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Archives of Microbiology (v.183, #6)
ω-Oxygenation of the alkyl sidechain of linear alkylbenzenesulfonate (LAS) surfactant in Parvibaculum lavamentivorans T by David Schleheck; Alasdair M. Cook (pp. 369-377).
Parvibaculum lavamentivorans T DS-1, an aerobic, heterotrophic bacterium, requires a biofilm on a solid surface (e.g. glass particles) when utilizing commercial linear alkylbenzenesulfonate surfactant (LAS; 20 congeners) for growth. Catabolism involves the undefined ‘ω-oxygenation’ and β-oxidation of the LAS side chain, and the organism excretes sulfophenyl carboxylates (SPC) quantitatively. A 3.5-l fermenter was developed which allowed gram-quantities of LAS-grown cells to be grown and harvested from medium with glass particles as the solid support. The catabolism of LAS was dominant: in diauxie experiments with acetate as second carbon source, LAS was utilized first. The biofilm-encoated LAS-grown cells were unsuitable for metabolic work in vitro because cell suspensions clumped and were not disrupted effectively, but the degradative enzymes were found to be expressed constitutively in acetate-grown cells, which formed no biofilm. LAS-dependent oxygen uptake was measured in acetate-grown cells at about 0.6 mkat (kg protein)−1, but not in extracts of cells. Whole cells converted LAS to SPC in the presence of molecular oxygen only, and the reaction could be saturably inhibited by metyrapone, which acts on e.g. cytochromes P450 (CYP). However, despite the presence of CYP153-like sequences in the genome of strain DS-1T, the difference spectra did not support the presence of a CYP in crude extracts, and the nature of the LAS-oxygenase remains unclear.
Keywords: Linear alkylbenzenesulfonate; Surfactant degradation; Parvibaculum lavamentivorans T ; ω-Oxygenation; LAS-monooxygenase
ω-Oxygenation of the alkyl sidechain of linear alkylbenzenesulfonate (LAS) surfactant in Parvibaculum lavamentivorans T by David Schleheck; Alasdair M. Cook (pp. 369-377).
Parvibaculum lavamentivorans T DS-1, an aerobic, heterotrophic bacterium, requires a biofilm on a solid surface (e.g. glass particles) when utilizing commercial linear alkylbenzenesulfonate surfactant (LAS; 20 congeners) for growth. Catabolism involves the undefined ‘ω-oxygenation’ and β-oxidation of the LAS side chain, and the organism excretes sulfophenyl carboxylates (SPC) quantitatively. A 3.5-l fermenter was developed which allowed gram-quantities of LAS-grown cells to be grown and harvested from medium with glass particles as the solid support. The catabolism of LAS was dominant: in diauxie experiments with acetate as second carbon source, LAS was utilized first. The biofilm-encoated LAS-grown cells were unsuitable for metabolic work in vitro because cell suspensions clumped and were not disrupted effectively, but the degradative enzymes were found to be expressed constitutively in acetate-grown cells, which formed no biofilm. LAS-dependent oxygen uptake was measured in acetate-grown cells at about 0.6 mkat (kg protein)−1, but not in extracts of cells. Whole cells converted LAS to SPC in the presence of molecular oxygen only, and the reaction could be saturably inhibited by metyrapone, which acts on e.g. cytochromes P450 (CYP). However, despite the presence of CYP153-like sequences in the genome of strain DS-1T, the difference spectra did not support the presence of a CYP in crude extracts, and the nature of the LAS-oxygenase remains unclear.
Keywords: Linear alkylbenzenesulfonate; Surfactant degradation; Parvibaculum lavamentivorans T ; ω-Oxygenation; LAS-monooxygenase
Veratrol-O-demethylase of Acetobacterium dehalogenans: ATP-dependent reduction of the corrinoid protein by Anke Siebert; Torsten Schubert; Tina Engelmann; Sandra Studenik; Gabriele Diekert (pp. 378-384).
