How and why vibrio cholerae got its bend
The curves of Vibrio cholerae
Vibrio cholerae, the causative agent of cholera has a characteristic curved shape. How is this shape achieved and what is it good for? To answer this question Bartlett and colleagues looked for mutant strains unable to form curved rods. One mutant they observed, forming straight rods just like many other bacteria, answered a bunch of questions about the curved vibrios.
A straight mutant revealed the molecular reason for bending
The mutant was defective in the protein CrvA, which formed periplasmic filaments on the inner side of the curvature. The impact of these filaments on peptidoglycan dynamics was assessed by subsequent cultivation of Vibrio cholerae in solutions of two different fluorescent precursors (D-Ala) of peptidoglycan. This way researchers could simultaneously monitor integration and removal of peptidoglycan percursors. According to this analysis CrvA-filaments induces curvature in Vibrio cholera by reduced peptidoglycan biosynthesis.
Straight mutants are less motile in dense media and less pathogenic
Mutants defective in CrvA forming straight rods were less motile in dense matrices and also showed less pathogenicity. The connection between curvature of Vibrio cholerae and pathogenicity is also documented by the finding that the expression of CrvA is regulated by quorum sensing. Vibrio cholerae in high densities produce particularly much CrvA, and are accordingly particularly curved and pathogenic.