Type VI secretion systems (T6SS) are bacterial molecu- lar machines translocating effector proteins into target cells. T6SS are widely present in Gram-negative bacte- ria where they predominantly act to kill neighboring bacteria. This secretion system is reminiscent of the tail of contractile bacteriophages and consists of a con- tractile sheath anchored in the bacterial envelope and an inner tube made of stacks of the Hcp protein. The Hcp tube is capped with a VgrG trimer and a spike pro- tein termed PAAR, which acts as the membrane- puncturing device. Francisella tularensis, the agent of tularemia, is an intracellular bacterium replicating within the host cytosol. Upon entry into the host cell, F. tularensis rapidly lyses the host vacuolar membrane to reach the host cytosol. This escape is dependent on the Francisella Pathogenicity Island (FPI), which is encod- ing an atypical T6SS. Among the 17 proteins encoded by the FPI, most of them required for virulence, eight have some homology to canonical T6SS proteins. We recently identified the function of one protein of un- known function encoded within the FPI, IglG. By three- dimensional modelling and following validation by different techniques, we found that IglG adopts a fold resembling the one of PAAR proteins. Importantly, IglG features a domain of unknown function DUF4280, pre- sent in numerous bacterial species. We thus propose to rename this domain of unknown function, PAAR-like domain, and discuss here the characteristics of this domain and its distribution in both Gram-negative and Gram-positive bacteria.