Final answer:
Most bacteria are beneficial, playing crucial roles in various ecosystems and within the human body. Although some bacteria can be pathogenic, they represent a small proportion of the bacterial world, with the majority being benign or beneficial to humans.
Step-by-step explanation:
Most bacteria are beneficial; in other words, they are harmless organisms that may perform useful functions. While it is a common misconception that all bacteria are harmful, the majority of bacterial species are actually either benign or beneficial to humans.
In environments ranging from the human body to soil ecosystems, these beneficial bacteria play crucial roles. They contribute to various biogeochemical cycles like nitrogen-fixation, help in decomposition, and are a key part of the human microbiota. They protect us against pathogenic bacteria, aid in digestion, and even produce essential vitamins.
Nonetheless, a small percentage of bacteria can be pathogenic. These can invade the body and cause diseases such as tetanus, diphtheria, pertussis, tuberculosis, and leprosy. However, these pathogenic bacteria are much less frequent compared to the beneficial ones.
Even among bacteria that live on or in the human body, such as the microbiota on our skin and in our gastrointestinal tract, most are either harmless or actively beneficial, engaging in a symbiotic relationship with us.