by Elio — You may not think of sex as hav­ing a mi­cro­bial ba­sis, but it does. That is true for many in­ver­te­brates that are col­o­nized by the en­dosym­bi­otic bac­terium Wol­bachia. Mem­bers of this genus are prob­a­bly the most com­mon ob­lig­ate in­tra­cel­lu­lar bac­te­ria on Earth and, for rea­sons dis­cussed be­low, among the most re­mark­able ones. They in­fect half or more of all in­sects, as well as isopods (crus­taceans), spi­ders, and even worms. In some of their hosts...