Bacteria Mutation should have killed us

[Elite Engineer]

Bacterial cells accomplish mitosis (replication) in 30 minutes. Human cells require 24 hours to accomplish mitosis. Mutations

 

in DNA occur roughly 1 in 100 million DNA replication cycles. This means DNA in one day bacteria replicate 48 more times

 

more than humans do. Now take the existence of the homo sapien, about 600,000 years relative to the existence of bacteria,

 

about 3 Billion years.

 

How is it that humans remain alive relative to the huge difference in bacterial mutations relative to human mutation. Sure

 

some mutations are bad, possibly fatal, but in the course of 3 Billion years, I would think bacteria would have been the end

 

all be all upon Earth, and would have wiped out all other existence.

 

Your thoughts,

 

EE

[CaptainPanic]

Maybe bacteria actually flourish because of our assistance? Our guts are absolutely full of them. In a human body, bacteria outnumber your own cells 10 to 1.

 

If the bacteria kill you, then they also lose their feeding grounds. If they keep you alive, they are fed too.

 

(Please note: I am absolutely no expert, and this answer is speculation... it makes sense to me though.).

[DARK HUNTER]

Generally Life doesn't seek to exterminate itself. It seeks to expand itself,from bacteria to protista to plants and animals.

And let's remember that there are more "good" bacteria which help us than there are "evil" ones which causes illness in humans.

 

I imagine that bacteria have no secret plans to conquer the planet (or do they? *dramatic music plays*)

 

.....Damn it,this question is difficult

[CharonY]

As CaptainPanic already explained killing off a suitable host is usually not a very good long-term strategy.

The core of evolution is successful proliferation, not the extinction of other species.

Edited May 30, 2013 by CharonY

[Elite Engineer]

All good points. I never thought of a mutual symbosis as to explaining why bacteria and eukaroytes still live together. What do you think about

 

the "fatal to humans" bactera (i.e. E-Coli, Tetanus, etc.). Do you think its a matter of time till they have a mutation that's deadly enough to wipe us out.

 

Though it doesn't look too promising, as I can only think of two cases where a bacteria/ virus (ya I know its not living) drastically affected the population,

 

those being The Black Death and Spanish Flu of 1918.

[ewmon]

Yet each of the billions of bacteria on one of us is an individual, one instance where a mutation could occur, compared to one of us, which is one instance of a mutation. This vastly increases the odds against us.

 

It is known that virulent viruses (and bacteria?) are known to eventually mutate to less virulent forms (eg, the "Spanish Flu" circa 1918) apparently all by themselves. As highly social beings, humans are very compassionate. It wasn't as though people began shunning Spanish Flu patients; people remained compassionate and provided care to them ... and some caught the flu.

 

Is anyone here meaning that our symbiotic bacteria/viruses are policing our bodies?? This would make sense, but I've never heard of it before.

[Delta1212]

Symbiotic bacteria do a variety of things, especially with regard to digestion. It's actually pretty fascinating if you look into. Changing the types of bacteria in your digestive tract can radically alter your metabolism, to the point that obese mice given guy bacteria from thin mice dropped considerable weight, and thin mice given gut bacteria from obese mice out on weight.

 

As far as "policing" goes, the good bacteria mostly occupy space and free resources in the body so that it's unavailable for more harmful bacteria to use. They don't generally attack "bad" bacteria on your behalf, but they do do the job of crowding them out.

 

 

And yes, especially deadly diseases tend to become less severe over time. Diseases that kill their hosts too quickly don't get a chance to spread, while less severe forms may go undetected or persist well after a more deadly form has killed its host, allowing more opportunities to infect others.

 

The especially deadly diseases are usually a result of species jumping, where a virus or bacteria that is settled in one species mutates in a way that allows it to infect another species that it isn't as well suited to and that it hasn't "learned" how to infect without causing serious damage.

 

The result is often a particularly deadly disease that will blow through a population that doesn't have a strong immunity to it. This creates a selection pressure on the population to become more resistant, and a selection pressure on the disease to become less deadly so it can spread better.

 

It's highly unlikely that a single disease would arise that would be able to wipe out all of humanity because of this settling effect, but several at once can have an incredibly devestating effect because those people with resistance to one disease, who would normally survive and increase the resistance of the general population, may be susceptible to another disease, wiping out immunities from the population.