The anaerobic veratrol O-demethylase mediates the transfer of the methyl group of the phenyl methyl ether veratrol to tetrahydrofolate. The primary methyl group acceptor is the cobalt of a corrinoid protein, which has to be in the +1 oxidation state to bind the methyl group. Due to the negative redox potential of the cob(II)/cob(I)alamin couple, autoxidation of the cobalt may accidentally occur. In this study, the reduction of the corrinoid to the superreduced [CoI] state was investigated. The ATP-dependent reduction of the corrinoid protein of the veratrol O-demethylase was shown to be dependent on titanium(III) citrate as electron donor and on an activating enzyme. In the presence of ATP, activating enzyme, and Ti(III), the redox potential versus the standard hydrogen electrode (E SHE) of the cob(II)alamin/cob(I)alamin couple in the corrinoid protein was determined to be −290 mV (pH 7.5), whereas E SHE at pH 7.5 was lower than −450 mV in the absence of either activating enzyme or ATP. ADP, AMP, or GTP could not replace ATP in the activation reaction. The ATP analogue adenosine-5′-(β,γ-imido)triphosphate (AMP-PNP, 2–4 mM) completely inhibited the corrinoid reduction in the presence of ATP (2 mM).
Keywords: Veratrol O-demethylase; Ether cleavage; Activation; Corrinoid protein; Methyltransferase I; Phenyl methyl ether; Redox potential
Veratrol-O-demethylase of Acetobacterium dehalogenans: ATP-dependent reduction of the corrinoid protein by Anke Siebert; Torsten Schubert; Tina Engelmann; Sandra Studenik; Gabriele Diekert (pp. 378-384).
The anaerobic veratrol O-demethylase mediates the transfer of the methyl group of the phenyl methyl ether veratrol to tetrahydrofolate. The primary methyl group acceptor is the cobalt of a corrinoid protein, which has to be in the +1 oxidation state to bind the methyl group. Due to the negative redox potential of the cob(II)/cob(I)alamin couple, autoxidation of the cobalt may accidentally occur. In this study, the reduction of the corrinoid to the superreduced [CoI] state was investigated. The ATP-dependent reduction of the corrinoid protein of the veratrol O-demethylase was shown to be dependent on titanium(III) citrate as electron donor and on an activating enzyme. In the presence of ATP, activating enzyme, and Ti(III), the redox potential versus the standard hydrogen electrode (E SHE) of the cob(II)alamin/cob(I)alamin couple in the corrinoid protein was determined to be −290 mV (pH 7.5), whereas E SHE at pH 7.5 was lower than −450 mV in the absence of either activating enzyme or ATP. ADP, AMP, or GTP could not replace ATP in the activation reaction. The ATP analogue adenosine-5′-(β,γ-imido)triphosphate (AMP-PNP, 2–4 mM) completely inhibited the corrinoid reduction in the presence of ATP (2 mM).
Keywords: Veratrol O-demethylase; Ether cleavage; Activation; Corrinoid protein; Methyltransferase I; Phenyl methyl ether; Redox potential
The glycolytic genes pfk and pyk from Lactobacillus casei are induced by sugars transported by the phosphoenolpyruvate:sugar phosphotransferase system and repressed by CcpA by Rosa Viana; Gaspar Pérez-Martínez; Josef Deutscher; Vicente Monedero (pp. 385-393).
In Lactobacillus casei BL23, phosphofructokinase activity was higher in cells utilizing sugars transported by the phosphoenolpyruvate:sugar phosphotransferase system (PTS). The phosphofructokinase gene (pfk) was cloned from L. casei and shown to be clustered with the gene encoding pyruvate kinase (pyk). pfk and pyk genes are cotranscribed and induced upon growth on sugars transported by the PTS. Contrarily to the model proposed for Lactococcus lactis, where the global catabolite regulator protein (CcpA) is involved in PTS-induced transcription of pfk and pyk, a ccpA mutation resulted in a slight increase in pfk–pyk expression in L. casei. This weak regulation was evidenced by CcpA binding to a region of the pfk–pyk promoter which contained two cre sequences significantly deviated from the consensus. The PTS induction of pfk–pyk seems to be counteracted by the CcpA-mediated repression. Our results suggest that the need to accommodate the levels of pfk–pyk mRNA to the availability of sugars is fulfilled in L. casei by a PTS/CcpA-mediated signal transduction different from L. lactis.
