THE FORMATION OF CELLULOSE MICROFIBRILS BY ACETOBACTER XYLINUM IN AGAR SURFACES

Abstract

The formation of extracellular cellulose microfibrils by Acetobacter xylinum on agar surfaces is remote from the cell membrane and does not involve an intermediate, amorphous high polymer, in agreement with conclusions from studies of liquid suspensions. Growth of individual microfibrils is at the tip(s) only and the rate of extension (0.2 μ per bacterial cell per minute at 34 °C) is comparable with that in liquid medium. The rate of nucleation of new microfibrils is about 40 per 10³ bacteria per minute at 34 °C. Both rates are constant after an induction period of about 30 seconds. Newly nucleated microfibrils could be identified unequivocally down to a length of 0.5 μ. A characteristic feature of growth of cellulose on agar surfaces is the formation of bundles of microfibrils with their axes roughly parallel. The results suggest that the rate-limiting step in the formation of these microfibrils has an activation energy of about 15 kc.