Heterologous reattachment of regular arrays of glycoproteins on bacterial surfaces

REGULAR arrays of macromolecular subunits have been observed on the surfaces of a wide range of bacteria in electron micrographs of negatively stained or freeze-etched preparations1,2. The regular patterns have mostly tetragonal or hexagonal symmetry and the centre-to-centre spacing between adjacent subunits varies from 6 to 15 nm. Chemical analyses of isolated subunits have shown that they are composed mainly of protein1 or glycoprotein (unpublished) with molecular weights ranging from 65,000 to 150,000. Studies of a few bacteria have shown that the isolated subunits can assemble spontaneously to form regular arrays with the same dimensions as those seen in intact bacteria3. In appropriate conditions the subunits also reattach to the surfaces of cell walls from which they have been detached. Little is known about the biological function of these regular arrays of macromolecules on bacterial surfaces. That they cover the surface, leaving no gaps2, suggests that they are important, for instance, in providing protection against adverse environmental conditions. Otherwise they would be expected to have been lost during evolution.