You should know that invisible microbes are present everywhere, because they can surviveeven under very inhospitable conditions. They are all around us, in the air we breathe, in thsoil, in food, ih water used for drinking or bathing and on all the objects we come in contacwith. You will be surprised to know that billions of them live on the skin of our body and inour mouths and intestinal tracts. One third of the dry human faeces is bacteria. However, only some of these micro-organisms cause infectious diseases. There are many others whicare beneficial and their activities are of central importance to the biosphere. Without them life on earth would perish! Long before we even knew of their-existence, we have been taking advantage of their activities, as in the case of making curds, and alcohol or baking cakes and bread. They decompose dead plants and animals, as well as sewage into harmlesbut indispensable chemicals like nitrogen, oxygen and carbon dioxide etc. They can also bused as biological factories to produce antibiotics.
In fact, the famous antibiotic, penicillinwas discovered from a culture of fungus. Certain kinds of bacteria live in human intestinesand provide vitamin B,, and vitamin K. Thus, though some microbes are harmful, athers aof great service to humanity. While the knowledge of gems has grown and some of it is used to save people from disease and death, several countries have used this knowledge fodestruction and warfare. You may have heard the word "geim warfare". These countries have collected deadly gems which can be spread in enemy countries to pollute air or wateor even to destroy crops and forests. Such warfare, obviously, kills people, not just soldierand as such it is internationally prohibited.