Keywords: Lactobacillus ; Glycolysis; CcpA; Phosphotransferase system
The glycolytic genes pfk and pyk from Lactobacillus casei are induced by sugars transported by the phosphoenolpyruvate:sugar phosphotransferase system and repressed by CcpA by Rosa Viana; Gaspar Pérez-Martínez; Josef Deutscher; Vicente Monedero (pp. 385-393).
In Lactobacillus casei BL23, phosphofructokinase activity was higher in cells utilizing sugars transported by the phosphoenolpyruvate:sugar phosphotransferase system (PTS). The phosphofructokinase gene (pfk) was cloned from L. casei and shown to be clustered with the gene encoding pyruvate kinase (pyk). pfk and pyk genes are cotranscribed and induced upon growth on sugars transported by the PTS. Contrarily to the model proposed for Lactococcus lactis, where the global catabolite regulator protein (CcpA) is involved in PTS-induced transcription of pfk and pyk, a ccpA mutation resulted in a slight increase in pfk–pyk expression in L. casei. This weak regulation was evidenced by CcpA binding to a region of the pfk–pyk promoter which contained two cre sequences significantly deviated from the consensus. The PTS induction of pfk–pyk seems to be counteracted by the CcpA-mediated repression. Our results suggest that the need to accommodate the levels of pfk–pyk mRNA to the availability of sugars is fulfilled in L. casei by a PTS/CcpA-mediated signal transduction different from L. lactis.
Keywords: Lactobacillus ; Glycolysis; CcpA; Phosphotransferase system
Functional characterization of Schizosaccharomyces pombe neutral trehalase altered in phosphorylatable serine residues by Alejandro Franco; Teresa Soto; Marisa Madrid; Jero Vicente-Soler; Mariano Gacto; José Cansado (pp. 394-400).
The activation of neutral trehalase (Ntp1) by metabolic and physical stresses in Schizosaccharomyces pombe is dependent on protein kinases Pka1 or Sck1. Mutant ntp1 alleles altered for potentially phosphorylatable serine residues within the regulatory domain of the enzyme were integrated under the control of the native promoter in an ntp1-deleted background. The trehalase variants were expressed to a level similar to that of wild type trehalase from control cells. Wild type trehalase protein accumulated and became activated upon stress while a single change in the evolutionary conserved perfect consensus site for Pka1-dependent phosphorylation (Ser71), as well as point mutations in two other putative phosphorylation sites (Ser6, Ser51), produced inactive trehalases unresponsive to stress. Trehalose content in the trehalase mutated strains increased upon salt stress to a level comparable to that shown by an ntp1-deleted mutant. When exposed to heat shock, trehalose hyperaccumulated in the ntp1-null strain lacking trehalase protein and this phenotype was shown by some (Ser71), but not all, strains with serine mutated trehalases. The mutant trehalases retained the ability to form complexes with trehalose-6-phosphate synthase. These data support a role of potentially phosphorylated specific sites for the activation of S. pombe neutral trehalase and for the heat shock-induced accumulation of trehalose.
Keywords: Trehalase; Fission yeast; Phosphorylation; Trehalose
Functional characterization of Schizosaccharomyces pombe neutral trehalase altered in phosphorylatable serine residues by Alejandro Franco; Teresa Soto; Marisa Madrid; Jero Vicente-Soler; Mariano Gacto; José Cansado (pp. 394-400).
