Bacteria get pieces of DNA from outside their bodies

In an astonishing new video, a bacterium

 reaches out into space, snatches a piece of DNA and stuffs that DNA into its own body. Its appendage, much longer than its own body, wanders and bends a little but seems to move with intention toward its target. And the whole act is part of the microbe's effort to evolve.

The video is the first direct observation of bacteria using appendages called pili to "harpoon" loose DNA and incorporate it into the bacteria's own genetic structures. It shows how the single-celled organisms pull off a neat trick called "horizontal gene transger" that lets them adapt quickly to new environments. This would be a bit like if a person who's allergic to pollen needed only to reach out, snatch some loose flesh from a nonallergic friend and swallow it to get through spring without sneezing.

Researchers already knew that bacteria needed their pili to pull off horizontal gene transfer, but they'd never seen the maneuver in action, in part because the pili are too tiny to easily observe through a microscope. A single pilus, according to the videographers, is less than one-ten-thousandth the width of a human hair. And the hole the bacteria use to haul the loose DNA into their own single-celled "bodies" is "almost the exact width of a DNA helix bent in half," the researchers said in a statement. .

So, to record the video, the researchers dyed the pili of Vibrio cholerae, the bacterium responsible for cholera, with fluorescent dye. The dye also covered the bacteria and the loose DNA. Then, the researchers stuck the bacteria and stray DNA under a regular microscope and waited to see what the now-glowing organism would do.

Reproduced from:
 https://www.livescience.com/62797-dna-harpoon-bacteria-evolution-horizontal-transfer.html
https://www.livescience.com/62797-dna-harpoon-bacteria-evolution-horizontal-transfer.html

The deep biosphere: a totally different biological world

The bacterial populations found in the deep levels of the mud and sediments of the oceanic bottoms have recently been studied.
At the deepest sedimentary levels the microenvironments of the fluids in the pores have very low oxygen levels, practically nonexistent (generating anaerobic environments) and minimal presence of nutrients of oceanic origin. (one)
When the bacteria of the deepest levels were cultivated in Petri dish, they were not able to survive or reproduce.
The hypothesis is that due to the shortage of nutrients and oxygen and the stability of the environment your metabolism is extremely slow.
It is indicated that the energy necessary for each of these microorganisms to live is very small, calculated at 10-21 watts (or 0.000000000000000000001 watts). This level would be the daily energy needed by a bacterium inhabiting the deep levels of oceanic sediments.
On the contrary, a bacterium on the surface of the planet, for example a bacterium that live in human throats requires 10-10 watts, that is, it needs 1,000,000,000 times more energy than an ultra-deep bacterium on the seafloor. That's because on the surface the bacteria and other organisms that live there use the energy of the sun that they obtain directly through photosynthesis or indirectly through the process of biological and chemical decomposition. This source of energy depends on the cycles of diurnal and annual variations with very fast periods of time, to which organisms have had to adapt. This did not happen in the deep biosphere, where there is a situation of great stability.
That means that its metabolic time scale is millions or billions of times faster in the surface biosphere than in the ultra-deep biosphere.
To compare we can remember that a human being to live needs approximately 100 watts a day.
By relating the bacteria of ultra-deep marine sediments with the hyperthermobacteria that inhabit the pores or fissures of rocks (which were defined by Thomas Gold in The Deep Hot Biosphere) we can come to a similar conclusion.
These bacteria, which are inside deep rocks (up to several thousand meters), receive their nutrients from the alteration of minerals or intergranular or interfisural fluids. These fluids circulate very slowly (millimeters per year or per century) and therefore very slowly provide their compounds or nutrients that allow the life of these organisms from the depth. For that reason, having adapted to this environment, they probably have a metabolic energy expenditure similar or even much lower than that of the deep ocean mud bacteria. This may mean that some metabolic functions (eg reproduction) can occur over very long periods, tens, hundreds or thousands of years.
In other words, in depth there is a different flow of time,
As life on the surface receives its energy directly or indirectly from the sun, metabolic functions have been accelerated by factors of millions, hundreds or billions of times.
The life in depth, both in the oceanic sediments and in the fissures and pores of the deep rocks, would be quite similar to what we imagine in the vital diffusion through the panspermia in comets, asteroires or meteorites. For these phenomena to transport life between star systems would require organisms (bacteria) that had an extremely slow metabolism, measurable in millions or hundreds of millions of years so that dispersion can actually be realized.
(1) (1) Theory originally developed by John Parkes, British microbial ecologist. 
References: https://www.ted.com/talks/karen_lloyd_this_deep_sea_mystery_is_changing_our_understanding_of_life
https://www.sciencenewsforstudents.org/article/living-long-beneath-sea

