Effectiveness of garlic in fighting bacteria
The hypothesis that the presence of garlic will kill bacteria and prevent its growth is proven to be true.
The antimicrobial properties of herbs and spices are useful for medicinal purpose and also for the preservation of food. However it is also true that different spices are effective in providing resistance and protection against different types of microbes.
Try repeating the experiment by boiling the garlic before extracting the garlic juice. Observe any differences in your results.
Try to repeat the experiment using onions or cloves instead of garlic.
The bacteria should be destroyed before disposal. Pour some bleach into the petri dishes to kill all the bacteria before disposing them in the trash.