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K Watson

Publications and source records attributed to K Watson.

At least 19 recordsLinked to original sources
PubMed2026

Genomic characterisation of Enterococcus cecorum isolated from broiler chickens in the United Kingdom.

Enterococcus cecorum is an important poultry pathogen associated with lameness and increased mortality, leading to major welfare and economic impacts. Treatment is often challenging because disease is frequently detected late and the organism can localise in bone and joints, limiting antimicrobial efficacy. Presence of antimicrobial resistance (AMR) genes may further complicate treatment. Despite increasing global genomic research, only one recent study has investigated the phylogeny of E. cecorum from conventional UK broiler farms, using limited samples and a restricted time frame. In this study, 283 E. cecorum isolates were analysed, including 158 from the United Kingdom and 125 global non‑UK isolates. UK isolates comprised 123 archived by the Animal and Plant Health Agency (APHA) between 2003 and 2022, predominantly from clinical outbreaks with increased welfare culling and mortality, and 35 isolates from a UK study including clinical and environmental samples. Genome sequencing was used to assess phylogeny, AMR determinants and virulence factors (VFs). Single nucleotide polymorphism phylogenetic analysis identified eight major UK lineages with limited intra‑lineage diversity, indicating that UK isolates were genetically distinct from non‑UK populations. Using a 60‑SNP threshold, APHA isolates formed 18 subclusters, consistent with long‑term persistence and recurrent farm transmission, while multiple subclusters detected on some farms suggested repeated introductions. UK isolates carried fewer AMR genes than non‑UK isolates, with erm(B), lnu(C), tet(M) and tet(L) most prevalent. Screening of VF genes identified nine genes present in all isolates, with the remainder variably distributed. A subset of 60 UK isolates was examined for 13 previously described virulence‑associated genes, with phylogenetic clustering indicating associations between gene presence or absence and clinical status or mortality classification. The capsular polysaccharide gene cpsO was assessed in this subset and most non‑clinical or environmental isolates were cpsO‑negative, although several isolates from high‑mortality outbreaks also lacked this gene. Overall, this study provides insight into the phylogeny, AMR profiles and virulence gene diversity of E. cecorum within the UK broiler sector, supporting targeted surveillance and investigation of pathogenic mechanisms.

Antimicrobial resistance↗
PubMed1992

Relationships between thermotolerance, oxidative stress responses and induction of stress proteins in human tumour cell lines.

Thermotolerance, resistance to oxidative stress and induction of stress proteins were examined in a panel of 10 human tumour cell lines. An inverse relationship was indicated between intrinsic thermotolerance (cell survival after treatment at 43.5 degrees for 3 hr) and thermotolerance induced by pretreatment at 42.5 degrees for 30 min. Similar levels of induction of hsp 70 were found in cell lines with high or low levels of intrinsic thermotolerance; induction of other stress proteins could not be detected. Cell survival following treatment with H2O2 correlated with that following streptonigrin treatment (P < 0.05). Pretreatment with buthionine sulphoximine or diamide synergistically increased the toxicity of heat, H2O2 and streptonigrin whereas reduced glutathione had the reverse effect. No direct correlation was found, however, between tolerance to heat and to oxidative stress, and hsp 70 was not induced by the latter. The stress protein heme oxygenase, detected by immunoblotting with the monoclonal antibody HO, was induced by H2O2 in melanoma cell lines but not in HeLa. Cadmium and arsenite ions, however, readily induced heme oxygenase in HeLa, indicating that in these cells induction of heme oxygenase by oxidative stress involves a different mechanism. Overall, the results suggest that tolerance to heat or oxidative stress in these cell lines may not necessarily be associated with the induction of heat shock proteins or heme oxygenase but that cell survival after both types of stress depends to a certain extent on cellular sulphydryls.

Adaptation, Physiological↗
PubMed1991

The involvement of transcriptional read-through from internal promoters in the expression of a novel endoglucanase gene FSendA, from Fibrobacter succinogenes AR1.

Two distinct mRNA transcripts were synthesized in Escherichia coli during expression of FSendA, an endoglucanase gene from Fibrobacter succinogenes AR1. Expression of FSendA required a ribosomal frameshift between open reading frame 1 (ORF1) and ORF2 to allow contiguous translation of a 453 amino acid protein (1). The primary transcript initiated upstream of ORF1 and the secondary transcript from within ORF1. Both transcripts terminated downstream of ORF2 and termination was essential for endoglucanase expression. Deletion of the primary transcript promoter region allowed read-through of the secondary transcript beyond the terminator region, indicating that a component of the intact FSendA gene allowed efficient transcription termination. The possibility of autogenous regulation by translation products is suggested.

Amino Acid Sequence↗
PubMed1991

Molecular cloning, expression, and characterization of endoglucanase genes from Fibrobacter succinogenes AR1.

