Xanthomonas immunity proteins protect against the cis-toxic effects of their cognate T4SS effectors

OKA, GABRIEL U; SOUZA, DIORGE P; SGRO, GERMÁN G; GUZZO, CRISTIANE R; DUNGER, GERMAN; FARAH, CHUCK S

EMBO Reports

EMBO

Año: 2024

Many bacteria kill rival species by translocating toxic effectors intotarget cells. Effectors are often encoded along with cognateimmunity proteins that could (i) protect against“friendly-fire”(trans-intoxication) from neighboring sister cells and/or (ii) pro-tect against internalcis-intoxication (suicide). Here, we distinguishbetween these two mechanisms in the case of the bactericidalXanthomonas citriType IV Secretion System (X-T4SS). We use aset ofX. citrimutants lacking multiple effector/immunity protein(X-Tfe/X-Tfi) pairs to show that X-Tfis are not absolutely requiredto protect againsttrans-intoxication by wild-type cells. Our inves-tigation then focused on the in vivo function of the lysozyme-likeeffector X-TfeXAC2609and its cognate immunity protein X-TfiXAC2610.In the absence of X-TfiXAC2610, we observe X-TfeXAC2609-dependentand X-T4SS-independent accumulation of damage in theX. citricellenvelope, cell death, and inhibition of biofilm formation. Whileimmunity proteins in other systems have been shown to protectagainst attacks by sister cells (trans-intoxication), this is anexample of an antibacterial secretion system in which the immunityproteins are dedicated to protecting cells againstcis-intoxication.