Isolation of bacteria able to utilize s-triazines as the sole and limiting nitrogen sources for growth is described. Three strains of Pseudomonas (A, D, and F) and two strains of Klebsiella pneumoniae (90 and 99) were examined. Strains D and F utilized N-ethylammelide, N-isopropylammelide, ammeline, ammelide, cyanuric acid, and ammonium ion as nitrogen sources. Strain A utilized melamine, ammeline, ammelide, cyanuric acid, ammonium ion, and deaminated N-ethylammeline and N-isopropylammeline. Strains 90 and 99 utilized ammelide, cyanuric acid, and ammonium ion. Growth yields of strains were independent of the nitrogen source, and specific growth rates with s-triazines were similar to those with ammonium ion as the nitrogen source (-0.3-0.6 h-l). Suspensions of nongrowing cells generally gave quantitative yields of ammonium ion from s-triazines, and ring carbon atoms were released as carbon dioxide. N-Alkylammelines in mixtures of strains A and D were quantitatively degraded to ammonium ion.Papers claiming microbial degradation of s-triazines, usually herbicides, are widespread, but reviewers have various interpretations of the rates of s-triazine degradation. Thus Alexander (1979) labels s-triazines recalcitrant, Cripps and Roberts (1978) imply ready degradability, whereas other reviewers refrain from comment (Esser et al., 1975;Kaufman and Kearney, 1970; Knuesli et al., 1969; Mikrobiologisches Institut, Eidgenossische Technische Hochschule, ETH-Zentnun, CH-8092 Zurich, Switzerland. Harris et al., 1968). Jordan et al. (1970) complement these data by citing extensive nonbiological degradation of striazines, usually on clay mineral surfaces. s-Triazines do not accumulate in the soils studied by Ramsteiner et al. (1972).Metabolites from s-triazines in experiments with animals, plants, and microorganisms have been reviewed by Fishbein (1975). Definitive proof of s-triazine metabolism by microorganisms in pure culture has been provided

The insecticidal delta endotoxin of Bacillus thuringiensis was labeled with iodine-125. Brush-border membrane vesicles, prepared from the midgut epithelium of Pieris brassicae larvae, known to be highly susceptible to the toxin, and from a non-target tissue: the small intestine of rat, were examined for binding of '251-toxin. The toxin was bound specifically only to insect vesicles. Its binding to the insect membrane system was competitively inhibited by '271-toxin and non-iodinated toxin, whereas the binding of the 1251-toxin to the mammalian membrane system was not affected by unlabeled toxin. Vesicles of P. brassicae possess two individual bindingsite populations for iodinated toxin with dissociation constants of 46 nM and 490 nM. The Hill coefficients of both sites were approximately 1 and the binding capacities were 0.2 pmol and 30 pmol/mg vesicle protein for the high and the low-affinity sites respectively. The estimation of the dissociation constant for non-iodinated toxin, using a competition experiment, revealed only one binding-site population which possessed a dissociation constant of 235 nM. It is concluded that this is the binding site for the native toxin. This site was sensitive towards treatment with proteases or mixed glycosidases. It is suggested that it is a protein or a glycoprotein.The delta endotoxin of Bacillus thuringiensis is a proteinaceous, crystalline insecticide, toxic to the larval stages of several important pest insects in agriculture and forestry. The crystals are composed of subunits (protoxin) with a molecular mass of about 130 kDa [l -31. The toxic moiety is located on the N-terminal half of the protein [4-61 and has a molecular mass of approximately 60 -68 kDa. The molecular mass of the protoxin and that of the activated toxin vary depending on the strain and on the proteolytic procedure used for the activation. In the case of the strain studied here, activation of the protoxin (136 kDa) by trypsin leads to toxic fragments with molecular masses of 55 kDa and 70 kDa. In vitro the protoxin needs proteolytic activation to exhibit toxicity against insect cell cultures [7, 81. In vivo the protoxin is enzymatically activated within the digestive tract. Furthermore, the toxins of various strains differ in their host spectrum [9, 101. The delta endotoxin destroys the gut epithelia of susceptible insect larvae [ll]; the results of several studies have shown that the permeability of the gut membrane undergoes changes (for review, see [12]).

1. The degradative pathway of melamine (1,3,5-triazine-2,4,6-triamine) was examined in Pseudomonas sp. strain A. 2. The bacterium grew with melamine, ammeline, ammelide, cyanuric acid or NH+4 as sole source of nitrogen, and each substrate was entirely metabolized. Utilization of ammeline, ammelide, cyanuric acid or NH+4 was concomitant with growth. But with melamine as substrate, a transient intermediate was detected, which was identified as ammeline by three methods. 3. Enzymes from strain A were separated by chromatography on DEAE-cellulose, and four activities were examined. 4. Melamine was converted stoichiometrically into equimolar amounts of ammeline and NH+4. 5. Ammeline was converted stoichiometrically into equimolar amounts of ammelide and NH+4; ammelide was identified by four methods. 6. Ammelide was converted stoichiometrically into equimolar amounts of cyanuric acid and NH+4; cyanuric acid was identified by four methods. 7. Cyanuric acid was converted by an enzyme preparation into an unidentified product with negligible release of NH+4. 8. The specific activities of the degradative enzymes (greater than or equal to 0.3 mkat/kg of protein) were high enough to explain the growth rate of the organism. 9. The bacterium converted 0.4 mM-melamine anaerobically into 2.3 mM-NH+4. 10. Two other pseudomonads and two strains of Klebsiella pneumoniae were also examined, with similar results. 11. The degradative pathway of melamine appears to be hydrolytic, and proceeds by three successive deaminations to cyanuric acid, which is further metabolized.

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