Question

most abundant bacteria

Answer 1

I think palagibacter but not sure

Answer 2

Lactobacillus species are the largest of them (which is found in your milk, yogurt., probiotic drinks etc).They are most abundant bacteria in our body.

They start from your mouth, through your gut, and also exit our from your feces in large quantities.  

But in terms of overall winner it is Pelagibacter ubique.

They form one third the population of all the bacteria in the ocean.