Potato zaps Restless Leg Syndrome
Andre Willers
30 Aug 2014
“Potatoes are masters of Maskirovka” … General картофель .
Synopsis:
Restless Leg Syndrome ameliorization by application of glycoalkaloids
to regulate micro-ecology of skin- and other bacteria .
Discussion :
1.Fancy speak for how and why the old Potato-in-the-bed trick
works .
An exotoxin is a toxin secreted by bacteria.[1] An exotoxin can cause damage to the host by destroying
cells or disrupting normal cellular
metabolism. They are highly potent and can cause major
damage to the host. Exotoxins may be secreted, or, similar to endotoxins, may be released during lysis of the cell. Gram negative pathogens may secrete outer
membrane vesicles containing lipopolysaccharide endotoxin and some virulence
proteins in the bounding membrane along with some other toxins as
intra-vesicular contents, thus adding a previously unforeseen dimension to the
well-known eukaryote process of membrane vesicle trafficking, which is quite active at the host-pathogen
interface.
3. Chemotaxis
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Chemotaxis: a physiological adapation
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A dramatic example of rapid adaptation is the process of
"chemotaxis", i.e. the
ability to movetoward nutrients (positive chemotaxis) and away
from noxious compounds (negative chemotaxis).
This is a valuable trait in bacteria, since it enages them
to swim to sources of nutrients and away from toxic chemicals.
Chemotactic responses are very rapid, they do not require
active gene expression.
How is it that bacteria move directionally? One way that some types of bacteria move involves
organelles known as flagella.
These are rotary motors powered by ion gradients across
the plasma membrane. This motor drives a helical propeller. The
basic motor can rotate in either a clockwise or a counterclockwise wise
direction.
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Because their three dimensional structure, when the flagellum
rotates in one direction (counterclockwise), the bacteria moves forward; when
rotating in the opposite direction, the bacteria tumbles.
Tumbling allows the bacteria to change direction.
When the motor switches back to the counter clockwise direction, the bacteria
swims off in a new direction.
The ability to control chemotaxis involves controlling the
probability that the motor will switch its direction of rotation.
In bacteria, motor rotation switching is controlled by a
receptor system that senses changing concentrations of attractants
(inhibiting switch) and repellants (induce switching).
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There are two possible ways to do this. One would be to
measure the difference in concentration between the two ends of the
bacterium. This is difficult, since the bacteria is very small (1-2 um long)
and the differences in concentration between two points separated by 1-2 um
is very small (perhaps we could calculate
this?)
An alternative approach is to measure the concentration
around the bacteria as a function of time. If it is increasing, the
bacteria is moving toward the source of the chemical; if it is decreasing, it
is moving away from thge source.
4. Thus, chemotaxis provides an important mechanism
for establishing the high local cell densities required for quorum-dependent
interactions.
5.They all sit and watch each other :
Interspecies quorum sensing is a way bacteria in a community can determine how many of their own
and other species are in an area. Bacteria secrete these molecules, which
increase in proportion to cell number. Once the molecule hits a certain
concentration it triggers the transcription of
certain genes such as virulence
factors. It has been discovered that bacteria can
not only interact via quorum sensing with members of their own species but
that there is a kind of universal molecule that allows them to gather
information about other species as well.[1] This universal molecule is called autoinducer 2 or AI-2.[1]
6. The Treatment:
Putting it all together :
6.1Chemotaxis induces the urge to move .
6.2 Clothing and bedding harbours bacteria ,
viruses and fungi that the body sees as threats .
6.3These threats are communicated via
exotoxins and endotoxins in the bioaerosol .
6.4 Diurnal rhythm : at night , switches on
because of higher risk .
6.5 Learned Helplessness :
If the system perceives threats from all
directions , but no gradients in concentration over time or direction , it
moves at random .
Prolonged exposure to this sort of stimulus
will surface as various disorders in the brain (eg Parkinsons , akathisia ,
some forms of dementia , etc) .
Neuronal Networks weights get randomized by
such stimuli .
7. This suggests some treatments :
7.1 Bacterial Maskirovka . (http://en.wikipedia.org/wiki/Maskirovka)
The potato has a potent arsenal of pesticides
(glycoalkaloids) (See Appendix A) that can be used to create artificial
gradients in threat signals . Most are in the potato skin , so only the peel
is really needed .
Soap will work as well . Anything that
disturbs the threat picture .
