▁battle ▁for ▁surv ival . ▁Duch es ne ▁observed ▁that ▁E . ▁col i ▁was ▁elimin ated ▁by ▁Pen ic ill ium ▁gla uc um ▁when ▁they ▁were ▁both ▁grown ▁in ▁the ▁same ▁culture . ▁He ▁also ▁observed ▁that ▁when ▁he ▁in oc ulated ▁labor atory ▁animals ▁with ▁le th al ▁dos es ▁of ▁ty ph oid ▁b ac illi ▁together ▁with ▁Pen ic ill ium ▁gla uc um , ▁the ▁animals ▁did ▁not ▁contract ▁ty ph oid . ▁Unfortunately ▁Duch es ne ' s ▁army ▁service ▁after ▁getting ▁his ▁degree ▁prevent ed ▁him ▁from ▁doing ▁any ▁further ▁research . ▁Duch es ne ▁died ▁of ▁t uber cul osis , ▁a ▁disease ▁now ▁treated ▁by ▁ant ib iot ics . ▁ ▁In ▁ 1 9 2 8 , ▁Sir ▁Alexander ▁F lem ing ▁post ulated ▁the ▁existence ▁of ▁pen ic ill in , ▁a ▁mole c ule ▁produced ▁by ▁certain ▁m olds ▁that ▁k ills ▁or ▁stops ▁the ▁growth ▁of ▁certain ▁kinds ▁of ▁b acter ia . ▁F lem ing ▁was ▁working ▁on ▁a ▁culture ▁of ▁disease - ca using ▁b acter ia ▁when ▁he ▁noticed ▁the ▁sp ores ▁of ▁a ▁green ▁m old , ▁Pen ic ill ium ▁ch rys ogen um , ▁in ▁one ▁of ▁his ▁culture ▁pl ates . ▁He ▁observed ▁that ▁the ▁presence ▁of ▁the ▁m old ▁killed ▁or ▁prevent ed ▁the ▁growth ▁of ▁the ▁b acter ia . ▁F lem ing ▁post ulated ▁that ▁the ▁m old ▁must ▁se crete ▁an ▁ant ib acter ial ▁subst ance ,