They occur in germ cell DNA, which are the cells that create sperm or Ova. For every 85 million nucleotides assembled in DNA during human sperm or Ova production, One will be a mutation
Just like humans and other animals, pathogenic bacterias also has the capability to evolve.
These pathogens usually come to life as soon as they enter a host. When you use antibiotics, the majority of them will die, but several of them could survive.
When these survivals replicate, it will creates more bacterias that has higher immune towards antibiotics compared to normal bacteria
autotroph would mean to self feed or you are are capable of feeding yourself