7.2 The potato must be somewhere accessible to
airborne particles (bioaerosols) .
Porous materials are no barrier . Carry the
peels in your pocket in a porous plaster .
7.3 A fan will have an effect .
7.4 The potato peels will obviously become
exhausted after a while and need replacement . The time will depend on the
poison concentrations in the potato .
7.5 Electronic tumbling of the bacteria (see
how chemotaxis works above) using swirling magnetic fields . Something like
APStherapy machines (http://www.apstherapy.com/)
Potato works for certain types of cancer cells
(warts) . It can work better if combined with swirling magnetic fields .
7.6 Numerous approaches suggest themselves .
Patches , baths , showers , ointments , radiation
, etc, etc .
8.Caution :
The idea is to disrupt or steer threat
patterns by manipulating poisons , not to kill off the patient .
Potato : Glycoalkaloids are strong cell
disruptors and neurotoxins . More is not better here .
9.Other disorders may be helped by this
approach .
Akathisia , urinal tract infections , SIBO ,
leaky guts , swollen legs caused by cellulitis , cellulitis . it’s little
sister cellulite (the potato goes OUTSIDE , not inside! ) , etc.
10. Aphrodisiac .
Hunt the wily wandering potato under the
covers .
A spud for all occasions .
Regards ,
Andre
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Appendix A
How Deadly Are Nightshades?
Nightshades have a reputation as bad actors in a variety of
chronic conditions, such as arthritis, fibromyalgia, and IBS. But what do we
really know about how these foods affect our health?
Meet the Nightshade
(Solanaceae) Family:
·
Tomatoes
·
Eggplant
·
Potatoes
·
Goji Berries
·
Tobacco
·
Peppers (bell peppers, chili peppers, paprika, tamales, tomatillos,
pimentos, cayenne, etc)
At first glance, the nightshades may look like a random
collection of foods that couldn’t possibly be related. However, every
nightshade plant produces fruits that all sport that same adorable little green
elfish hat. Of the foods above, only tomatoes, eggplants, goji berries
and peppers are “fruits” (the potato is a tuber and tobacco is a leaf).
The fruits of potato and tobacco plants wear the same telltale hat, but we don’t
eat the fruits of those plants.
Nightshades of all types were considered inedible prior to the
1800’s, because some varieties, such as “deadly nightshade” (atropa belladonna)
were known to be so toxic. However, today most Americans eat “edible”
nightshades every day in the form of French fries, mashed potatoes, salsa,
spaghetti sauce, ketchup, and many other popular foods.
What are glycoalkaloids?
Glycoalkaloids are natural pesticides produced by nightshade
plants. [They are also present in small amounts in a few non-nightshades:
cherries, apples, and sugar beets.] Glycoalkaloids are bitter compounds
which are found throughout the plant, but especially in leaves, flowers, and
unripe fruits. They defend the plants against bacteria, fungi, viruses,
and insects. How do these chemicals kill pests?
Glycoalkaloids bind strongly to the cholesterol in the cell
membranes of predators, disrupting the structure of their membranes, and
causing their cells to leak or burst open upon contact—acting like invisible
hand grenades.
Glycoalkaloids have another powerful trick up their sleeves—they
also act as neurotoxins, by blocking the enzyme cholinesterase.
This enzyme is responsible for breaking down acetylcholine, a vital
neurotransmitter that carries signals between nerve cells and muscle
cells. When the enzyme is blocked, acetylcholine can accumulate and
electrically overstimulate the predator’s muscle cells. This can lead to
paralysis, convulsions, respiratory arrest, and death. Military “nerve
gases” work exactly the same way.
Ok, so glycoalkaloids are clearly nightmarish compounds for tiny
creatures daring to storm the nightshade’s citadel, but how much do we know
about their effects on human health?
Proposed glycoalkaloid
health benefits
Health benefits? From a pesticide? Hmmm…
Glycoalkaloids are structurally similar to glucocorticoids, such
as our body’s stress hormone, cortisol. Cortisol has many roles in the
body, one of which is to reduce inflammation. Therefore, perhaps it is
not so surprising that glycoalkaloids have been shown to have anti-inflammatory
properties in laboratory studies of animals.
It should also not be surprising that glycoalkaloids have been
shown in laboratory studies to possess antibiotic and antiviral properties,
since this is what nature designed them for.
In laboratory (in vitro) studies, glycoalkaloids can trigger
cancer cells to self-destruct. This process is called “apoptosis.”