The activation of neutral trehalase (Ntp1) by metabolic and physical stresses in Schizosaccharomyces pombe is dependent on protein kinases Pka1 or Sck1. Mutant ntp1 alleles altered for potentially phosphorylatable serine residues within the regulatory domain of the enzyme were integrated under the control of the native promoter in an ntp1-deleted background. The trehalase variants were expressed to a level similar to that of wild type trehalase from control cells. Wild type trehalase protein accumulated and became activated upon stress while a single change in the evolutionary conserved perfect consensus site for Pka1-dependent phosphorylation (Ser71), as well as point mutations in two other putative phosphorylation sites (Ser6, Ser51), produced inactive trehalases unresponsive to stress. Trehalose content in the trehalase mutated strains increased upon salt stress to a level comparable to that shown by an ntp1-deleted mutant. When exposed to heat shock, trehalose hyperaccumulated in the ntp1-null strain lacking trehalase protein and this phenotype was shown by some (Ser71), but not all, strains with serine mutated trehalases. The mutant trehalases retained the ability to form complexes with trehalose-6-phosphate synthase. These data support a role of potentially phosphorylated specific sites for the activation of S. pombe neutral trehalase and for the heat shock-induced accumulation of trehalose.
Keywords: Trehalase; Fission yeast; Phosphorylation; Trehalose
Identification of IS elements in Acidithiobacillus ferrooxidans strains grown in a medium with ferrous iron or adapted to elemental sulfur by Tamara F. Kondrat’eva; Vasily N. Danilevich; Svetlana N. Ageeva; Grigory I. Karavaiko (pp. 401-410).
IS elements were identified in the genomes of five Acidithiobacillus ferrooxidans strains isolated from various media. IST2 elements were revealed in all the strains grown in a medium with ferrous iron, ISAfe1 elements were detected in four strains (TFBk, TFL-2, TFV-1 and TFO). Three strains (TFV-1, TFN-d and TFO) were found to contain IS elements, ~600 bp long. These were named preliminary as ISAfe600. Partial sequencing of the 5′- and 3′-terminal nucleotide stretches of an ISAfe1 element in TFBk and TFL-2 strains and complete sequencing of the ISAfe1 element in the TFBk strain has revealed nucleotide substitutions as compared to the prototype, i.e., the ISAfe1 element of an ATCC 19859 strain. Partial sequencing of the 5′- and 3′-terminal nucleotide stretches of the IST2 elements in TFO, TFBk and TFL-2 strains has shown numerous nucleotide substitutions when compared to the IST2 element of an ATCC 19859 strain. Complete sequencing of the IST2 element in the TFBk strain has revealed: the divergence between the IST2 elements in the TFBk strain and the prototype was 21.2%. Southern hybridization of EcoRI fragments of the chromosomal DNA from five A. ferrooxidans strains grown in a medium with ferrous iron using an internal region of ISAfe1, a full-length ISAfe1 or a full-length IST2 as probes has shown them to differ in the number of copies of IS elements and their localization on the chromosomes. Adaptation to elemental sulfur in A. ferrooxidans strains caused changes in the number, intensity and localization of hybridization bands. The authors discuss the role of IS elements in the adaptation of A. ferrooxidans to the new energy substrate.
Keywords: Acidithiobacillus ferrooxidans ; IS elements; Energy substrate
Identification of IS elements in Acidithiobacillus ferrooxidans strains grown in a medium with ferrous iron or adapted to elemental sulfur by Tamara F. Kondrat’eva; Vasily N. Danilevich; Svetlana N. Ageeva; Grigory I. Karavaiko (pp. 401-410).
