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J Kieboom

Publications and source records attributed to J Kieboom.

10 recordsLinked to original sources
PubMed2005

Acid resistance variability among isolates of Salmonella enterica serovar Typhimurium DT104.

AIMS: Acid resistance could be an indicator of virulence since acid resistant strains are able to better survive the human stomach passage and in macrophages. We studied the acid resistance of several Salmonella Typhimurium DT104 strains isolated from food and humans and identified cellular parameters contributing to the enhanced acid resistance of these isolates. METHODS AND RESULTS: Acid resistance was tested in 37 Salmonella enterica Typhimurium serovar DT104 (S. Typhimurium DT104) strains. Acid adaptation at pH 5 followed by exposure for 2 h at pH 2.5 in the 27 human, nine nonhuman, and in two reference strains, revealed strong variation of acid survival. After 2 h at pH 2.5 six strains of S. Typhimurium DT104 were considered high acid resistant as they displayed a level of survival >10%, 14 strains were considered intermediate acid resistant (level of survival was <10% and >0.01%) and 19 strains were considered low acid resistant (level of survival <0.01%). Six strains were selected for further studies and proteomics revealed a relatively high amount of phase 2 flagellin in an acid-sensitive strain and a relatively high amount of the beta component of the H(+)/ATPase in an acid-resistant strain. Two strains were slightly more heat resistant possibly as the result of increased levels of DnaK or GroEL. CONCLUSIONS: A significant difference could be detected between human and food isolates regarding their acid resistance; all high acid-resistant strains were human isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: S. Typhimurium DT104 is known for two decades and has a great impact on human health causing serious food-borne diseases. Our results suggest the existence of a positive correlation between acid resistance and pathogenicity in S. Typhimurium DT104 as all high acid-resistant strains were isolated from humans.

Acids↗
PubMed2001

Transposon mutations in the flagella biosynthetic pathway of the solvent-tolerant Pseudomonas putida S12 result in a decreased expression of solvent efflux genes.

Fourteen solvent-sensitive transposon mutants were generated from the solvent-tolerant Pseudomonas putida strain S12 by applying the TnMod-KmO mutagenesis system. These mutants were unable to grow in the presence of octanol and toluene. By cloning the region flanking the transposon insertion point a partial sequence of the interrupted genes was determined. Comparison of the deduced amino acid sequences with a protein database revealed the following interrupted putative gene products: organic solvent efflux proteins SrpA and SrpB, the flagellar structural proteins FlgK, FlaG, FliI, FliC, and FliH, the transcriptional activator FleQ, the alternative RNA polymerase sigma factor RpoN, and the flagellum-specific RNA polymerase sigma factor FliA (RpoF). The transposon mutants, except for the organic solvent efflux mutants, were nonmotile as determined by a swarm assay and the formation of the flagellum was totally impaired. Expression studies with a srp promoter probe showed a decreased expression of the SrpABC efflux pump in the nonmotile mutants.

Bacterial Proteins↗
PubMed2001

Production of 3-nitrocatechol by oxygenase-containing bacteria: optimization of the nitrobenzene biotransformation by Nocardia S3.

Twenty-one microorganisms were screened for their ability to convert nitroaromatics into 3-nitrocatechol as a result of the action of an oxygenase. Cultures containing toluene dioxygenases and phenol monooxygenases accumulated 3-nitrocatechol during incubation with nitrobenzene and nitrophenol, respectively. Nocardia S3 was selected and studied in more detail. Toluene-pregrown cultures were able to degrade nitrobenzene with a concomitant formation of 3-nitrocatechol. The rates of nitrobenzene utilization decreased throughout the biotransformation period and finally the accumulation ceased. The gradual deterioration of the biotransformation rates was not a consequence of depletion of the NADH pool, but was due to the accumulation of 3-nitrocatechol. The inhibition of nitrobenzene biotransformation by 3-nitrocatechol greatly impacts 3-nitrocatechol production processes.

Biotransformation↗
PubMed2001

Identification and molecular characterization of an efflux system involved in Pseudomonas putida S12 multidrug resistance.

The authors previously described srpABC, an operon involved in proton-dependent solvent efflux in the solvent-tolerant Pseudomonas putida S12. Recently, it was shown that organic solvents and not antibiotics induce this operon. In the present study, the authors characterize a new efflux pump, designated ArpABC, on the basis of two isolated chloramphenicol-sensitive transposon mutants. The arpABC operon is involved in the active efflux of multiple antibiotics, such as tetracycline, chloramphenicol, carbenicillin, streptomycin, erythromycin and novobiocin. The deduced amino acid sequences encoded by the three genes involved show a striking resemblance to proteins of the resistance/nodulation/cell division family, which are involved in both organic solvent and multiple drug efflux. These findings demonstrate that ArpABC is highly homologous to the MepABC and TtgABC efflux systems for organic solvents and multiple antibiotics. However, ArpABC does not contribute to organic solvent tolerance in P. putida S12 but is solely involved in multidrug resistance.

