SUMMARYFrom a large number of cultures of cellulolytic bacteria isolated from rumen contents of sheep conditioned to low-protein teff hay through the use of both a selective medium containing finely ground cellulose as energy source and a less selective medium containing cellobiose, xylan and starch, thirty isolates, representing three morphological types, were selected for detailed characterization. Nineteen isolates of Gram-negative curved rods belonged to the genus Butyrivibrio. Of these one was identical with and ten closely related to B. Jibrisolvens. The remaining eight Butyrivi brio cultures differed in several respects from the only other defined species within this genus, B. alactacidigens. Four coccal isolates were identified as Rminococcus albus and five as R.j ¶avefaciens. Two strains of sporeformers belonged to the genus Clostridium but could not be identified with any of the cellulolytic species of this genus listed by Bergey's Manual.

Symbiosis involves responses that maintain the plant host and symbiotic partner’s genetic program; yet these cues are far from elucidated. Here we describe the effects of lumichrome, a flavin identified from Rhizobium spp., applied to lotus (Lotus japonicus) and tomato (Solanum lycopersicum). Combined transcriptional and metabolite analyses suggest that both species shared common pathways that were altered in response to this application under replete, sterile conditions. These included genes involved in symbiosis, as well as transcriptional and metabolic responses related to enhanced starch accumulation and altered ethylene metabolism. Lumichrome priming also resulted in altered colonization with either Mesorhizobium loti (for lotus) or Glomus intraradices/G. mossea (for tomato). It enhanced nodule number but not nodule formation in lotus; while leading to enhanced hyphae initiation and delayed arbuscule maturation in tomato.

Distinct diel rhythms of leaf and cladode expansion growth were obtained in crassulacean acid metabolism (CAM) plants under water-limited conditions, with maxima at mid-day during phase III of CO2 assimilation. This pattern coincided with the availability of CO2 for photosynthesis and growth during the decarboxylation of malic acid, with maximum cell turgor due to the nocturnally accumulated malic acid, and with the period of low cytoplasmic pH associated with malic acid movement from vacuole to cytosol. Maximum growth rates were generally only 20% of those in C3 plants and were reached at a different time of the day compared with C3 plants. The results suggest that malic acid, as a source of carbohydrates, and a determinant of turgor and cytoplasmic pH, plays a major role in the control of diel growth dynamics in CAM plants under desert conditions. The observed plasticity in phasing of growth rhythms under situations of differing water availability suggests that a complex network of factors controls the diel growth patterns in CAM plants and needs to be investigated further.

A method is described for the isolation in pure culture of the predominant cellulolytic bacteria which occur in the ovine rumen. Ten isolates of cocci were obtained from the rumen contents of one sheep conditioned to lucerne hay, and were identified as Ruminococcus albus. All ten isolates degraded xylan in addition to cellulose and cellobiose and a comparative study of the end-products of fermentation of xylan and cellobiose was made. The rates of growth on cellulose and cellobiose were compared, and the role of these cocci in the breakdown of the fibrous part of the diet assessed.