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A Schroeter

Publications and source records attributed to A Schroeter.

At least 37 records · Page 2Linked to original sources
PubMed1986

Role of relA mutation in the survival of amino acid-starved Escherichia coli.

Amino acid-starved cells of Escherichia coli relA+, which contain a large number of glycogen particles, are able to survive in phosphate buffer for a longer time period than their relaxed counterparts. With regard to NH4+ starvation differences in the survival of both strains were not found. NH4+ starved cells of E. coli relA are able to synthesize glycogen but amino acid-starved cells of the relA strain are not. We suggest that the synthesis of glycogen triggered by guanosine tetraphosphate during amino acid starvation is responsible for the prolonged viability of the E. coli relA+ strain.

Amino Acids↗
PubMed1985

[Synthesis of alkaline phosphatase in a stringent and a relaxed strain of Escherichia coli under amino acid and phosphate limitation].

Synthesis of alkaline phosphatase in Escherichia coli is derepressed under phosphate starvation in the stringent strain CP78 as well as in its relaxed counterpart CP79. During limitation of phosphate as well as of amino acids a decrease of enzyme activity is observed, especially in the relaxed strain, which can not produce ppGpp under this conditions. After phosphate limitation synthesis of ppGpp is not stimulated and the kinetics of RNA synthesis is similar in both strains. We suggest that ppGpp is not directly involved in the regulation of gene expression during phosphate starvation.

Alkaline Phosphatase↗
PubMed1984

[3H-thymidine incorporation following isoleucine limitation in stringent and relaxed controlled strains of Escherichia coli].

Stringent and relaxed strains of E. coli subjected to isoleucine starvation were examined by follow-wing the incorporation of 3H-thymidine into chromosomal DNA. After valine treatment to trigger an isoleucine deprivation (p)ppGpp is synthesized in the stringent strain only. Remarkable differences in the morphology of the amino acid starved cells of the stringent and relaxed strains can be observed. Upon isoleucine limitation 3H-thymidine incorporation into DNA is reduced in both strains, but this inhibition is remarkably delayed in the relaxed strain. Our result show that the reduction of chromosomal DNA synthesis during amino acid limitation occurs also without ppGpp, but in the presence of ppGpp this process is accelerated.

Chloramphenicol↗
PubMed1983

[Replication and expression of plasmid pBR 322 during discontinuous culture of a stringent and relaxed Escherichia coli strain].

The E. coli strains CP78 and CP79 carrying the plasmid pBR 322 display similar growth kinetics in discontinuous culture. During limitation of amino acids the stringent strain CP78 is able to synthesize guanosine-5'diphosphate-3'-diphosphate (ppGpp) and guanosine-5'-triphosphate-3' diphosphate, but the relaxed strain can not produce highly phosphorylated guanosine nucleotides. During the logarithmic phase of growth both strains contain similar amounts of plasmid DNA. During amino acid starvation plasmid DNA is amplified in the relaxed strain only, whereas in the stringent strain the plasmid content per cell remains constant. In stationary phase cells of CP78 a higher activity of plasmid-coded beta-lactamase than in CP79 cells was detected. Furthermore, remarkable differences between both strains were observed in the composition of proteins derived from the periplasmic fraction and separated by polyacrylamide gel electrophoresis. Our results might indicate a negative control of pBR 322 DNA replication by ppGpp during amino acid starvation.

Amino Acids↗
PubMed1983

Replication of pBR322 DNA in stringent and relaxed strains of Escherichia coli.

Synthesis of both chromosomal and plasmid (pBR322) DNA was measured in E. coli strains differing in their relA allele (relA+:CP78; relA:CP79). It was found that upon limitation of a required amino acid or after valine treatment to trigger a stringent response synthesis of pBR322 DNA was stimulated only in the relaxed strain and was inhibited in its stringent counterpart. The results suggest that replication of plasmid DNA is negatively controlled by the relA+ allele.

Chloramphenicol↗
PubMed1983

Characterization of the glucocorticoid receptor in human skin.

