Microbial Diversity

Obligate intracellularity is a bit like unculturability – dogma that was popular decades ago but is now being questioned given advances in our technology and methodologies for cultivation. Who wouldn’t be inspired by the recent ability to cultivate Coxiella or Hamiltonella ? Remember the 99.9% uncultivable microbes? Many studies ( here and here , for example) have revealed that it was our methods - the media conditions - that limited our ability to culture many microbes. Yet, for my favorite bacterium,  Wolbachia pipientis, obligate intracellularity is like a badge of honor (or shame!);  I cannot tell you how many times I’ve written obligate intracellular in grant proposals and manuscripts to describe the bug.  Wolbachia, you see, is part of the ancient intracellular Rickettsiales clade - including Ehrlichia, Anaplasma, Rickettsia, and none of these microbes have been cultivated outside of host cells. They have reduced genomes and generally infect arthropod...

We've been thinking a lot lately about how our favorite endosymbiont Wolbachia manipulates host biology . Because Wolbachia are not genetically tractable - or even culturable outside of host cells - it's pretty difficult to figure out the mechanisms used by the bacterium. However, we can start with some assumption about our expectation: Wolbachia likely secrete proteins into the host cell and change cell biology to facilitate infection. This is not ground breaking or novel in any way - invading intracellular microbes must deal with the host during infection - and many do this via secretion of proteins, called " effectors ." We know that these effectors often contain eukaryotic domains and homologies because they interface with the eukaryotic cell - a completely different domain of life. But how do we identify the proteins secreted by Wolbachia, or any symbiont? There have been some pretty clever work arounds. For example, John Beckmann and Anne Fallon used mass spec...