Unfortunately, they can also cause healthy non-cancerous cells to do the same
thing. Cancer studies in live animals and humans (in vivo) have not yet
been conducted.
“…the undifferentiating destruction of both cancer and
noncancerous cell lines…leads to questions of therapeutic uses of
glycoalkaloids due to safety considerations. However, it is difficult to translate
the results of an in vivo trial in vitro. Therefore, both animal and human
experiments are essential to confirm or disprove the in vivo data observed in
these studies.” [Milner 2011].
The other side of the
sword:
Research has shown that glycoalkaloids can burst open the
membranes of red blood cells and mitochondria (our cells’ energy generators).
Some scientists have wondered whether glycoalkaloids could be
one potential cause for “leaky gut” syndromes due to their ability to poke
holes in cells:
“…glycoalkaloids, normally available while eating potatoes,
embed themselves and disrupt epithelial barrier integrity in a dose-dependent
fashion in both cell culture models and in sheets of mammalian
intestine…animals with the genetic predisposition to develop IBD, demonstrated
a greater degree of small intestinal epithelial barrier disruption and
inflammation when their epithelium was exposed to the potato glycoalkaloids
chaconine and solanine.”
Glycoalkaloids are also known to cause birth defects in
laboratory animals.
Fruits vs
vegetables: here we go again!
Those of you who are familiar with my philosophy about plant
foods know that I believe vegetables are far less trustworthy when it comes to
health effects than edible fruits, and nightshades make this point
nicely. The only nightshade vegetable humans eat is the potato; the rest
of the nightshades (other than tobacco, which is smoked, not eaten) are fruits,
because they contain seeds—eggplant, tomatoes, goji and peppers. As you
will see below, even though fruits contain glycoalkaloids, they are far less
likely to harm us. [To watch my Ancestral Health Symposium video about
vegetables vs. fruits, click HERE.]
Potato glycoalkaloids
Nightshade potatoes include all potatoes except for
sweet potatoes and yams.
Potatoes make two glycoalkaloids: alpha-chaconine and
alpha-solanine. These are the most toxic glycoalkaloids found in the
edible nightshade family. Alpha-chaconine is actually more potent than
alpha-solanine, but solanine has been studied much more thoroughly, and is
therefore more familiar.
Most of us do not associate potatoes with illness, probably
because the amount of glycoalkaloid most of us eat every day is not very high.
There are numerous cases of livestock deaths from eating raw potatoes, potato
berries, and potato leaves, but people do not eat these things. However,
there are well-documented reports of people getting glycoalkaloid poisoning
from potatoes, typically from eating improperly stored, green, or sprouting
potatoes. At low doses, humans can experience gastrointestinal symptoms,
such as vomiting and diarrhea. At higher doses, much more serious
symptoms can occur, including fever, low blood pressure, confusion, and other
neurological problems. At very high doses, glycoalkaloids are fatal.
Another reason why many people may not be bothered by potatoes
is that glycoalkaloids are very poorly absorbed by the gastrointestinal tract,
so, if you have a healthy digestive tract, most of the
glycoalkaloid won’t make it into your bloodstream. However, if you eat
potatoes every day, levels can build up over time and accumulate in the body’s
tissues and organs, because it takes many days for them to be cleared.
Also, since glycoalkaloids have the ability to burst cells open, they can
theoretically cause damage to the cells that line your digestive system as they
are passing through (this has been proven in animal studies but there are no
human studies, to my knowledge).
Due to known toxicity, the FDA limits the glycoalkaloid content
in potatoes to a maximum of 200 mg/kg potatoes (91 mg per pound). Human
studies show that doses as low as 1 mg glycoalkaloid per kg body weight can be
toxic, and that doses as low as 3 mg/kg can be fatal. This means that, if
you weigh 150 lbs, then doses as low as 68 mg could be toxic, and doses as low
as 202 mg could be fatal.
Potato processing
101
The vast majority of glycoalkaloid is in the potato skin, so
peeling will remove virtually all of it. Glycoalkaloid levels can be
dangerously high in unripe and sprouting potatoes; any greenish areas or “eyes”
should be removed or avoided.
