Give two examples to explain why microorganisms are beneficial to human health.

Microorganisms will affect people's production and life, and they play an extremely important role in transforming soil materials and promoting plant growth. For example, rhizobia and chromobacter are microorganisms that activate nitrogen for plants to use. Microorganisms can also be used in bioengineering. Yeast brewing, lactic acid bacteria yogurt, Mucor sufu. It can also be used as biological pesticides, such as Bacillus thuringiensis and Bacillus japonicas. These bacteria are harmless to people and animals and harmful to insects, so they are relatively green pesticides. However, some microorganisms belong to animal and plant bacteria and viruses, which bring harm to agricultural production, such as tobacco mosaic virus and avian influenza virus. In life, microorganisms often affect human health. Both bifidobacteria and lactic acid bacteria are beneficial to human health. When beneficial bacteria such as Bifidobacterium and Lactobacillus grow and multiply in the intestine, it will prevent pathogens from invading the intestine and build a biological barrier. Moreover, the intestine is the largest immune organ of human body, and beneficial bacteria can secrete some antigen substances to activate and strengthen the immune system of the intestine. There are also some microorganisms that we often hear are harmful to people's health, such as mycobacterium tuberculosis, influenza virus and so on.