, ▁in ▁the ▁absence ▁of ▁ant ib acter ial ▁comp ounds . ▁Add itional ▁mut ations , ▁however , ▁may ▁compens ate ▁for ▁this ▁fit ness ▁cost ▁and ▁can ▁aid ▁the ▁surv ival ▁of ▁these ▁b acter ia . ▁ ▁Pale ont ological ▁data ▁show ▁that ▁both ▁ant ib iot ics ▁and ▁ant ib i otic ▁resistance ▁are ▁ancient ▁comp ounds ▁and ▁mechan isms . ▁Use ful ▁ant ib i otic ▁targets ▁are ▁those ▁for ▁which ▁mut ations ▁neg atively ▁impact ▁b acter ial ▁reprodu ction ▁or ▁vi ability . ▁ ▁Several ▁mole cular ▁mechan isms ▁of ▁ant ib acter ial ▁resistance ▁exist . ▁In tr insic ▁ant ib acter ial ▁resistance ▁may ▁be ▁part ▁of ▁the ▁gen etic ▁make up ▁of ▁b acter ial ▁stra ins . ▁For ▁example , ▁an ▁ant ib i otic ▁target ▁may ▁be ▁absent ▁from ▁the ▁b acter ial ▁gen ome . ▁Ac quired ▁resistance ▁results ▁from ▁a ▁mut ation ▁in ▁the ▁b acter ial ▁chrom os ome ▁or ▁the ▁ac quisition ▁of ▁extra - chrom os om al ▁DNA . ▁Ant ib acter ial - produ cing ▁b acter ia ▁have ▁evol ved ▁resistance ▁mechan isms ▁that ▁have ▁been ▁shown ▁to ▁be ▁similar ▁to , ▁and ▁may ▁have ▁been ▁transferred ▁to , ▁ant ib acter ial - res istant ▁stra ins . ▁The ▁spread ▁of ▁ant ib acter ial ▁resistance ▁often ▁occurs ▁through ▁vertical ▁transmission ▁of ▁mut ations ▁during ▁growth ▁and ▁by ▁gen etic ▁recom bin ation ▁of ▁DNA ▁by ▁horizontal ▁gen etic ▁exchange . ▁For