No abstract

Biodegradabilities of chelating agents were tested with activated sludge. Ethylenediaminetetraacetic acid (EDTA) remained intact in the effluent even after acclimation for 100 days, but propanediamine-N,N'-disuccinic acid (PDDS) and nitrilotriacetic acid (NTA) were biodegraded after acclimation for 5 and 23 days, respectively. Optical isomers of ethylenediamine-N,N'-disuccinic acid (EDDS) had different biodegradabilities: SS- and RS-isomers were susceptible to biodegradation, but the RR-isomer was resistant. SS-isomer was degraded even by activated sludge without acclimation.

The nitrile hydratase of Rhodococcus sp. N-774 was purified and crystallized. The enzyme is composed of two different subunits (molecular masses: subunit ~t, 28 500 Da; subunit fl, 29 000 Da). The amino-terminal amino acid sequence of each subunit was determined. There is no sequence homology between the two subunits, suggesting that the peptides originate from different cistrons. The activity of the purified enzyme did not decrease during incubation in the dark, whereas it gradually decreased in intact cells.

We have isolated numerous mutants containing mutations in the salvage pathways of purine synthesis. The mutations cause deficiencies in adenine phosphoribosyltrangferase (adeF), in hypoxanthine-guanine phosphoribosyltransferase (guaF), in adenine deaminase (adeC), in inosine-guanosine phosphorylase, (guaP), and in GMP reductase (guaC). The physiological properties of mutants containing one or more of these mutations and corresponding enzyme measurements have been used to derive a metabolic chart of the purine salvage pathway of Bacillus subtilis.