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Dissolved inorganic carbon fixation of
Thaumarchaeota vs. Bacteria in the meso- and
upper bathypelagic waters of the world´s oceans
differenciated with the use of metabolic inhibitors
Marta M. Varela, Gerhard Herndl, Eva Sintes, Eva Teira, & Josep Gasol
Instituto Español de Oceanografía-IEO. CO-Coruña
Universidade de Viena
Universidade de Vigo.
Institut de Ciències del Mar. CMIMA , CSIC
WHY?
Recent studies suggest that unidentified
prokaryotes fix inorganic carbon at
significant rates in the dark ocean
(Reinthaler et al. 2010; Varela et al. 2011)
DI14C-positive cells in percent
Water Mass
0
10
20
30
40
50 0
Subsurface
Subsurface
upper O2min
upper O2min
lower O2min
lower O2min
MSOW
MSOW
AAIW
AAIW
upper
NEADW
upper
NEADW
Picoplankton
lower
NEADW
Bacteria
DI14C-positive cells in percent
10
20
30
lower
Crenarchaeota
NEADW
eastern-Atlantic
mid-Atlantic
40
50
Genomic and physiological studies
have
shown
evidences
that
Thaumarchaeota should play an
important role in the carbon cycle
(Herndl et al. 2005; Walker et al.
2010)
Some Bacteria showed high
chemoautotrophic activity
Alonso-Sáez et al. 2010, Varela
et al. 2011)
GOAL OF THE STUDY:
To examine the contribution of Thaumarchaeota vs.
Bacteria to total prokaryotic fixation of dissolved
inorganic carbon (DIC) in the meso- and upper
batypelagic waters of the world oceans.
 Global ocean prokaryotic community composition:
Major groups of prokaryotes: Bacteria, Eury- and Thaumarchaeota
Bacteria: SAR 11, SAR202, Alteromonas, SAR 406, SAR324
 Global ocean and deep water bulk uptake of bicarbonate,
differentiating Bacteria and Thaumarchaeota contribution
(Yokokawa et al.
 Single-cell identification of active dark bicarbonate fixers
HOW ?
Prokaryotic community composition:
by Fluorescence In Situ Hybridization
(CARD-FISH):
target
probe
Dissolved inorganic carbon
(DIC) fixation: incorporation of
14C-bicarbonate,
by
using
Erythromycin
to
discriminate
archaeal from bacterial activity
(Yokokawa et al. 2012)
Group Specific Activity: by
microautoradiography combined
with FISH (MICRO-CARD-FISH)
Bicarbonate assimilation
Radiolabeled
Substrate
(14C)
Fixation &
Filtration
MICRO-CARD-FISH
Radioactive
cell
Incubation
Non-Radioactive
cell
STUDY SITE
Malaspina 2010 Circumnavigation Expedition: Global Change and
Biodiversity Exploration of the Global Ocean" (December 2010-July 2011)
Indian Ocean: 46; 52; 57; 60; 66
Pacific Ocean: 86; 89; 93; 98; 105; 110; 116; 124
Atlantic Ocean: 130; 132; 135; 138; 143
8000
6000
50º N
98
0º
EQ
4000
Atlantic
Ocean
93
89
86
105 110
116
138
132135
130
2000
143
124
00
Pacific Ocean
46
52 57 60
2000
66
4000
Indian Ocean
50º S
6000
150º W
100º W
50º W
0º
0
50º E
100º E
150º E
8000
WHAT ?
Bacteria vs. Eury- and Thaumarchaeota
+ cells (% of DAPI counts):
Mesopelagic
Indian Ocean
Pacific Ocean
30%
17%
6%
55%
3%
16%
12%
61%
n= 4
Bathypelagic
1%
6%
26%
26%
2%
11%
61%
67%
n=9
n=
Atlantic Ocean
SAR11, SAR 202, Alteromonas,
SAR 406, SAR 324 + cells (% of Eub + cell):
Indian Ocean
Mesopelagic
16%
Pacific Ocean
5%
3%
10%
58%
18%
3%
30%
18%
12%
8%
19%
n= 4
Bathypelagic
Atlantic Ocean
n= 13
19%
24%
29%
43%
9%
10%
10% 9%
n=9
3%
7%
16%
21%
n= 11
DIC fixation by the prokaryotic community
(bulk uptake of 14C-bicarbonate):
DI14C fixation (µmol C m-3 d-1)
0.00
0
0.01
0.10
1.00
10.00 100.00
0.00
0.01
0.10
1.00
10.00 100.00
0.00
0.01
0.10
1.00
10.00 100.00
control
200
Erythromycin
Depth (m)
400
600
800
1000
1200
1400
1600
Indian Ocean
control
control
Erythromycin
Erythromycin
Pacific Ocean
Atlantic Ocean
Contribution of Bacteria vs.
Thaumarchaeota to DIC fixation :
Contribution to DI14C incorporation rate (%)
0
20
40
60
80
100
0
200
Depth (m)
400
600
800
1000
1200
1400
1600
Bacteria
Thaumarchaeota
Bacteria
Bacteria
Thaumarchaeota
Thaumarchaeota
Indian Ocean
Pacific Ocean
Atlantic Ocean
% of Bacteria or Thaumarchaeota
incorporating bicarbonate:
SUMMARY
 Bacteria dominated throughout the water column in the three world
oceans (54% of the total DAPI counts) and did not change with depth.
By contrast, the abundance of Cren was generally higher in the bathypelagic
layers than in the mesopelagic waters (reaching values up to 29% of the total
DAPI counts in the Pacific Ocean).
 SAR11 contributed 8, 33 and 18% to total prokaryotic inorganic carbon
incorporation in the Indian, Pacific and Atlantic world oceans, respectively,
over the entire water column.
 Archaea contributed 8, 33 and 18% to total prokaryotic inorganic carbon
incorporation in the Indian, Pacific and Atlantic world oceans, respectively,
over the entire water column.
 The Archaea contribution to total prokaryotic carbon incorporation tends to
increases with depth, particularly at the Atlantic waters below 1000m and in
the lower mesopelagic zone of the Pacific Ocean.
Single-cell analysis
ACKNOWLEDGMENTS
 We thank all the people
involved in the MALASPINA
2010 project who helped
with the cruise preparation
and sampling.
 We also thank the officers and crew of the R/V
Hespérides, as well as the staff of the Technical
Support Unit (UTM), for their support during the
work at sea.
This research was supported contracts MALASPINA
(CSD 2008-00077), BIO-PROF and MODUPLAN.