Answer:
they are the basis of decay and decomposition, which helps waste disintegrate. it`s the only reason earth isnt overrun with biodegradable waste
they enhance soil fertility. ever seen farmer put manure in fertilizer? its bc the bacteria helps plants grow
specific bacterias are used in medicines. there are good and bad kinds, and we use the good kinds to fight bad ones off (antibiotics)
the bacteria in our bodies helps break down the food we digest so that we can absorb the nutrients and excrete waste to keep our bodies healthy
other bodily bacteria can fight off diseases, viruses, etc. this could summarized into the immune system
hope this helps :)