Slow-Motion Bacteria Buried Deep in the Ocean's Floor
An investigation in bacteria extracted from deep sediments of the ocean floor shows the extreme slowness of its metabolism taking hundreds of years to reproduce. Maybe that's the rule in the universe where energy is not always readily available (unlike what happens in general on Earth)

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The sea bottom sediments environment

When algae die, they drift to the ocean floor, their bodies becoming one with the seabed’s muck. This algal rain falls constantly, and as layers of organic matter build up over the years, they bury the bacteria that grow on the seabed. Subsumed in the mire, many bacteria die. But some, a hardy few, survive. And when geochemists and biologists drill down into the seabed and pull up long, black cores that reflect hundreds or thousands of years of accumulation, they find the living descendants of the original bacterial internees.

How do the microbes manage to stay alive down there? Since nothing comes in or out, they must have some way of subsisting on the remains of the algae that buried their ancestors so long ago. So one answer might be that they’ve evolved to make more efficient use of the extremely scanty resources they’re entombed with.

But a recent study in PNAS suggests that something very different is true: The bacteria living meters down, under 5,000 years of dead algae, hardly seem to be evolving at all. In fact they are reproducing extremely slowly, so any adaptation, if it’s happening, would not have much chance to take effect. Although many bacteria double in number every few minutes, these researchers’ calculations suggest that in seabed bacteria, it takes on the order of hundreds of years.

Seabed bacteria are thought to be a peculiar bunch, says Kasper Kjeldsen, a biochemist at Aarhus University in Denmark. You’d have to be, to live like them: “There’s very little energy available when you have to continue eating from the same lunch box” for thousands of years, he says. “It is one of the most energy-limited environments on our planet.” But it has been difficult to study the microbes’ biology, because they will not grow in a Petri dish. Instead, researchers have had to develop techniques for inferring things about them from their DNA, which they can extract from the columns of muck. Because different depths represent known eras—the mud’s age can be pinpointed with carbon dating—it’s possible to study the bacteria’s change over time.

To that end, Kjeldsen and colleagues extracted cores from four sites in Aarhus Bay, and took samples from five different points along each core’s length. Then they sequenced the DNA of individual bacteria from each time point, and compared it with all the others’. They found that the species of bacteria that live in the depths exist on the seabed’s surface as well, though they are comparatively rare among the populations there. That reinforces the idea of a select bunch, better fit for the challenges of being buried alive, persisting after the others die.

The team also found that once the microbes were buried, their DNA did not change. “What we saw was there is a very low genetic diversity with a population across depth and time, in the sediment,” says Kjeldsen. “This tells us that the evolutionary change over time is very, very, very low.”

He continues: “It basically means that those bacteria you find at the surface of the sediment are more or less genetically identical to those that subsist under extreme energy limitation in the deep subsurface sediment. … They possess this ability already from the beginning.”

Next, the researchers monitored the bacteria’s metabolism, using radioactive isotopes. They could estimate how much time it would take, at the observed rate of converting food into energy, for the bacteria to create enough new biomass to replicate themselves. In 400-year-old sediment, the rate was about a replication per year. Deeper, in the 4,900-year-old layer, it was on the order of one per hundred years. This isn’t even the longest generation time ever calculated for bacteria; even deeper in the muck, there are others estimated to grow much more slowly, says Kjeldsen. But these numbers fit with what other groups have found at this depth.