 

This is actually part of the reason that Native American groups had as high as 90% population loss in some areas in the early years of colonization.

[CharonY]

Technically one would probably refer to the interaction we have with bacteria as mutualism rather than true symbiosis, though there is no strict distinction.

But obviously our bacterial flora influences us to a large extent during non pathogenic interaction. In addition ot effects on the digestive syste, they modulate our immune response or change their respective niches that in turn affects the flora we have. As such they provide us with a passive defense against colonization of novel bacteria that may be infectious by virtue of outcompeting newcomers and so on.

[EdEarl]

This recent news may be relevant to this discussion. Although, it did not kill infected birds the disease became more virulent over time, which is a different scenario than discussed herein.

 

http://www.nsf.gov/news/news_summ.jsp?cntn_id=127992&org=NSF&from=news

 

The team experimentally infected wild-caught, house finches, then measured how sick the birds got with each sample. The researchers kept the birds in cages as they fell ill then recovered (none of the birds died from the disease).

 

Contrary to expectations, the biologists found that in both regions--California and the Eastern Seaboard--the disease had evolved to become more virulent over time.

 

Birds exposed to later disease strains developed more swollen eyes that took longer to heal.A less-virulent strain spread westward across the continent. Once established in California, however, the bacteria again began evolving higher virulence.

[Delta1212]

This recent news may be relevant to this discussion. Although, it did not kill infected birds the disease became more virulent over time, which is a different scenario than discussed herein.

 

http://www.nsf.gov/news/news_summ.jsp?cntn_id=127992&org=NSF&from=news

With the caveat that, obviously, I don't know exactly why this is, I would hazard a guess that the fact that none of the tested birds died might indicate some part of why. A major reason that diseases tend to evolve to be less severe over time is that the more rapidly and consistently the disease kills its host, the less opportunity it has to spread and replicate. If the disease is exceedingly unlikely to kill the host, even in more virulent forms, this restriction is, if not eliminated (because this is obviously laboratory conditions), then at least greatly lessened. If the more severe symptoms help the bacteria spread, and don't greatly increase the likelihood of the host dying, then I don't see why it wouldn't evolve to be more severe.

 

Again, that's pure speculation on my part.

[BTF/PTM]

Invasive bacteria can and do kill us. The original poster is correct, the replication rate and subsequent invasion rate of bacteria, compared to our own cell replication rates, leaves us pretty much defenseless should a hostile bacteria invade unchecked. On top of that, human immune systems aren't very good at killing bacteria, they're much better suited for eliminating viruses. Hence, we use antibiotics of various sorts (be it a modern pill or a plant oil or whatever) to keep a bacterial infection from getting out of control.

 

Bacterial infections are, in my opinion, another example of the fact that we are not finished evolving yet, or at the very least that we are nowhere near the top of the food chain. A cat's spleen, for example, is proportionally far larger than ours is, they can survive infections that would reduce us to compost. Nature has plenty of ways to put us in our place, and bacteria are just one example.

[Delta1212]

Invasive bacteria can and do kill us. The original poster is correct, the replication rate and subsequent invasion rate of bacteria, compared to our own cell replication rates, leaves us pretty much defenseless should a hostile bacteria invade unchecked. On top of that, human immune systems aren't very good at killing bacteria, they're much better suited for eliminating viruses. Hence, we use antibiotics of various sorts (be it a modern pill or a plant oil or whatever) to keep a bacterial infection from getting out of control.

 

Bacterial infections are, in my opinion, another example of the fact that we are not finished evolving yet, or at the very least that we are nowhere near the top of the food chain. A cat's spleen, for example, is proportionally far larger than ours is, they can survive infections that would reduce us to compost. Nature has plenty of ways to put us in our place, and bacteria are just one example.

Nothing is ever finished evolving until it's extinct.

[CharonY]

On top of that, human immune systems aren't very good at killing bacteria, they're much better suited for eliminating viruses. Hence, we use antibiotics of various sorts (be it a modern pill or a plant oil or whatever) to keep a bacterial infection from getting out of control.

 

Citation needed. Also, how did we survive until now and what types of antibiotics do all the other mammals use?