Are these bacteria colonies in my canned sardines?
The white specs are not colonies of bacteria, but in fact, crystallized oils. This phenomena is common in many tinned fish rich in fatty oils. This is normal and completely safe to eat.

If it bothers you too much, you can try reheating it, which should dissolve the crystallized oils back into the sauce. Just remember not to microwave anything metal. 

This link provides some information about it too.
http://ayambrand.com.sg/mackerel/46-about/frequently-asked-questions/about-our-quality/37-what-to-do-with-the-fish-oil-white-particles.html