Glycoalkaloids survive most types of cooking and
processing. In fact, deep frying will increase levels if the oil isn’t
changed frequently, so fried products such as potato skins and french fries can
contain relatively high amounts:
“Mechanical damage to potato tissue increases the concentration
of glycoalkaloids available for consumption. In addition, frying potatoes at
high temperatures does not inactivate but instead serves to preserve and
concentrate glycoalkaloids within the potato, leaving them available for
ingestion and delivery to the intestine…” [Patel 2002]
·
Boiling—reduces
glycoalkaloids by a few percentage points
·
Microwaving—reduces
glycoalkaloids by 15%
·
Deep frying at 150C
(300F)—no effect (McDonald’s uses 340F degree oil)
·
Deep frying at 210C
(410F)—reduces glycoalkaloid content by 40%
Glycoalkaloid levels of a few prepared potato products are available
[Milner 2006]:
·
Potato chips, 1 oz bag:
0.36 to 0.88 mg chaconine and 0.29 to 1.4 mg solanine. Total
glycoalkaloid concentration ranges from 2.7 to 12.4 mg per bag.
·
Fried potato skins, 4
oz: 4.4 to 13.6 mg chaconine and 2.0 to 9.5 mg solanine. Total
glycoalkaloid concentration ranges from 6.4 to 23.1 mg per 4 oz serving.
Tomato glycoalkaloids
Tomato nightshades include all types of tomatoes: cherry
tomatoes, green tomatoes, yellow tomatoes and ripe red tomatoes.
Tomatoes produce two glycoalkaloids: alpha-tomatine and
dehydrotomatine. The majority is in the form of alpha-tomatine, so we’ll
focus on that one here.
As tomatoes ripen, alpha-tomatine levels drop dramatically, from
about 500 mg/kg in green tomatoes to about 5 mg/kg in ripe red tomatoes, or 2.3
mg/lb. [For those of you keeping score at home—that’s Fruits: 1, Veggies:
0.] Artificially ripened fruits may contain higher amounts than sun-ripened
fruits.
Tomato glycoalkaloids are about 20 times less toxic than potato
glycoalkaloids. (Fruits: 2, Veggies: 0). There are no dosage studies of
tomatine in humans, but studies in mice tell us that 500 mg tomatine per 1 kg
body weight (or 227 mg per pound) is the median lethal dose (“LD50”).
This doesn’t tell us how much it would take to kill a 150 lb person; all we
know is that it would take 34 grams of tomatine to kill a 150 pound
mouse. Since ripe tomatoes contain 5 mg/kg or 2.3 mg/lb of tomatine, it
would take nearly 15,000 pounds of tomatoes to kill this Mighty Mouse (probably
many fewer pounds if you were to simply hurl them in his general direction from
across the room). Since green tomatoes contain 100 times more tomatine,
it would only take 150 pounds of green tomatoes to kill the overgrown
rodent. We do not understand the effect of low doses of tomatine on any
type of animal, including humans, over time.
Eggplant
Centuries ago, the common eggplant was referred to as “mad
apple” due to belief that eating it regularly would cause mental illness.
Eggplants produce two glycoalkaloids: alpha-solamargine and
alpha-solasonine. Solamargine is more potent than solasonine.
Whereas potato glycoalkaloids are located mainly in the skin, in
eggplants, glycoalkaloids are found primarily within the seeds and flesh; the
peel contains negligible amounts.
The common eggplant (solanum melongena) contains 10-20 mg of
glycoalkaloid per kg (or 4.5 to 9 mg per pound of eggplant). Eggplant
glycoalkaloids are considered relatively nontoxic compared to potato
glycoalkaloids (Fruits: 3, Veggies: 0).
The median lethal dose (LD50) in rodents is 1.75 mg/kg.
This means that it would take at least 13 pounds of eggplant to kill a
150 lb monster mouse. [Note to self—when facing a giant rodent in a dark
alley, go for the eggplants, not the tomatoes].
What about peppers and
goji berries?
Your guess is as good as mine…I could not locate any scientific
information about glycoalkaloids in these foods. Peppers, because they
are fruits and because they are in a different subfamily than the rest of the
nightshade foods, may contain much less glycoalkaloid? Or none at
all? Peppers are famous for containing hot and spicy “capsaicinoids”, not
glycoalkaloids (I’ll write about peppers and capsaicinoids in a future
article).
Nightshades and
Nicotine
Nightshade foods also contain small amounts of nicotine,
especially when unripe. Nicotine is much higher in tobacco leaves, of
course. Scientists think that nicotine is a natural plant pesticide,
although it is unclear exactly how it works to protect plants from invaders. The
amount of nicotine in ripe nightshade foods ranges from 2 to 7 micrograms per
kg of food. Nicotine is heat-stable, therefore, it is found in prepared foods
such as ketchup and French fries. The health effects of these small doses
is not known, but some scientists wonder whether the nicotine content of these
foods is why some people describe feeling addicted to them.
