Pollen-based biome reconstruction for southern Europe and Africa 18,000 yr bp

Pollen data from 18,000 ¹⁴C yr bp were compiled in order to reconstruct biome distributions at the last glacial maximum in southern Europe and Africa. Biome reconstructions were made using the objective biomization method applied to pollen counts using a complete list of dryland taxa wherever possible. Consistent and major differences from present‐day biomes are shown. Forest and xerophytic woods/scrub were replaced by steppe, both in the Mediterranean region and in southern Africa, except in south‐western Cape Province where fynbos (xerophytic scrub) persisted. Sites in the tropical highlands, characterized today by evergreen forest, were dominated by steppe and/or xerophytic vegetation (cf. today’s Ericaceous belt and Afroalpine grassland) at the last glacial maximum. Available data from the tropical lowlands are sparse but suggest that the modern tropical rain forest was largely replaced by tropical seasonal forest while the modern seasonal or dry forests were encroached on by savanna or steppe. Montane forest elements descended to lower elevations than today.     

Polyacetylenes in Hawaiian bidens

Leaves and roots of 19 species and six subspecies of Hawaiian Bidens were examined for polyacetylenes. Eleven C₁₃ hydrocarbons, aromatic and thiophenyl derivatives, one C₁₄ tetrahydropyran and three C₁₇ hydrocarbons were isolated all identified. All can be derived from a common precursor, oleic acid. Polyacetylenes were not detected in the leaves of 13 taxa although they are found in the roots of all. The occurrence of 2-[2-phenyl-ethyne-1-yl]-5 acetoxymethyl thiopene in Bidens has not been previously reported. Its ubiquitous presence is consistent with other evidence that the Hawaiian species are all derived from a single ancestral immigrant to the islands. Most taxa could be distinguished by their complement of polyacetylenes in roots and leaves. No variation was found to occur within taxa except in B. torta, in which each population had a unique array of polyacetylenes. Above the species level there appeared to be no taxonomically significant pattern to the distribution of polyacetylenes in this group.     

Genetic Analysis of the Heterochromatin of Chromosome 3 in Drosophila Melanogaster. II. Vital Loci Identified through Ems Mutagenesis

Chromosome 3 of Drosophila melanogaster contains the last major blocks of heterochromatin in this species to be genetically analyzed. Deficiencies of heterochromatin generated through the detachment of compound-3 chromosomes revealed the presence of vital loci in the heterochromatin of chromosome 3, but an extensive complementation analysis with various combinations of lethal and nonlethal detachment products gave no evidence of tandemly repeated vital genes in this region. These findings indicate that the heterochromatin of chromosome 3 is genetically similar to that of chromosome 2. A more thorough genetic analysis of the heterochromatic regions has been carried out using the chemical mutagen ethyl methanesulfonate (EMS). Seventy-five EMS-induced lethals allelic to loci uncovered by detachment-product deficiencies were recovered and tested for complementation. In total, 12 complementation groups were identified, ten in the heterochromatin to the left of the centromere and two to the right. All but two complementation groups in the left heterochromatic block could be identified as separate loci through deficiency mapping. The interallelic complementation observed between some EMS-induced lethals, as well as the recovery of a temperature-sensitive allele for each of the two loci, provided further evidence that single-copy, transcribed vital genes reside in the heterochromatin of chromosome 3. Cytological analysis of three detachment-product deficiencies provided evidence that at least some of the genes uncovered in this study are located in the most distal segments of the heterochromatin in both arms. This study provides a detailed genetic analysis of chromosome 3 heterochromatin and offers further information on the genetic nature and heterogeneity of Drosophila heterochromatin.     

Fermentation of molasses using a thermotolerant yeast,Kluyveromyces marxianus IMB3: simplex optimisation of media supplements

 The use of molasses as a substrate for ethanol production by the thermotolerant yeast Kluyveromyces marxianus var. marxianus was investigated at 45°C. A maximum ethanol concentration of 7.4% (v/v) was produced from unsupplemented molasses at a concentration of 23% (v/v). The effect on ethanol production of increasing the sucrose concentration in 23% (v/v) molasses was determined. Increased sucrose concentration had a similar detrimental effect on the final ethanol produced as the increase in molasses concentration. This indicated that the effect may be due to increased osmotic activity as opposed to other components in the molasses. The optimum concentration of the supplements nitrogen, magnesium, potassium and fatty acid for maximum ethanol production rate was determined using the Nelder and Mead (Computer J 7:308–313, 1965) simplex optimisation method. The optimum concentrations of the supplements were 0.576 g l^-1 magnesium sulphate, 0.288 g l^-1 potassium dihydrogen phosphate and 0.36% (v/v) linseed oil. Added nitrogen in the form of ammonium sulphate did not affect the ethanol production rate. Received: 29 January 1996/Received revision: 23 April 1996/Accepted: 29 April 1996     

