Is it possible for a microbe not to grow in nutrient agar?

Answer 1

Yes, it is possible. It's true that the majority of microbes (mainly bacteria) will grow on nutrient agar, but microbes need specific compounds for growth that are not in nutrient agar, which is pretty much considered "general purpose media." Some examples include Legionella pneumophila, which will only grow on special agar infused with charcoal (weird, I know). Then, Neisseria gonorrhoeae grows only on chocolate agar, which contains lysed red blood cells (another weird one).

Sometimes microbes that do grow on nutrient agar may grow better on other types media, like Streptococcus spp.

It's also important to note that "microbes" include bacteria, viruses, fungi, and microscopic parasites. Viruses (except phage) and parasites require tissue culture, not agar, for growth; and fungi grow much better on media with lower pH and higher sugar concentrations than nutrient agar, like Potato Dextrose Agar.

Answer 2

You've already got some great answers. Let me sum it all up by saying that microorganisms will grow only under certain conditions.
These include access to all necessary nutrients, temperature, osmotic pressure, pH, oxygen availability etc. If you have a given strain that doesn't grow on nutrient agar it could be for any of those reasons.
The most common reasons are using plates with wrong antibiotics or having a strain with a deletion in a biosynthetic enzyme and you need to add more of that metabolite in your media.

Finally, not all micro-organisms can be easily cultured in labs. That's where the field of metagenomics comes in. Have a look at
http://en.wikipedia.org/wiki/Metagenomics
about it. It's really interesting.

Answer 3

it is possible if the nutrient agar has antibiotics in it.

if the microbe is an auxotroph (such as a mutant) it will have a nutritional requirement that needs to supplemented in the media.

nutrient agar contains beef broth, peptone, and of course agar. most kinds of fungi and bacteria will grow on nutrient agar, but some find it too much -- others find it too deficient. halophilic bacteria for example do not like to grow on nutrient agar.

Answer 4

yes it's possible, every microbe has certain nutrition requirements. Nutrient agar can be prepared with other substance such as blood to help an organism grow