Potential use of pineapple (ananas comosus L.) and cadmium tolerant bacteria to reduce cadmium toxicity in soil

PhD ThesisCadmium (Cd) is a toxic metal that occurs in the environment naturally and as a pollutant from industrial and agricultural sources. The Cd concentration of agricultural soils in Thailand has increased during the last few decades as a consequence of mining activities. This toxic metal is allocated to edible plant parts and moves into the food chain via rice grains in some provinces in the Northern part of Thailand. Pineapple (Ananas comosus L.) is the most widely cultivated tropical fruit in Thailand and possesses the photosynthetic specialisation of crassulacean acid metabolism (CAM). Since CAM plants are generally tolerant to abiotic stress, it was hypothesised that pineapple would be relatively tolerant to Cd and could potentially be grown as a crop in Cd-contaminated soils. The present study determined the effect of Cd on photosynthetic performance, growth and Cd accumulation in different parts of pineapple. Pineapple plants grown in Cd-contaminated soil did not show any visual symptoms of toxicity and whilst light use efficiency (Fv/Fm) and rates of net dark CO2 uptake were reduced by Cd treatment, biomass reductions were only 14% of control at the highest concentration of Cd (150 mg Cd kg-1). Levels of Cd accumulated by pineapple increased as the Cd concentration in soil increased. Pineapple plants took up Cd from the soil, resulting in lower Cd concentrations in the rhizosphere soil compared with the bulk soil. The soil-extractable Cd decreased over time which may have been due to the uptake of Cd by plant and to remaining metal ions becoming more tightly bound with organic materials or root exudates. Calculated as Cd μg per g dry weight, roots accumulated higher amount of Cd than shoots. Short-term and long-term exposure to Cd resulted in a reduction in the numbers and diversity of soil microbes as indicated using plate count and DGGE techniques. The pineapple rhizosphere exhibited increased numbers of bacteria and fungi and a distinct and more diverse bacterial population when compared to bulk soil. Cd pollution of soil reduced both microbial numbers and bacterial diversity of all soil samples. Certain bacteria in the phyla Nitrospirae, Verrucomicrobia, Acidobacteria and Chloroflexi were only present in Cd-contaminated soil. Cd-resistant bacteria were isolated from the rhizosphere of pineapple grown in Cd-contaminated soil and were subsequently used as inoculants in an effort to improve plant growth and reduce Cd toxicity. Nine isolates of Cd-resistant bacteria were isolated from the rhizosphere soil of pineapple. Two bacterial strains, Bacillus firmus and Arthrobacter humicola were identified as having the potential to alleviate Cd toxicity in soil since both isolates were found to accumulate Cd at 17.21 and 19.83 mg Cd per g biomass at an initial Cd level of 50 mg Cd l-1. Application of B. firmus and A. humicola near the root zone of pineapple grown in Cd-contaminated soil resulted in an increased uptake of nutrients compared with non-inoculated plants. In addition, soil inoculation resulted in higher rates of dark CO2 uptake, reduced Cd accumulation and increased biomass of pineapple plants grown in Cd-contaminated soil as compared with non-inoculated plants. Overall it would appear that pineapple could be grown commercially in Cd contaminated soils as it is relatively Cd resistant and it would also reduce total and extractable Cd soil levels over time. Bacterial inoculation of soil could be used to improve pineapple growth but the financial viability of this would need to be determined.Royal Thai Governmen

Cinétique de la nutrition minérale et métabolisme du carbone et de l'azote dans des suspensions cellulaires hétérotrophes et photomixotrophes : aspects physiologiques et biochimiques chez Abrus precatorius L. (Leguminosae)

