What type of bacteria is considered harmless and beneficial?

Nonpathogenic bacteria are those that do not cause disease and can often be beneficial to humans and the environment. These bacteria play essential roles in various applications, such as digestion, fermentation, and even in the production of vitamins. An example of beneficial nonpathogenic bacteria is those found in the human gut microbiome, which aid in digestion and keep harmful bacteria in check.

The other categories of bacteria mentioned are typically associated with harmful effects. Pathogenic bacteria are known to cause illness and disease in humans and other organisms. Virulent bacteria are those that have the ability to overcome the host's defenses and thus are more capable of causing disease. Infectious bacteria are responsible for infections, affecting health negatively. In contrast, nonpathogenic bacteria provide support and contribute positively to environmental and physiological processes, highlighting their important role in maintaining overall health.