A 4.6 KB DNA REGION OF RHIZOBIUM-MELILOTI INVOLVED IN DETERMINING UREASE AND HYDROGENASE ACTIVITIES CARRIES THE STRUCTURAL GENES FOR UREASE (UREA, UREB, UREC) INTERRUPTED BY OTHER OPEN READING FRAMES

Miksch G, Arnold W, LENTZSCH P, PRIEFER UB, Pühler A. A 4.6 KB DNA REGION OF RHIZOBIUM-MELILOTI INVOLVED IN DETERMINING UREASE AND HYDROGENASE ACTIVITIES CARRIES THE STRUCTURAL GENES FOR UREASE (UREA, UREB, UREC) INTERRUPTED BY OTHER OPEN READING FRAMES. MOLECULAR & GENERAL GENETICS. 1994;242(5):539-550.A 4.6 kb DNA region of the Rhizobium meliloti strain AK631 was found to contain seven open reading frames (ORFs), all oriented in the same direction. The putative gene products of four of these ORFs were highly homologous to UreA, UreB and UreC of Klebsiella aerogenes, Proteus mirabilis, Proteus vulgaris and Canavalia ensiformis. The overall organisation of the DNA region analysed was ORF1, ureA (ORF 2), ORF3, ureB (ORF4), ORF5, ORF6 and ureC (ORF7), indicating that the organisation of the urease structural genes in R. meliloti differs from that of other urease genes so far characterized. ORF1 was incomplete; only the 3' end of the coding region was present. The six complete ORFs coded for polypeptides of 11.1 (UreA), 8.9 (ORF3), 10.8 (UreB), 15.0 (ORF5), 13.8 (ORF6) and 60.7 kDa (UreC). No sequence homology to known polypeptides could be detected for the gene products of ORF1, ORF3, ORF5 and ORF6. Using a lacZ fusion and insertional mutagenesis it was shown that the seven ORFs identified were all located in the same transcription unit. For mutational analysis a resistance gene cassette was introduced into each of the complete ORFs resulting in apolar mutations. Mutations in ureA, ureB and ureC, but not in ORF3, ORF5 and ORF6, abolished urease activity in R. meliloti. The determination of hydrogen uptake in these R. meliloti mutants revealed that only ORF6 and ureB are necessary for hydrogen uptake

A psychometric appraisal of the DREEM

<p>Abstract</p> <p>Background</p> <p>The quality of the Educational environment is a key determinant of a student centred curriculum. Evaluation of the educational environment is an important component of programme appraisal. In order to conduct such evaluation use of a comprehensive, valid and reliable instrument is essential. One of most widely used contemporary tools for evaluation of the learning environment is the Dundee Ready Education Environment Measure (DREEM). Apart from the initial psychometric evaluation of the DREEM, few published studies report its psychometric properties in detail. The aim of this study was to examine the psychometric quality of the DREEM measure in the context of medical education in Ireland and to explore the construct validity of the device.</p> <p>Methods</p> <p>239 final year medical students were asked to complete the DREEM inventory. Anonymised responses were entered into a database. Data analysis was performed using PASW 18 and confirmatory factor analysis performed.</p> <p>Results</p> <p>Whilst the total DREEM score had an acceptable level of internal consistency (alpha 0.89), subscale analysis shows that two subscales had sub-optimal internal consistency. Multiple group confirmatory factor analysis (using Fleming's indices) shows an overall fit of 0.76, representing a weak but acceptable level of fit. 17 of the 50 items manifest fit indices less than 0.70. We sought the best fitting oblique solution to the 5-subscale structure, which showed large correlations, suggesting that the independence of the separate scales is open to question.</p> <p>Conclusions</p> <p>There has perhaps been an inadequate focus on establishing and maintaining the psychometric credentials of the DREEM. The present study highlights two concerns. Firstly, the internal consistency of the 5 scales is quite variable and, in our sample, appears rather low. Secondly, the construct validity is not well supported. We suggest that users of the DREEM will provide basic psychometric appraisal of the device in future published reports.</p