The Salmonella Enteritidis wild-type strain Sal18 and its ΔtatB and ΔtatC derivatives were Gram stained, and the cell morphology was observed. The wild-type cells, as well as the plasmid-complemented cells, displayed the classic rod-like shape of Gram-negative bacteria, while the mutant cells showed an elongated shape and chain formation. (A) ΔtatB, cat removed (LS39); (B) ΔtatB pLP198 (tatA+B+C+); (C) ΔtatB pLP199 (tatA+B+C+D+); (D) ΔtatC, cat removed (LS106); (E) ΔtatC pLP198 (tatA+B+C+); (F) wild-type Sal18.