Pathogenic organisms

Infectious microbes
Disease-causing bacilli
Bacteria, viruses, fungi and other microscopic organisms, broadly known as microbes or germs, cause many of the infectious diseases in the world and millions of deaths annually.
Our lives are crucially reliant on microbes. They provide, in one way or another, all of our daily food and that of other animals too -- ruminants could not digest grass without them. Pedigree strains are responsible for creating gastronomic delights such as fine wines and cheeses. Microbes were the original source of the world's abundant oil supplies and are the active agents in the process of sewage disposal and composting. [Escherichia coli] is the principal bacterium of the biotechnology industry which is producing life-saving drugs such as insulin and anti-blood clotting factors. [Clostridium acetobutylicum] made acetone for the WW I munitions industry.
Aggravated by 
(D) Detailed problems