Amino Acid Sequence↗
PubMed2000

An insertion sequence prepares Pseudomonas putida S12 for severe solvent stress.

The novel insertion sequence ISS12 plays a key role in the tolerance of Pseudomonas putida S12 to sudden toluene stress. Under normal culturing conditions the P. putida S12 genome contained seven copies of ISS12. However, a P. putida S12 population growing to high cell density after sudden addition of a separate phase of toluene carried eight copies. The survival frequency of cells in this variant P. putida S12 population was 1000 times higher than in "normal" P. putida S12 populations. Analysis of the nucleotide sequence flanking the extra ISS12 insertion revealed integration into the srpS gene. srpS forms a gene cluster with srpR and both are putative regulators of the solvent resistance pump SrpABC. SrpABC makes a major contribution to solvent tolerance in P. putida S12 and is induced by toluene. The basal level of srp promoter activity in the P. putida S12 variant was seven times higher than in wild-type P. putida S12. Introduction of the intact srpRS gene cluster in the variant resulted in a dramatic decrease of survival frequency after a toluene shock. These findings strongly suggest that interruption of srpS by ISS12 up-regulates expression of the solvent pump, enabling the bacterium to tolerate sudden exposure to lethal concentrations of toxic solvents. We propose that P. putida S12 employs ISS12 as a mutator element to generate diverse mutations to swiftly adapt when confronted with severe adverse conditions.

ATP-Binding Cassette Transporters↗
PubMed1998

Identification and molecular characterization of an efflux pump involved in Pseudomonas putida S12 solvent tolerance.

Bacteria able to grow in aqueous:organic two-phase systems have evolved resistance mechanisms to the toxic effects of solvents. One such mechanism is the active efflux of solvents from the cell, preserving the integrity of the cell interior. Pseudomonas putida S12 is resistant to a wide variety of normally detrimental solvents due to the action of such an efflux pump. The genes for this solvent efflux pump were cloned from P. putida S12 and their nucleotide sequence determined. The deduced amino acid sequences encoded by the three genes involved show a striking resemblance to proteins known to be involved in proton-dependent multidrug efflux systems. Transfer of the genes for the solvent efflux pump to solvent-sensitive P. putida strains results in the acquisition of solvent resistance. This opens up the possibilities of using the solvent efflux system to construct bacterial strains capable of performing biocatalytic transformations of insoluble substrates in two-phase aqueous:organic medium.

Amino Acid Sequence↗
PubMed1998

Active efflux of organic solvents by Pseudomonas putida S12 is induced by solvents.

Induction of the membrane-associated organic solvent efflux system SrpABC of Pseudomonas putida S12 was examined by cloning a 312-bp DNA fragment, containing the srp promoter, in the broad-host-range reporter vector pKRZ-1. Compounds that are capable of inducing expression of the srpABC genes include aromatic and aliphatic solvents and alcohols. General stress conditions such as pH, temperature, NaCl, or the presence of organic acids did not induce srp transcription. Although the solvent efflux pump in P. putida S12 is a member of the resistance-nodulation-cell division family of transporters, the srpABC genes were not induced by antibiotics or heavy metals.

Anti-Bacterial Agents↗
PubMed1995

Continuous degradation of trichloroethylene by Xanthobacter sp. strain Py2 during growth on propene.

Propene-grown Xanthobacter sp. strain Py2 cells can degrade trichloroethylene (TCE), but the transformation capacity of such cells was limited and depended on both the TCE concentration and the biomass concentration. Toxic metabolites presumably accumulated extracellularly, because the fermentation of glucose by yeast cells was inhibited by TCE degradation products formed by strain Py2. The affinity of the propene monooxygenase for TCE was low, and this allowed strain Py2 to grow on propene in the presence of TCE. During batch growth with propene and TCE, the TCE was not degraded before most of the propene had been consumed. Continuous degradation of TCE in a chemostat culture of strain Py2 growing with propene was observed with TCE concentrations up to 206 microns in the growth medium without washout of the fermentor occurring. At this TCE concentration the specific degradation rate was 1.5 nmol/min/mg of biomass. The total amount of TCE that could be degraded during simultaneous growth on propene depended on the TCE concentration and ranged from 0.03 to 0.34g of TCE per g of biomass. The biomass yield on propene was not affected by the cometabolic degradation of TCE.

Alkenes↗
PubMedDate not supplied

Coping and living well with diabetes and nephropathy.

Coping and living with diabetes and nephropathy is not easy. The illness may affect quality of life and can influence the person physically, psychologically and socially. Once on dialysis unfortunately, quality of life is influenced even more. In addition, health professionals demand a great deal of self-discipline in the care and management of the person's illness. To support the person with these demands it is important to provide good education, treatment and care with the aid of the multi-disciplinary team-approach involving a nephrologist/diabetologist, nurse-educator, dietician, exercise specialist and a social worker/counsellor. With a treatment plan in each discipline and regular aftercare appointments it is hoped that the person will be able to master his illness.

Adaptation, Psychological↗