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.

The virally encoded K28 killer toxin of Sacchsmmyces cerewisiae kills sensitive cells by a receptor-mediated process. DNA synthesis is rapidly inhibited, cell viability is lost more slowly and cells eventually arrest, apparently in the S phase of the cell cycle with a medium-sized bud, a single nucleus in the mother cell and a pre-replicated (In) DNA content. Cytoplasmic microtubules appear normal, and no spindle is detectable. Arrest of a sensitive haploid yeast strain by a-factor a t START gave complete protection for a t least 4 h against a toxin concentration that killed non-arrested cells a t the rate of one log each 2.5 h. Cells released from a-factor arrest were killed by toxin a t a similar rate; arrest occurred with medium-sized buds within the same cell cycle. Cells arrested by hydroxyurea, with unreplicated DNA, or by the spindle poison methylbenzimidazol-2yl-carbamate, with unseparated chromosomes, both arrest at the checkpoint at the C2/M boundary; these arrested cells were not protected against toxin, losing about one log of viability every 4 h. Following release from the cell cycle block, a majority of these toxin-exposed cefls progressed through the Celt cycle and arrested in the following S-phase, again with medium-sized buds. Killing by K28 toxin apparently requires entry into the nuclear division and bud cycles, but can result from inhibition of either early or late events in these cycles. Morphogenesis in moribund cells is uniformly blocked in early S-phase with an immature bud. Toxin action causes either independent blockage of both DNA synthesis and the budding cycle, or inhibits some unknown step required for both events. M. J. S C H M I T T a n d O T H E R S that retained its hypersensitivity. Cells that had been arrested in different stages of the cell cycle were exposed to more rapidly lethal concentrations of K28 toxin and phenotypes were determined following release from the cell cycle block in the continued presence o r absence of toxin. We demonstrated that tuxin-treated cells arrest in the budded phase of the cell cycle with an unreplicated (Gl) content of DNA in a single nucleus located in the mother cell. While cells arrested with a-factor at START were protected against toxin action, cells arrested at the G2/M checkpoint because of inhibition of DNA synthesis or microtubular function remained sensitive ; following removal of the cell-cycle inhibitor, these moribund cells progressed through the cell cycle to arrest again in the following S-phase, even in the absence of additional toxin. toxins and the outer 1,3-~-linked mannose residues of cell wall mannoproteins in the case of K28 killer toxin (Hutchins 8r Bussey, 1983; Schmitt Br Radler, 1988).Synthesis and assembly oE these primary cell-wall binding sites requires a whole set of chromosomal KRE and MiVN genes, the products of which are involved in glucan and mannop ro tein synthesis , respectively (Busse y, 1991; Tipper & Schmitt, 1991). Mutations within these nuclear genes lead to failure in cell-wall binding of toxin and a s...

The yeast Zygosaccharomyces builii strain 412 was found to liberate a killer toxin (KT412) lethal to sensitive strains of Saccharomyces cerevisiae and Candidu glubrutu. Culture supernatants of the killer strain were concentrated by ultrafiltration and the extracellular protein was purified by gel filtration and ion-exchange chromatography. Gel filtration and SDS-PAGE of the electrophoretically homogeneous killer protein indicated an apparent molecular mass of 10 kDa. The killer toxin KT412 is probably not glycosylated since it did not show any detectable carbohydrate structures. KT412 was bound to sensitive but not to resistant yeast cells. The mannan, and not the glucan, fraction of the cell wall of the sensitive yeast was the primary target for the killer toxin binding. The killer strain 2. bailii 412 contained three double-stranded RNA plasmids of 1.9, 2.9 and 4.0 kb. Curing by cycloheximide resulted in the concomitant loss of killer activity and the 1.9 kb dsRNA species that is therefore regarded as equivalent to the killer-toxin-coding M-plasmids of S. cerevisiae.

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To identify specific marker sequences for the rapid identification of Oenococcus oeni, we sequenced the 23S-5S internal transcribed spacer (ITS-2) region and the 5S rDNA of five different O. oeni strains and three phylogenetically related lactic acid bacteria (LAB). Comparative analysis revealed 100% identity among the ITS-2 region of the O. oeni strains and remarkable differences in length and sequence compared to related LAB. These results enabled us to develop a primer set for a rapid PCR-identification of O. oeni within three hours. Moreover, the comparison of the 5S rDNA sequences and the highly conserved secondary structure provided the template for the design of three fluorescence-labeled specific oligonucleotides for fluorescence in situ hybridization (FISH). These probes are partial complementary to each other. This feature promotes the accessibility to the target sequence within the ribosome and enhances the fluorescence signal. For the rapid identification of Oenococci both the 5S rRNA gene and the ITS-2 region are useful targets.