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A novel method for the directional cloning of native PCR products was developed. Abasic sites in DNA templates make DNA polymerases stall at the site during synthesis of the complementary strand. Since the 5' ends of PCR product strands contain built-in amplification primers, abasic sites within the primers result in the formation of 5' single-stranded overhangs at the ends of the PCR product, enabling its direct ligation to a suitably cleaved cloning vector without any further modification. This "autosticky PCR" (AS-PCR) overcomes the problems caused by end sensitivity of restriction enzymes, or internal restriction sites within the amplified sequences, and enables the generation of essentially any desired 5' overhang.

An autotrophic biological process for the treatment of nitrate-contaminated drinking water was studied in the laboratory, with the objective of developing a continuous system which would be simple, stable and amenable to upscaling. Hydrogen generated by electrolysis of the water to be treated was the source of energy for denitrifying microorganisms. Two main process configurations were compared: (1) a single reactor where both the generation of hydrogen and denitrification took place, and (2) a two-reactor system where water was first enriched with hydrogen in an electrolysis cell prior to entering a packed-bed bioreactor. The reactors were operated in a continuous mode and granulated activated carbon served as physical support for the biomass. Although the highest rates of denitrification (0.45 kg N m -3 d -1 ) and the shortest residence times (removal of 18 mg N l -1 in 17 min) were obtained in the single-reactor system, the two-reactor system was more stable and more suitable for upscaling.

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