Abstract Cellular structures involved in the attachment of Ruminococcus albus strain D3 to microcrystalline cellulose avicel

C.C. Sieo¹, N. Abdullah^2*, S. Jalaludin³ and Y.W. Ho¹

¹Institute of Bioscience, ²Department of Biochemistry and Microbiology, ³Department of Animal Science,
Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.

(Received 7 June 1999 / Accepted 14 October 1999)

Abstract.
Electron microscopy, both scanning electron microscopy and transmission electron microscopy, was used to study the mode of attachment and morphological characteristic of structures involved in the attachment of Ruminococcus albus to avicel. The cell of Ruminococcus albus was found to be enclosed by a thick layer (0.06-0.08 um) of extracellular material called the glycocalyx. Fine fibril like structures (0.18-0.23 Put long) projecting from the glycocalyx facilitated the attachment of R. albus to avicel. Initial attachment by these fine fibril like structures, which were found to be permanent structures of the bacteria, were observed after 10 min of incubation with avicel. Multiple points of attachment were observed initially. At longer incubation period (18 h), the Surface layer of the avicel was eroded and at the point of contact between the bacteria and the substrate, the glycocalyx of the bacteria was irregular and less defined than the part which was not in contact with the substrate. The glycocalyx also seemed to diffuse into the substrate. After 30-36 h of incubation, digestion was particularly evident at the point of contact with formation of pits in the avicel corresponding to the bacterial shape.

Keywords: Attachment, avicel, cellulolytic bacteria, Ruminococcus albus, glycocalyx, microcrystalline cellulose