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

NaCl-Regulated gene expression in Distichlis

NaCl-induced and -repressed cDNA clones had previously been isolated by differential screening of a cDNA library, prepared from poly(A(^+)) RNA isolated from Distichlis spicata (salt grass) cell cultures grown in the presence of 260 mM NaCl (Zhao, et al., 1989). Eight of these cDNA clones have now been subcloned and/or sequenced and the predicted polypeptides compared with owl sequence data base. Three clones pDZ6.2, pDZVIII 1.2.1 and pDZIX 3.1 encode proline rich proteins, containing an amino acid repeat [PPKKDH(H)Y(Y)]. They have similar amino acid usage to proline-rich cell wall proteins, being rich in P, K, H and Y. The first 20 amino acid residues encode a putative leader sequence, supporting the proposed extracellular role as a cell wall protein. This N-terminal sequence (MPLLVALLLVLAVVAAAGAD) shares some similarity with die leader sequence of a soyabean proline-rich cell wall protein precursor and other extracellular proteins (the conserved residues are underlined). There is an increase in abundance of transcripts hybridising to the inserts from pDZ6.2 and pDZVUI 1.2.1 in response to either 520 mM NaCl or 100 µM ABA, but a decrease in response to 5 mM exogenous proline. It is suggested that the corresponding gene(s) are regulated at the level of either transcription or transcript stability, in response to elevated NaCl, with ABA as a mediator of (or part of) tills response. pDZ6.2 and pDZXI 3.1 have identical nucleotide sequences, whilst pDZVni 1.2.1 differs in three base paks within the putative open reading frame, suggesting that there may be at least two members of a multi gene family. A 68 bp OA repeat has been found in the 5' untranslated region of pDZ6.2 and a corresponding transcript identified by northern analysis using this OA sequence as a probe. Such nucleotide repeats can form triplexes (DNA) or hakpin loops (RNA), which is dependent on pH and ionic conditions. Therefore this OA repeat may play a role in the regulation of the gene corresponding to pDZ6.2 at the level of transcription or translation, possibly by attenuation of these processes, either by the formation of triplexes or hah-pins, or the binding of a protein to this GA region, at low ionic strength. However initial in vitro ttanscription experiments, to compare the transcriptional activity of pDZ6.2 and pDZVin 5.1.1 at different ionic strengths, proved inconclusive. An attempt was also made to identify the corresponding genomic region from D. spicata by anchored PGR.A fourth clone pDZ2.8L encodes a histone 2B protein, having 97.9% similarity to a wheat histone 2B. Its transcript abundance decreased in response to either 520 mM NaCl, 5 mM proline or 100 µM ABA. The sequences of the remaining clones either revealed no significant similarity to any known sequences or were assigned as being cloning artefacts .D. spicata cells accumulate proline within eight hours of exposure to 260 mM NaCl (Heyser, et al., 1989b). An unsuccessful attempt was also made to isolate a pyrroline-5- carboxylate reductase gene homologue from D. spicata, by heterologous probing of Southern blots with a soyabean cDNA pProCl and PCR

GENETIC VARIATION FOR FRUIT DEVELOPMENT OF PISUM SATIVUM L., WITH SPECIAL REFERENCE TO THE EFFECTS OF THE RUGOSUS LOCUS

This study has compared various aspects of pea fruit development, using two green-podded lines near-isogenic except for the r locus and a yellow-podded mutant having the genotype gpgp. The gp gene is associated with reduced chlorophyll in the pod wall which then appears yellow. The r gene is associated with a wrinkled appearance of mature dried seed and cotyledonary starch grains which are small and fissured. An ultrastructural survey of tissues from pods, testas and cotyledons showed there to be no effect of the r locus on chloroplast structure. The structure of amyloplasts however, appeared to be affected by the r locus; starch grains in the cotyledons having a rugged outline in the wrinkled type. Chloroplasts from the inner tissues of the yellow pod were similar to those in leaves, green pods, green-podded testas and cotyledons. Chloroplasts in the yellow pod mesocarp and in the testa of yellow pods had dilated thylakoids, less starch and more lipid than the green-podded types. Growth analysis of the near-isogenic lines showed there to be no difference between the round (RR) and wrinkled (rr) lines in pod and testa growth, but embryo growth differed. The wrinkled embryo contained more water during development but had a lower final dry weight than the round embryos. Water potential (an indication of the osmotic regulation) was lower in the wrinkled embryos than in the round embryos, except very early in development when it was higher in the wrinkled embryos. In vitro culture of embryos showed that optimum growth was obtained in liquid media containing 10% sucrose as a carbon source. Replacing sucrose with mannitol determined that it was the sucrose which was important, not its resulting water potential. These gp and r gene effects and their relevance to future breeding programmes are discussed with other biochemical studies on similar genotypes.Department of Biological Sciences Plymouth Polytechnic Drake Circus Plymouth PL4 8AA and Department of Applied Genetics John Innes Institute Colney Lane Norwich NR4 7U

The degradation of starch by the oral streptococci.

