▁the ▁first ▁time ▁in ▁ 1 9 7 6 . ▁The ▁general ▁use ▁was ▁accepted ▁at ▁the ▁" First ▁International ▁Work shop ▁on ▁Cry st all ine ▁B acter ial ▁Cell ▁Sur face ▁L ay ers , ▁Vienna ▁( A ust ria )" ▁in ▁ 1 9 8 4 , ▁and ▁in ▁the ▁year ▁ 1 9 8 7 ▁S - layers ▁were ▁defined ▁at ▁the ▁European ▁M ole cular ▁Bi ology ▁Organ ization ▁Work shop ▁on ▁“ C ry st all ine ▁B acter ial ▁Cell ▁Sur face ▁L ay ers ”, ▁Vienna ▁as ▁“ Two - dimensional ▁arrays ▁of ▁protein ace ous ▁sub un its ▁forming ▁surface ▁layers ▁on ▁pro k ary otic ▁cells ” ▁( see ▁" P ref ace ", ▁page ▁VI ▁in ▁S ley tr ▁" et ▁al . ▁ 1 9 8 8 "). ▁For ▁a ▁brief ▁summary ▁on ▁the ▁history ▁of ▁S - layer ▁research ▁see ▁references ▁ ▁Location ▁of ▁S - layers ▁▁▁ ▁In ▁Gram - negative ▁b acter ia , ▁S - layers ▁are ▁associated ▁to ▁the ▁li pop ol ys ac char ides ▁via ▁ion ic , ▁car bo h yd rate – car bo h yd rate , ▁protein – car bo h yd rate ▁interactions ▁and / or ▁protein – prote in ▁interactions . ▁ ▁In ▁Gram - pos itive ▁b acter ia ▁whose ▁S - layers ▁often ▁contain ▁surface ▁layer ▁hom ology ▁( SL H ) ▁domains , ▁the ▁binding ▁occurs ▁to ▁the ▁pe pt id og ly can ▁and