The genes that produce the enzymes needed to break down lactose are not expressed.
The source of lactose is cow's milk.
There are different types of food that are a good source of hydrogen. This mostly includes sugars like lactose, fructose and sucrose among others.
Probably because that is where the gram negative bacteria have found a food source. Lactose is not the perfered diet, but it works and they are most likely there because they can tolerate the environment, and survive (on lactose) when their #1 food source is not available.
That depends if you're lactose intolerant or not. If you are then you end up with undigested food in your gut, which may lead to nausea, diarrhea, or vomiting. If you're not intolerant, then you just get fat.
If an animal loses their food source, in the wild, they will try to find a sustainable source to have food to survive. If they cannot find a worthy source of food/water, they starve or become dehydrated and pass away.
they get extinct
A ferret can eat cat food, but not as a main source. They should be eating food made especially for ferrets only. A high quality kitten food can be a second source of food for ferrets.
milk
Sucrose, Lactose, Maltose
Possibly I think anything except for lactose things so they need to be lactose free
The lac regulatory system is a vital part of the bacteria. This is because, the most common source of food is sugar lactose and it is required by the enzymes all the time.
The presence of lactase in food products can benefit individuals with lactose intolerance by helping them digest lactose, the sugar found in dairy products. Lactase breaks down lactose into simpler sugars that are easier for the body to absorb, reducing symptoms like bloating, gas, and diarrhea that occur when lactose intolerant individuals consume dairy products.