Host-Microbe Relationships

Please answer the bolded text at the bottom after reading the paragraph thanks.

Mutualism

A mutualistic relationship is when two organisms of differing species work in cooperation with each benefiting from the activities of the other. One example of a mutualistic relationship is that of humans and plants. Humans use the plants for food as well as utilizing the oxygen they produce while exhaling the carbon dioxide that plants need. Plants use the carbon dioxide that humans produce and give off the oxygen that humans use. Humanity could not exist on earth without plant life.

Organisms in a mutualistic relationship have evolved together and survived the eons because of each other. Each organism was a part of the other's environment and as they adapted to that environment, they utilized each other in a way that benefited both.

Are there any microbes that we have a mutualistic relationship with? If so, how do we help each other?

Are there any other mutualistic relationships in nature (macro- or microbiological) that you can find?