Mutations often arise from mistakes in DNA made when cells duplicate themselves. And if there’s so little energy that replication happens only very slowly, then it makes sense that mutations would only arise very rarely—and that if any of them happened to be helpful, it would take corresponding ages for them to out-compete less-fit brethren. It’s a world moving in slow motion, encased in Jell-O—or rather, in sediment.

Still, the techniques that undergird the paper use certain assumptions, cautions Kjeldsen. For instance, he’s not sure whether the bacteria are actually making new cells, or whether they’re just using the energy to repair themselves. There could be very small genetic changes that the technique doesn’t reveal, too.

“What we don’t know,” he says, “is how much genetic change does it take to gain a competitive advantage? There’s a limit to how subtle of genetic differences we can detect with our method here.” These smaller changes might still be able to make a difference, somehow, in a microbe's ability to survive in a resource-scarce environment. “This is something we are trying to address now,” he says.
Reference:
https://www.theatlantic.com/science/archive/2017/04/bacteria-buried-alive/524214/

Bacteria get pieces of DNA from outside their bodies

In an astonishing new video, a bacterium

 reaches out into space, snatches a piece of DNA and stuffs that DNA into its own body. Its appendage, much longer than its own body, wanders and bends a little but seems to move with intention toward its target. And the whole act is part of the microbe's effort to evolve.

The video is the first direct observation of bacteria using appendages called pili to "harpoon" loose DNA and incorporate it into the bacteria's own genetic structures. It shows how the single-celled organisms pull off a neat trick called "horizontal gene transger" that lets them adapt quickly to new environments. This would be a bit like if a person who's allergic to pollen needed only to reach out, snatch some loose flesh from a nonallergic friend and swallow it to get through spring without sneezing.

Researchers already knew that bacteria needed their pili to pull off horizontal gene transfer, but they'd never seen the maneuver in action, in part because the pili are too tiny to easily observe through a microscope. A single pilus, according to the videographers, is less than one-ten-thousandth the width of a human hair. And the hole the bacteria use to haul the loose DNA into their own single-celled "bodies" is "almost the exact width of a DNA helix bent in half," the researchers said in a statement. .

So, to record the video, the researchers dyed the pili of Vibrio cholerae, the bacterium responsible for cholera, with fluorescent dye. The dye also covered the bacteria and the loose DNA. Then, the researchers stuck the bacteria and stray DNA under a regular microscope and waited to see what the now-glowing organism would do.

Reproduced from:
 https://www.livescience.com/62797-dna-harpoon-bacteria-evolution-horizontal-transfer.html
https://www.livescience.com/62797-dna-harpoon-bacteria-evolution-horizontal-transfer.html

Something to think about

An investigation in bacteria extracted from deep sediments of the ocean floor shows the extreme slowness of its metabolism taking hundreds of years to reproduce. Maybe that's the rule in the universe where energy is not always readily available (unlike what happens in general on Earth)

The Slow-Motion Bacteria Buried Deep in the Ocean's Floor

When algae die, they drift to the ocean floor, their bodies becoming one with the seabed’s muck. This algal rain falls constantly, and as layers of organic matter build up over the years, they bury the bacteria that grow on the seabed. Subsumed in the mire, many bacteria die. But some, a hardy few, survive. And when geochemists and biologists drill down into the seabed and pull up long, black cores that reflect hundreds or thousands of years of accumulation, they find the living descendants of the original bacterial internees.

How do the microbes manage to stay alive down there? Since nothing comes in or out, they must have some way of subsisting on the remains of the algae that buried their ancestors so long ago. So one answer might be that they’ve evolved to make more efficient use of the extremely scanty resources they’re entombed with.

But a recent study in PNAS suggests that something very different is true: The bacteria living meters down, under 5,000 years of dead algae, hardly seem to be evolving at all. In fact they are reproducing extremely slowly, so any adaptation, if it’s happening, would not have much chance to take effect. Although many bacteria double in number every few minutes, these researchers’ calculations suggest that in seabed bacteria, it takes on the order of hundreds of years.

