There's a big difference though; if you were to eliminate all the microscopic life-forms in your body, and be fed sterile (but nutrient-rich) foods [in laboratory conditions] you would die from malnutrition. Microscopic life is an essential part of your digestive system, and in some ways your intestines are like a compost pile ~ needing microbiotics to process the organic substances there.
Therefore, it makes sense that one way to correct a deficient digestive tract (and some serious infections) would to be to introduce enough antibiotics to kill off virtually the whole microbiotic population and then repopulate the digestive tract with known-good microbiotics. (Similar to the wiping and reinstalling of an OS to be rid of a virus.)
Well, the food would have to be formulated differently than what we normally regard as a diet. It would have to have the bacterial breakdown already performed on it.
Correct. One would die from a result of malnutrition.
One of the vitamins you need is vitamin K. K plays a crucial role in proper blood clotting.
The reason K was not discovered and obvious like Vitamin C is that few people are deficient because it is made by bacteria in the gut.