What kind of bacteria are harmful and can cause diseases?

The term 'pathogenic bacteria' specifically refers to bacteria that are capable of causing disease in hosts, including humans, animals, and plants. These organisms possess various mechanisms to invade the host's tissues, evade the immune response, and produce toxins that can result in illness. Pathogenic bacteria are responsible for numerous infections and illnesses, ranging from mild ailments like strep throat to serious conditions such as pneumonia, tuberculosis, and foodborne illnesses.

In contrast, commensal bacteria and beneficial bacteria play a role in maintaining health and homeostasis. Commensal bacteria live on or in a host without causing harm and can even provide beneficial effects, such as aiding in digestion and protecting against pathogenic species. Beneficial bacteria, often referred to as probiotics, are known for their role in promoting health and preventing infections. Non-pathogenic bacteria are generally harmless and do not cause disease, often existing in symbiosis with their host or playing essential roles in environmental processes.

Understanding the distinction between these types of bacteria is crucial in the field of health and microbiology, particularly when addressing infections and treatments.