Do you have nightshade
sensitivity?
As with any food sensitivity, the only way to find out is to
remove nightshades from your diet for a couple of weeks or so to see if you
feel better. There are ZERO scientific articles about nightshade
sensitivity, chronic pain, or arthritis in the literature, however, the
internet is full of anecdotal reports of people who have found that nightshades
aggravate arthritis, fibromyalgia, or other chronic pain syndromes. I
personally am very sensitive to nightshades; they cause me a variety of
symptoms, most notably heartburn, difficulty concentrating, pounding heart,
muscle/nerve/joint pain, and profound insomnia. Everyone is different, so
as always, you’ll need to discover for yourself whether these foods may pose
problems for your individual chemistry. However, given what we know about
nightshade chemicals, common sense tells us that these foods are well worth
exploring as potential culprits in pain syndromes, gastrointestinal syndromes,
and neurologic/psychiatric symptoms.
REFERENCES
Friedman M. Tomato glycoalkaloids: role in the plant and in the
diet. J Agric Food Chem2002; 50:5751-5780. UDSA, Albany California.
Hansen AA. Two fatal cases of potato poisoning.
Science 1925; 61(1578): 340-341.
Korpan YI et al. Potato glycoalkaloids: true safety or
false sense of security? Trends in Biotechnology 2004; 22(3): 147-151.
McMillan M and Thompson JC. An outbreak of suspected
solanine poisoning in schoolboys: examinations of criteria of solanine
poisoning. Q J Med 1979; 48(190): 227-243.
Mensinga TT et al. Potato glycoalkaloids and adverse
effects in humans: an ascending dose study. Regulatory Toxicology and
Pharmacology 2005;41: 66-72. University of Utrecht, The Netherlands.
Milner SE et al. Bioactivities of
glycoalkaloids and their aglycones from Solanum species. J Agric Food Chem
2011; 59: 3454–3484. University College, Cork Ireland.
Patel B et al. Potato glycoalkaloids adversely
affect intestinal permeability and aggravate inflammatory bowel disease. Inflammatory
Bowel Diseases 2002; 8 (5): 340-346.
Sanchez-Mata MC et al. r-Solasonine and r-Solamargine
Contents of Gboma (Solanum macrocarpon L.) and Scarlet (Solanum aethiopicum L.)
Eggplants J Agric Food Chem 2010; 58: 5502–5508.
Siegmund B et al. Determination of the nicotine content of
various edible nightshades (Solanaceae) and their products and estimation of
the associated dietary nicotine intake. J Agric Food Chem
1999;47: 3113−3120.
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Appendix B
SIBO
The study, which was published in the journal Movement Disorders,
found that sufferers of Parkinson’s disease had a higher prevalence of a
condition called small intestinal bacterial overgrowth, or SIBO.
In SIBO, normally harmless bacteria proliferate in large
numbers in the small intestine.
Symptoms include excess gas, abdominal bloating, diarrhoea
and abdominal pain. Nobody is sure how many people have it, as it often goes undiagnosed or is confused with irritable bowel syndrome, but
estimates are of up to 300,000 British
sufferers.
And the researchers suggest that the bacteria may produce
chemicals that affect the nerves in the gut, which pass on the damage to the
brain – and result in Parkinson’s and MS.
Dr Emmanuel said: ‘We now think that neurological diseases
such as MS and Parkinson’s are linked to the gut being more leaky, permitting pathogens into the
bloodstream and causing an antibody
response. Either the pathogens,
directly, or the immune response, indirectly, may damage nerve tissue.’
The damaged nerves then transmit these detrimental signals
to the brain.
Rumbly tummy: The 'butterflies in the stomach' feeling could
be linked to Parkinson's disease and multiple sclerosis
In Parkinson’s, a small part of the brain becomes
progressively damaged over many years, something that affects mainly older people.
MS is the most common neurological disease in young adults and occurs when the
immune system attacks the nervous system.
The two diseases affect about 100,000 and 127,00 people in
the UK respectively. Both have wide-ranging symptoms, affecting movement as
well as causing tiredness, pain and depression. There are drugs that can ease
symptoms, but no cure or even treatments that significantly slow down
progression of the diseases.
