I think it's amazing what we're learning about viruses. Just recently, we have the ability to discover that there are far more viruses than we would have ever imagined, a number that's a 1 followed by 31 zeros, that's how many viruses we think there are on planet Earth. So this suggests they must be doing something that's absolutely critical to maintain such a high number. And in fact they are: they are killing 40 to 50% of the bacteria in Earth's oceans everyday. This releases organic molecules that the bacteria have been able to synthesize and bacteria are able to draw certain elements out of the environment and put them into organic compounds. Higher life depends upon these types of molecules being available to them. So, viruses that kill the bacteria release these organic and biogenic molecules for the use of higher organisms. And so bacteria contribute in a huge way to the bio/geo-chemical cycles on our planet.