IS elements were identified in the genomes of five Acidithiobacillus ferrooxidans strains isolated from various media. IST2 elements were revealed in all the strains grown in a medium with ferrous iron, ISAfe1 elements were detected in four strains (TFBk, TFL-2, TFV-1 and TFO). Three strains (TFV-1, TFN-d and TFO) were found to contain IS elements, ~600 bp long. These were named preliminary as ISAfe600. Partial sequencing of the 5′- and 3′-terminal nucleotide stretches of an ISAfe1 element in TFBk and TFL-2 strains and complete sequencing of the ISAfe1 element in the TFBk strain has revealed nucleotide substitutions as compared to the prototype, i.e., the ISAfe1 element of an ATCC 19859 strain. Partial sequencing of the 5′- and 3′-terminal nucleotide stretches of the IST2 elements in TFO, TFBk and TFL-2 strains has shown numerous nucleotide substitutions when compared to the IST2 element of an ATCC 19859 strain. Complete sequencing of the IST2 element in the TFBk strain has revealed: the divergence between the IST2 elements in the TFBk strain and the prototype was 21.2%. Southern hybridization of EcoRI fragments of the chromosomal DNA from five A. ferrooxidans strains grown in a medium with ferrous iron using an internal region of ISAfe1, a full-length ISAfe1 or a full-length IST2 as probes has shown them to differ in the number of copies of IS elements and their localization on the chromosomes. Adaptation to elemental sulfur in A. ferrooxidans strains caused changes in the number, intensity and localization of hybridization bands. The authors discuss the role of IS elements in the adaptation of A. ferrooxidans to the new energy substrate.
Keywords: Acidithiobacillus ferrooxidans ; IS elements; Energy substrate
NhaK, a novel monovalent cation/H+ antiporter of Bacillus subtilis by Makoto Fujisawa; Ayumi Kusumoto; Yuko Wada; Takahiro Tsuchiya; Masahiro Ito (pp. 411-420).
Four Na+/H+ antiporters, Mrp, TetA(L), NhaC, and MleN have so far been described in Bacillus subtilis 168. We identified an additional Na+/H+ antiporter, YvgP, from B. subtilis that exhibits homology to the cation: proton antiporter-1 (CPA-1) family. The yvgP-dependent complementation observed in a Na+(Ca2+)/H+ antiporter-defective Escherichia coli mutant (KNabc) suggested that YvgP effluxed Na+ and Li+. In addition, effects of yvgP expression on a K+ uptake-defective mutant of E. coli indicated that YvgP also supported K+ efflux. In a fluorescence-based assay of everted membrane vesicles prepared from E. coli KNabc transformants, YvgP-dependent Na+ (K+, Li+, Rb+)/H+ antiport activity was demonstrated. Na+ (K+, Li+)/H+ activity was higher at pH 8.5 than at pH 7.5. Mg2+, Ca2+ and Mn2+ did not serve as substrates but they inhibited YvgP antiport activities. Studies of yvgP expression in B. subtilis, using a reporter gene fusion, showed a significant constitutive level of expression that was highest in stationary phase, increasing as stationary phase progressed. In addition, the expression level was significantly increased in the presence of added K+ and Na+.
Keywords: Bacillus subtilis ; Na+/H+ antiporter; K+/H+ antiporter; Li+/H+ antiporter; Rb+/H+ antiporter; Transcriptional analysis; CPA-1 transporter family
NhaK, a novel monovalent cation/H+ antiporter of Bacillus subtilis by Makoto Fujisawa; Ayumi Kusumoto; Yuko Wada; Takahiro Tsuchiya; Masahiro Ito (pp. 411-420).
