Introduction

That living microorganisms can attach to each other and to solid surfaces in the form of films is well known [1]. Such attachment occurs in dental plaque, algal and fungal slimes, bacterial film on soil particles [2], on plant or animal tissues such as intestine and rumen [3] and in chicken crop epithelia [4]. The same effect is also observed in the tendency of many bacteria to assume chain structure. Cell adherence, a phenomenon of great importance in monolayer cell culture because it allows easy manipulation of growing cells, has recently been reviewed [5, 6].