Clostridium thermocellum JW20 (ATCC 31549), which was isolated from a Louisiana cotton bale, grew on cellulose, cellobiose, and xylooligomers and, after adaptation, on glucose, fructose, and xylose in the pH range of 7.5 to 6.1 with Topt of 60°C, Tmax of 69°C, and Tmin of above 28°C. Doubling times during growth on cellulose and cellobiose were 6.5 and 2.5 h, respectively. The G+C content of the DNA was 40 mol% (chemical analysis). Growth on cellulose as substrate was totally inhibited in the presence of more than 125 mM sodium sulfate, 300 mM sodium chloride, 250 mM potassium chloride, 200 mM calcium chloride, 125 mM magnesium chloride, 40 mM lactate, or 250 mM acetate. The ratio of the fermentation products ethanol to acetate plus H2 decreased when the culture was agitated. Agitation otherwise increased the rate of cellulose degradation in a growing culture but not under nongrowth conditions or with cell-free culture supernatant containing the extracellular cellulase. Shaking lowered the concentration of H2 in the culture broth and thus minimized inhibition by the H2 formed. Externally added H2 caused an increased formation of ethanol during growth on cellulose or cellobiose. However, at an atmospheric pressure as high as 355 kPa (50 lb/in2), H2 did not cause significant growth inhibition beyond an increasing lag phase (up to 24 h). Several criteria to specifically prove the purity of C. thermocellum cultures were suggested. was necessary. Although some special properties of C. thermocellum JW20 have been published and are therefore not further described in this report, a general description of strain JW20 becomes important owing to the published work on its cellulase (5, 12, 21; L. G. Ljungdahl, M. P. Coughlan, and F. Mayer, unpublished results). The strain proved to be well suited for ethanol production from cellulose in coculture with Thermoanaerobacter ethanolicus (L. G. Ljungdahl and

Hemicellulose fractions with a predetermined distribution of xylose, xylooligomers, and xylan fractions were obtained through steam explosion of wood by the steam explosion-extraction process of BFA-Hamburg, Hamburg, Federal Republic of Germany. A differential utilization of various molecular-weight fractions by several thermophilic anaerobic bacteria was determined during their growth on the hemicellulose preparations. Clostridium thermocellum (60°C) first utilized the high-molecular-weight fractions (polymerization degree of 15 to 40 xylose units). Xylose and xylooligomers of n = 2 to 5 accumulated while C. thermocellum was not growing, as evident from the fermentation products formed. Whereas the xylan was hydrolyzed and the small oligoxylans were utilized after more than 100 h of incubation, xylose was not significantly utilized. In contrast to this, C. thermohydrosulfuricum (70°C) and Thermoanaerobium brockii (70°C) utilized xylose first and then xylooligomers of n = 2 to 5, but xylooligomers of n greater than 6 were only slowly utilized. Thermoanaerobacter ethanolicus (70°C), Thermobacteroides acetoethylicus (70°C), and C. thermosaccharolyticum (60°C) utilized xylose preferentially. Xylooligomers of n = 2 to 5 and n = 6 and greater were apparently concomitantly utilized without significant differences. In contrast to C. thermocellum, the non-cellulolytic organisms grew during xylan hydrolysis, producing ethanol, lactate, acetate, C02, and H2.

Polypeptides from stems, leaves, sepals, corollas, stamens and pistils of the Japanese morning glory (Ipomoea nil Roth (Pharbitis nil Chois.)) were separated by one- and two-dimensional gel electrophoresis and visualized by silver staining. The majority of polypeptides were expressed in two or more organs, while those specific to only one organ were comparatively rate. Among the polypeptides of the former class were two which appeared to be floral-specific. A 46-kDa (kilodalton) polypeptide was expressed in corollas, stamens and pistils, whereas a 32-kDa polypeptide was observed only in extracts prepared from reproductive organs. Polypeptide spots from the various organs were compared with those from leaves, and it was found that sepals and stems shared 40-50% of their polypeptides with leaves, whereas corollas, stamens and pistils shared 20% or less. The latter organs shared 120 polypeptides or roughly 15% of those identified in the floral extracts. Floralorgan-specific polypeptides comprised nearly 10% of the total floral polypeptides identified.

Abstract. An unknown substance(s) produced in the cotyledons of seedlings of the Japanese morning glory (Pharbitis nil) during a defined period of darkness triggers the subsequent initiation of floral buds at apical and axillary meristems. Recent studies have concentrated on characterizing molecular changes as a possible mechanism associated with its synthesis, but these have failed to eliminate interference due to lack of development unity in the sampled population and to consider different kinetic alternatives of those potential changes. The current study demonstrates that numerous age-related changes occur in polypeptides from cotyledons during growth under noninductive conditions, but that these are minimal in older seedlings selected for improved synchrony of the floral response. Polypeptides from older seedlings sampled at various times during and after a dark inductive period were examined by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). No differences associated with floral induction could be detected. The results indicate that changes in gene expression correlated with floral-induction do not occur in the abundant polypeptide fraction within the limitations of the techniques employed.Floral initiation in many plants is triggered by changes in day length, a process termed photoperiodic induction, and is believed to result from the synthesis of a substance (or substances) within the leaves and cotyledons of the induced plant (for a review see Kinet et al. 1985). Although many attempts have been made to isolate and identify this floral-inducing substance, no success has been reported to date. Changes in gene expression have been proposed as one possible mechanism regulating or accompanying the synthesis of a floralinducing substance. Recent studies have supported this hypothesis in a number of experimental systems (Kannangara et al. 1990, Lay-Yee et al. 1987a,b, Warm 1984. However, other researchers have failed to find evidence for rapid changes in gene expression during induction (Friedman et al. 1987, Kimpel and Doss I989, Ono et al. 1988), suggesting that evidence testing this hypothesis and perhaps the hypothesis itself should be critically reevaluated.We have examined polypeptides present in vivo in cotyledons of the Japanese morning glory cv. Violet during growth and floral induction. The aim of the growth studies was to catalogue age-related differences in polypeptide profiles of seedlings that are capable of responding to photoperiodic induction and to determine morphological markers (after Lamoreaux et al. 1978) that correlate with these differences as criteria for selecting populations with improved synchrony. These populations were then used to examine cotyledon polypeptides during photoperiodic induction. The goal of these studies was to confirm whether or not changes in gene expression accompany this process, as some have reported, including changes that might arise as a consequence of posttranslational modification. We find no evidence of photoinduction-specific changes in t...