Xanthomonas citri


Xanthomonas citri is a Gram-negative, rod-shaped bacterium. Although it is harmless for humans, it is a phytopathogen, known for being the causing agent of citrus canker.
Many pathovars are misclassified as X. cissicola, X. campestris, or X. axonopodis. A 2022 study proposes moving 20 pathovars in these three into X. citri. However, based on the principle of priority, all "X. citri" should become instead named under the earliest-published name, X. cissicola like in GTDB. The two proposals do not affect the independence of X. campestris and X. axonopodis, as their type strains are sufficiently distinct from X. citri/cissicola to be their own species.

Pathovars included

Uncited entries are based on Bansal et al., either in the article's own results or in its description of earlier results. Pathovars that include the type strain of either X. citri or X. cissicola are shown in bold.
The list is unlikely to be complete.

Bacterial killing via a secretion system

Xanthomonas citri uses its type [IV secretion system] to kill other Gram-negative bacterial species in a contact-dependent manner. The secretion of the effector proteins requires a conserved C-terminal domain, and its bacteriolytic activity is neutralized by a cognate immunity protein.

Defense against predators

Xanthomonas citri also uses type VI secretion system in defense against the predatory amoeba Dictyostelium discoideum.