Biomedical subjects

Elizabeth M H Wellington

Publications and source records attributed to Elizabeth M H Wellington.

8 recordsLinked to original sources

PubMed2025

The mhqPOD gene cluster in lignin-degrading Paenibacillus sp. B2 encodes a pathway for the degradation of lignin-derived 5,5'-di(dehydrovanillic acid) (DDVA).

Lignin-degrading bacteria Paenibacillus sp. B2, Agrobacterium sp. B1, and Ochrobactrum sp. each contain mhqO genes encoding ring cleavage dioxygenase enzymes whose biochemical function is unknown. Each of these strains was found to degrade the biphenyl-containing lignin fragment 5,5'-di(dehydrovanillic acid) (DDVA) on solid media. An operon of five mhq genes in Paenibacillus sp. B2 was analysed via gene expression using quantitative PCR, and all five genes were highly induced (400-1000-fold overexpression) by the presence of DDVA. Recombinant azoreductase MhqP was found to demethylate DDVA to its monodemethylated derivative. Hence, these genes are proposed to be responsible for DDVA degradation, via a pathway involving the same biochemical steps as that studied in Sphingobium lignivorans SYK-6, but using several unrelated genes. Decarboxylation of later pathway intermediate 5-carboxyvanillic acid in Paenibacillus sp. B2 is proposed to be catalysed by decarboxylase UbiD, whose gene is also upregulated in the presence of DDVA. Degradation of the other fragment 4-carboxy-2-hydroxypentadienoic acid is proposed to occur via hydratase UxuA, whose gene is also upregulated by DDVA, and 4-hydroxy-4-methyl-2-oxoglutarate aldolase.

Paenibacillus↗

PubMed2005

PCR detection of oxytetracycline resistance genes otr(A) and otr(B) in tetracycline-resistant streptomycete isolates from diverse habitats.

A range of European habitats was screened by PCR for detection of the oxytetracycline resistance genes otr(A) and otr(B), found in the oxytetracycline-producing strain Streptomyces rimosus. Primers were developed to detect these otr genes in tetracycline-resistant (Tc(R)) streptomycete isolates from environmental samples. Samples were obtained from bulk and rhizosphere soil, manure, activated sludge and seawater. The majority of Tc(R) streptomycetes originated from bulk and rhizosphere soil. Fewer Tc(R) streptomycetes were isolated from manure and seawater and none from sewage. By PCR, three out of 217 isolates were shown to contain the otr(A) gene and 13 out of 217 the otr(B) gene. Surprisingly, these genes were detected in taxonomic groups not known as tetracycline-producing strains. The majority of the otr gene-carrying strains was assigned to S. exfoliatus or S. rochei and originated from all habitats from which Tc(R) streptomycetes were obtained. Our results indicated that the occurrence of otr(A) and otr(B) genes in natural environments was limited and that otr(B), in comparison to otr(A), seemed to be more common.

Bacterial Proteins↗

PubMed2005

Soil invertebrates disrupt carbon flow through fungal networks.

Annual carbon flux through soil respiration is ten times greater than fossil fuel combustion, but its component parts are poorly understood because they are the product of complex multitrophic interactions between soil organisms. A major component of carbon flux from plants to soil occurs through networks of symbiotic arbuscular mycorrhizal fungi. Here, using 13CO2 pulse labeling, we show that natural densities of the numerically dominant fungal feeding invertebrate Protaphorura armata (order Collembola) reduces 13C enrichment of mycorrhizosphere respiration by 32%. Our findings emphasize the importance of multitrophic interactions in regulating respiration of recent plant photosynthate from soil.

Animals↗

PubMed2005

Molecular detection of Mycobacterium bovis and Mycobacterium bovis BCG (Pasteur) in soil.

