What is the primary characteristic of a stable and healthy human microbiome?

A high population of a single, dominant bacterial species.

The complete absence of all bacteria, creating a sterile environment.

A wide variety of many different types of coexisting bacteria.

The presence of only a few, highly specialized microbes.

Which of the following scenarios is the best analogy for how a diverse microbiome protects against harmful bacteria?

A thriving, dense rainforest with many native species naturally resists the invasion of non-native weeds.

An empty parking lot that can be easily and quickly filled by any type of car arriving first.

A garden containing only one type of rose is vulnerable to a single disease that targets that specific plant.

A library with only one book is very simple to manage and keep organized.

They signal the immune system to attack any new microbes that enter the body.

They directly attack and consume harmful bacteria in a predator-prey relationship.

They limit the resources, such as space and nutrients, that are available for harmful bacteria to grow.

They create more physical space, allowing the body to more easily flush out harmful bacteria.

A more efficient absorption of all nutrients from food.

The colonization and overgrowth of a single harmful, pathogenic bacterium.

A rapid increase in the population of the remaining helpful bacteria.

The permanent elimination of all microbes from the gut.