Seabed bacteria are thought to be a peculiar bunch, says Kasper Kjeldsen, a biochemist at Aarhus University in Denmark. You’d have to be, to live like them: “There’s very little energy available when you have to continue eating from the same lunch box” for thousands of years, he says. “It is one of the most energy-limited environments on our planet.” But it has been difficult to study the microbes’ biology, because they will not grow in a Petri dish. Instead, researchers have had to develop techniques for inferring things about them from their DNA, which they can extract from the columns of muck. Because different depths represent known eras—the mud’s age can be pinpointed with carbon dating—it’s possible to study the bacteria’s change over time.

To that end, Kjeldsen and colleagues extracted cores from four sites in Aarhus Bay, and took samples from five different points along each core’s length. Then they sequenced the DNA of individual bacteria from each time point, and compared it with all the others’. They found that the species of bacteria that live in the depths exist on the seabed’s surface as well, though they are comparatively rare among the populations there. That reinforces the idea of a select bunch, better fit for the challenges of being buried alive, persisting after the others die.

The team also found that once the microbes were buried, their DNA did not change. “What we saw was there is a very low genetic diversity with a population across depth and time, in the sediment,” says Kjeldsen. “This tells us that the evolutionary change over time is very, very, very low.”

He continues: “It basically means that those bacteria you find at the surface of the sediment are more or less genetically identical to those that subsist under extreme energy limitation in the deep subsurface sediment. … They possess this ability already from the beginning.”

Next, the researchers monitored the bacteria’s metabolism, using radioactive isotopes. They could estimate how much time it would take, at the observed rate of converting food into energy, for the bacteria to create enough new biomass to replicate themselves. In 400-year-old sediment, the rate was about a replication per year. Deeper, in the 4,900-year-old layer, it was on the order of one per hundred years. This isn’t even the longest generation time ever calculated for bacteria; even deeper in the muck, there are others estimated to grow much more slowly, says Kjeldsen. But these numbers fit with what other groups have found at this depth.

Mutations often arise from mistakes in DNA made when cells duplicate themselves. And if there’s so little energy that replication happens only very slowly, then it makes sense that mutations would only arise very rarely—and that if any of them happened to be helpful, it would take corresponding ages for them to out-compete less-fit brethren. It’s a world moving in slow motion, encased in Jell-O—or rather, in sediment.

Still, the techniques that undergird the paper use certain assumptions, cautions Kjeldsen. For instance, he’s not sure whether the bacteria are actually making new cells, or whether they’re just using the energy to repair themselves. There could be very small genetic changes that the technique doesn’t reveal, too.

“What we don’t know,” he says, “is how much genetic change does it take to gain a competitive advantage? There’s a limit to how subtle of genetic differences we can detect with our method here.” These smaller changes might still be able to make a difference, somehow, in a microbe's ability to survive in a resource-scarce environment. “This is something we are trying to address now,” he says.
Reference:
https://www.theatlantic.com/science/archive/2017/04/bacteria-buried-alive/524214/

Extremophiles: Hot Environments

Relationship between Organisms and their Environment

The high temperatures and geochemistry found in terrestrial and marine geothermal sites are unique. Volcanically derived gases and products from water–rock reactions support chemolithoautotrophic-based microbial communities in what has been termed the deep, hot biosphere. Endolithic microbial communities are pervasive in these environments and likely contribute significantly to subsurface biomass production, which may constitute a significant portion of the total biomass on the planet. The subsurface biosphere is a largely unknown and untapped natural resource. Thermophiles and hyperthermophiles inhabit these environments and serve as model organisms for microbial processes that occur at high in situ temperatures. Although known hyperthermophiles may comprise only a small minority of the total microbial population in a geothermal environment, their metabolisms are likely reflections of the kinds of processes occurring within them. Because they are typically not found in nongeothermal background fluids, they can serve as tracers of in situ chemical and physical conditions within geothermal environments.