Scientists hope that this discovery will pave the way for
new treatments for both these disabling conditions.
They are now mapping the ‘bacterial genome’, which will
identify the bacteria in an individual’s gut – something they hope will
ultimately allow doctors to prescribe tailored treatments for leakiness of the
gut, improving neurological symptoms in turn.
Until then, the doctors’ body United European
Gastroenterology urges people to maintain a healthy diet, including foods that
boost good bacteria and encourage efficient digestion. This may have an
especially positive effect on mood disorders such as anxiety and depression.
They recommend eating plenty of fibre and probiotics such as
live yogurt, as well as limiting sugar, processed foods, animal fat and the use
of antibiotics, antacids and anti-inflammatories, as these cause imbalances in
the gut.
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Appendix C
Motion to Form a Quorum
Sungsu Park,1 Peter M. Wolanin,2 Emil A. Yuzbashyan,1
Pascal Silberzan,3 Jeffry B. Stock,2* Robert H. Austin1
Bacterial gene expression is frequently regulated
by small molecules secreted into the
surrounding medium. These autoinducers
build up with increasing cell number until a
critical population density or “quorum” is
achieved, at which point the cells produce a
response such as virulence or biofilm formation
that requires the coordinated activity of
large numbers of individuals. It has generally
been assumed that quorum formation derives
primarily from conditions favorable for
growth to high cell density (1).
Numerous studies have shown that motility
promotes biofilm formation, but this
dependence has been attributed to random
transport of cells from
the bulk medium to
a surface (2). Such
experiments have
been conducted with
smooth surfaces that
have no preferred surface
sites or flow
chambers where gradients
of attractant
chemicals will be dispersed.
Here we show
that, given appropriate
surface topologies,
bacteria can use chemotaxis
to associate
and form a quorum.
Thus, chemotaxis provides
an important
mechanism for establishing
the high local cell densities required
for quorum-dependent interactions.
A culture of Escherichia coli grown to moderate
density (approximately 2 _ 108 cells/ml) in
either rich media or in minimal media was used
to uniformly fill a microfluidic chamber (7 mm
by 3 mm by 30 _m) with a small central enclosure
(250 _m by 250 _m) constructed from
silicone elastomer. Over the course of 1 to 3
hours (depending on the media), the cells migrate
from the chamber into the central enclosure
through a narrow (40 _m) channel (Fig. 1A).
This behavior is not observed with a mutant
strain that is motile but deficient in chemotaxis.
Cells accumulate in the enclosure because
they are attracted to each other due to their
secretion of amino acids, such as glycine, that
are chemoattractants. We detected this secretion
by analysis of the free amino acid content of the
growth media over time. The serine receptor,
Tsr, is the most abundant chemotaxis receptor in
E. coli, whereas the aspartate receptor, Tar, is
also present at relatively high levels (3). The
redox-sensing aerotaxis receptor, Aer, is present
at low levels but still effectively modulates chemotaxis.
Tsr binds L-serine with the highest
affinity, but it also binds L-alanine, L-cysteine,
and glycine (4). Whereas strains with tsr deleted
were unable to accumulate in the enclosure, tar
or aer deletion had little or no effect. Moreover,
addition of saturating levels of L-serine (0.5
mM), which effectively competes with glycine,
completely blocked accumulation of wild-type
cells. Saturating concentrations of L-aspartate
had no effect. The particular amino acid that is
most important in mediating self attraction
seems to depend on the conditions of growth
before nutrient depletion. It has previously been
shown that E. coli grown in succinate secrete
aspartate, which acts through Tar to cause cells
to associate into dense colonies in soft agar (5).
Chemotaxis has generally been considered as a
mechanism for cell dispersal. In nutrient-depleted
environments, however, the cells themselves
become sources of attractant molecules. Movement
toward the amino acids secreted by the
cells is enhanced by the ability of the chemotaxis
system to adjust its sensitivity so that it can
respond to very low concentrations of attractant
chemicals (6). Accumulation of a high local
density of cells may offer advantages such as
enhanced genetic exchange or communal degradation
of antibiotics, as well as the enabling of
quorum-dependent behaviors.
