11th ICRS Abstract book - Nova Southeastern University

8-5
Biofilms: Coral Surface Mucus Layers, Settlers And Their Bacterial Inhabitants
Reia GUPPY* 1 , John BYTHELL 1
1 School of Biology, Newcastle University, Newcastle upon Tyne, United Kingdom
There is growing evidence that the surface mucus layer (SML) bacterial community on
corals is deterministic. However, although this community appears to be quite different
from the one in the water column, all surfaces support a distinct community to the water
column and the extent to which the SML bacterial community is ‘cultured’ by its host
and/or represents a settler community has not been greatly explored. An initial
assessment of the 16S rRNA gene bacterial diversity of coral SML taken from five
species of coral (Montastraea faveolata, Diploria strigosa, Goniastrea aspera, Acropora
aspera, and Porites lutea) and biofilms developing on glass plates was conducted using a
combination of gel profiling and sequencing techniques. Species differences were
observed, and non-metric multidimensional scaling (nMDS) of DGGE fingerprints
suggested that some overlap exists (~30 %) between the coral SML and biofilm surfaces,
but sequencing and ARDRA techniques suggest otherwise (~10%). The presence in the
coral SML and not the glass biofilm of several bacterial ribosomal sequences from
bacteria that inhabit mucus layers of other organisms also point to a mucus-specific
bacterial community rather than passive settlement from the water column.
8-6
Visualising The Coral Surface Mucus Layer
John BYTHELL* 1 , Reia GUPPY 1 , Amita JATKAR 1 , Barbara BROWN 1 , Nick
MORRIS 2 , Jeff PEARSON 3
1 School of Biology, Newcastle University, Newcastle upon Tyne, United Kingdom,
2 School of Biomedical Sciences, Newcastle University, Newcastle upon Tyne, United
Kingdom, 3 Institute for Cell and Molecular Biosciences, Newcastle University,
Newcastle upon Tyne, United Kingdom
The coral surface mucus layer (SML) plays a number of roles in the biology of reef corals
including ciliary-mucus transport and protection from desiccation, pollutants and
microbial invasion. Importance of the SML is demonstrated by the fact that the coral
invests such a substantial proportion of its carbon and nitrogen budget into mucus
production. Recent work also indicates that while there are variations in depth, a mucus
layer is continuously present on the coral surface, suggesting that protection is one of the
key roles. While there have been numerous studies investigating coral mucus, all of these
have used artificial collection techniques or histological techniques that do not preserve
the in situ mucus layer in its native state. This is particularly important for understanding
the spatial structure and dynamics of microbial communities of the SML. Here we report
novel techniques for the preservation and analysis of the SML.
Oral Mini-Symposium 8: Coral Microbial Interactions
8-7
Bacteria-Bacteria Antagonism Within The Coral Surface Mucus Layer
Jessica WARD* 1 , Farooq AZAM 1
1 Marine Biology Research Division, Scripps Institution of Oceanography, La Jolla, CA
The discovery of high prokaryote diversity associated with scleractinian corals and consistent
associations between coral species and certain bacteria suggest that bacteria may form close
associations with corals, including symbioses. One hypothesized role of coral-associated
bacteria is disease resistance. Coral-associated bacteria may interact with each other and with
‘non-native’ bacteria to influence the ability of potential pathogens to colonize and/or
proliferate within the mucus layer. Here we test the hypothesis that bacteria-bacteria
antagonism occurs among coral-associated bacteria and between coral-associated bacteria and
potential pathogens. We further test the effects of temperature on these interactions. Bacteria
were isolated from the surface of healthy Montastrea annularis collected in the Florida Keys,
USA and 69 were tested for antagonism using Burkholder agar diffusion assays. Of the tested
isolates, 47.8% of isolates tested were antagonistic against at least one other isolate.
Temperature exerted variable effects on antagonism – 32 isolates were more susceptible to
antagonism at 25°C than at 31°C while 12 were more susceptible at 31°C than at 25°C. Three of
the isolates obtained from the healthy coral are potential coral pathogens including
Thalassomonas loyana, a proteobacterium associated with black band disease, and Vibrio
coralliilyticus. Bacteria-bacteria antagonism may be an important structuring force, both in
terms of diversity and spatial structure, within the coral mucus layer. The presence of potential
pathogens on apparently healthy coral coupled with our observation that many isolates are
antagonistic suggests that antagonistic interactions among bacteria within the community may
be an important factor in keeping potential pathogens at bay.
8-8
Potential For Transport Of Bacteria Between Fish Farms And Coral Reefs
Melissa GARREN* 1 , Steven SMRIGA 1 , Farooq AZAM 1
1 Marine Biology Research Division, Scripps Institution of Oceanography, La Jolla, CA
To better understand the interactions between a coral and its associated microbial community, it
is useful to examine the microbial environment in which the holobiont exists. Coastal coral
reefs are under pressure from many environmental stressors, one of which is pollution. Fish
farming is a growing industry that can create point sources of pollution directly on or adjacent
to coral reefs. To understand how the presence of fish farms influences coral-microbe
interactions, we examined the relationship among a milkfish (Chanos chanos) farm, water
quality, microbial communities, and coral reefs in Bolinao, The Philippines. We found steep
gradients in the concentrations of dissolved organic carbon (70-160μM), total dissolved
nitrogen (7-40μM), chlorophyll a (phytoplankton biomass proxy; .25-10μg/l), particulate
matter (106-832μg/l), bacteria (5x105-1x106 cells/ml), and viruses (1-7x107/ml) that correlate
with distance from the fish farms. Dominant members of the microbial communities found on
corals, as determined by denaturing gradient gel electrophoresis (DGGE) of 16S rRNA
genes, were distinct from the dominant members of the water column community. However,
we also observed rare phylotypes (not detected by DGGE) from the water column community
using culturing and isolation techniques. Some of these rare water column phylotypes
(belonging to the orders alteromonadales and vibrionales) isolated from the fish pens were
dominant community members on healthy corals as far as 10km away from the pens. Thus,
while corals may exclude many water column microbes from their surfaces, some
bacteria phylotypes, present at undetectable levels in the water column by DGGE
analysis, may be associated with corals. Fish farms and other point sources of pollution
may introduce bacteria to the water column that have the potential to associate with and become
abundant on corals. Our study raises the question whether these bacteria may alter the ‘normal’
coral microbial community, and whether such changes might have important ecological effects.
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