The carnitine acts as an intracellular carrier molecule, and is involved in fatty acid metabolism. Choline serves as a lipogenic factor in synthesis of phosphatidyl-choline and as a component of the neurotransmitter acetylcholine. It is provided in the diet as its chloride salt. When properly assembled, these components comprise a chemically defined diet. This is one of the two or three most highly refined diets produced for any animals.
Various microbes can provide nutritional requirements to insects.
To maintain the chemical definition, this medium must be sterilized by autoclaving it, and the fruitfly eggs must be surface sterilized to prevent inoculating the medium with microbes. Sterilization is verified by inoculating the infusion broth with samples of the medium. These points are important for two reasons. First, we have seen that microbes provide micronutrients to insects, and second, heavy microbial infections can retard normal growth and development. Yes, they can.