Transcript Document

University of Essex
BIODEEP-WP5
Understanding of ecological relations between
the
microbial
communities
and
the
functioning of DHAB environments
Andrea Sass , Terry McGenity, Boyd McKew
Proteobacteria:
mostly from interfaces
some sulfur-oxidizing bacteria
many related to bacteria found in deep-sea environments
all grow on sea water medium, some extremely halotolerant
 isolates are marine bacteria derived from the oxic
water column
 some isolates could benefit from the conditions in
the interface (particularly sulfur-oxidizing bacteria)
Future: investigation of an extremely halotolerant,
aerobic, aerotactic strainn from Urania basin interface
Bacillus related isolates:
almost all derived from sediments
 no correlation between phylogeny and basin of origin
 vast majority of tested strains only halotolerant
 (some very halotolerant and also facultatively anaerobic)
 probably derived from dormant spores

six strains obligately halophilic (no growth
below 3.5% salt, optimum at 5-10% salt)
 two strains isolated anaerobically in highly
saline medium

Strain AS4
0.5
Series1
3%
O.D.
0.4
Series2
5%
0.3
10%
Series3
0.2
15%
Series4
0.1
20%
Series5
0
0
5
10
15
20
25
30
Time (h)
0.6
0.5
O.D.
0.4
Series1
20%
25 %
Series2
0.3
30%
Series3
0.2
0.1
0
0
100
200
Time (h)
300
400
Strain US13
0.5
Series1
5%
Series2
10%
0.4
O.D.
Series3
15%
0.3
20%
Series4
22%
Series5
0.2
25%
Series6
0.1
27%
Series7
30%
Series8
0
0
100
200
300
400
Time (h)
0.4
Series1
5%
0.3
Series2
10%
O.D.
15%
Series3
20%
Series4
0.2
22%
Series5
25%
Series6
27%
Series7
0.1
30%
Series8
0
0
10
20
Time (h)
30
other characteristics:
 anaerobic growth, also at high salt concentrations
 favours moderate temperatures and pH
 substrates used: amino acids, betaine, organic acids,
yeast extract
possibly active in situ
Future: characterization of Halobacillus-related
strains growing anaerobically at 20% salt
Physiological properties of anerobic isolates
 Halanaerobiaceae :
 all except one (from DS) extremely halophilic
 distinct species from each basin, some isolated repeatedly
 strains derived from BI similar to isolate from another DHAB (Red Sea)
 CFB: moderately halophilic
 Clostridia: moderately halophilic
 Methanogens: extremely halophilic
 e-Proteobacterium: moderately halophilic, reduces sulfur compounds and nitrate
 Halorhabdus sp.: facultative anaerobe, extremely halophilic
Active in situ?
 Methanogens, Haloanaerobiaceae and
Halobacterium possibly active in situ in the
brines
 e-Proteobacterium and CFB could thrive in
the interface
 Clostridia probably derived from dormant
spores
Sequences similar to three cultivates strains
were also found in clone libraries made from the basins
Archaea:
AN-AI3 (Halorhabdus utahensis 99%):
!
99% identity to clone DLIA-31
AN-AS7 (Methanohalophilus mahii 99%):
!
99% identity to clones ULIA-84, DLIA-189,
ALIA-123, ABBA-51
Eubacteria:
AN-BI4 (CFB):
! 98% identity to clone BBBB-69
(tRFLP-fragments with lengths analogous to fragments
derived from AN-BI4 occur in samples from interfaces and
brines)
l‘Atalante sediment:
 extremely halophilic fermenting organisms
isolated from top layers
Bannock sediment:
 only organisms probably not active in situ isolated
 t-RFLP profile like that from brine
 no anaerobic isolates from brines
l‘Atalante basin upper sediments contain bacterial
population different from brine
some organisms possibly active in the brines/interfaces
could be cultivated
vast majority of organisms inhabiting the DHAB
remain uncultivated
cultivation-independent approaches needed
for understanding the function of DHAB
environments