What are symbiotic bacteria?

• A. Bacteria that live in (or on) another organism involving benefit
• B. Bacteria that cause disease
• C. Bacteria used in fermentation
• D. Bacteria found in soil

Answer: (A)

Symbiotic bacteria are bacteria that live in or on another organism in a close, long-lasting relationship that provides a benefit to at least one partner. This can be mutually beneficial, as when gut bacteria help digest food and produce vitamins for the host, or when nitrogen-fixing bacteria in plant roots supply usable nitrogen to the plant while obtaining nutrients and a habitat in return. The word implies an intimate association with a host rather than just being present in the environment or causing disease. So, bacteria that simply cause illness aren’t described by this term, and examples like fermentation organisms or soil-dwelling bacteria illustrate activities or environments rather than the living partnership with another organism.