Bacteria will undergo mitosis and split itself into two exact copies. When both copies are ready, they will both be able to split again. This is exponential growth,because the bacteria is growing exponentially. Bacteria use this to regain numbers from very small to very large in a few days. That is why Addie's bacteria came back, because there were enough leftover bacteria that exponential growth was able to save them
When bacteria undergo mitosis, they make exact copies of themselves, including the traits they have. This means that when bacteria with less pores copy themselves, there will now be 2 copies of low pore bacteria. As more high pore bacteria die off and more low pore bacteria stay alive, more low pore bacteria can undergo mitosis and more high pore bacteria die, increasing the number ofresistant bacteria in the population.
Eventually,the entire population of bacteria is overrun and all bacteria are copies of resistant bacteria while the non-resistant are all dead. This is called natural selection, where the organisms that cannot live in the current environment die off, leaving the organisms that can survive the only organisms that can reproduce, which means they can pass their genes that made them survive to the next generation.