Because of the profound importance glucocorticoids have in dermatologic therapy, we studied the glucocorticoid receptor in human skin. A cytosol fraction was prepared from frozen skin by homogenization and centrifugation. When reacted with [3H]dexamethasone, this cytosol contained saturable, low-capacity binding. The glucocorticoid binding was stabilized by a protease inhibitor, phenylmethylsulfonylfluoride, and by sodium molybdate and was destroyed by trypsin. Sedimentation analysis of the glucocorticoid binding protein showed an 8S to 4S transition in high salt, a property of many known steroid hormone receptors. The binding was steroid specific, supporting the conclusion that this binding protein was a glucocorticoid receptor. The receptor molecule had a frictional ratio of 1.60 and a Mr of about 226,000 under low-salt conditions (0.05 M KCl) and a frictional ratio of 1.86 and a Mr of about 100,000 under high-salt conditions (0.3 M KCl) consistent with a nonglobular, elongated molecule. Isoelectric focusing showed that the receptor had 2 molecular species with isoelectric points of approximately 5.8 and 7.5. Quantitation of receptor in human skin showed 4-7 times more receptors in the epidermis and papillary dermis than in the lower dermis and nearly equal numbers in epidermis and papillary dermis. The concentration of receptors varied in different anatomic areas, with male foreskin showing the highest concentration, followed by female face, breast, and abdominal skin. Interestingly, the concentration of glucocorticoid receptors also varied with age; the highest levels were present at the extremes of life and a significantly lower level at midlife.

Aging↗
PubMed1981

[Lysine biosynthesis of Pseudomonas aeruginosa PAO1. III. Further characterization of lysine auxotrophic mutant of Ps. aeruginosa PAO1].

A number of lysine-auxotrophic mutants of Pseudomonas aeruginosa PAO1 were isolated through mutagenesis by means of N-methyl-N-nitrosoguaniine (Mach et al., unpublished). Using the cross feeding test and growth tests classification of lysine mutants was not possible. The investigation of diaminopimelic acid decarboxylase (DAP-DC) showed, that none of these mutants had an active enzyme, except for the mutants with a high number of revertants. The appearance of only one mutant type is attributed to the insufficient availability of DAP.

Bacterial Proteins↗
PubMedDate not supplied

Evaluation of molecular typing methods for Salmonella enterica serovar Typhimurium DT104 isolated in Germany from healthy pigs.

The discriminatory power of four different DNA based typing methods was tested for the molecular subtyping of Salmonella Typhimurium phage type DT104 isolates. German DT104 strains (n = 133) originating from slaughter pigs were analysed by plasmid profiling, and 32 of them by pulsed-field gel electrophoresis (PFGE) using the restriction enzymes XbaI, SpeI or BlnI, random amplification of polymorphic DNA (RAPD) using 13 different primers and IS200 typing. A resulting subtyping scheme was obtained which is based on the most discriminatory power of the individual methods i.e. plasmid profiling and PFGE with all three enzymes. The index of discrimination obtained by the subtyping scheme was 0.909 closely approaching the maximum value of one. Although minor differences occurred in the molecular DNA pattern of single DT104 strains, a dominating subtyping pattern was observed confirming other studies which showed, that S. Typhimurium DT104 isolates are highly clonal.

Animals↗
PubMedDate not supplied

Resistance of Salmonella isolates in Germany.

During 2000-2002 the National Veterinary Reference Laboratory for Salmonella (NRL-Salm) in Germany typed 11,911 isolates from animals, food, feed and the environment. All of them were tested for their susceptibility to 17 anti-microbial agents. Sixty-three per cent of all isolates were resistant and 40% were multiresistant (resistant against more than one anti-microbial). This general resistance level was strongly influenced by those specific serotypes which dominate the Salmonella epidemiology in Germany. Salmonella Typhimurium DT104 isolates from pig and cattle, and their resulting food products, were multiresistant in 98 and 94% of the cases respectively. During the period 2000-2003 an increasing quinolone resistance especially in Salmonella isolates from poultry and poultry meat (to 26%) and in S. Paratyphi B D-tartrate positive isolates (to 64%) could be observed. This increase was accompanied by a shift towards higher minimal inhibitory concentrations for ciprofloxacin.

Animals↗