The expression of Escherichia coli type 1 fimbriae is phase-variable i.e. the bacterial cell is either fimbriated or non-fimbriated. The transition from one state to the other is caused by the change in configuration of an invertible DNA segment harbouring the promoter of the fimA gene. The position of this phase switch is controlled by two proteins, FimB and FimE, which mediate an 'on' or 'off' configuration of the switch, respectively. In this study, we have investigated how these proteins control the switch by means of fim-lac fusions on low-copy-number plasmids. It was found, by in trans and cis complementation, that the ratio of fimB to fimE and the total concentration of the gene products determine the configuration of the switch as well as the frequency of phase switching. It was also shown that transcription occurs from the promoter located at the phase switch when this is in the 'off' configuration. This suggests a regulatory mechanism, since the resulting transcript would be anti-sense to the fimE transcript.

In plants the enzyme coproporphyrinogen oxidase catalyzes the oxidative decarboxylation of coproporphyrinogen III to protoporphyrinogen IX in the heme and chlorophyll biosynthesis pathway(s). We have isolated a soybean coproporphyrinogen oxidase cDNA from a cDNA library and determined the primary structure of the corresponding gene. The coproporphyrinogen oxidase gene encodes a polypeptide with a predicted molecular mass of 43 kDa. The derived amino acid sequence shows 50% similarity to the corresponding yeast amino acid sequence. The main difference is an extension of 67 amino acids at the N-terminus of the soybean polypeptide which may function as a transit peptide. A full-length coproporphyrinogen oxidase cDNA clone complements a yeast mutant deleted of the coproporphyrinogen oxidase gene, thus demonstrating the function of the soybean protein. The soybean coproporphyrinogen oxidase gene is highly expressed in nodules at the stage where several late nodulins including leghemoglobin appear. The coproporphyrinogen oxidase mRNA is also detectable in leaves but at a lower level than in nodules while no mRNA is detectable in roots. The high level of coproporphyrinogen oxidase mRNA in soybean nodules implies that the plant increases heme production in the nodules to meet the demand for additional heme required for hemoprotein formation.

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The Danish strategy for waste management is to increase recycling while simultaneously reducing the volume of land-filled waste, in order to avoid loss of resources. An important part of this strategy is waste incineration on a grate, which is a well established thermal treatment technology in Denmark and in several other countries in Europe, North America, and Japan. The method is flexible with respect to operation, allows for recovery of energy, and reduces the volume of solid waste significantly (typically by a factor of 8−10). Furthermore, new and advanced flue gas cleaning technologies ensure very low emissions from modern incineration plants. The presence of inorganic constituents such as alkali metals, Cl, S, and heavy metals is a serious challenge in waste incineration, both with respect to operational [slagging, fouling, and corrosion] and environmental issues. Metals, S, Cl, and ash (oxide species) released or entrained from the grate may cause ash deposition of chemically very aggressive species such as chlorides and sulfates, and thereby promote subsequent corrosion of heat transfer surfaces in the plant. As a consequence, the steam temperatures in superheaters of waste-to-energy (WtE) plants, are usually kept relatively low, that is, in the range 400−430 °C, in order to avoid the excessive corrosion problems usually experienced by deposited alkali and heavy metal chlorides at higher steam temperatures. However, low final steam temperatures means low electrical efficiency of the plant. The present work focuses on deposit formation in the 22 MWth FASAN WtE plant, Næstved, Denmark, with particular focus on the influence of feedstock composition (i.e., firing of different waste types) and operation of the plant on ash deposition. Is it possible to affect deposit amount (i.e., flux of deposit), and chemistry, by playing with the fuel feedstock composition and/or the grate operation? Samples of bottom ash, fly ash, aerosols, deposits, and flue gas were taken while firing different waste fractions or while changing the grate operation (air distribution, oxygen content, length of fire on the grate), respectively. The formation of deposits was then quantified by air-cooled probes, and the chemical analyses of the different deposits were compared and related to the feedstock composition and the operation of the grate, through boiler mass balances. The results indicated that the grate operation may indeed affect the chemical composition and the extent [i.e., the flux (g deposit/area/time)] of deposit formation significantly, whereas the feedstock in the actual campaign did−with shredder waste and PVC as important exceptionsnot differ enough from the base waste fired to cause any serious changes in the extent [flux] and chemistry of the deposit.

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