Final answer:
The symbiotic relationship where both partners benefit, such as E. coli in the human gut providing vitamins and bacteriocins, is known as mutualism.
Step-by-step explanation:
The type of symbiosis where both partners benefit from the relationship, as in the case of human gut flora such as certain strains of Escherichia coli providing vitamin K and B vitamins along with producing bacteriocins, is called mutualism. Also, the environment within the human gut gives the E. coli a protected habitat and abundant nutrients, exemplifying a mutualistic interaction. In mutualism, both species involved in the symbiotic relationship derive benefits from each other, which can include nutritional support, protection, or other forms of advantage that enhance survival and wellbeing.