Outsider bug.

Another very geeky joke.

There are two types of bacteria (eubacteria if you want to go into detail): gram-positive (that get coloured by a stain called "gram") and gram-negative (that dont stain). Famous gram-positive are the bacilus (like anthrax) and celebrity gram-negative is, for example, the popular E. coli.

And wherever theres division there is segregation.

Shame on you, gram-positives!!!