Microorganisms as pathogens — A/L Biology

A. Normal Microbiota Definition: The collection of microorganisms that normally inhabit various parts of the human body without causing disease under normal conditions. Explanation: Normal microbiota refers to the diverse community of microorganisms (bacteria, fungi, viruses) that live in and on our bodies in a symbiotic relationship. These microbes colonize specific body sites like skin, mouth, gut, and reproductive tract. They play crucial roles in digestion, vitamin production, and protection against pathogens by occupying space and resources. The composition varies between individuals and body sites, and disruption of this balance can lead to opportunistic infections. Think of it as: Like a garden with beneficial plants that prevent weeds from growing - the normal microbiota prevents harmful pathogens from establishing themselves. Real-world application: Understanding normal microbiota helps explain why antibiotics can cause diarrhea (by killing gut bacteria) and why probiotics are used to restore healthy microbial balance after illness or antibiotic treatment. B.