A thesis submitted to the Faculty or Science, University of the Witwatersrand Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy.Two carbohydrates predominate in modern diets namely sucrose and starch. They are metabolized by oral microorganisms to products implicated in dental caries. The influence of sucrose and its metabolites is well documented but starches have received less attention. This study investigated the secretion of starch hydrolysing enzymes by oral streptococci and the production of sugars, acids and polysaccharides from the two ccmponents of starch, amylose and amylopectin. ( Abbreviation abstract )AC201

Catalytic Conversion of Lignocellulosic Biomass to Carboxylic Acids and Derivatives

The transition from today’s fossil fuel based economy to a sustainable economy that is grounded in renewable biomass is driven by concern of climate change and anticipation of dwindling fossil fuel resources. Biofuel is a central theme of the sustainable transition due to the large market demand in the transportation sector. However, transformation of biomass into high value added chemicals is advantageous to secure optimal use of the biomass resources from economical and ecological perspectives. Therefore, it is important for a modern biorefinery to integrate fuel and chemical production from biomass derived platform chemicals. The aim of this dissertation is to design and develop a novel and environmentally benign process to produce carboxylic acids and their derivatives, which are the building blocks for biofuels and biobased chemicals, from various lignocellulosic biomass types using recyclable heterogeneous catalysts in water and/or alcohol solutions. In this process, wet lignocellulosic biomass is pre-treated by low-temperature partial oxidation that selectively converts lignin to carboxylic acids or phenolics in aqueous-phase solutions. The remaining structured hemicellulose and cellulose are catalytically converted to lactic acid or its esters which can be further upgraded to liquid hydrocarbon fuels or value added chemicals.Although a variety of lignocellulosic biomass can be used as feedstocks in designed conversion processes, the arid-land adapted, highly water-use efficient CAM (crassulacean acid metabolism) species, (e.g., Agave tequilana and Opuntia ficus-indica) which are unique biomass species compared to other C3 and C4 plants, are especially promising. In Chapter 2, Agave and Opuntia were characterized by a series of standard biomass analytical procedures wherein both species were found to contain high water contents which would be potentially useful for aqueous phase processing of biomass, as well as low lignin and high para-crystalline cellulose contents, making them more amenable to deconstruction. In Chapter 3, a lignin model compound, guaiacol, was selectively oxidized with H2O2 as the oxidant and titanium silicate (TS-1) catalyst at low temperatures. The value-added dicarboxylic acid, maleic acid, was obtained in this TS-1/H2O2 catalytic aqueous-phase partial oxidation reaction system. In Chapter 4, hemicellulosic biomass, xylan, and xylose can be converted to lactic acid using ZrO2 catalyst in pH-neutral hydrothermal solutions. The yields of lactic acid, up to 25% and 18%, were produced from xylose and xylan, respectively. The Lewis acid property of ZrO2 was demonstrated to effectively facilitate the retro-aldol condensation of xylose, which is the initial step of the conversion of xylose to lactic acid. In Chapter 5, the mesoporous Zr-SBA-15 materials with increased Lewis acidity compared to ZrO2 were synthesized in order to increase the yields of lactic acid esters. Alkyl lactates were produced from sugars and cellulose with this catalyst in relevant alcohols in a one-pot reaction. The yields of methyl lactate at up to 41 % and 44% were produced from pentose and hexose, respectively, with methanol solvent, while the yield of up to 31% ethyl lactate was directly produced from cellulose in ethanol-water solutions with the Zr-SBA-15 catalyst. Lastly, in Chapter 6, the conclusion remarks and future research directions are given

Plant centromere compositions

The present invention provides for the nucleic acid sequences of plant centromeres. This will permit construction of stably inherited recombinant DNA constructs and minichromosomes which can serve as vectors for the construction of transgenic plant and animal cells