Before one can use these organisms as models of biogeochemical processes in geothermal environments, there are a number of fundamental questions that must be addressed related to the relationship between high-temperature organisms and their environment. For example, what are the physical and chemical constraints on metabolic processes? Are different forms of thermophile and hyperthermophile metabolism spatially and temporally segregated on the basis of fluid chemistry? Clearly, the presence of thermoacidophiles, thermoneutrophiles, and thermoalkaliphiles shows how pH can influence microbial distributions and metabolisms, but can these types of changes be observed on a finer scale even within the same organism? What are the different ways in which organisms assimilate CO2or respire a given compound? Are these differences rooted in environmental factors that favor one metabolism over another? Many hyperthermophiles have a requirement for tungsten to meet the needs of certain enzymes found in central metabolic pathways. Are there other unique cofactors used by these organisms? What do these mean with respect to the natural history of these organisms?

In conclusion, extremophiles from hot environments have moved from mere curiosity to a group of organisms that have significant medical and biotechnological applications and are useful for the study of the evolution and biochemistry of metabolic pathways and the biogeochemistry of geothermal environments. Many thermophiles and most hyperthermophiles belong to the Archaea, which is the third superkingdom of life for which there is still much to be learned. Because physiology and ecology go hand in hand, the continued study of high-temperature organisms from these two perspectives should expand our appreciation for these organisms and the function they have in nature.

Reproduced from. 

J.F. Holden in Encyclopedia of Microbiology, 2009

Survival of bacteria in the space vacuum

Reproduced from panspermia.org   

by Brig Klyce

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 

"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 determined that the germs were inside the camera when it was retrieved, so they must have been there before the Surveyor 3 was launched. Apparently, these bacteria had survived for 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 near-vacuum 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 in the camera recovered from the moon would have 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 

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.

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".

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." And there were.

The space colonists

Reproduced from panspermia.org

“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 determined that the germs were inside the camera when it was retrieved, so they must have been there before the Surveyor 3 was launched. Apparently, these bacteria had survived for 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 near-vacuum 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 in the camera recovered from the moon would have 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:

"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.

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".

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." And there were.”

http://panspermia.org/bacteria.htm

What Energy Sources Would There be for Underground Life?

Thomas Gold, 1997

Microbial life could only flourish if there was a supply of the element carbon and a chemical energy source, a "food" for them. The heat that surrounds each microbe can supply no energy; energy can be derived only from the flow of heat from a hot body to a colder one, and the microbes in the rocks are far too small for any temperature differences across their bodies to arise. ("You can sit in a hot tub as much as you like, but you will still need to eat.")     Hydrocarbons are a chemical energy source, but only in the presence of oxygen, so that it becomes possible for the microbiology to mediate the energy-giving process of oxidizing them. On the surface of the Earth this is easy, the atmosphere provides virtually unlimited amounts of free oxygen. But where is the oxygen deep down in the pores of the rocks where we find oil?

The rocks contain oxygen in abundance, only most of it is bound too tightly, and it would take more energy to free this oxygen than could be obtained by the oxidation of the hydrocarbons. There are just a few commonly occurring substances in the rocks that have sufficiently loosely bound oxygen to allow the oxidation of hydrocarbons to be an energy source. Highly oxidized iron is one of them, sulfates (oxidized sulfur compounds) are another. Microorganisms can then feed on the combination of hydrocarbons with some oxygen they can take off these substances. One must then expect to see the accumulation at least of the solid end- products of some or all of these processes in hydrocarbon-rich areas. Search for Life on Other Planetary Bodies.

