Why do most natural antibiotics come from soil fungi and bacteria?
Why do they produce them? ANSWER 1 : A simple, though possibly simplistic, explanation is that these organisms use antibiotics to protect their food supply. Soil bacteria and fungi live by digesting and recycling dead plant material such as leaves and seed cases. Obviously it is impossible for the bacteria to carry away their prized food supply and therefore it is argued that they lace surrounding food with compounds that are toxic to those of other species. While there is some lab-based experimental evidence to support this hypothesis, it has been difficult to prove this theory in the wild. Antibiotics that work just fine in the lab may be absorbed or diluted by different soils and clays to the point of being rendered useless, while organisms that are typically found in the soil may have robust resistance to antibiotics. A second explanation is that antibiotic production is rooted in the plant material that is the food source. This material is typically carbon-rich and nitrogen-poor.