolution
Eugene ROSENBERG 1 , Eugene ROSENBERG* 2
1 Mol. Microbiology & Biotechnology, Tel Aviv University, Ramat Aviv, Israel, 2 Mol
Microbiol & Biotechnology, Tel Aviv University, Ramat Aviv, Israel
In 1995 we demonstrated that Vibrio shiloi was the causative agent of bleaching the coral
Oculina patagonica. Subsequently, it was shown that Vibrio coralliilyticus was
responsible for bleaching the coral Pocillopora damicornis in the Indian Ocean and Red
Sea. From 1996 to 2002 we studied the infection of O. patagonica by V. shiloi both in the
field and laboratory and reported that the pathogen is chemotactic to the coral mucus,
adheres to a galactose-containing receptor on the coral surface, and penetrates into the
exoderm where it differentiates into the VBNC state, multiplies intracellularly and
produces a peptide photosynthesis inhibitor. The marine fireworm Hermodice carunculata
is a winter reservoir and spring-summer vector for transmitting the bleaching disease.
Starting in 2003, we observed that O. patagonica developed resistance to V. shiloi.
Healthy corals taken from the sea could no longer be infected with the pathogen, and V.
shiloi could no longer be isolated from corals. When we inoculated corals with V. shiloi,
the bacteria adhered, penetrated and then were killed, aborting the infection. To explain
these findings we presented the coral probiotic hypothesis, which posits that the corals
acquired bacteria in their mucus and/or tissues that can kill V. shiloi. We now generalize
from this hypothesis and present the hologenome theory of evolution-the role of
symbiotic microorganisms in the evolution of animals and plants.
8-2
Tools For Investigating Nutrient And Signal Exchange Between Corals And Their
Associated Microbes
Max TEPLITSKI* 1 , Kim RITCHIE 2 , Mengsheng GAO 1 , Cory KREDIET 3 , Stephanie
HALBIG 4 , Ali AL AGELY 4
1 Soil and Water Science, University of Florida, Gainesville, FL, 2 Mote Marine
Laboratory, Sarasota, FL, 3 Interdisciplinary Ecology, University of Florida, Gainesville,
FL, 4 University of Florida, Gainesville, FL
The stability of symbioses depends on precisely timed signal exchange among symbiotic
partners. To contribute to the development of tools for investigating interactions between
corals and associated microbes we 1) developed assays to identify components of
Acropora palmata mucus, 2) optimized reporters for identifying bacterial quorum sensing
signals and their inhibitors, and 3) developed a broad host range plasmid-reporter for
quantifying gene expression in vivo. Because induction of lytic enzymes depends on the
availability of a substrate, the identification of enzymatic activity indicates presence of
the corresponding substrates and bonds in a complex mixture (such as coral mucus).
Incubation of Serratia marcescens with A. palmata mucus resulted in the differential
activities of N-acetyl-b-D-galactosaminidase, a-D-galactopyranosidase, b-Dgalactopyranosidase,
a-D-glucopyranosidase, a-L-arabinopyranosidase, and a-Lfucopyranosidase.
These data provide hints about the structure of coral mucus and offer
an opportunity to investigate dynamics of coral mucus colonization by pathogens and
symbionts. Many symbioses between bacteria and their eukaryotic hosts require a
bacterial cell-to-cell communication system called “quorum sensing” (QS). Libraries of
coral-associated bacteria were screened for their ability to activate or inhibit bacterial QS
reporters. Activities that induced or inhibited QS receptor-based reporters were detected.
These observations suggest QS signals, antagonists, or other inhibitory molecules, are
present. Since little is known about in situ interactions between bacteria and coral/algal
hosts, a portable RIVET (recombinase-based in vivo expression technology) reporter
plasmid was developed. RIVET can be used to document and quantify bacterial gene
expression in ecological niches that are un-accessible to other common reporter systems.
