[spirochete]

Title says it all.  I can't seem to decide whether there are two stereocenters in this molecule making it meso (since it does have a plane of symmetry and also an inversion center for good measure), or if it's just achiral with no stereocenters. 

And what thought process would you follow to decide that?

[azmanam]

Try this:

http://www.cem.msu.edu/~reusch/VirtualText/sterism3.htm#isom19 (and scroll down)

To determine if there are stereocenters, start from one of the substituted carbon atoms and work your way around until you get to the first point of differentiation.  Where is the first point of differentiation?  Is there a first point of differentiation?  If not, is that carbon atom a stereocenter?

[spirochete]

Yeah what's weird is I know that system yet my example was still tripping me up.  Now I see it's just achiral (not meso) because if you treat each potential stereocenter individually you see both are only attached to 3 different groups.