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Program Updates
Issue #19
July & August, 2006
Contents:
Welcome...........................................................................................................................................................................1
Probably more than you care to know about bacteria .........................................................................2
Microbial spore formation......................................................................................................................................3
Bacteria, the space colonists................................................................................................................................5
Welcome!
Oh yes, it’s been an insanely busy summer. And I fell behind in sending the updates. So
sorry!
This summer I’ve started writing a book – finally. Many of you have asked for a printed
version of the on-line text. Well, this will be better. In fact once the book is done
(actually there will be 2 volumes) it will also become the new and improved totally
revised website. Volume one will be ready in December, and then it’s just a matter of
putting it online. Because it only deals with the first part of the course the new
website will run parallel to the current one, accessible from the main menu. It’s been
four years since I wrote the online text, and after several incarnations of teaching the
material in the classroom I would now organize and integrate it differently. You’ll see
soon.
In the meantime here is more than you probably care to know about bacteria….
Enjoy your summer – it’s glorious!
Heide
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Probably more than you care to know about bacteria!
Posting to the US Composting Council Discussion Forum
Post by: [email protected]
May 3, 2006
Source: http://mailman.cloudnet.com/pipermail/compost/2006-May/014025.html
Dear Sludge Students,
My colleagues have got me thinking about the long life of bacteria and the role of sewage
treatment in conferring and spreading antibiotic resistant traits. This is a fascinating
business...looking at how microbes react in the stressful conditions of a sewage treatment
plant, and how they react to stressors like the chlorine, detergents, metals, and antibiotics
flushed to the sewers and digested in the sewage treatment plant.
Clearly those microbes that are sensitive to antibiotics and antimicrobials will die off. The more
resistant strains of microbes will survive and reproduce. As conditions get more stressful and
food more scarce some will form spores, and will desiccate if left out to dry.
In Southern Ontario the epidemic of Methicillin-resistant Staphylococcus aureus took off in
1996. - See graph - http://microbiology.mtsinai.on.ca/data/images/qmp-ls01.gif
This is the same year that a massive land application program of Ontario's city sewage sludges
was initiated. The Great Lakes protection legislation required sewage treatment plants on the
Great Lakes to have secondary digestion by the year 1995. The secondary digester sludge was
mixed with the primary sludges and this diluted the heavy metals from our urban sewers
sufficiently to meet Provincial Guidelines for land application for most muncipal sludges (the
1996 Guideline for the Use of Biosolids and Other Wastes on Agricultural Lands).
But while we know that "Class B" sludges containing as much as or more than 2 million fecal
coliform per gram are allowed to be spread on farmland in the USA and Canada, it may also be
that the further treated sludges ..so called 'Class A'...that are supposed to have less than 1,000
fecal coliform per gram, may be carrying very high loads of viable but non-culturable bacteria
spores (with antibiotic resistance) that subsequently rehydrate into viable micro-organisms
once land applied where the conditions are favorable.
Given that virtually all hospital fecal waste, and virtually all the used and unused antibiotics
(even the special reserved ones like vancomycin...the antibiotic of last resort) are disposed of
into the toilets of our homes and hospitals and then digested together with all our urban
sewage...doesn't it make sense to investigate the role of sewage treatment plants and the land
application of sewage sludge in regard to this epidemic of antibiotic resistant diseases that are
now ravaging our communities?
The sludge we land apply is full of the microbes and spores of organisms that have developed
antibiotic resistance in our sewage treatment plants. These micro-organisms can then flourish
once they are rehydrated in a growth medium on a farm field.
If we were setting about to farm and produce antibiotic resistant organisms and distribute
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them throughout our communties and into the food chain we couldn't do a better job of it
than in this institutionalized production and dispersion of sludge.
Microbial Spore Formation
Spore forming inside a bacterium
Stahly, MicrobeLibrary
Source: http://www.microbe.org/microbes/spores.asp
You may have read elsewhere in this site that bacteria
sometimes form protective spores to help them survive
through tough times. Some other kinds of microbes do, too.
Here's how that transformation takes place.
First off, you might think of a bacterial spore roughly as a
mummified bacterium. The spore has a hard protective
coating that encases the key parts of the bacterium—think
Spore forming inside a bacterium
of this coating as the sarcophagus that protects a mummy. Stahly, MicrobeLibrary
The spore also has layers of protective membranes, sort of
like the wrappings around a mummy. Within these membranes and the hard coating, the
dormant bacterium is able to survive for weeks, even years, through drought, heat and even
radiation. When conditions become more favorable again—when there’s more water or more
food available—the bacterium "comes to life" again, transforming from a spore back to a cell.
Some bacterial spores have possibly been revived after they lay underground for more than
250 million years!
Ok, so how do bacteria turn themselves into spores? First, the bacterium senses that its home
or habitat is turning bad: food is becoming scarce or water is disappearing or the temperature
is rising to uncomfortable levels. So it makes a copy of its chromosome, the string of DNA that
carries all its genes.
Then, the rubbery cell membrane
that surrounds the bacterial cell
fluid begins pinching inward around
this chromosome copy, until there’s
a little cell within the larger
bacterial cell. This little cell is called
the "daughter cell" and the bigger,
original one, what starts out as the
"vegetative cell" in this illustration,
is now called the "mother cell."
