Proffered papers 9.30–10.00 Monday 15 September 2003

Both the original Bethesda system and the current UK classifications of cervical cytology have proved robust but each has a major weakness in the area of abnormalities of uncertain significance. Cytologists recognize that sometimes it is simply impossible to differentiate between reactive and dyskaryotic material. For this reason, the Australian version of the Bethesda system introduced a new category of 'high grade inconclusive' with a recommendation for referral to colposcopy. Approximately 60% of such cases are found to have high grade lesions at colposcopy (Schoolland M, Sterrett G, Knowles S et al .). The present UK system even with the proposed changes requires of the pathologist, a decision as to whether such cases are probably high grade (=a report of moderate dyskaryosis) or not (= a report of borderline). This continues to ignore the fact that sometimes you just cannot tell, even on review. We have taken a consecutive series of 50 referral smears, reported as moderate dyskaryosis, where the histological outcome (by loop cone) is known. These cases were rescreened and then reviewed blind by a pathologist with extensive experience of the Australian NH & MRC modified Bethesda system. On review, the material was reclassified along NH & MRC lines. The results were compared with the biopsy findings in order to determine whether the category of 'inconclusive' might be of value in the context of the NHSCSP.     

The low mutational flexibility of the EPSP synthase in Bacillus subtilis is due to a higher demand for shikimate pathway intermediates

Glyphosate (GS) inhibits the 5-enolpyruvyl-shikimate-3-phosphate (EPSP) synthase that is required for aromatic amino acid, folate and quinone biosynthesis in Bacillus subtilis and Escherichia coli. The inhibition of the EPSP synthase by GS depletes the cell of these metabolites, resulting in cell death. Here, we show that like the laboratory B. subtilis strains also environmental and undomesticated isolates adapt to GS by reducing herbicide uptake. Although B. subtilis possesses a GS-insensitive EPSP synthase, the enzyme is strongly inhibited by GS in the native environment. Moreover, the B. subtilis EPSP synthase mutant was only viable in rich medium containing menaquinone, indicating that the bacteria require a catalytically efficient EPSP synthase under nutrient-poor conditions. The dependency of B. subtilis on the EPSP synthase probably limits its evolvability. In contrast, E. coli rapidly acquires GS resistance by target modification. However, the evolution of a GS-resistant EPSP synthase under non-selective growth conditions indicates that GS resistance causes fitness costs. Therefore, in both model organisms, the proper function of the EPSP synthase is critical for the cellular viability. This study also revealed that the uptake systems for folate precursors, phenylalanine and tyrosine need to be identified and characterized in B. subtilis.