The search for sub-surface life on other planetary solid bodies such as the Moon, Mars, and many asteroids and satellites of the major planets, will now become a high priority item in planetary research. The surface conditions on the other solid planetary bodies are all quite different from those we have here, where the conditions are remarkably favorable for the development of surface life. But the sub-surface conditions will be similar to ours on most of these bodies, though depth dependence of pressure and temperature will be different. The possibility of developing life in them may then be not too different from the circumstances here. Hydrocarbons on them are known, and sub-surface liquid water can be expected on many of them. The rocks will contain some oxidized components that will serve as oxygen donors. The scene would be set for the existence of microbiology there. The recommendations I made specifically for Mars (in the paper mentioned above) included the search for evidence of microbial life in the carbonaceous Martian meteorites that had been found in Antarctica (a search that is still in progress now). For future interplanetary missions that could return a sample back to Earth, I thought that it would be best to go to locations where material is exposed now, that must once have been at some depth. The outstanding case is the floor of the deep "Vallis Marineris," where massive landslides have exposed material that must once have been at a depth well into the liquid water domain.

What are the Solid Products of this Microbial Activity?

The liquid or gaseous products will generally escape in short times and would not be maintained in a small meteorite on a long space flight. Where iron oxides served as the oxygen donors, the end product will be iron in a less oxidized state in which it is magnetic. Magnetite is the most common form. A further removal of oxygen, such as the step to metallic iron, requires more energy than is available in the reaction. Where sulfur oxides were the oxygen donors, one must expect to see just sulfur or unoxidized sulfur compounds such as hydrogen sulfide or metal sulfides. The product of the oxidation of the hydrocarbons will be carbon dioxide and water, and in many rocks this will react with oxides of calcium or magnesium to make solid carbonates. Those are the carbonate cements that fill up small pore spaces, and must have been transported by a liquid before precipitating.

From:  http://j_kidd.tripod.com/b/103.html

There is life everywhere in the Universe where temperature is not too high

Even in extreme cold interplanetary and interstellar space there may be viable bacterian spores (and even  actual active bacteria).

A new revolutionary paradigm on life in small celestial bodies like comets, asteroids, dwarf planets  and  Kuiper belt objects has been considered by astronomers Fred Hoyle, Chandra Wikramasinghe and M.K. Wallis. We agree with them and even could go one step further.    Surprinsingly objects located very far from the Sun, with temperatures lower than -230o Celsius (40-45 K), have shown to have intense geological activity (i.e, Pluto and Triton). Probably inside this faraway bodies temperatures are no as cold as traditionally believed.  In the interior of some larger dwarf planets and remote asteroids, and  even in comets, temperatures may be high enough allow the presence of liquid and gas fluids. These fluids are often linked to the presence of organic molecules, including bacterian spores which can eventually  be activated.  In other words according to this new paradigm, life may be present everywhere when temperatures are not too high. This theory changes completely the scope of the present dominant approach which is very reluctant to accept life outside our planet.

The following text is reproduced from panspermia.org    

Anomalous Behavior by Some Comets

When a typical comet nears the sun, it vents gases and dust from various places. This has been thought to happen because the sun's heat on the comet's irregular surface causes cometary material to boil off asymmetrically. However, some comets like Chiron and Schwassmann-Wachmann 1 exhibit unusual behavior; they sputter and brighten too far from the sun for this mechanism to work (34-37). Hale-Bopp is another comet in this category . Even Halley's comet had an unexpected outburst in 1991; it brightened by a factor of 300 while it was outbound and well beyond the orbit of Saturn. The strictly chemical explanations of these anomalous events rely on processes that would run out of supplies within a few hundred years.

M. K. Wallis and Wickramasinghe proposed another explanation; namely, that a cycle of surface freezing, compression, and cracking may cause compressed liquid or gas to squirt from a comet's interior. A third possibility, which Hoyle and Wickramasinghe have considered, is that cellular metabolism may be under way on some comets. This metabolism could generate gasses that could, directly or indirectly, account for the brightening. The recent discovery of abundant methane and ethane in the coma of comet Hyakutake strengthens this possibility. In any case, the anomalous brightening of these comets needs explaining. The presence of liquid water or even life on the comets could help explain it. More research would help here as well.

http://www.panspermia.org/comets.htm