Genetic Methods

1
Bacterial Dynamo Duke University Genetically
Engineered Machines 2006 Eric Josephs, Hattie
Chung, Thom LaBean, and Jingdong Tian Durham,
North Carolina 27708, U.S.A.
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 cm2 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 hard- baked Shipley 1813 positive photoresist i
s 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.

• Introduction
• Flagellar Motion
• It uses its extremely efficient
• flageller motors to spin its
• flagella and propel itself.
• (those arrows show spinning)
• Do you see those black spots? Magnetospirillum
  sp. AMB-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.

Applications 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. 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.
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 long-lasting. 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.
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
108 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
Acknowledgements
Chanda Drennen (University of Southern California)