The sites at which cells accumulate depend
on the geometry of their surroundings. Results
with cells in percolated lattices formed from silicone
elastomer indicate that E. coli tend to accumulate
in any areas of these mazes where the
geometry provides a sufficiently enclosed space,
such as dead ends and cul-de-sacs. Self-attractive
behavior in chemotaxis has been modeled using
the Keller-Segel equations (7). Our analysis of
these equations indicates that for a small volume
connected by a small opening to a large volume,
such as our enclosure within a relatively large
microfluidic chamber (Fig. 1A) or the dead ends
in a maze (Fig. 1B), random fluctuations in cell
number that cause an increase in the density of
bacteria inside the small volume can increase irreversibly
to produce a dense accumulation of cells.
Our results suggest that self attraction could
readily produce local cell densities that exceed
the threshold necessary for quorum-dependent
processes. This notion was supported by the observation
that, after coming together within the
chamber, wild-type E. coli tended to exhibit a
further association to form dense granular aggregates.
A proposed E. coli quorum sensing signal,
AI-2, is produced by the LuxS enzyme (8). A
strain with luxS deleted accumulated into the
enclosure just like wild type, but was never observed
to form dense aggregates. Vibrio harveyi,
a highly motile marine bacterium, exhibits a similar
tendency to accumulate in confined spaces.
These cells produce light in regions of high population
density (Fig. 1, B and C). This bioluminescence,
which is one of the most well-studied
of quorum-dependent responses (8), confirms
that chemotaxis-mediated associations facilitated
by closed geometries can lead to activation of
quorum sensing–dependent genes and their associated
behaviors.
References and Notes
1. S. Swift et al., Adv. Microb. Physiol. 45,
199 (2001).
2. J. W. McClaine, R. M. Ford, Biotechnol. Bioeng. 78,
179 (2002).
3. S. Clarke, D. E. Koshland Jr., J. Biol. Chem. 254,
9695
(1979).
4. J. Adler, Annu. Rev. Biochem. 44, 341
(1975).
5. E. O. Budrene, H. C. Berg, Nature 376, 49
(1995).
6. J. E. Segall, S. M. Block, H. C. Berg, Proc. Natl.
Acad.
Sci. U.S.A. 83, 8987 (1986).
7. M. P. Brenner, L. S. Levitov, E. O. Budrene, Biophys.
J.
74, 1677 (1998).
8. M. G. Surette, M. B. Miller, B. L. Bassler, Proc.
Natl.
Acad. Sci. U.S.A. 96, 1639 (1999).
9. Materials and Methods are available as supporting
online material on Science Online.
10. We thank E. C. Cox for insightful comments on the
manuscript; J. S. Parkinson for strains RP437, RP2361,
RP5700, and UU1117, and for helpful advice; H. C. Berg
for strain HCB317 and for comments and advice; and B.
Bassler for strains BB120 and BB170 and for the gift of
AI-2 produced in vitro. We also gratefully acknowledge
M. Taga and K. Xavier for advice and assistance; N. C.
Darnton, P. Silberzan, H. Lin, and C. Gabel for discussions;
W. Austin for technical assistance; and J. Chen for
swarm plate assays. Supported by grants from DARPA
(MDA972-00-1-0031), NIH (R01 HG001506 and F32
GM064228 to P.M.W.), and the State of New Jersey
(NJCST 99-100-082-2042-007).
Supporting Online Material
www.sciencemag.org/cgi/content/full/301/5630/188/
DC1
Materials and Methods
References
28 October 2002; accepted 16 April 2003
1Department of Physics, 2Department of Molecular
Biology, Princeton University, Princeton, NJ 08544,
USA. 3Institut Curie, 75005 Paris, France.
*To whom correspondence should be addressed. Email:
jstock@princeton.edu
Fig. 1. E. coli and V. harveyi accumulation
and quorum sensing. (A) Epifluorescence
images of green fluorescent protein (GFP)–labeled E. coli
in M9 minimal
media as they accumulate into a central 250 _m by 250 _m
enclosure via a
40-_m-wide channel through 100-_m-wide walls. After 3 hours
the density of
cells is more than seven times greater inside than outside.
The rectangles are
silicone pillars that support the roof of the chamber. (B)
Dark-field image of V.
harveyi after 8 hours in the maze. The narrowest
passages are 100 _m wide.
Lines corresponding to the walls of the maze are overlaid
for clarity. (C)
Photon-counting image of the intrinsic luminescence,
indicating active quorum
sensing in areas where the cells have accumulated at high
density (9).
B R E V I A
188 11 JULY 2003 VOL 301 SCIENCE www.sciencemag.org
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