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Coral Health and Disease
in the Face of Climate Change
Kim B. Ritchie
Mote Marine Laboratory, Sarasota Florida
Coral algal endosymbiont = “Zooxanthellae” =
Symbiodinium spp.
Vibrio shifts
Microbial Shift During Bleaching R
ela
tive %
Before
bleaching
During
bleaching Bleached
During
recovery
Completely
recovered
Ritchie and Smith, 2004
Ritchie (2006) MEPS 322:1-14
Mucus from the elkhorn coral inhibits the growth
of many bacteria
Growth
medium
Growth
medium
+Sterile
Mucus
Control mucus treated
Measure growth inhibition on
mucus-treated plates
Mucus Inhibition Range
• Coral mucus is active against Gram
negative and Gram positive tester strains
• E. coli, Serratia marcescens, Salmonella,
Shigella
• Enterococcus faecalis, Bacillus subtilis,
Staphylococcus aureus
Ritchie (2006) MEPS 322:1-14
Bacillus
MRSA
S. aureus Streptococcus
Pseudomonas
Antibiotic Spectrum Screening
MRSA, MSSA, VRE, Enterococcus facaelis, E.coli O157:H7, S. typhimurium, Bacillus subtilis, Shigella, Serratia marcescens Agrobacterium tumefaciens
Antibiotic producers
• Of 776 tested, roughly 20% of cultured
isolates produce antibacterials against one
or more tester strains
• Potentially a much higher percentage
Ritchie (2006)
Shnit-Orland and Kushmaro (2008)
Impact of Seasonality on Bacterial dynamics
in Acropora palmata
• Mucus from A. palmata has
antibiotic activity that is lost
when temperatures increase
• A. palmata harbors antibiotic-producing bacteria that are lost
or replaced by potentially
pathogenic bacteria as temps
increase
Ritchie (2006) MEPS 322:1-14
• May explain why corals are more susceptible to disease during warming trends
Coral Surface
coral surface
mucus layer
water column
Coral Surface
coral surface
mucus layer
water column
Increased
Sea Surface
Temperature
Increase in
diseases
and bleaching
( ( ) )
( )
(1 )
N P S
PP
S
S
dN NI b A P b S N
dt K N
b A PNdPI P
dt K N
b SNdSS
dt K N
b SNdAA
dt K N
Mao-Jones et al, 2010, PLoS Biology
,P Sb b
: maximum growth rates of pathogen and beneficial bacteria.
K : half-saturation constant for nutrient uptake
: mucus sloughing-off rate
: fraction of nutrient uptake that beneficial bacteria use to make antibiotics.
Impact of seasonality on pathogen dynamics
0
20
40
60
80
100
120
Apr
-05
May
-05
Jun-
05
Jul-0
5
Aug
-05
Sep
-05
1/1/
2006
Feb-0
6
Mar
-06
Apr
-06
May
-06
Jun-
06
Jul-0
6
Aug
-06
% V
ibri
os
15
17
19
21
23
25
27
29
31
Sea S
urf
ace T
em
p C
% Vibrios in mucus % Vibrios in water column mean SST
Hysteresis - pathogen adherence to and overgrowth in mucus results in
pathogen persistence even after conditions return to favorable conditions
for healthy state microbiota
Point
• Suggests a lag time in actual coral
recovery after a warming event.
• May explain why corals are more susceptible to disease during, and after, a warming trend
Antibiotic contributions to
coral mucus?
• Coral Host?
• Bacteria?
• Symbiodinium???
Symbiodinium spp.
• endosymbionts of many marine organisms – clams
– anemones
– Jellyfish
– Foraminifera, and others
• Subdivided into “clades” A, B, C, D, E, F, etc… – Appear evolutionarily distinct
– Different host niches
– Functionally diverse
Symbiodinium can be cultured
outside of the coral host
Plus antibiotics
Minus antibiotics
(Or over time)
No growth
Growth
Culturable bacteria associated with
Symbiodinium cultures
B1
Marine Agar GASWA Marine Agar GASWA
C1 D2
F2
A1
E1
Groups based on both
culture and molecular methods
Bacterial Groups Symbiodinium Clades
Roseobacter Clade A1, B1, C1, D1a, D2, E1, F2
Marinobacters A1, B1, C1, D1a, D2, E1, F2 aCFB Group A1, B1, C1, D2, F2
aCytophaga-Flavobacterium-Bacteroides (CFB)
Growth Curve
-200
0
200
400
600
800
1000
1200
0 100 200 300 400 500 600
Time elapsed after treatment (hrs)
Perc
en
t ch
an
ge i
n c
ell
den
sit
y
Control
Antibiotic
Roseobacter
Marinobacter
Hours
Cell
Counts
Bacillus
Many Roseobacters produce
antimicrobial compounds
Roseobacters are likely to be
important in coral biology
Are there roles for native bacteria in
coral health?
