Biology Reference
In-Depth Information
It is intriguing to speculate on the molecular mechanisms that contribute to the
enhanced electrochemical activity of 7Ca. For example, the presence of gain of func-
tion mutations affecting biofi lm formation, nanowire formation, cell membrane elec-
tron transfer, metabolic, and respiration capacities, regulatory components for these
functions, and/or combinations of all the above, could contribute to the observed pow-
er output. In this regard, it is notable that previous genetic studies in
S. oneidensis
MR-1
revealed several genes that are directly involved in electricity generation, including
mtrA
,
mtrB
,
omcA
/
mtrC
,
cymA
,
fur
, and
crp
. Deletion of these genes caused severe
reductions in current production [42]. Gain of function mutations at these candidate
loci may therefore confer enhanced MFC power generating properties. Similarly, an
engineered strain of
Geobacter sulfurreducens
generated by Izallalen et al. displayed en-
hanced electrochemical activity due to increased respiration rates [22]. Despite these
molecular insights, there has been a paucity of functional studies that directly measure
the electrochemical activities of environmental microbes. In fact, the electrochemical
activities of only a handful of microbial species have been characterized in MFC sys-
tems [3]. Although MFCs using wastewater treatment and sediment nutrient sources
have defi ned electrochemically active microbial consortia [43], the electrochemical
activities of individual species within these consortia remain largely unexplored. It
is likely that the MFC array system reported here will facilitate and accelerate these
kinds of studies.
CONCLUSION
A microfabricated MFC array, a compact and user-friendly platform for the identifica-
tion and characterization of electrochemically active microbes, was developed. The
MFC array consisted of 24 integrated anode and cathode chambers, which functioned
as 24 independent miniature MFCs. The electricity generation profiles of spatially
distinct MFC chambers on the array loaded with
Shewanella oneidensis
MR-1 dif-
fered by less than 8%. The utility of the MFC array was demonstrated by screening
environmental microbes and resulted in the identification of a microbe that displayed
2.3-fold higher power output than the
S. oneidensis
MR-1 reference strain. The MFC
array consumed 380 fold less samples and reagents compared to a single H-type MFC,
and 24 parallel analyses could be conducted simultaneously. We expect to further scale
up the MFC array into a 96-well MFC array.
KEYWORDS
•
Microfabrication techniques
•
Proton exchange membrane
•
Shewanella
sp.
ACKNOWLEDGMENTS
The authors would like to thank for the insightful comments from Drs. Martin B.
Dickman and Steven M. Wright (Texas A&M University).
