12/4/2013
BSC 541/441
Group Project
Bacteria species
Interactions between Two Bacteria
Hahella and Microbulbifer
• Two bacteria were found on the saltmarsh detritus
• Identified by 16S rRNA gene sequencing
• Utilize glucose and cellulose
Daniel Yijie Deng
Christopher VanEtten
Robert Hutto
Sarah Beth
Hahella sp. (H)
Microbulbifer sp. (M)
A4
More …..
Me an Max OD
0.8 00
0.7 00
W a t Mea n Ma x OD
0.6 00
0.5 00
OD
M grows faster than Hahella.
M can utilize agar as its carbon source.
Hahella produces a red-pigmented antibiotic.
0.4 00
0.3 00
0.2 00
0.1 00
Me an Min OD
0.0 00
250
Bacteria H inhibits M
300
350
400
450
W at Me an Min OD
500
550
600
650
Wavelength (nm)
Bacteria M does not inhibit H
Prodigiosin production by Hahella
1.4
1.2
Prodigiosin
1
A534
H
0.8
0.6
0.4
0.2
0
M
0
5
10
15
20
25
30
35
Time
1
12/4/2013
Questions
Methods
 Does competition occur between bacteria
Hahella (H) and Microbulbifer (M) ?
Grow two bacteria in culture medium separately and
together and measure the growth of each population
across the time.
 What strategies do they use to compete
with the other?
Do they compete?
Hypothesis: Each bacteria population grow slower or
reach lower abundance in coculture than in single
cultures.
Population Growth Curve
0.6
H
0.4
Coculture
0.3
Growth of Hahella (H)
M
Growth of Microbulbifer (M)
35
600
0.1
0
0
5
10
15
20
Time
25
30
35
Million CFU/mL
30
0.2
Million CFU/ml
OD 595
0.5
25
H
20
H-Co
15
10
500
400
M
300
M-Co
200
100
5
0
0
0
5
10
15
-5
Time (hr)
20
25
30
35
0
-100
10
20
30
40
Time (hr)
2
12/4/2013
Interactions between M and H
100000000
Bacteria M
H
1000000
Abundance (CFU/ml )
1.0E+08
1.0E+08
Log (H)
H-Co
Log (M)
1.0E+07
1.0E+06
M
1.0E+07
M-Co
1.0E+06
1.0E+05
1.0E+05
100000
10000
1000
H-Co
100
M-Co
10
Time (hr)
1
Time (hr)
1.0E+04
Relative abundance of H and M
10000000
1.0E+09
0
Time (hr)
10
20
30
100000000%
18000000
10000000%
%
1000000%
100000%
10000%
1750%
1000%
210%
100%
30%
10% 0
10
20
30
40
3%
1%
40
Time
(H/M ) %
Bacteria H
1.0E+09
1.0E+04
0
10
20
30
0
10
20
30
Growth of two species in the coculture
Questions
 Does competition occur between bacteria
Hahella (H) and Microbulbifer (M) ?
 What strategies do they use to compete
with the other?
Hypotheses
• Bacteria might scavenge glucose faster for
growth in the presence of competitor.
(Exploitative competition)
• Hahella might produce more antibiotic in the
coculture as a strategy against the competitor.
(Interference competition)
M grows faster and
reaches higher density in
monocultures.
3
12/4/2013
Do competitors induce more antibiotic production?
Cell-specific Prodigiosin Production
5
**
4.5
Antibiotic production
nmol / 1000 CFU
H
H-Co
1.85
mmol / flask
4
3.5
1.86
1.9
1.8
4.14
1.75
3
2.5
2.33
2
1.5
1.75
1
1.7
0.5
1.65
0
H
1.6
H-Co
About 80% increase in antibiotic production per capita in
the presence of competitors ( t3 = 3.182, P=0.008)
What is the Trade-Off ?
Fitness of bacteria under different conditions
Growth rate comparison
Doubling time (hr)
Pure
Coculture
H
1.8 hr
4.0 hr
M
1.1 hr
--
Relative abundance (H : M) in
glucose medium
Relative abundance (H : M) in
Zobell medium
100000000%
Bacteria H
1.0E+09
H
1000000%
1.0E+08
Log (M)
Log (H)
H-Co
1.0E+07
M
1.0E+07
10000%
1750%
1000%
1.0E+06
1.0E+05
1.0E+05
100%
0
10
20
10%
Time (hr)
1.0E+04
0
10
1%
30
6%
10
20
30
Time
0.1000%
0.0100%
3%
Time
30
0.0001%
0.0000%
0.0000%
0%
Time (hr)
1.0E+04
20
0
0.0010%
M-Co
1.0E+06
10.0000%
1.0000%
100000%
(H/M) %
1.0E+08
124%
100.0000%
18000000%
(H/M) %
1.0E+09
1000.0000%
10000000%
Bacteria M
0
10
20
30
4
12/4/2013
Conclusion
• Hahella and Microbulbifer compete against
each other for resources.
• Trade-off between survival and ‘reproduction’
• Hahella allocate energy to produce more
antibiotic in the presence of the competitor.
• Their interactions might depend on culture
conditions.
5