Teplitski and Ritchie, 2009
Trends in Ecology and Evolution
Teplitski and Ritchie, TREE 2010
Antimicrobial functions on
coral surfaces
Experiments show that signals regulating microbiota are
produced in situ
Inhibit swarming and biofilm formation in a coral
pathogen, Serratia marscecens
Coral and Symbiodinium associated bacteria can inhibit
swarming and biofilm formation in coral pathogens
Alagely, Krediet, Ritchie, Teplitski. ISME J. 2011
reverse-phase C18 Si
or HP20SS resin
Biocontrol with native coral bacteria
Alagely, Krediet, Ritchie, Teplitski. ISME J. in press
Control
PDL
100
PDL100
Marino
PDL100
Roseo Marino Roseo
Model polyp
Aiptasia
pallida
What about bacteria in early life stages of
corals?
Broadcast
Spawners
Brooders
External
fertilization
Internal
fertilization
Planula larvae
(from Ritson-Williams et al. 2009)
Most corals acquire bacteria during early
life stages
• Most corals do not acquire bact until
post-settlement stages
(Sharp et al., 2010)
• Roseobacter clade bacteria are
consistently present in early life
stages of many corals (Apprill et al, 2009;
Ceh et al., 2010; Littman et al., 2011; Sharp et
al., 2011) (Sharp, et al., 2010)
At Least Two Groups of Bacteria Are
Consistently Associated P. astreoides Larvae
(Sharp et al., 2011)
Coral-associated Roseobacter clade (RCA) Coral-associated Marinobacter sp.
Two groups of bacteria present across all sampled larvae
4 years of sampling
3 locations across the Caribbean
full coverage of early development (from newly released until post-settlement)
SUGGESTS BACTERIA ARE TRANSMITTED VERTICALLY (parentally)
IN BROODING CORALS
Microbial biofilms are necessary for larval settlement
(Sharp and Ritchie, 2012)
Scoring Settlement of P. astreoides
• Swimming planula
• Swimming but metamorphosed
• Attached, settled, and
metamorphosed
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
SW Control MB Control Roseivivax Marinobacter Pseudoalteromonas
Me
an
Pe
rce
nt
Se
ttle
me
nt
Specific bacteria encourage coral
Porites astreoides larval settlement
n = 10
20 larvae per dish
Bars: SE
Bacteria mediate larval settlement in
several coral species
All Symbiodinium-associated Roseobacters
tested produce Gene Transfer Agents
All Symbiodinium-associated
alpha-proteobacteria tested
produce Gene Transfer Agents
(McDaniel et al, in review)
Gene Transfer Agents (GTAs)
•Resemble bacteriaphage
•Package random pieces of host genome
•First described in 1974 in
Rhodobacter capsulata
•Present in many alpha-
proteobacteria
Gene Transfer Agents (GTAs)
Found in genomes of many marine
Alpha-Proteobacteria
Host
Specificity
Factor (?)
oxid
ore
ducta
se
, FA
D-b
indin
g p
rote
in
Puta
tive
la
rge
te
rmin
ase
port
al pro
tein
, H
K97 f
am
ily p
rote
in
CO
G1196 C
hro
mosom
e s
egre
gation A
TP
ases
phage p
rohead p
rote
ase,
HK
97 f
am
ily p
rote
in
majo
r capsid
pro
tein
, H
K97 f
am
ily p
rote
in
head
-tail
adapto
r, p
uta
tive
majo
r ta
il pro
tein
, T
P901
-1 f
am
ily p
rote
in
puta
tive p
hage t
ail
min
or
pro
tein
CO
G0
79
1 C
ell
wa
ll-associa
ted h
ydro
lases (
invasio
n-a
ssocia
ted p
rote
ins)
serine O
-acety
ltra
nsfe
rase
2000 4000 6000 8000 10000 12000 14000 16000
Gene transfer via
GTAs is
100 million times
higher in the reef
environment
(McDaniel et al, Science, 2010)
Attached or Swimming Settled
Roseobacters and Gene Transfer Agents
greatly increase coral larvae settlement
Conclusions
• There are a number of bacteria associated with corals that produce antibiotics
• Many coral bacteria can inhibit coral pathogens (QS)
• Roseobacters and Marinobacters are likely important in coral biology, increase growth rates in Symbiodinium and increase coral larvae survival and settlement
• Roseobacters associated with corals and Symbiodinium produce Gene Transfer Agents that are capable of transferring genes to a variety of bacterial types
Questions
• What is the nature of these partnerships and what are the services provided?
• Are these associations stable?
• Are genes transferred
to corals or zoox?
Acknowledgements
• Koty Sharp, Ocean Genome Legacy
• Max Teplitski, UF
• Cory Krediet, UF
• John Paul, USF
• Lauren McDaniel, USF
• Valerie Paul, Smithsonian
• Chris Voolstra, KAUST
