▁different ▁types ▁based ▁on ▁their ▁specific ▁structure , ▁composition ▁and ▁activity . ▁These ▁major ▁differences ▁can ▁be ▁distinguished ▁between ▁Gram - negative ▁and ▁Gram - pos itive ▁b acter ia . ▁But ▁the ▁classification ▁is ▁by ▁no ▁means ▁clear ▁and ▁complete . ▁There ▁are ▁at ▁least ▁eight ▁types ▁specific ▁to ▁Gram - negative ▁b acter ia , ▁four ▁to ▁Gram - pos itive ▁b acter ia , ▁while ▁two ▁are ▁common ▁to ▁both . ▁Gener ally , ▁prote ins ▁can ▁be ▁secret ed ▁through ▁two ▁different ▁processes . ▁One ▁process ▁is ▁a ▁one - step ▁mechanism ▁in ▁which ▁prote ins ▁from ▁the ▁cy top las m ▁of ▁b acter ia ▁are ▁transport ed ▁and ▁delivered ▁directly ▁through ▁the ▁cell ▁memb rane ▁into ▁the ▁host ▁cell . ▁Another ▁involves ▁a ▁two - step ▁activity ▁in ▁which ▁the ▁prote ins ▁are ▁first ▁transport ed ▁out ▁of ▁the ▁inner ▁cell ▁memb rane , ▁then ▁depos ited ▁in ▁the ▁peri pl asm , ▁and ▁finally ▁through ▁the ▁outer ▁cell ▁memb rane ▁into ▁the ▁host ▁cell . ▁ ▁Sec ▁system ▁ ▁The ▁general ▁secret ion ▁( Sec ) ▁involves ▁secret ion ▁of ▁unfold ed ▁prote ins ▁that ▁first ▁remain ▁inside ▁the ▁cells . ▁In ▁Gram - negative ▁b acter ia , ▁the ▁secret ed ▁protein ▁is ▁sent ▁to ▁either ▁the ▁inner ▁memb rane ▁or ▁the ▁peri pl asm . ▁But ▁in ▁Gram - pos itive ▁b acter ia , ▁the ▁protein ▁can ▁stay ▁in ▁the ▁cell ▁or ▁is ▁mostly ▁transport ed ▁out ▁of ▁the ▁b acter ia ▁using