Bacteria in the brain?

Just a quick post on an intriguing tidbit in Michael Specter's Oct 22, 2012 New Yorker story, "Germs are Us" on the role of bacteria in our health (the so-called 'microbiome').  On the second page:

The passengers in our microbiome contain at least four million genes, and they work constantly on our behalf: they manufacture vitamins and patrol our guts to prevent infections, they help to form and bolster our immune systems, and digest food. Recent research suggests that bacteria may even alter our brain chemistry, thus affecting our moods and behavior.

Will have to see what more I can find out about that!