Download Poster - iGEM 2006

Bacterial Dynamo
Duke University Genetically Engineered Machines 2006
Eric Josephs, Hattie Chung, Thom LaBean, and Jingdong Tian
Durham, North Carolina 27708, U.S.A.
Introduction
Applications
Flagellar Motion:
It uses its extremely efficient
flageller motors to spin its
flagella and propel itself.
(those arrows show spinning)
A system such as this, which is small in
size and has a relatively high theoretical
power output, could be used in giant
arrays for large scale power distribution,
or in smaller ones for 'natural' batteries.
Do you see those black spots? Magnetospirillum sp. AMB-
Abstract
We proposed and are in the process of
building a bacterial dynamo system, a
voltage-generating apparatus. We employ a
species of bacteria that grow chains of
intracellular magnetic crystals and has
been genetically engineered to tether to
the surface of a coil. When the flagella are
anchored, the cell bodies of these tethered
bacteria will spin and create a rotating
magnetic field, which by Faraday's Law
induces an AC voltage in the coil. While
previous attempts to create a similar
system were limited by the lifetime of the
anchoring anti-flagellin antibodies, our
system relies on the incorporation of an
engineered flagellin protein with a peptide
sequence screened to bind to hard-baked
positive photoresist allowing our bacterial
dynamo to be self-assembled and longlasting.
The design of the dynamo is shown in the
box below with spinning grey bacteria
anchored to red coloured photoresist above
an orange coil with wires extending from
the base.
Design
1, a species of bacteria known to grow a chain of
magnetic particles within its cell body.
Now Consider the following:
1) Flagellin genes are highly conserved across species,
well studied and easy to manipulate.
2) When a flagella binds to a surface (as in flagellar
display), the motor forces the cell body to spin.
3) A spinning magnetic field ( from the intracellular
magnet chain) generates a voltage in a coil.
Researchers have pursued the evolution
of species of bacteria to obtain energy
from a multitude of substances. Thus, It
is conceivable that if this AMB-1 species
is modified further, it would be possible
to convert the chemical energy of
almost anything (pollution, nuclear
waste, etc) into electric power with
almost 100% efficiency.
Genetic Methods
In trying to create a dynamo, our first step was to modify the magnetic bacteria to grow ‘sticky’ flagella
(Figure 1.1). We screened 10^8 random 12-AA peptides which were placed into a rigid thioredoxin protein
structure within the variable region of the E. coli flagellin gene to ensure the sequence was exported to the
surface of the flagella (Figure 1.2). These mutants were washed over hard-baked positive photoresist to
screen for a peptide sequences that would naturally bind to the surface. Once a few potential sequences had
been identified, we began to ligate the ‘sticky’ sequence with its thioredoxin structure into the variable
region to create the fusion protein (Figure 1.3). Once this protein is placed into a suicide vector to knockout
and replace the original flagellin gene, we will have sticky magnetic bacteria. We will use the modified
bacteria with a coil apparatus on which the bacteria will bind (Fabrication Methods).
Figure 1.1
Figure 1.2
Figure 1.3
Conclusions
With the coil apparatus completed, we are now preparing a vector that will use to insert our evolved
“sticky” peptide sequence into the variable region of the AMB-1 major flagellar subunit. Once completed
we will have created a ‘sticky’ strain of AMB-1, allowing for power generation from magnetic bacteria with
significantly improved longevity.
In the future the Standard Registry of Biological Parts may provide an ideal repository for parts that allow
bacteria to stick to easily micro-patterned surfaces. Once our studies are complete we will submit our
sticky brick.
Fabrication Methods
In order to make a coil on a scale such
that the field effects of spinning
magnetic nanocrystals can be felt,
microfabrication techniques must be
employed:
!) A cleaned sheet
of silicon is patterned
with photoresist in the
shape of a .5 cm^2
coil and contact,
masks having been
made from projector transparencies.
2) A 300 Å layer of
chromium and a
500 Å layer of
gold is evaporated
Onto the silicon and
developed.
3) An insulating
layer of hardbaked Shipley
1813 positive
photoresist
is patterned atop
the coil.
4)A second
contact is
patterned with
a thick layer of
gold evaporated
atop the first layer.
5) A final layer of
hard-baked
Shipley 1813
positive
Photoresist is
patterned directly
atop the coil to provide a specific place to
anchor the sticky magnetic bacteria.
Acknowledgements
Chanda Drennen (University of Southern California)