Production of ethanol by the thermotolerant yeastKluyveromyces marxianus IMB3 during growth on lactose-containing media

Summary The thermotolerant yeast strain,Kluyveromyces marxianus IMB3 was shown to be capable of growth and ethanol production on lactose containing media at 45°C. On media containing 4% (w/v) lactose, ethanol production increased to 6.0g/l within 50h and this represented 29% of theoretical yield. During growth on lactose containing media the organism was shown to produce a cell-associated β-galactosidase and no significant enzyme could be detected in the extracellular culture filtrate. Addition of β-galactosidase, released fromKluyveromyces marxianus IMB3 cells, to active fermentations, resulted in increasing ethanol production to 53% of theoretical yield at 45°C.     

Partial characterization of β-glucosidase activity produced by Kluyveromyces marxianus IMB3 during growth on cellobiose-containing media at 45°C

Summary We report- the partial characterization of a -glucosidase produced during growth of the thermotolerant yeast, K. marxianus IMB3 on lactose-containing media at 45°C. The enzyme had Km values of 1.1mM and 14.8mM for the substrates p-nitrophenyl--D-glucoside and cellobiose, respectively. The enzyme had a pH optimum of 5.5 and was optimally active at 50°C. It was stable up to 125 hours at 25°C and 35°, with half-lives of 45 hours and 2 hours at 45°C and 50°C, respectively. The enzyme was inhibited to varying degrees in the presence of metal ions and was completely inactivated by Hg²⁺. Ethanol concentrations [1–10% (v/v)] had little effect on activity. Glucose (20mM) caused inhibition when p-nitrophenyl--D-glucoside was used as substrate, whereas lactose at similar concentrations had no effect.     

The effects of Mn2+ on ethanol production by Kluyveromyces marxianus IMB3 during growth on lactose-containing media at 45°C

Summary It has previously been demonstrated that the thermotolerant yeast strain, K. marxianus IMB3 is capable of growth and ethanol production on lactose containing media at 45°C. Although the organism is capable of producing a -galactosidase, that enzyme has been shown to be extremely thermolabile at 45°C and this has been reflected in reduced efficiencies with respect to conversion of lactose to ethanol. In this paper we demonstrate that addition of Mn²⁺ ions to enzyme preparations contributes significantly to enzyme stability at 45°C. We also demonstrate that addition of Mn²⁺ to fermentations results in increased efficiency of conversion of lactose to ethanol at this temperature.     

Studies on the use of a thermotolerant strain of Kluyveromyces marxianus in simultaneous saccharification and ethanol formation from cellulose

 The thermotolerant yeast strain, Kluyveromyces marxianus IMB3, was found to be capable of ethanol production during growth at 45°C on media containing milled paper and exogenously added commercial cellulase. At maximum achievable cellulose concentrations in shake-flask cultures, ethanol production increased to 6.6 g/l at 45°C, representing an overall level of conversion of 21% of the maximum theoretical yield. Subsequent studies involving variations in added cellulase concentrations to the batch systems demonstrated that ethanol yields could be increased to 10 g/l at 45°C, which represented 39% of the maximum theoretical yield. As a result of ethanol production at 45°C in the systems examined, we suggest that the thermotolerant ethanol-producing yeast strain K. marxianus represents a novel candidate for use in simultaneous saccharification and conversion of the resulting substrates to ethanol. Received: 9 June 1994/Received revision: 8 August 1994/Accepted: 12 August 1994     

The role of microtubules and cell-wall deposition in elongation of regenerating protoplasts of Mougeotia

Protoplasts of the filamentous green alga Mougeotia sp. are spherical when isolated and revert to their normal cylindrical cell shape during regeneration of a cell wall. Sections of protoplasts show that cortical microtubules are present at all times but examination of osmotically ruptured protoplasts by negative staining shows that the microtubules are initially free and become progressively cross-bridged to the plasma membrane during the first 3 h of protoplast culture. Cell-wall microfibrils areoobserved within 60 min when protoplasts are returned to growth medium; deposition of microfibrils that is predominantly transverse to the future axis of elongation is detectable after about 6 h of culture. When regenerating protoplasts are treated with either colchicine or isopropyl-N-phenyl carbamate, drugs which interfere with microtubule polymerization, they remain spherical and develop cell walls in which the microfibrils are randomly oriented.