Toxic component of one of 6 LXG toxin-immunity modules in this strain. They promote kin selection, mediate competition in biofilms, and drive spatial segregation of different strains, indicating that LXG toxins may help avoid warfare between strains in biofilms. Mediates intercellular competition during biofilm formation; disruption of the operon disadvantages the bacteria, but overexpression of the cognate immunity protein restores growth in competition with wild-type. Overexpression alone in situ causes growth arrest but not cell lysis; no effect is seen on DNA or rRNA. Co-overexpression with cognate immunity protein YwqK does not cause growth arrest. The toxic effect is dependent on the epsA and tapA operons which are required for biofilm formation (PubMed:34280190). Its toxic effects are probably neutralized by its cognate immunity protein YwqK, but not by immunity proteins specific to other toxins with the LXG domain (Probable). May have deaminase activity (Probable). Probably interacts with cognate immunity protein YwqK but not with non-cognate immunity proteins. The interaction inhibits the toxic activity of YwqJ. Delivery to target cells requires the type VII secretion system (T7SS) and YukE. Expressed on rich and minimal solid media likely in early stationary phase; dependent on DegSU. Not expressed in liquid LB, but only under conditions that promote biofilm formation. Deletion of the ywqH-ywqI-ywqJ-ywqK-nfi operon has no visible growth phenotype, however it is out-competed by wild-type cells. In the N-terminal section; belongs to the LXG family.