▁to ▁a ▁secondary ▁cell ▁wall ▁polym er ▁( e . g ., ▁te ich o ic ▁ac ids ). ▁In ▁the ▁absence ▁of ▁SL H ▁domains , ▁the ▁binding ▁occurs ▁via ▁electro static ▁interactions ▁between ▁the ▁posit ively ▁charged ▁N - ter minus ▁of ▁the ▁S - layer ▁protein ▁and ▁a ▁neg atively ▁charged ▁secondary ▁cell ▁wall ▁polym er . ▁In ▁L act ob ac illi ▁the ▁binding ▁domain ▁may ▁be ▁located ▁at ▁the ▁C - ter minus . ▁ ▁In ▁Gram - negative ▁arch ae a , ▁S - layer ▁prote ins ▁possess ▁a ▁hydro ph ob ic ▁anchor ▁that ▁is ▁associated ▁with ▁the ▁underlying ▁li pid ▁memb rane . ▁ ▁In ▁Gram - pos itive ▁arch ae a , ▁the ▁S - layer ▁prote ins ▁bind ▁to ▁pseud om ure in ▁or ▁to ▁m eth ano ch ond roit in . ▁ ▁Bi ological ▁functions ▁of ▁the ▁S - layer ▁ ▁For ▁many ▁b acter ia , ▁the ▁S - layer ▁represents ▁the ▁outer most ▁interaction ▁zone ▁with ▁their ▁respective ▁environment . ▁Its ▁functions ▁are ▁very ▁diverse ▁and ▁vary ▁from ▁species ▁to ▁species . ▁In ▁many ▁arch ae al ▁species ▁the ▁S - layer ▁is ▁the ▁only ▁cell ▁wall ▁component ▁and , ▁therefore , ▁is ▁important ▁for ▁mechanical ▁and ▁os m otic ▁stabil ization . ▁Add itional ▁functions ▁associated ▁with ▁S - layers ▁include : ▁ ▁protection ▁against ▁b acter i oph ages , ▁Bd ello v ib rios , ▁and ▁ph ag oc yt osis ▁ ▁resistance ▁against ▁low ▁p