Aims: To demonstrate the occurrence of cellulolytic bacteria in the termite Zootermopsis angusticollis. Methods and Results: Applying aerobic cultivation conditions we isolated 119 cellulolytic strains from the gut of Z. angusticollis, which were assigned to 23 groups of aerobic, facultatively anaerobic or microaerophilic cellulolytic bacteria. 16S rDNA restriction fragment pattern and partial 16S rDNA sequence analysis, as well as numerical taxonomy, were used for the assignment of the isolates. The Gram-positive bacteria of the actinomycetes branch could be assigned to the order Actinomycetales including the genera Cellulomonas/Oerskovia, Microbacterium and Kocuria. The Gram-positive bacteria from the order Bacillales belonged to the genera Bacillus, Brevibacillus and Paenibacillus. Isolates related to the genera A®pia, Agrobacterium/Rhizobium, Brucella/Ochrobactrum, Pseudomonas and Sphingomonas/Zymomonas from the a-proteobacteria and Spirosoma-like from the``Flexibacteriaceae'' represented the Gram-negative bacteria. Conclusions: A cell titre of up to 10 7 cellulolytic bacteria per ml, determined for some isolates, indicated that they may play a role in cellulose digestion in the termite gut in addition to the cellulolytic¯agellates and termite's own cellulases. Signi®cance and Impact of the Study: The impact of bacteria on cellulose degradation in the termite gut has always been a matter of debate. In the present survey we investigated the aerobic and facultatively anaerobic cellulolytic bacteria in the termite gut.

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A novel cellulolytic and xylanolytic bacterium, strain MX5T, was isolated from the hindgut contents of the Australian termite Mastotermes darwiniensis (Froggatt). The isolate was a facultative anaerobe and had a Gram-positive cell-wall profile. The rod-shaped bacterium formed irregular coryneform and coccoid cells during growth. Phylogenetic analysis of the 16S rDNA provided evidence that the organism was closely related to the as-yet undescribed cellulolytic strain SR272 and the non-validly described species 'Cellulomonas pachnodae' as well as Promicromonospora citrea and Promicromonospora sukumoe. Strain MX5T was assigned to the genus Cellulosimicrobium on the basis of phylogenetic and chemotaxonomic criteria. The murein of strain MX5T contained the diamino acid lysine. N-Glycolylmuramic acid, mycolic acids and hydroxy fatty acids were absent. The major neutral sugar in the cell wall was galactose and the major quinone was menaquinone MK-9(H4). The predominant fatty acids were ai-C15:0, i-C15:0, i-C16:0 and C16:0. The G+C content of the DNA was in a range 70-72 mol%. On the basis of 16S rDNA sequence similarities and chemotaxonomic features, MX5T was clearly different from Cellulosimicrobium cellulans and other validly described species within this phylogenetic group. For this reason, a novel species is described, for which the name Cellulosimicrobium variabile sp. nov. is proposed.

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