Four Na+/H+ antiporters, Mrp, TetA(L), NhaC, and MleN have so far been described in Bacillus subtilis 168. We identified an additional Na+/H+ antiporter, YvgP, from B. subtilis that exhibits homology to the cation: proton antiporter-1 (CPA-1) family. The yvgP-dependent complementation observed in a Na+(Ca2+)/H+ antiporter-defective Escherichia coli mutant (KNabc) suggested that YvgP effluxed Na+ and Li+. In addition, effects of yvgP expression on a K+ uptake-defective mutant of E. coli indicated that YvgP also supported K+ efflux. In a fluorescence-based assay of everted membrane vesicles prepared from E. coli KNabc transformants, YvgP-dependent Na+ (K+, Li+, Rb+)/H+ antiport activity was demonstrated. Na+ (K+, Li+)/H+ activity was higher at pH 8.5 than at pH 7.5. Mg2+, Ca2+ and Mn2+ did not serve as substrates but they inhibited YvgP antiport activities. Studies of yvgP expression in B. subtilis, using a reporter gene fusion, showed a significant constitutive level of expression that was highest in stationary phase, increasing as stationary phase progressed. In addition, the expression level was significantly increased in the presence of added K+ and Na+.
Keywords: Bacillus subtilis ; Na+/H+ antiporter; K+/H+ antiporter; Li+/H+ antiporter; Rb+/H+ antiporter; Transcriptional analysis; CPA-1 transporter family
Transcription in the prpC-yloQ region in Bacillus subtilis by Adam Iwanicki; Krzysztof Hinc; Simone Seror; Grzegorz Węgrzyn; Michal Obuchowski (pp. 421-430).
The prpC and prkC genes encode two proteins with opposing activities, eukaryotic-like protein phosphatase and protein kinase involved in the sporulation and biofilm formation processes. The prpC gene overlaps 3 bp of the prkC gene; prkC is followed by the essential gene, yloQ. The organisation of the prpC, prkC and yloQ genes is conserved among several Gram-positive bacteria. In this work, we have found two promoters which function within the region of these genes and we also described conditions in which these promoters become activated. One promoter appears to be located upstream of prpC resulting in transcription of both prpC and prkC, as well as the yloQ gene. A second promoter is located 7 bp upstream of the start codon of yloQ. The yloQ promoter was activated during ethanol stress, but was sigmaB-independent. We also showed that prpC, prkC and yloQ genes form an operon.
Keywords: Bacillus subtilis ; Weak promoters; Protein kinase; Protein phosphatase; GTP-binding proteins
Transcription in the prpC-yloQ region in Bacillus subtilis by Adam Iwanicki; Krzysztof Hinc; Simone Seror; Grzegorz Węgrzyn; Michal Obuchowski (pp. 421-430).
The prpC and prkC genes encode two proteins with opposing activities, eukaryotic-like protein phosphatase and protein kinase involved in the sporulation and biofilm formation processes. The prpC gene overlaps 3 bp of the prkC gene; prkC is followed by the essential gene, yloQ. The organisation of the prpC, prkC and yloQ genes is conserved among several Gram-positive bacteria. In this work, we have found two promoters which function within the region of these genes and we also described conditions in which these promoters become activated. One promoter appears to be located upstream of prpC resulting in transcription of both prpC and prkC, as well as the yloQ gene. A second promoter is located 7 bp upstream of the start codon of yloQ. The yloQ promoter was activated during ethanol stress, but was sigmaB-independent. We also showed that prpC, prkC and yloQ genes form an operon.
Keywords: Bacillus subtilis ; Weak promoters; Protein kinase; Protein phosphatase; GTP-binding proteins
The puf operon of the purple sulfur bacterium Amoebobacter purpureus: structure, transcription and phylogenetic analysis by Christian Tuschak; Molly M. Leung; J. Thomas Beatty; Jörg Overmann (pp. 431-443).
