Your friend believes that prokaryotes are always detrimental and pathogenic. How would you explain to them that they are wrong?
Remind them of the important roles prokaryotes play in decomposition and freeing up nutrients in biogeochemical cycles; remind them of the many prokaryotes that are not human pathogens and that fill very specialized niches. Furthermore, our normal bacterial symbionts are crucial for our digestion and in protecting us from pathogens.
Many people use antimicrobial soap to kill bacteria on their hands. However, overuse may actually increase the risk of infection. How could this occur?
Soap indiscriminately kills bacteria on skin. This kills harmful bacteria, but can also eliminate “good” bacteria from the skin. When the non-pathogenic bacteria are eliminated, pathogenic bacteria can colonize the empty surface.