Next, the membrane of the mother
cell surrounds and swallows up the
smaller cell, so that now two
Merkel, MicrobeLibrary
membrane layers surround the
daughter cell. Between these two membranes a thick wall forms made out of stuff called
peptidoglycan <pep-tid-oh-gly-can>, the same stuff found in bacteria’s rigid cell walls. Finally, a
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tough outer coating made up of a bunch of proteins forms around all this, closing off the
entire daughter cell, which is now a spore. As the mother cell withers away or gets blasted by
all kinds of environmental damage, the spore lies dormant, enduring it all, just waiting for
things to get better.
Not all bacteria can form spores. But several types that live in the soil can. Bacteria in the
Bacillus <buh-sill-us> and Clostridium <clah-strih-dee-um> groups are spore-formers. Their
spores are called endospores.
Another group of bacteria called Methylosinus <meth-ill-oh-sigh-nus> produces spores called
exospores. The difference between endospores and exospores is mainly in how they form.
Endospores form inside the original bacterial cell, as described above. Exospores form outside
by growing or budding out from one end of the cell. Exospores also don’t have all the same
building blocks as endospores, but they’re similarly durable.
Members of the Azotobacter <ay-zoh-toe-back-ter>, Bdellovibrio <dell-oh-vih-bree-oh>,
Myxococcus <mix-oh-cah-cuss> and Cyanobacteria <sigh-an-oh-back-teer-ee-uh> groups form
protective structures called cysts <cists>. Cysts are thick-walled structures that, like spores,
protect bacteria from harm, but they’re somewhat less durable than endospores and
exospores.
Bacteria aren’t the only microbes that can form protective spores, however. Some protists
can, too. For example, a group of parasitic protozoa called Microsporidia <mike-row-spore-ihdee-uh> encase themselves in protective spores when they infect their hosts. Microsporidia
are found mainly in the guts of insects and the skin and muscles of fish, although a few species
can cause illness in people.
Microsporidia spores are usually round, oval or rod-shaped,
although many species have elaborately shaped spores
that may help hide them from their host immune systems.
The spores help the protozoa survive while outside of a
host’s body. Typically, hosts are infected when they
Microsporidium spore with tube
swallow Microsporidia spores. Once the spores reach the
gut, they poke a tube through their spore coats. This tube thrust into host cells Courtesy of
stabs through the host’s gut wall and other tissues. Then CDC
the Microsporidia cell fluid and nucleus—a cell's central command center—move through the
hollow tube from the spore into the host cells. As Microsporidia reproduce in the host cells,
new spores are formed that are typically passed out of the body with feces.
Note: The spores we’re talking about on this page are protective spores. A group of bacteria
called Actinomycetes <ack-tin-oh-my-see-tees> and many kinds of fungi produce seed-like
structures during reproduction that are also called spores. If you’ve ever stomped on a puffball
mushroom, the brown cloud that jets out is a cloud of these reproductive spores. Like seeds,
reproductive spores have tough outer coatings on them, but they aren’t as durable as
protective spores or cysts.
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What’s New?
Bacteria: The Space Colonists
Source: http://www.panspermia.org/bacteria.htm
I always thought the most significant thing that we ever found on the
whole goddamn Moon was that little bacteria who came back and lived and
nobody ever said shit about it. — Pete Conrad (1)
On April 20, 1967, the unmanned lunar lander Surveyor 3 landed near
Oceanus Procellarum on the surface of the moon. One of the things aboard
was a television camera. Two-and-a-half years later, on November 20, 1969,
Apollo 12 astronauts Pete Conrad and Alan L. Bean recovered the camera.
When NASA scientists examined it back on Earth they were surprised to
find specimens of Streptococcus mitis that were still alive. Because of the
precautions the astronauts had taken, NASA could be sure that the germs
were inside the camera when it was retrieved, so they must have been
there before the Surveyor 3 was launched. These bacteria had survived for
Conrad
31 months in the vacuum of the moon's atmosphere. Perhaps NASA
shouldn't have been surprised, because there are other bacteria that thrive under nearvacuum pressure on the earth today. Anyway, we now know that the vacuum of space is not a
fatal problem for bacteria.
What about the low temperature and the possible lack of liquid water in space? The bacteria
that survived on the moon suffered huge monthly temperature swings and the complete lack
of water. Freezing and drying, in the presence of the right protectants, are actually two ways
normal bacteria can enter a state of suspended animation. And interestingly, if the right
protectants aren't supplied originally, the bacteria that die first supply them for the benefit of
the surviving ones! English microbiologist John Postgate discusses this fact in The Outer
Reaches of Life (2):
"When a population of bacteria dries out without a protectant, many of the cells break open
and release their internal contents. Among these contents are proteins, gums and sugars, all of
which are protective. If the population is sufficiently dense, so that significant amounts of
protectant are released, material released from the majority which died first can protect a few
of their surviving fellows.
