The genome annotations of all sequenced Dehalococcoides strains lack a citrate synthase, although physiological experiments have indicated that such an activity should be encoded. We here report that a Re face-specific citrate synthase is synthesized by Dehalococcoides strain CBDB1 and that this function is encoded by the gene cbdbA1708 (NCBI accession number CAI83711), previously annotated as encoding homocitrate synthase. Gene cbdbA1708 was heterologously expressed in Escherichia coli, and the recombinant enzyme was purified. The enzyme catalyzed the condensation of oxaloacetate and acetyl coenzyme A (acetyl-CoA) to citrate. The protein did not have homocitrate synthase activity and was inhibited by citrate, and Mn 2؉ was needed for full activity. The stereospecificity of the heterologously expressed citrate synthase was determined by electrospray ionization liquid chromatography-mass spectrometry (ESI LC/MS). Citrate was synthesized from [2-13 C]acetyl-CoA and oxaloacetate by the Dehalococcoides recombinant citrate synthase and then converted to acetate and malate by commercial citrate lyase plus malate dehydrogenase. The formation of unlabeled acetate and 13 C-labeled malate proved the Re face-specific activity of the enzyme. Shotgun proteome analyses of cell extracts of strain CBDB1 demonstrated that cbdbA1708 is expressed in strain CBDB1.Dehalococcoides species are known for their ability to use a wide range of persistent halogenated compounds as terminal electron acceptors in an anaerobic respiration with hydrogen as the electron donor. Apart from this organohalide respiration, no other mode of energy conservation has been described for Dehalococcoides species, although several strains have been isolated and physiologically characterized (1,4,12,13,23). Also, genome analyses of several Dehalococcoides strains have not indicated further energy fixation capabilities (20,24,29).The anabolism of Dehalococcoides species relies on acetate as a carbon source (1, 23). In our model organism, Dehalococcoides strain CBDB1, six acyl coenzyme A (acyl-CoA) (EC 6.2

Pseudomonas aeruginosa ATCC 17933 growing aerobically on ethanol uses a pyrroloquinoline quinone-dependent ethanol oxidation system. A mutant with an interrupted putative mqo gene, in which malate :quinone oxidoreductase (MQO), an enzyme involved in the citric acid cycle/glyoxylate cycle, was defective, showed a severe growth defect on ethanol and was unable to grow on acetate. Glucose, lactate, succinate or malate supported growth of the mutant. However, an NAD-dependent malate dehydrogenase activity could not be detected. Complementation of the mutant by the wild-type allele of the mqo gene restored wild-type behaviour. The wild-type expressed the dyedependent MQO and NAD(P)-dependent malic enzymes (MEs). Pyruvate carboxylase (PC) was found upon growth of the wild-type and the mutant on all substrates studied. PC activity in the wild-type was induced on glucose and lactate and was always higher on all substrates in the mqo mutant. In P. aeruginosa ATCC 17933, an active MQO is required for growth on ethanol or acetate, while with glucose, lactate, succinate or malate an apparent bypass route operates, with MEs using malate for generating pyruvate, which is carboxylated to oxaloacetate by PC. To the authors' knowledge, this is the first time that a specific mutant MQO phenotype has been observed, caused by the inactivation of a gene encoding MQO activity. mqo of P. aeruginosa ATCC 17933 corresponds to mqoB (PA4640) of the P. aeruginosa PAO1 genome project.

Pseudomonas aeruginosa ATCC 17933 uses a pyrroloquinoline quinonedependent ethanol oxidation system. Two mutants of P. aeruginosa, unable to grow on ethanol and showing no acetyl-CoA synthetase (ACS) activity under standard test conditions, were complemented by cosmid pTB3018. Subcloning led to the isolation of a gene which encodes a protein with high similarity to acetyl-CoA synthetases. Interruption of the putative acsA gene by a kanamycin-resistance cassette resulted in a mutant also unable to grow on ethanol and with very low residual acetyl-CoA-forming activity. Complementation by the wild-type allele of the acsA gene restored growth and led to the expression of ACS activity in excess of that of wild-type cells. In wild-type P. aeruginosa, ACS activity was induced upon growth on ethanol, 2,3-butanediol, malonate and acetate. The wild-type and mutants defective in ACS activity showed an active acetate kinase (ACK) under the growth conditions used ; however, phosphotransacetylase (PTA) could not be detected. The data indicate that P. aeruginosa requires active acsA gene product for growth on ethanol.

