▁surface ▁re cept ors ▁for ▁co operation ▁and ▁competition . ▁ ▁This ▁has ▁been ▁widely ▁observed ▁in ▁b acter ia . ▁For ▁instance , ▁b acter ia ▁can ▁attach ▁to ▁each ▁other ▁through ▁the ▁binding ▁of ▁outer ▁memb rane ▁prote ins ▁Tra A ▁and ▁Tra B ▁to ▁facil itate ▁a ▁process ▁called ▁outer ▁memb rane ▁exchange ▁( O ME ) ▁that ▁allows ▁b acter ial ▁cells ▁to ▁swap ▁memb rane ▁lip ids , ▁sug ars , ▁and ▁to x ins . ▁Cell ▁recognition ▁and ▁O ME ▁can ▁only ▁be ▁achieved ▁if ▁Tra A ▁and ▁Tra B ▁variants ▁from ▁the ▁same ▁recognition ▁group ▁bind . ▁These ▁interactions ▁can ▁generate ▁the ▁phys i ological ▁divers ity ▁required ▁for ▁ant ib i otic ▁resistance ▁in ▁b acter ial ▁populations . ▁The ▁E scher icia ▁col i ▁memb rane ▁protein ▁Chi A ▁is ▁involved ▁in ▁the ▁process ▁of ▁contact - dependent ▁in hib ition ▁( C DI ) ▁in ▁which ▁it ▁bind s ▁to ▁re cept ors ▁on ▁rival ▁E . coli ▁stra ins ▁and ▁releases ▁a ▁to x in ▁that ▁prevents ▁growth ▁of ▁those ▁stra ins ▁while ▁the ▁in hib iting ▁cell ▁and ▁members ▁of ▁that ▁stra in ▁are ▁protected . ▁The ▁b acter ium ▁Prote us ▁m ira bil is ▁uses ▁the ▁T 6 SS ▁protein ▁to ▁initi ate ▁sw arm ing ▁and ▁destruction ▁of ▁other ▁b acter ial ▁colon ies ▁upon ▁recognition , ▁either ▁by ▁release ▁of ▁to x ins ▁or ▁by ▁release ▁of ▁signal ▁prote ins ▁to ▁other ▁P . ▁m ira bil