Oral Mini-Symposium 8: Coral Microbial Interactions
8-3
Regulation Of Quorum Sensing By Gorgonian Corals: Stimulation And Antagonism
Laura HUNT* 1 , Kelsey DOWNUM 1 , Laura MYDLARZ 1
1 Biology, University of Texas at Arlington, Arlington, TX
Gorgonian corals synthesize many novel secondary metabolites that may mediate coralbacterial
interactions. One mechanism of control may be to regulate prokaryotic cell-to-cell
communication, known as quorum sensing (QS). Many bacteria use QS signals to facilitate
colonization of higher organisms. In the present study, we are examining extracts of various
healthy gorgonian corals, from the Caribbean for QS regulatory activity, using a specific
Pseudomonas aeruginosa JP2 QS-gfp biosensor system sensitive to long chain acyl homoserine
lactones (AHL). Preliminary results using lipid-based extracts of a subsample of our gorgonian
collection (Plexaura flexuosa, Briareum sp., Pseudoplexaura sp., and Eunicea laciniata)
showed a range of activity. Briareum and P.flexuosa ethanol extracts had the most potent
inhibitory effect on QS, with a 90% and 80% reduction in signal respectively. Less pronounced
effects (20% signal reduction) were observed with E.laciniata extracts. All of these extracts
showed a dose-response effect. Interestingly, Pseudoplexaura ethanol extracts stimulated QS
activity in the absence of AHL with a striking 10-fold increase in signal over background
fluorescence. The stimulation of QS by Pseudoplexaura or other elements of the holobiont, may
encourage colonization or recruitment of specific microbial species. Active coral extracts will
be further tested for specific processes controlled by QS that are relevant to the marine
environment, such as biofilm formation. The presence of stimulatory and inhibitory compounds,
in corals, may indicate ongoing crosstalk between the coral-prokaryotic boundary and
interspecies bacterial communication. Overall this has potential implications for microbial
ecology and host-pathogen interactions.
8-4
The Host As A Habitat Divided
Nathan D. OLSON* 1 , Tracy AINSWORTH 2 , Mali'o KODIS 1 , Ruth D. GATES 3 , Misaki
TAKABAYASHI 1
1 Marine Science, University of Hawaii at Hilo, Hilo, HI, 2 University of Queensland, Brisbane,
Australia, 3 Hawaii Institute of Marine Biology, Kane`ohe, HI
Scleractinian corals are now viewed as complex holobiont systems comprising the animal host
and a consortium of microbial symbionts. This conceptual shift has led us to consider the coral
host as a habitat. When viewed as a habitat, the coral can be subdivided into three
compartments or interacting systems; the endolith, tissue, and mucus. Microbes in these
compartments are speculated to be linked to the rest of the holobiont community through
nitrogen interdependency. In order to assess the identity and potential roles of symbiotic
microbes in the nitrogen cycle of the coral holobiont, we examined the microbes present in each
of these three compartments of Hawaiian corals of genus Montipora. The prevalence of
endolithic fungi in Montipora capitata was analyzed across an environmental gradient present
in Kaneohe Bay through the use of culturing techniques. The results indicate a mean
prevalence of 75% (n = 120) with no statistically significant difference in prevalence at sites
that cross the gradient. The mean prevalence of endolithic fungi is higher in Kaneohe Bay,
Hawaii than reported for other reef systems. Within the coral tissue compartment, nifH
sequence data obtained from M. capitata tissue indicates the presence of bacteria capable of
nitrogen fixation belonging to the taxa Vibrio. Fluorescent in situ hybridization of tissue
sections of M. capitata using probes specific to the bacterial genus Vibrio revealed that the
bacteria are localized within the coral epidermal tissue layer. Lastly, the diversity of microbial
ribotypes present in the mucus of M. patula was analyzed using molecular approaches.
Collectively, these data contribute a more thorough characterization of the complexity of
microbial communities in corals and allow for the generation of hypotheses regarding the role
of each microbial member in the nitrogen cycling within the coral holobiont.
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