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Screening Geobacillus Strains for Heavy Metal Resistance
Heather Wheeler, Sanborn Regional High School, Kingston, New Hampshire
Kang Wu, Department of Chemical Engineering, University of New Hampshire
Abstract: The resistance of certain extremophile bacteria to heavy metals is of growing interest because of the extreme toxicity of heavy metals in groundwater pollution and the potential
for use of bacterial strains in the bioremediation of such pollution. The resistance of 62 strains of Geobacillus to copper, nickel, manganese, cobalt, molybdenum, cadmium, zinc, mercury,
and potassium at a high and medium concentration were tested. Of these, 14 strains demonstrated resistance to one or more of these metals and will be the subject of further investigation.
Results
Background
MnCl2
Co(NO3)2
Na2MoO4
K2Cr2O7
HgCl2
ZnCl2
NiSO4
CuSO4
CdSO4
91A1T
W9A103
W9A44
W9A72
http://www.bbsrc.ac.uk
Geobacillus thermoglucosidasius
95A2
Geobacillus is a genus of thermophilic bacteria that are isolated
from various geothermal environments such as compost, waste
water, or oil polluted soil. They can grow over a range of 45-75
°C and are capable of surviving in non-optimal conditions in
their sporulated form for long periods of time. Many have
shown strong potential for bioremediation, like hydrocarbon
degradation, dye detoxification, and heavy metal removal. In
this study, we have characterized the resistance of 62
Geobacillus strains to nine heavy metals to screen the ones with
high heavy metal tolerance for further investigation of the
underlying mechanisms and optimization of strains for heavy
metal bioremediation.
W9A14
96A5
W9A85
92A1T
W9A86
W9A50
94A1T
96A1T
W9A2
Methods
Table 2. Resistance of 14 Geobacillus strains to each heavy metal.
White: limited resistance; light blue: moderate resistance; dark blue:
high resistance.
•Individual strains of Geobacillus were grown on solid TBAB
medium plates at 60 °C overnight, then a single colony was
picked to inoculate 10ml of seed culture in TGP liquid medium.
It was cultured for 6-7 hours at 60 °C on a shaker.
•50µl of seed culture was used to inoculate an overnight culture
in 250µl TGP or LB medium prepared with each metal at the
specified concentrations (Table 1).
•100µl of each culture was transferred to a 96-well microplate
and the Optical Density at 600nm was measured to determine
bacterial growth.
MnCl2
Concentration 1 10mM
Concentration 2 20mM
Co(NO3)2 Na2MoO4 K2Cr2O7 HgCl2
1mM
2mM
1mM
2mM
1mM
2mM
ZnCl2
0.25mM 0.5mM
0.5mM
3mM
NiSO4
CuSO4
CdSO4
1mM
1mM
0.5mM
3mM
3mM
Table 1. Concentration of Heavy Metals used in this study.
1mM
Future Work
• Sequence the genome of the selected Geobacillus strains to
identify the underlying pathway for heavy metal resistance.
Reference
Figure 1. Growth of two representative Geobacillus strains in presence of each heavy
metal compared with that in absence of heavy metal.
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Acknowledgements – This research was generously supported with funding from the National Science Foundation’s Research Experience for Teachers in Engineering Grant (ENG-1132648)