PCR primers specific for the Mycobacterium tuberculosis complex were used to detect the presence of Mycobacterium bovis BCG (Pasteur) in soil microcosms and Mycobacterium bovis in environmental samples taken from a farm in Ireland with a history of bovine tuberculosis. M. bovis genes were detected in soil at 4 and 21 months after possible contamination. Gene levels were found in the range of 1 x 10(3) to 3.6 x 10(3) gene copies g of soil(-1), depending on the sampling area. Areas around badger setts had the highest levels of detectable genes and were shown to have the highest levels of gene persistence. M. bovis-specific 16S rRNA sequences were detected, providing evidence of the presence of viable cells in Irish soils. Studies of DNA turnover in soil microcosms proved that dead cells of M. bovis BCG did not persist beyond 10 days. Further microcosm experiments revealed that M. bovis BCG survival was optimal at 37 degrees C with moist soil (-20 kPa; 30% [vol/wt]). This study provides clear evidence that M. bovis can persist in the farm environment outside of its hosts and that climatic factors influence survival rates.

Agriculture↗

PubMed2004

In situ monitoring of streptothricin production by Streptomyces rochei F20 in soil and rhizosphere.

The onset of streptothricin (ST) biosynthesis in Streptomyces rochei F20 was studied by using reverse transcription-PCR (RT-PCR) to detect transcripts of ST genes during growth in liquid medium, soil, and the rhizosphere. In situ results correlated with those obtained in vitro, illustrating the growth phase-dependent manner of ST production by F20. Maximal transcription of ST resistance (sttR) and biosynthesis (sttA) genes occurred during the transition between the exponential and stationary phases of growth, when the specific growth rate (micro) started to decline. A higher level of gene expression of sttR versus sttA was observed in all experiments. In liquid culture, maximal transcript accumulation of the sttA gene was only ca. 40% that of the sttR gene. sttA and sttR mRNAs were detected in soil containing approximately 10(6) CFU of growing cells g of soil(-1). sttR mRNA was detected in sterile and nonsterile rhizosphere colonized with growing mycelium of F20 at 1.2 x 10(6) and 4.0 x 10(5) CFU g of soil(-1), respectively. However, neither sttR nor sttA transcripts were detected by RT-PCR in the rhizoplane, which supported a lower population density of F20 than the rhizosphere.

Culture Media↗

PubMed2004

Gene cluster in Micromonospora echinospora ATCC15835 for the biosynthesis of the gentamicin C complex.

Gentamicin is a 4,6-disubstituted aminocyclitol antibiotic complex synthesised by some members of the actinomycete genus Micromonospora. In a search for the gentamicin biosynthetic gene cluster we identified, using a cosmid library approach, a region of the M. echinospora ATCC15835 chromosome that encodes homologues of aminoglycoside biosynthesis genes including gntB-a close homologue of the 2-deoxy-scyllo-inosose synthase gene (btrC) from butirosin-producing Bacillus circulans. Insertional inactivation was achieved by homologous recombination with an internal gntB fragment-containing suicide plasmid, delivered by conjugal transfer from Escherichia coli. gntB disruptants were gentamicin nonproducing mutants as assayed by an ELISA antibiotic detection system, proving the association of gntB (or a downstream region) with gentamicin biosynthesis. The function of some open reading frames within the cluster, predicted by nucleotide database homology searching, is discussed with regards to their potential roles in gentamicin biosynthesis. The discovery of this genetic region represents the first report of a gene cluster involved in the biosynthesis of a 4,6-disubstituted aminocyclitol antibiotic.

Gentamicins↗

PubMed2003

Isolation of high molecular weight DNA from soil for cloning into BAC vectors.

Isolation of high molecular weight DNA fragments from soil, in excess of 1 Mb, and of sufficient quality for cloning into an Escherichia coli-streptomycete artificial chromosome vector is described. The combination of indirect extraction of cells, using a nycodenz extraction technique, followed by lysis of biomass immobilised in agarose plugs, allowed fragments in excess of 1 Mb to be purified.

Bacteria↗

PubMed2003

Resolving functional diversity in relation to microbial community structure in soil: exploiting genomics and stable isotope probing.

The microbial ecology of soil still presents a challenge to microbiologists attempting to establish the ways in which bacteria and fungi actively metabolise substrates, link into food webs and recycle plant and animal remains and provide essential nutrients for plants. Extraction and in situ analysis of rRNA has enabled identification of active taxa, and detection of mRNA has provided an insight into the expression of key functional genes in soil. Recent advances in genomic analysis and stable isotope probing are the first steps in resolving the linkage between structure and function in microbial communities.

Bacteria↗