Toxic component of a type IV toxin-antitoxin (TA) system (PubMed:14594833, PubMed:28257056, PubMed:28931012). Acts as a dual toxin inhibitor that blocks cell division and cell elongation in genetically separable interactions with FtsZ and MreB (PubMed:28931012). Overexpression results in inhibition of growth in liquid cultures (PubMed:14594833, PubMed:28257056, PubMed:28931012). Overexpression leads to formation of lemon-shaped cells; inactivated by overexpression of cognate antitoxin YfjZ but not when the 2 genes are coexpressed from the same plasmid (PubMed:28257056). Also neutralized by overexpression of non-cognate antitoxins YafW and CbeA (PubMed:28257056). Interacts with FtsZ but not MreB (PubMed:28257056). Another group finds interaction with FtsZ and MreB (PubMed:28931012). Expressed in mid-log phase at lower levels than toxin relE. Single deletion leads to an approximately 100-fold reduction in resistance to oxidative stress, deletion of 3 type IV toxin genes (cbtA, ykfI, ypfJ) leads to a slight reduction in resistance to oxidative stress, has no effect on cell growth. Encoded in prophage CP4-57. Belongs to the CbtA/YkfI/YpjF toxin family.