"Comparable considerations apply to death from freezing.... Protective substances such as
glycerol are well known and widely used; they are called cryoprotectants. Bacteria frozen
without such chemicals leak internal contents, among which are many substances that are
cryoprotective."
Postgate says that bacteria have apparently survived for 4,800 years in the brickwork of
Peruvian pyramids, and maybe even 300 million years in coal, using the drying strategy. He also
describes bacteria that apparently survived for 11,000 years in the gut of a well-preserved
mastodon, although in this case the colony may have continued to live and multiply using
nutrients available in the carcass. Postgate gives several other examples of long-surviving
bacteria, and he is careful to mention the possibility that some of the bacterial cultures may
have been contaminated, so not all of the reports are necessarily reliable.
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Some bacteria have another even more effective survival strategy: they form spores. Spores
are bacterial cells in complete dormancy, with thick protective coats. In terms of our computer
analogy, a bacterial spore is like a handheld calculator that has repackaged itself into its original
protective shipping carton and turned itself off.
"The resistance of some bacterial cells to environmental destruction is impressive. Some
bacteria form resistant cells called endospores. The original cell replicates its chromosome, and
one copy becomes surrounded by a durable wall. The outer cell disintegrates, but the
endospore it contains survives all sorts of trauma, including lack of nutrients and water,
extreme heat or cold, and most poisons. Unfortunately, boiling water is not hot enough to kill
most endospores in a reasonable length of time.... Endospores may remain dormant for
centuries" (3).
Postgate concludes his chapter on spores, entitled "Immortality and the Big Sleep," by saying,
"There may be much older spores out there, waiting for energetic microbiologists to revive
them."
Thirty Million-Year Sleep: Germ Is Declared Alive!
There were much older spores waiting to be
revived. On May 19, 1995, The New York Times
carried a front-page story about them (4).
Biologists Raul Cano and Monica Borucki had
extracted bacterial spores from bees preserved in
amber in Costa Rica. Amber is tree-sap that
hardens and persists as a fossil. This amber had
entrapped some bees and then hardened between
25 and 40 million years ago. Bacteria living in the
bees' digestive tracts had recognized a problem
Ancient bee in amber
and turned themselves into spores. When placed in
a suitable culture, the spores came right back to
life. As a control, the two biologists also attempted to culture from the same amber a number
of samples that contained no bee parts. These cultures were negative, adding credibility to the
experiment. This finding was originally reported in the journal Science (5) to general
acceptance.
Postgate, upon learning of this discovery, wrote an article for The
Times of London that concluded as follows (6):
"... could life on this planet be descended from alien spores?
...Panspermia, the view that the seed of life is diffused throughout the
universe, has been favored by a minority of thinkers since the Greek
Anaxagoras in the 5th century BC. He, Arrhenius and Fred Hoyle may
yet have the laugh on us doubters."
When the first bacteria colonized the earth, almost four billion years
ago, it was by our standards a hostile place. There was no free oxygen
to breathe and no ozone to block out the sun's damaging ultraviolet
radiation. Nuclear radiation came from decaying U235, which was about
fifty times more abundant then than now (7). The air was hot and full
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Revived bacteria
of noxious chemicals such as sulphurous gases released by volcanoes. Not for nothing is it
called the Hadean Eon. However, there are bacteria which can live, even thrive, in a very wide
variety of conditions that seem unfriendly to us (8).
"Life manages very well without oxygen, evolving into flourishing communities of anaerobes.
Acidity... presents no problem, as sulphur bacteria and their co-habitants illustrate, nor does a
considerable degree of alkalinity bother alkophiles.... Water purity is a trivial matter: saturated
salt brines support abundant bacterial life. And pressure is quite irrelevant, with bacteria
growing happily in a near vacuum or at the huge hydrostatic pressure of deep ocean trenches.
Temperature, too, presents little problem: boiling hot springs support bacterial life, and
bacteria have been found growing at 112 C in superheated geothermal water under
hydrostatic pressure; conversely, other types of bacteria thrive at well below zero, provided
the water is salty enough not to freeze. And even if they do get frozen, many bacteria revive
when their habitat thaws. Even organic food is not a prerequisite...."
There are bacteria that metabolize iron, nitrogen, sulphur, and other inorganic materials. There
are bacteria today that can live without sunlight. Archaebacteria that can withstand extreme
heat have been found thriving in oil reservoirs a mile underground (9). Some species of
cyanobacteria are highly resistant to ultraviolet radiation. The only thing absolutely essential
for bacteria to live, grow, and multiply is liquid water. We are confident that the early Earth
had plenty of water. Scientists believe that concentration of water in the earliest atmosphere
for which they have data, over four billion years ago, was far higher than it is today.
Bacteria have the ability to colonize an unfriendly planet like the Hadean Earth. Not just had
the ability but have the ability. These are not make believe stories. All of the bacteria we have
considered, with all of their unusual abilities to survive extreme environments, are alive today!
What'sNEW
You could take E. coli and rapidly cool it to 10° K and leave it for 10 billion years and then put it
back in glucose, and I suspect you would have 99 percent survival — Leslie Orgel (10)
BE SURE TO CHECK OUT THE REFERENCES ON THE SOURCE WEBSITE!!!
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