How Did airborne bacteria get into the air in the first place?
400069
Some are carried on particles of dust or hairs or skin cells shed by animals.\n\nMany are carried in tiny droplets of water, then the water evaporates, leaving the salts and bacteria etc to drift slowly to earth, but these tiny particles are so light that disturbance of the air can keep them afloat for ages.\n\nThese tiny droplets are called aerosols. They form every time a fluid is shaken, splashed or touched by something that is then lifted away; a trail of droplets is left, as the item leaves the water surface.\n\nThis is why we do some procedures in biohazard cabinets, in microbiology labs; the bactera (and fungi, and viruses) in the sample will be aerosolised as we handle the sample, sampling it with scalpels, pipettes + / or bacteriological loops. The filters of the cabinet draw the air from around the sample then through high efficiency filters which trap the aerosols and the infectious agents.  The cleaned air can then be returned to the room.  These cabinets are sometimes called "laminar flow" cabinets.\n\nWhen we cough, sneeze, speak, or even open our mouths, we are creating aerosols, and sometimes also droplets big enough to see, with the unassisted eye.  Thus, respiratory infections are spread efficiently by coughs and sneezes, and by talking near other people.
205103
They evolved lungs which enabled them to breathe air.
765409
Unlike bacteria that multiply in the correct conditions of their own volition, viruses have to invade a cell and change it to spread.  They can't just be, they have to take something over.
1050315
It depends on what sort of microorganisms you wish to grow.  If you'd like protists, just go to any local pond, take a sample of the water and you'll have an instant microcosm.  If you're specifically interested in bacteria or fungi- all you really need to do is leave out some moist, fatty nutrient-rich substance (like milk) and soon enough mold spores (mold is a fungus, by the way) in the air will settle and grow, as will bacteria.  (It's important to note that there is no such thing as "spontaneous generation" - These microorganisms will grow from air-borne spores or spores that are already present in the container / within the substance you grow them.  They don't just simply generate from nothing.)
616795
yup Bacteria it was.. See we've earned the right to live on this planet cause we were able to survive against the bacterias, we've build himune system against them buggers but it took us THOUSANDS OF YEARS to accomplish that!! Those tripod didn't think of it when they planed to attack the planet. Earth is all about survival of the fittest baby!!! VIVE LES MICROBES!
110846
Particulates from 'smoke'.\nSoil that has been eroded by the wind.\nSalt crystals lifted off the sea.\nPollen\nSeeds from plants such as dandelionor orchids.\nWindborne microbes or their spores.\nAnimals, mainly birds and insects, but also spiders and other animals that are blown from place to place.\n\n\n________\n\n>>>> none they are all gases\n\nYeah, like all the material in the ocean is a liquid, right? And all the material in the ground is a solid?\n\nDid you even stop to think before answering?
142782
IT MEANS THAT AIR HAD ENTERED IT
536246
Because of bacteria and germs growing in it.
7688
Actually, the micro-organisms in the soil emanate some gases when their lifeline, water reaches them. U dont need a rain for that smell. Water ur garden, u will start smellin it in 1 min.
129046
Airborne mold spores are dangerous to your health:\n\nhttp://dede.essortment.com/airbornemold_riri.htm
4800
Normally on Earth, smoke rises and spreads because 1) the smoke particles are lighter than air, 2) the heat from whatever is burning creates an upward current of air, and 3) air is always moving.\n\nIf this vacuum is on Earth, than the smoke particles will fall to the bottom of the container or room.  If the vacuum is in space, then it depends on how the smoke is generated.  The smoke particles might either just sit there or fly straight out.
897178
Usually its ambient gram-positive bacteria or any of a host of fungi that float in the air on dust and dead skin cells.  Poor sterile technique can cause these to contaminate tubes.  You should always briefly heat up the lids of tubes over a flame before and after adding anything to them to create and outward convection of air.  Furthermore, you need to heat innoculation loops over flame until they are red-hot before scraping a colony.  Let it cool first, though.
418957
Extremely possible. To illustrate my answer, I'll refer to the space shuttle Columbia. As we all know it was a disaster, but when scientists examined the debris from space shuttle, they found that bacteria that had been aboard the space shuttle (maybe taken for research purposes) had still survived!! \n\nIf bacteria can survive under such extreme conditions, its entirely possible, that some bacteria could be lodged in a meteorite that could have struck Earth millions of years ago. Also its possible that the same meteorites could have caused bacteria from Earth to travel into space on the dislodged debris from impact. This earth bacteria could possibly do the same thing by evolving into life on a different planet. So its possible that we might meet aliens someday that look very similar to us :)
473070
chicken pox and influenza (both respiratory infections).  however, i wouldn't say they spread "by air" but rather by aerosols coughed up by an infected person.
14899
Bacteria and bacteria waste, and other stuff gets stuck on the roof of you nose. This will make your nose sensitive enough to start sniffling and ejecting a mucus. The mucus changes from a clear liquid to gunky green.
435045
I'm quite sure that it does since bar soap has touched your body. It also probably collects bacteria from the air. Actually, pretty much everything has bacteria on it.
406464
Yes.  There is a very small amount of matter that enters the atmosphere from space (meteorites), but essentially it is all just being recycled. Some atoms of oxygen you breathe in may have been breathed by a dinosaur, or one of the pharoahs!