Stability of alginate-immobilized algal cells.

Investigations were carried out using immobilized Chlorella cells to determine the diameter, compressibility, tolerance to phosphate chelation, and ability to retain algal cells during incubation of various alginate beads. These physical bead characteristics were found to be affected by a variety of interactive factors, including multivalent cation type (hardening agent) and cell, cation, and alginate concentration, the latter exhibiting a predominant influence. The susceptibility of alginate beads to phosphate chelation was found to involve a complex interaction of cation type, concentration, and pH of phosphate solution. A scale of response ranging from gel swelling to gel shrinking was observed for a range of conditions. However, stable calcium alginate beads were maintained in incubation media with a pH of 5.5 and a phosphate concentration of 5 microM. A preliminary investigation into cell leakage from the beads illustrated the importance of maintaining a stable gel structure and limiting cell growth to reduce leakage.

The effects of pesticides on algae.

This paper reviews the effect on algae of organochlorine, carbamate, organophosphorus and other groups of pesticides, but excluding herbicides and general metabolic inhibitors. Existing data are often fragmentary and contradictory. Possible reasons for contradictory data are explored and discussed and the value of existing standard algal toxicity tests for environmental impact assessment is seriously questioned.

Nitroimidazoles as anaerobic electron acceptors for xanthine oxidase.

The rates of anaerobic nitroreduction of 15 nitroimidazoles by xanthine-xanthine oxidase were measured. The compounds studied were mainly 2-nitroimidazoles, including misonidazole and analogues of potential value in cancer therapy; most 5-nitroimidazoles such as metronidazole and nimorazole reacted too slowly for measurement under the conditions used. Using 0.1 mM nitroimidazole, reduction rates varied between ca. 4 and 680 nmole min-1 U-1 xanthine oxidase at 37 degrees and pH 7.4. These rates were correlated with the reduction potential characterizing one-electron reduction to the nitro radical-anion, and compared with those for other nitroaryl compounds and with reduction by free flavin mononucleotide.

Glycollate formation during the photoassimilation of acetate by Chlorella.

When (3)H-(14)C-acetate was supplied to Chlorella pyrenoidosa in the light, glycollic acid became rapidly labelled with tritium and (14)C. The [Formula: see text]ratio of glycollate was 10, whilst the ratio was 4 in the acetate added. Both (3)H and (14)C from acetate were present in glycollate before they were present in Calvin cycle intermediates, so that glycollate was not formed as a C2-fragment from the Calvin cycle.