The puf operon, encoding photosynthetic reaction center and light-harvesting genes, of the purple sulfur phototrophic bacterium Amoebobacter purpureus was cloned and sequenced. This revealed an unusual operon structure of the genes pufB 1 A 1 LMCB 2 A 2 B 3 A 3. The sequence represents the second complete puf operon available for Chromatiaceae. So far, additional sets of light-harvesting 1 (LH1) genes, pufB 2 A 2 and pufB 3 A 3 in the region downstream of pufC have only been described for Allochromatium vinosum. Along with reports of multiple LH1 polypeptides found in some Ectothiorhodospiraceae by direct protein sequencing, our results indicate that multiple LH1 genes may occur frequently in phototrophic γ-proteobacteria. Phylogenetic analyses suggested a coevolution of the core puf genes pufB 1 A 1 LM. Separate analysis of the LH1 α and β polypeptides revealed a high intraspecies relatedness for the secondary LH1β polypeptides, possibly caused by functional constraints. In contrast, LH1α subunits of Amb. purpureus and Alc. vinosum are closely related (85% sequence identity) which could reflect horizontal gene transfer. RNA analyses suggested co-transcription of all puf genes in Amb. purpureus as a 5.5 kb primary transcript which appears to be more stable than the puf operon primary transcripts of purple non-sulfur bacteria. The 5′ end of the transcript mapped to a putative promoter, which contains a −35 region located in an inverted repeat DNA sequence.
Keywords: puf genes; Light-harvesting complexes; Reaction center; Purple sulfur bacteria; Chromatiaceae
The puf operon of the purple sulfur bacterium Amoebobacter purpureus: structure, transcription and phylogenetic analysis by Christian Tuschak; Molly M. Leung; J. Thomas Beatty; Jörg Overmann (pp. 431-443).
The puf operon, encoding photosynthetic reaction center and light-harvesting genes, of the purple sulfur phototrophic bacterium Amoebobacter purpureus was cloned and sequenced. This revealed an unusual operon structure of the genes pufB 1 A 1 LMCB 2 A 2 B 3 A 3. The sequence represents the second complete puf operon available for Chromatiaceae. So far, additional sets of light-harvesting 1 (LH1) genes, pufB 2 A 2 and pufB 3 A 3 in the region downstream of pufC have only been described for Allochromatium vinosum. Along with reports of multiple LH1 polypeptides found in some Ectothiorhodospiraceae by direct protein sequencing, our results indicate that multiple LH1 genes may occur frequently in phototrophic γ-proteobacteria. Phylogenetic analyses suggested a coevolution of the core puf genes pufB 1 A 1 LM. Separate analysis of the LH1 α and β polypeptides revealed a high intraspecies relatedness for the secondary LH1β polypeptides, possibly caused by functional constraints. In contrast, LH1α subunits of Amb. purpureus and Alc. vinosum are closely related (85% sequence identity) which could reflect horizontal gene transfer. RNA analyses suggested co-transcription of all puf genes in Amb. purpureus as a 5.5 kb primary transcript which appears to be more stable than the puf operon primary transcripts of purple non-sulfur bacteria. The 5′ end of the transcript mapped to a putative promoter, which contains a −35 region located in an inverted repeat DNA sequence.
Keywords: puf genes; Light-harvesting complexes; Reaction center; Purple sulfur bacteria; Chromatiaceae
Effect of glutathione on UV induction of prophage lambda by Yancheng Liu; Qiuju Zhang; Chengxiang Fang; Shiqiao Zhu; Yali Tang; Shaoyi Huang (pp. 444-449).
The effect of glutathione (GSH) on the ultraviolet (UV) induction of lambda prophage was investigated in lysogenic Escherichia coli. The data showed that extracellular GSH could inhibit the UV induction of lambda prophage. The inhibitory rates were concentration dependent, and the maximal rate obtained was 94% with 3.0 M GSH. The effect was also measured in three different lambda lysogens: a wild-type strain (wt), an isogenic GSH-deficient strain, and an isogenic strain producing increased amounts of GSH. The result showed that when subjected to UV irradiation (254 nm, 60 J m−2), GSH-deficient strain was approximately fivefold more sensitive to be lysed than wt, whereas the strain with higher intracellular GSH levels was only 28% susceptible to be lysed. With electron spin resonance and spin trapping techniques, we observed that free radical signals occurred in the suspensions of UV irradiated lysogenic cells and the intensity of signals was influenced by GSH levels. These results indicate that GSH can significantly inhibit the UV induction of lambda prophage, and that this effect is correlated to its capacity to scavenge free radicals generated after UV irradiation.