A cosmid gene library was constructed in Escherichia coli from genomic DNA isolated from the ruminal anaerobe Fibrobacter succinogenes AR1. Clones were screened on carboxymethyl cellulose, and 8 colonies that produced large clearing zones and 25 colonies that produced small clearing zones were identified. Southern blot hybridization revealed the existence of at least three separate genes encoding cellulase activity. pRC093, which is representative of cosmid clones that produce large clearing zones, was subcloned in pGem-1, and the resulting hybrid pRCEH directed synthesis of endoglucanase activity localized on a 2.1-kb EcoRI-HindIII insert. Activity was expressed from this fragment when it was cloned in both orientations in pGem-1 and pGem-2, indicating that F. succinogenes promoters functioned successfully in E. coli. A high level of endoglucanase activity was detected on acid-swollen cellulose, ball-milled cellulose, and carboxymethyl cellulose; and a moderate level was detected on filter paper, Avicel, lichenan, and xylan. Most activity (80%) was localized in the periplasm of E. coli, with low but significant levels (16%) being detected in the extracellular medium. The periplasmic endoglucanase had an estimated molecular weight of 46,500, had an optimum temperature of 39 degrees C, and exhibited activity over a broad pH range, with a maximum at pH 5.0.

Bacteroides↗
PubMed1991

endAFS, a novel family E endoglucanase gene from Fibrobacter succinogenes AR1.

The complete nucleotide sequence of endAFS, an endoglucanase gene isolated from the ruminal anaerobe Fibrobacter succinogenes AR1, was determined. endAFS encodes two overlapping open reading frames (ORF1 and ORF2), and it was proposed that a -1 ribosomal frameshift was required to allow contiguous synthesis of a 453-amino-acid endoglucanase. A proline- and threonine-rich region at the C terminus of ORF1 and rare codons for arginine and threonine were coincident with the proposed frameshift site. ENDAFS is proposed to be a member of subgroup 1 of family E endoglucanases, of which endoglucanases from Thermomonospora fusca and Persea americana (avocado) are also members. Endoglucanases from Clostridium thermocellum and Pseudomonas fluorescens form subgroup 2.

Amino Acid Sequence↗
PubMed1991

Primary pancreatic tuberculosis.

A 71-year-old man developed weight loss, nausea, and night sweats. A PPD skin test was positive; chest films were normal. Abdominal computerized tomography revealed a mass in the head of the pancreas. Laparotomy revealed a 3 cm by 5 cm multi-loculated abscess cavity. Cultures grew Mycobacterium tuberculum. The diagnostic criteria for abdominal tuberculosis include skin test positivity, localized disease, and culture verification. This is the first reported case that fulfills diagnostic criteria for primary pancreatic tuberculosis.

Aged↗
PubMed1990

Microbial stress proteins.

There is general agreement that a function, perhaps the major function, of stress proteins under normal physiological conditions is to help assembly and disassembly of protein complexes and to catalyse protein-translocation processes. It remains unclear, however, as to what role these processes play in stressed cells. It could be that cells under stress produce abnormal, misfolded or otherwise damaged proteins and that increased synthesis of stress proteins is required to counter protein modifications. A role for stress proteins in recovery of cells from stress, as opposed to a role in helping cells to withstand a lethal stress, is thus suggested. The intracellular location of stress proteins, in the unstressed and stressed cell, is worthy of further studies. Members of the hsp70 family are associated with the cytosol, mitochondria and endoplasmic reticulum. There is evidence, particularly from studies on mammalian cells (Tanguay, 1985; Welch and Mizzen, 1988; Arrigo et al., 1988), that following stress hsps migrate to various cellular compartments and subsequently delocalize after stress. However, there is little comparable data from microbial systems for this phenomenon (e.g. Rossi and Lindquist, 1989). The question as to the role of stress proteins in the transient acquisition of thermotolerance remains to be answered. It is insufficient to equate the kinetics of stress-protein synthesis with acquisition of thermotolerance. Quantitative data on the amount of stress protein present at various times, including the recovery period, is required. The demonstration that microbial stress proteins are important antigenic determinants of micro-organisms causing major debilitating diseases in the world is an exciting observation. Studies on the interplay of pathogen and host, both carrying similar antigenic hsp determinants, will be a challenging area for future research. It is likely that E. coli and Sacch. cerevisiae, with their well-established biochemical and genetic properties, will continue to be the experimental systems of choice for studies on stress proteins. On the other hand, it is encouraging that studies on other micro-organisms have expanded in the past few years and have made substantial contributions towards our understanding of the stress response. The ubiquitous nature of the stress response and the remarkable evolutionary conservation of the stress proteins continue to be attractive areas for research.

Bacterial Proteins↗