What is a characteristic of bacteria in relation to humans?

Bacteria play a complex role in the environment, and their relationship with humans is equally diverse. The correct option highlights that bacteria can indeed be both beneficial and harmful.

On one hand, some bacteria are essential for human health; for instance, the gut microbiota consists of beneficial bacteria that aid in digestion, produce vitamins, and protect against pathogenic organisms. These "good" bacteria contribute to our overall well-being and are a fundamental aspect of various probiotic foods.

Conversely, certain bacteria can cause diseases and infections, which demonstrates their potential to be harmful. This duality is critical in understanding how bacteria function in relation to humans, emphasizing the importance of context and specific strains when considering their effects.

Other options incorrectly simplify the relationship: suggesting that bacteria are always harmful ignores the beneficial roles they play; claiming they exclusively cause infections does not account for the substantial beneficial effects; and stating they only affect plants excludes the vast array of bacteria that interact with humans and animals. This perspective is crucial for a nuanced understanding of food safety and health implications related to bacterial presence in food and our bodies.