Biomedical subjects

A D Davison

Publications and source records attributed to A D Davison.

6 recordsLinked to original sources

PubMed1999

5-Chloropicolinic acid is produced by specific degradation of 4-chlorobenzoic acid by Sphingomonas paucimobilis BPSI-3.

We have previously shown that the bacterium Sphingomonas paucimobilis BPSI-3, isolated from PCB-contaminated soil, can degrade halogenated biphenyls, naphthalenes, catechols and benzoic acids. However, before such an organism can be used in bioremediation, it is important to characterise the degradation products and determine the degradation pathways to ensure that compounds more toxic or mobile than the original contaminants are not produced. In the degradation of 4-chlorobiphenyl, S. paucimobilis BPSI-3 produces a novel chlorinated picolinic acid. In this paper, we show that 4-chlorobenzoate is an intermediate in this degradation and, through (15)N-labelling, that 5-chloropicolinate is the only nitrogenous metabolite isolated under the extraction conditions used. The position of the chlorine indicates that degradation of 4-chlorocatechol occurs exclusively via a 2,3-extradiol cleavage. These data allow us to postulate a more definitive catabolic pathway for the biodegradation of 4-chlorobiphenyl to 5-chloro-2-hydroxymuconic acid semialdehyde via 4-chlorobenzoate in S. paucimobilis BPSI-3.

Journal Article↗

PubMed1999

Sphingomonas paucimobilis BPSI-3 mutant AN2 produces a red catabolite during biphenyl degradation.

The biphenyl degradation pathway of Sphingomonas paucimobilis BPSI-3 was investigated using a degradation-deficient mutant generated by 1-methyl-3-nitro-1-nitrosoguanidine (NTG) mutagenesis. The mutant, designated AN2, was confirmed as originating from BPSI-3 through the use of ERIC (Enterobacterial Repetitive Intergenic Consensus) PCR and by detection of the diagnostic pigment, nostoxanthin, in cellular methanol extracts. Mutant AN2 produced a yellow followed by red extracellular substance when grown in the presence of biphenyl. In the presence of 2,3-dihydroxybiphenyl, yellow followed by red then yellow compounds were formed over time. This colour change was consistent with the characteristics of a quinone, 1-phenyl-2,3-benzoquinone, which could arise from the oxidation of 2,3-dihydroxybiphenyl. A quinone was synthesised from 2,3-dihydroxybiphenyl and compared to the red compound produced by mutant AN2. Gas chromatography-mass spectrophotometry (GC-MS) confirmed that a similar quinone (4,5-dimethoxy-3-phenyl-1,2-benzoquinone) compared to the structure of the proposed biogenic compound, had been formed. This compound was also found after GC-MS analysis of mutant AN2 culture extracts. Spectrophotometric analysis of the quinone synthesised and the red product produced revealed almost identical spectral profiles. A likely inference from this evidence is that the mutant AN2 is blocked, or its activity altered, in the first gene cluster, bphA to C, of the biphenyl degradation pathway.

Journal Article↗

PubMed1999

Isolation of Terrabacter sp. strain DDE-1, which metabolizes 1, 1-dichloro-2,2-bis(4-chlorophenyl)ethylene when induced with biphenyl.

Terrabacter sp. strain DDE-1, able to metabolize 1,1-dichloro-2, 2-bis(4-chlorophenyl)ethylene (DDE) in pure culture when induced with biphenyl, was enriched from a 1-1-1-trichloro-2, 2-bis(4-chlorophenyl)ethane residue-contaminated agricultural soil. Gas chromatography-mass spectrometry analysis of culture extracts revealed a number of DDE catabolites, including 2-(4'-chlorophenyl)-3,3-dichloropropenoic acid, 2-(4'-chlorophenyl)-2-hydroxy acetic acid, 2-(4'-chlorophenyl) acetic acid, and 4-chlorobenzoic acid.

Bacteria, Aerobic↗

PubMed1998

Methods for microbial DNA extraction from soil for PCR amplification.

Amplification of DNA from soil is often inhibited by co-purified contaminants. A rapid, inexpensive, large-scale DNA extraction method involving minimal purification has been developed that is applicable to various soil types (1). DNA is also suitable for PCR amplification using various DNA targets. DNA was extracted from 100g of soil using direct lysis with glass beads and SDS followed by potassium acetate precipitation, polyethylene glycol precipitation, phenol extraction and isopropanol precipitation. This method was compared to other DNA extraction methods with regard to DNA purity and size.

Journal Article↗

PubMed1997

PCR amplification of crude microbial DNA extracted from soil.

A rapid, inexpensive, large-scale DNA extraction method involving minimal purification has been developed that is applicable to various soil types. DNA was extracted from 100 g of soil using direct lysis with glass beads and sodium dodecyl sulphate (SDS) followed by polyethylene glycol precipitation, potassium acetate precipitation, phenol extraction and isopropanol precipitation. The crude extract could be used in PCR directed at high-copy number (bacterial small subunit rRNA) and single-copy (fungal beta-tubulin) genes.

Base Sequence↗

PubMed1996

Halopicolinic acids, novel products arising through the degradation of chloro- and bromo-biphenyl by Sphingomonas paucimobilis BPSI-3.

Sphingomonas paucimobilis BPSI-3 was previously isolated from a mixed microbial consortium growing on biphenyl as the sole source of carbon and energy. Transformation of 4-chlorobiphenyl (4CBP) was demonstrated by this strain, although little or no growth was observed. In minimal salts medium supplemented with 4CBP or bromobiphenyl and dextrose, yellow coloured product(s) were rapidly formed. Gas chromatography-mass spectrometry (GC-MS) revealed single-ring N-heterocyclic compounds that were identified as halopicolinic acids. We believe this to be the first report of such compounds being formed via biological transformation of halobiphenyls. A mechanism is proposed for their formation.

Biodegradation, Environmental↗