Motility effect of Serratia marcescens CC-YM2-1 and
Chryseobacterium sp. CC-H3-2 during transportation in
flow-through saturated soil columns
92-EC-17-A-10-SI-0013
Hui-Ling Lu, Fo-Ting Shen, Zhen-Chin Chao and Chiu-Chung Young
Dept. Soil and Environmental Sciences, National Chung Hsing University, Taiwan
ABSTRACT
Understanding transport mechanisms of microorganisms has become apparent in
bioremediation. Deliberate additions of nonindigenous populations of bacteria to
organically contaminated aquifers sediments are now conducted to enhance in situ
bioremediation rates in laboratory experiments and in field-scale bioaugmentation.
The success of bioaugmentation will depend mainly on the rapidity and capacity of
the introduced microorganisms to reach the contaminants and on the in situ survival
with other factors affecting contaminant bioavailability. In the present study two
strains of bacteria including a gram-negative motile rod (CC-YM2-1) and a
gram-negative nonmotile rod (CC-H3-2) were investigated (Fig 1). Bacterial motility
was tested with swarming and twitching agar plates (Media used for swarming assay
consisted of 0.5% (w/v) Difco bacto-agar with 8 g/l HIMEDIA nutrient broth, to
which 5 g/l glucose was added. Twitching assay was accomplished by stab assay with
LB broth (10 g/l tryptone / 5 g/l yeast extract / 10 g/l NaCl) solidified with 1% (w/v)
Difco bacto-agar.). The influence of motility on bacterial transport was examined in
specially designed flow-through saturated columns with constant volumetric water
flow. Experiments were repeated with two different flow velocities (12-18 ml/hr;
25-30 ml/hr), in a 10 cm long acrylic column packed with loamy soil (bulk density
1.284 g/cm3). The total cells transported as a fraction of input was calculated. Vertical
translocation of the introduced bacteria were visualized after 3 h and strain
CC-YM2-1 were detected (106 CFU/ml) and found distributed throughout the depth
of column whereas, CC-H3-2 was absent in the 9th and 10th layers at high flow
velocity and 6th, 7th, 8th, 9th, 10th layers at low flow velocity (Fig 2a, 2b). Similar
results were obtained when a non-constant volumetric saturated soil column system
was used (data not presented). Transport of nonmotile strain CC-H3-2 resulted in a
significantly lower number in comparison with motile strain CC-YM2-1 at both flow
velocities indicates that the motility being a biotic factor influence the transport
behavior of bacteria and can be advantageous in bioremediation.
Swarming test
Twitching test
log CFU ml
-1
Fig 1. Motility assays of strain CC-YM2-1 after 72 h
10
9
8
7
6
5
4
3
2
1
0
YM2-1(25.8 ml/hr)
H3-2 (29.5 ml/hr)
1
2
3
4
5
6
7
8
9
10
Depth (cm)
Fig 2a. Bacterial numbers of strain CC-YM2-1 and CC-H3-2 in different depth
log CFU ml
-1
of column under high flow velocities (after 3 h of infiltration)
10
9
8
7
6
5
4
3
2
1
0
YM 2-1(17.5 ml/hr)
H3-2 (12.5 ml/hr)
1
2
3
4
5
6
7
8
9
10
Depth (cm)
Fig 2b. Bacterial numbers of strain CC-YM2-1 and CC-H3-2 from various
depths of column under low flow velocities (after 3 h of infiltration)