[Genotoxicity of stack gas condensates of Bavarian waste incineration plants. II. Suitability of fast bacterial tests of emission monitoring]. / Zur Genotoxizität von Rauchgaskondensaten bayerischer Abfallverbrennungsanlagen. II. Eignung bakterieller Kurzzeit-Tests zum Emissionsmonitoring.

The genotoxicity of stack gas condensates of 21 waste incineration plants (located in Bavaria) was examined in the years 1990-1995 using two bacterial short time tests. The SOS chromotest was carried out with the tester strains Escherichia coli PQ37, PQ243 and PQ300. In addition, for the purpose of comparison, the Ames-Test was performed for selected examples with the tester strains Salmonella typhimurium TA97, TA98, TA100 and TA1537. In a pilot study, carried out in the years 1990 to 1991, the stack gas condensates from five plants were examined. They showed clear genotoxic and mutagenic effects. On the other hand, in subsequent tests we generally discovered only weak inductions for 9 of 18 crude and 24 of 78 clean gas condensate extracts, mostly after metabolic activation. Four plants were tested continuously in the years 1992 to 1995. Three of them showed a clear reduction of the detectable genotoxic potential. The fourth one gave negligible SOS inducing emissions in the whole examining period. On the other hand, for 6 of the 21 tested plants we found chromotest positive results even at the last test point. Correlations between the SOS inducing potential of the stack gas condensates and the analytical parameters detected at the same time (6 summary parameters, 24 inorganic and 63 organic chemical parameters) were not evident. Only the two highest emissions of nitropyrenes were associated with SOS inductions. Organic substances which are not analytically detected or synergistic effects might be responsible for the SOS inducing potency of the other genotoxic stack gas condensates.

Induction of the SOS response by hydrogen peroxide in various Escherichia coli mutants with altered protection against oxidative DNA damage.

The induction of the SOS response by H2O2 was measured in Escherichia coli by means of a sfiA::lacZ operon fusion. The effects of mutations in genes involved in DNA repair or DNA metabolism on the SOS response were investigated. We found that in an uvrA mutant, H2O2 induced the SOS response at lower concentrations than in the uvr+ parent strain, indicating that some lesions induced by H2O2 may be repaired by the uvrABC-dependent excision repair system. A nth mutation, yielding deficiency in thymine glycol DNA glycosylase, had no detectable effect on SOS induction, indicating that thymine glycol, a DNA lesion expected to be induced by H2O2, does not participate detectably in the induction of the SOS response by this chemical under our conditions. H2O2 still induced the SOS response in a dnaC(Ts) uvrA double mutant under conditions in which no DNA replication proceeds, suggesting that this chemical induces DNA strand breaks. Induction of the SOS response by H2O2 was also assayed in various mutants affected in genes suspected to be important for protection against oxidative stress. Mutations in the catalase genes, katE and katG, had only minor effects. However, in an oxyR deletion mutant, in which the adaptative response to H2O2 does not occur, SOS induction occurred at much lower H2O2 concentrations than in the oxyR+ parent strain. These results indicate that some enzymes regulated by the oxyR gene are, under our conditions, more important than catalase for protection against the H2O2-induced DNA damages which trigger the SOS response.

Phenylalanyl-tRNA synthetase of Escherichia coli K10. Effects of zinc(II) on partial reactions of diadenosine 5',5"'-P1,P4-tetraphosphate synthesis, conformation, and protein aggregation.

The synthesis of diadenosine 5',5"'-P1-,P4-tetraphosphate (Ap4A) catalyzed by phenylalanyl-tRNA synthetase in the presence of Zn2+ involves the same partial reactions (synthesis of phenylalanyladenylate and transfer of the adenylate moiety to ATP) as occur in the absence of this metal ion. However, transfer is strongly stimulated while adenylate synthesis is depressed. Also inhibited are pyrophosphorolysis of phenylalanyladenylate and transfer of phenylalanine from the adenylate to cognate tRNA, because overall tRNA phenylalanylation is depressed [Mayaux, J.-F., & Blanquet, S. (1981) Biochemistry 20, 4647-4654], whereas binding of tRNA to the synthetase is not. At moderate concentrations of Zn2+, and in the presence of 5 microM phenylalanine and 0.5 mM ATP, transfer of AMP is rate limiting, while at higher concentrations of Zn2+ synthesis of adenylate is rate determining. The Zn2+ concentration optimum for stimulation depends on the concentration of phenylalanine and ATP. The effects of Zn2+ are mediated through two classes of binding site(s) on the synthetase, the half-saturations of which are 1-4 and 20-30 microM Zn2+, respectively. Binding of Zn2+ to the second class of site(s) causes inhibition of the synthetase, whereas binding to the first class is responsible for activation and inhibition, which may be caused by a conformational change. Evidence for the latter is the observed decrease in protein intrinsic fluorescence intensity and the decrease in fluorescence intensity of 6-(p-toluidinyl)naphthalene-2-sulfonate, which is used as a reporter group. The kinetics of the binding reaction show a saturation dependence on Zn2+, also suggesting that a conformational change occurs.(ABSTRACT TRUNCATED AT 250 WORDS)