Expert: Walter Hintz - 5/23/2007

Question
My 5th grade son is doing his science fair project comparing who has more bacteria between human, dog and cat. He has grown the bacteria and duplicated the results.  Clearly the human had the most, then dog and then cat.  He has been trying to find research data that would explain the differences but not finding much.  Any help would be appreciated.  Thanks.

Answer
The reasons behind the different numbers can be a lot of things.  For example what did each eat last and did the person brush his teeth first. All that can be done is to suggest possibilities.  It would be difficult to answer.  However I do not think that is important in this study.  The hypothesis was a comparison of the numbers found in the mouth and that is what was done.  The real differences lie in the type of bacteria and this takes advanced experiments.