Keywords: Glutathione; Lambda prophage; UV induction; Free radical
Effect of glutathione on UV induction of prophage lambda by Yancheng Liu; Qiuju Zhang; Chengxiang Fang; Shiqiao Zhu; Yali Tang; Shaoyi Huang (pp. 444-449).
The effect of glutathione (GSH) on the ultraviolet (UV) induction of lambda prophage was investigated in lysogenic Escherichia coli. The data showed that extracellular GSH could inhibit the UV induction of lambda prophage. The inhibitory rates were concentration dependent, and the maximal rate obtained was 94% with 3.0 M GSH. The effect was also measured in three different lambda lysogens: a wild-type strain (wt), an isogenic GSH-deficient strain, and an isogenic strain producing increased amounts of GSH. The result showed that when subjected to UV irradiation (254 nm, 60 J m−2), GSH-deficient strain was approximately fivefold more sensitive to be lysed than wt, whereas the strain with higher intracellular GSH levels was only 28% susceptible to be lysed. With electron spin resonance and spin trapping techniques, we observed that free radical signals occurred in the suspensions of UV irradiated lysogenic cells and the intensity of signals was influenced by GSH levels. These results indicate that GSH can significantly inhibit the UV induction of lambda prophage, and that this effect is correlated to its capacity to scavenge free radicals generated after UV irradiation.
Keywords: Glutathione; Lambda prophage; UV induction; Free radical
Physiological regulation of the properties of alcohol dehydrogenase II (ADH II) of Zymomonas mobilis: NADH renders ADH II resistant to cyanide and aeration by Uldis Kalnenieks; Nina Galinina; Malda M. Toma (pp. 450-456).
The variable cyanide-sensitivity of the iron-containing alcohol dehydrogenase isoenzyme (ADH II) of the ethanol-producing bacterium Zymomonas mobilis was studied. In aerobically grown permeabilized cells, cyanide caused gradual inhibition of ADH II, which was largely prevented by externally added NADH. Cyanide-sensitivity of ADH II was highest in cells grown under conditions of vigorous aeration, in which intracellular NADH concentration was low. Anaerobically grown bacteria, as well as those cultivated aerobically in the presence of cyanide, maintained higher intracellular NADH levels along with a more cyanide-resistant ADH II. It was demonstrated that cyanide acted as a competitive inhibitor of ADH II, competing with nicotinamide nucleotides. NADH increased both cyanide-resistance and oxygen-resistance of ADH II.
Keywords: Alcohol dehydrogenase; Cyanide-resistance; Oxygen-resistance; Zymomonas mobilis
Physiological regulation of the properties of alcohol dehydrogenase II (ADH II) of Zymomonas mobilis: NADH renders ADH II resistant to cyanide and aeration by Uldis Kalnenieks; Nina Galinina; Malda M. Toma (pp. 450-456).
The variable cyanide-sensitivity of the iron-containing alcohol dehydrogenase isoenzyme (ADH II) of the ethanol-producing bacterium Zymomonas mobilis was studied. In aerobically grown permeabilized cells, cyanide caused gradual inhibition of ADH II, which was largely prevented by externally added NADH. Cyanide-sensitivity of ADH II was highest in cells grown under conditions of vigorous aeration, in which intracellular NADH concentration was low. Anaerobically grown bacteria, as well as those cultivated aerobically in the presence of cyanide, maintained higher intracellular NADH levels along with a more cyanide-resistant ADH II. It was demonstrated that cyanide acted as a competitive inhibitor of ADH II, competing with nicotinamide nucleotides. NADH increased both cyanide-resistance and oxygen-resistance of ADH II.
Keywords: Alcohol dehydrogenase; Cyanide-resistance; Oxygen-resistance; Zymomonas mobilis