The diversity of bacteria associated with the deer tick (Ixodes scapularis) was assessed using PCR amplification, cloning, and sequencing of 16S rRNA genes originating from seven ticks collected from Nantucket Island and Wellfleet, Cape Cod, Mass. The majority of sequences obtained originated from gram-negative proteobacteria. Four intracellular bacteria were detected including strains of Ehrlichia, Rickettsia, and Wolbachia and an organism related to intracellular insect symbionts from the Cytophaga-Flavobacterium-Bacteroides group. Several strains of members of the Sphingomonadaceae were also detected in all but one tick. The results provide a view of the diversity of bacteria associated with I. scapularis ticks in the field.

Suspension cultures of Triticum monococcum L., Triticum vulgare Vill. var. Thatcher, Hordeum vulgare L. var. Gateway, and Hordeum vulgare L. var. Gateway mutant yv2 have been established. The cultures were derived from root sections of seedlings and cultured in a denned medium consisting of mineral salts, sucrose, B vitamins, and 2,4-dichlorophenoxyacetic acid, with nitrate and ammonia as the sources of nitrogen. In the early period of the cultures the cell aggregates readily, differentiated to form roots, but this characteristic diminished after several generations of subculture. The cells and medium contained a number of glucanases. The presence of a laminaranase (endo-β-(1 → 3)-D-glucan glucanohydrolase (EC 3.2.1.99)) that did not attack lichenan was established. The culture media of the wheat contained an oligosaccharide which on acid hydrolysis yielded galactose, arabinose, and xylose. Hydrolysis of a cell-wall fraction yielded the same sugars in addition to glucose and mannose.

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This article sets forth a simple cellulase assay procedure. Cellulose is variable in nature, insoluble and resistant to enzymatic attack. As a result there have been a bevy of bewildering cellulase assays published that yielded irrational results. Certain protocols focused on the rapidity of the assay while ignoring that only the most readily susceptible cellulose regions were being hydrolyzed. Other assays simplified the system by using modified soluble substrates and yielded results that bore no relationship to the real world hydrolysis of insoluble cellulose. In this study Mandels, Andreotti and Roche utilized a common substrate, Whatman filter paper. Hydrolysis of a 50 mg sample of the paper was followed to roughly 4% degradation, which circumvented the problems of attack of only the most susceptible zones. This common hydrolysis target range also resulted in some balance with regard to the interaction of the several cellulase components. The method was subsequently widely adopted.

The expression of cellobiohydrolase I mRNA from Trichoderma reesei, measured by Northern blot hybridization, is controlled by the nature ofcarbon sources used in the culture medium. Cellulose and the soluble disaccharide sophorose, but not glycerol or glucose, act as inducers. Cellobiohydrolase I mRNA was undetectable when antibodies to the major members of the cellulolytic system were present in the culture medium prior to the addition of cellulose. These antibodies had no repressive effect if sophorose was used as an inducer. The results strongly suggest that a low constitutive cellulolytic system catalyzes the formation of a soluble inducer from cellulose and that this inducer triggers the expression of the cellobiohydrolase I gene transcript, most probably at the transcription level.In nature, the cycling of carbon is of the utmost importance to living systems. It is estimated that the photosynthetic process produces 1.5 x 1011 tons ofdry plant material annually, almost half of which is cellulose (1). This plant polysaccharide is used as an energy carbon source by numerous and diverse microorganisms, including fungi and bacteria occupying a variety of habitats (2). Solubilization of this insoluble polymer is via extracellular cellulase systems that catalyze the hydrolysis of cellulose to glucose. Among the best characterized of these systems are the inducible cellulases of the filamentous fungus Trichoderma reesei (3). This cellulase system consists of three The utilization of cellulose by T. reesei is enigmatic, as the product of cellulolysis (glucose) represses the expression of the cellulase system (5). At present, it is not understood how an insoluble polymer such as cellulose, which is unable to enter the fungal cell, can regulate expression of the cellulolytic enzyme system. It has been suggested (6, 7) that T. reesei expresses low, constitutive, levels of the cellulase system and that the activity of these enzymes on cellulose produces a soluble inducer, which can enter the cell and effect induction. Sophorose (2-0-,3-glucopyranosyl-Dglucose) is the most potent soluble inducer of the cellulase system in T. reesei so far identified (7,8). Sophorose as well as other glucose disaccharides were detected during growth of T. reesei on cellobiose (6) and after treatment of cellulose with the T. reesei cellulase system (9), most probably produced by the transglycosylation activity of,-glucosidase (10, 11).In preparation for investigating the molecular mechanisms responsible for regulating cellulase gene expression, we have prepared antibodies to the major members of the cellulolytic system and have also isolated a clone carrying the gene encoding cellobiohydrolase I. Using these antibodies to block the activity of the cellulase system and the CBH-I clone as a DNA probe, we present evidence that low constitutive levels of the cellulase system are responsible for triggering the expression of the CBH-I gene at the pretranslational level. Methods. Preparation of enzymes and antibodies. Enzymes were purifi...