Pseudomonas aeruginosa ATCC 17933 is capable of growing aerobically on ethanol as sole source of carbon and energy. This requires the glyoxylate cycle for replenishing C4-compounds to the TCA cycle. The enzyme isocitrate lyase (ICL) catalyzes the first step of this glyoxylate shunt. Its activity was induced more than 10-fold in response to the carbon sources ethanol or acetate instead of glucose or succinate. We could prove that in P. aeruginosa ICL is essential for aerobic as well as anaerobic utilization of C2-sources. Transcriptional regulation of icl gene (aceA) expression was monitored on different carbon sources by using an aceA-lacZ gene fusion. A strong correlation between promoter and ICL activity indicated regulation at the transcriptional level. But ICL was not simply induced by the mere presence of ethanol in the growth medium as was demonstrated by cultivation on mixed substrates. P. aeruginosa showed diauxic growth on media containing ethanol-succinate or ethanol-glucose mixtures and did not transcribe the aceA gene to metabolize ethanol until succinate or glucose, respectively, were exhausted. Inactivation of the chromosomal aceA gene in P. aeruginosa led to an inability to grow on ethanol and acetate. Promoter activity studies showed that all genes necessary to oxidize ethanol were downregulated in the ICL-negative mutant. But on mixed substrates like ethanol-succinate or ethanol-glucose the mutant exhibited growth and utilized ethanol as well, probably as energy source only.

Various Rochow contact masses have been characterized by catalytic tests as well as by X-ray diffraction with respect to q-Cu,Si percentage and particle size. The presence of q-CuSi in the contact masses is neither a necessary nor a sufficient precondition of catalytic activity, but a certain contribution of dispersed q-Cu3Si to the activity cannot be excluded. The results can be explained consistently by assuming highly dispersed or even two-dimensional Cu-Si species, not detectable by X-rays, as catalytically active species. The promoters zinc, antimony and tin do not significantly change the percentage and particle size of q-Cu3Si.

Pseudomonas aeruginosa ATCC 17933 is able to oxidize ethanol to acetate under aerobic conditions. The P. aeruginosa acetyl-CoA synthetase (ACS) gene acsA was previously identified, and the ACS enzyme described to be required for growth on ethanol as the sole source of carbon and energy. Here, we investigated the transcriptional regulation of the acsA gene using an acsA::lacZ fusion. Transcription of acsA was regulated by the carbon source, and expression was maximal on ethanol, acetate and propionate. In addition, the induction depended on the response regulator ErdR, which also regulates hierarchically arranged genes for ethanol oxidation. Transcription of the acsA gene was repressed by addition of succinate to an ethanol-containing medium. This repression required Crc, the product of the catabolite repression control gene crc.

The oxidation of phase pure ZnS in the wurtzite and sphalerite modification upon heating in an air flow has been studied by simultaneous thermogravimetry‐differential thermal analysis and in‐situ X‐ray diffraction at high temperature (high temperature camera and electron synchrotron). The oxidation of wurtzite starts at higher temperature, ZnO is formed without any detectable side or intermediate products. Sphalerite oxidation starts at lower temperature, ZnSO4 and Zn3O(SO4)2 are formed intermediately in side reactions yielding finally ZnO.

The dissolution of polycrystalline quartz strained by compression and shear or by impact crushing in 1-N NaOH lead to different results. The defects of the impact crushed quartz grains, measured as crystallinity by X-ray methods, are not preferentially concentrated in regions near the surface. It is assumed that in this case the corners and edges of the quartz grains are preferred centers of defects.Es wurden Loseversuche in 1 n NaOH von polykristallinem Quarz nach Druck-und Scherbeanspruchung und nach Prallbeanspruchung durchgefuhrt, die zu prinzipiell unterschiedlichen Aussagen fiihren. Nach Prallbeanspruchung sind die rontgenographisch durch die Kristallinitat erfal3ten Storungen nicht bevorzugt in den oberflachennahen Bereichen konzentriert. Es wird angenommen, daB es durch die Prallbeanspruchung bevorzugt zu einer starken Storung von Ecken und Kanten der Quarzkorner kommt.