Ever hear of white blood cells?

How are you defining "taking over the world"? Bacteria are by far the most numerous life form, and all other organisms depend on them for survival. If bacteria die out, so does everything else. Sounds like they’re already pretty dominant to me.

"there are approximately five nonillion (5×1030) bacteria on Earth, forming much of the world’s biomass." -Wikipedia

The exponent is a 30, on the scientific notation there.

An interesting question 🙂

Competition and lack of nutrition are probably the main reasons – just like with any organisms, and to a much lesser extent inhospitable environments And like mith said, other species are capable of defending themselves.

For example, some eucaryotic unicellular organisms eat bacteria, and bacteria compete for nutrients against one another, as well as against other microorganisms living in the same ecological niche. For example, many molds secrete substances that kill or inhibit bacterial growth.

And even if there wasn’t any direct competition by other organisms, bacteria couldn’t "take over the world", if by that we mean that they’d cause the extinction of all other life forms and would be the sole survivors on this planet: there’d always be lots of habitats that are inhabitable for bacteria – mainly very dry (or cold) places, where vegetative bacteria survive only when living as symbiots or parasites on multicellular organisms that can survive there. So in other words, even if bacteria could rid the world of other living creatures, it would be against their best interests in many cases, and thus natural selection wouldn’t direct their evolution that way.

I would say that bacteria have taken over the world:
In numbers – more bacteria than any other living organism
Geographic – bacteria will basically survive in any place that supports other life and also some places that won’t.

As Biohazard rightly pointed out, however, it is far more benefical for bacteria to have other life forms e.g. humans as we are part of the environment (and the world) that some bacteria rely on to exist.

It all comes down to how you define "take over the world". If it’s just numbers, then hell yeah bacteria rule the earth. But if the organism in question has to completely dominate or annihilate all other living creatures on this planet, I don’t think any species or genus or whatnot will achieve that any time soon 🙂

I can’t wait until we can introduce bacteria to some sterile planet and sit back and watch what happens.

We should make a reality tv show out of it and broadcast it across the galaxy.

Haha, that would be the greatest hit ever! (…for a handful of biologists or such)

Tremble Big Brother!!

I was thinking more along the lines of the aliens on Southpark producing a reality show about Earth and broadcasting it across the galaxy.

Welcome to the Truman show. And no we are not the main characters 😉

bacteria"small stick organism" are unicque organism, they can leave everywhere, as "cosmopolite" bacteria will growth rapidly…

So would anyone disagree that another limiter of the growth of a bacterial population would be their own waste? An increase in the number of bacteria would result in an increase in the amount of waste produced, would it not? And that waste is waste to said bacteria for a reason…

Yeah their waste does play a factor, but just like everything else there are ways to get rid of it. One species’ waste is another species’ food supply, after all. So I think the extent to which it would limit bacterial growth would have to do with what else is present in the environment.

i ever read microbe have important role because almost every activity in the world influenced by microbe.because my teacher ever said and i ever read, microbes found anytime,everywhere, and any condition…in the air, marine,our body, etc. one of example, in our body, microbe found in intestine and have influenced on digestion system.if there aren’t microbe our digestion will be perfect 😉