Bacteria can be beneficial. which of these is an example of how bacteria are beneficial?

Answer;
 Here are a few ways: 
Bacteria in human intestines aid in the digestion of certain foods; 
Production of cheese, yogurt, and other foods 
Decomposition and recycling of dead organisms 
Fixation of nitrogen from the atmosphere into useable nitrogen in soils 
Production of antibiotics 
Photosynthetic bacteria produce oxygen

Bacterias such as l casi boost the immune system