Abstract

Effect of carbon source on the cellulosomal subpopulations of Clostridium cellulovorans. Microbiology 151: 1491-1497. 2005. S.O. Han, H. Yukawa, M. Inui and R.H. Doi.

Clostridium cellulovorans produces a cellulase enzyme complexcalled the cellulosome. When cells were grown on different carbonsubstrates such as Avicel, pectin, xylan, or a mixture of allthree, the subunit composition of the cellulosomal subpopulationsand their enzymic activities varied significantly. Fractionationof the cellulosomes (7-11 fractions) indicated thatthe cellulosome population was heterogeneous, although the compositionof the scaffolding protein CbpA, endoglucanase EngE and cellobiohydrolaseExgS was relatively constant. One of the cellulosomal fractionswith the greatest endoglucanase activity also showed the highestor second highest cellulase activity under all growth conditionstested. The cellulosomal fractions produced from cells grownon a mixture of carbon substrates showed the greatest cellulaseactivity and contained CbpA, EngE/EngK, ExgS/EngH and EngL.High xylanase activity in cellulose, pectin and mixed carbon-growncells was detected with a specific cellulosomal fraction whichhad relatively larger amounts of XynB, XynA and unknown proteins(35-45 kDa). These results in toto indicate thatthe assembly of cellulosomes occurs in a non-random fashion.

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