Streptococcus mutans obtains energy by oxidizing sucrose. This bacterium is abundant in the mouths of Western European and North American children and is a prominent cause of cavities. The organism is virtually absent in children from East Africa, where tooth decay is rare. Propose a hypothesis to explain this observation. Outline the design of a study that would test your hypothesis.

Video transcript

Welcome back, Let's look at our next question. It says the abundance of streptococcus mutants in Children's mouths can be attributed to well streptococcus mutants um is a commonly found bacteria sort of in everybody's mouths. But as our question indicates, it's an especially high rates in Children's mouths. And streptococcus mutants metabolizes sucrose, otherwise known as table sugar. And as it does that it produces lactic acid and lactic acid is our primary culprit in tooth decay. Um D mineral izing the enamel of the teeth allowing dental carries to occur. It also uses sucrose to produce a sticky policy cried that forms a biofilm that we call plaque um contributing obviously to that tooth decay because the uh streptococcus americans is living very happily in the plaque and digesting away all that sucrose being taken in in the food that people eat. So why is it that there's a particular abundance of streptococcus mutants, mutants and Children's mouths. Let's look through our answer choices here choice A says high fiber intake. Well this is not our answer. High fiber actually causes an increased production of saliva which dilutes sugars in the food um which produces less food for the streptococcus mutants so that would not be responsible for an abundance of streptococcus mutants. But in fact the reverse choice B says high calcium intake. High calcium does not help the streptococcus mutants in any way does strengthen your teeth but not going to cause a greater abundance of streptococcus mutants. Choice C says high protein intake. Again, not going to particularly help s mutants in anyway, so not going to be responsible for the greater abundance in Children's mouths. So we're left with Choice D high sugar intake and this is our correct answer. Uh Dietary sugars are generally sucrose table sugar and that is the primary source of food for the s mutants. So high sugar intake, giving more food will cause a greater abundance of streptococcus mutants in Children's mouths. So our answer is Choice D, high sugar intake. See you in the next video.