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 arthropods - although s

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

*update: Seth Bordenstein let me know that they DID codon optimize their constructs. The text below reflects this change. **update, part 2: below I note some comments ( in blue ) as a result of interactions with lead author John Beckmann via the twitter. He was kind enough to participate in a long public and then private exchange - thanks to him. This morning I was pleased to see that J ohn Beckmann's manuscript describing some enzymatic functional activity of candidate CI genes was just made available on the Nature Microbiology page.  So, today, we will dive again into the world of CI-inducing loci and explore what this manuscript can tell us about the mechanisms behind CI and what these two proteins might do in the insects. Beckmann et al start out with a different premise from that of Le Page et al.  in that John had already identified two candidates, wPa_0282 and wPa_0283, from another study, which focused on proteins found in Wolbachia -modified mosquito sperm. They state

The once-obscure alpha-proteobacterium Wolbachia pipientis, was catapulted into medical relevance by the discovery that it inhibits the replication of RNA viruses .  However, it was first discovered for its odd quirk of manipulating insect reproduction . That's right, Wolbachia were called "reproductive parasites" and for a long time, no fitness benefit was attributed to them.  These intracellular masters do things like kill male offspring, feminize male offspring, induce parthenogenesis, and the most common phenotype, sperm-egg incompatibility (also known by its more complicated name: cytoplasmic incompatibility or CI) (Figure 1).   Figure 1. Modified from Werren et al., 2008 .  Wolbachia cause four distinct reproductive phenotypes in a range of arthropod orders (top).  The mechanisms behind CI - meaning how does  Wolbachia  induce it -  have been a mystery for some time.   When you make a cross between infected males and uninfected  Nasonia  females, unviable em

I've ranted about bacterial nomenclature in the past (see h ere ), but this post is specifically about Wolbachia pipientis, and how we should name strain-level variants within a particular host-associated clade (such as w Mel, for example).  Currently, there seem to be multiple ways to write these names and to present them in databases or the literature.  For example: For variants within w Mel, we find examples of the following types of strain names: w MelPop-<insert specific substrain here after the dash> The stuff that comes after the strain name ( w MelPop) sometimes refers to the host insect from which the strain was isolated, or where it currently resides (such as in w MelPop-PYGP) or sometimes refers to how the strain was altered, through sequential passage (such as in w MelPop-CLA).  This variability in the naming schemas used in Wolbachia could lead to confusion down the road. We are currently adding strain level information to some of the stocks that are now