A very poorly transformable mutation at the threonine deaminase locus in Bacillu subtilis

Summary An isoleucine requiring mutant of Bacillus subtilis which displays some novel properties has been studied. The strain lacks threonine deaminase activity and is also more sensitive than the wild type to the action of mitomycin C without being more sensitive to UV light. The two features (isoleucine requirement and mitomycin sensitivity) are transferred simultaneously in transformation. The isoleucine marker of this strain is situated at the right end in the map of the threonine deaminase locus. It is at present the nearest known marker to the terminus of the B. subtilis chromosome. Relative transformation frequency for this marker is very low suggesting a low integration efficiency. This is true for both alleles (wild type and mutant) of the marker. SP 10 transduction frequency is almost nil whereas PBS-1 transduction is as effective as for any other marker in that region. Any treatment which causes breakage of the strands in wild type DNA (dilution, shearing, deoxyribonuclease I action) brings about a very important decrease in the relative frequency of transformation for this marker. The marker is more sensitive to these treatments than the weak linkage of two very distant markers. Results agree with the hypothesis that the mutation in this strain corresponds to a deletion in the terminal region of the chromosome. The deletion (suggested also by the absence of reversion) should nevertheless be very long, probably exceeding the average length of a transforming DNA segment. However, an alternative hypothesis has been considered and discussed.     

DNA synthesis by Escherichia coli B/r/l synchronized and grown under conditions of slow growth

Escherichia coli B/r/l was synchronized by a novel method and its growth was followed in a minimal salts medium containing glucose, acetate, aspartate or succinate as the sole carbon source. Thymine incorporation experiments showed agreement with the Cooper-Helmstetter model for DNA synthesis, during the division cycle, both in glucose grown culture with a doubling time 57.5 min and in acetate, aspartate and succinate where the doubling time was extended up to 90 min. The ratio C/C+D was identical or close to that predicted by the model. Prolonged growth of the synchronized cultures prior to each experiment was practised in order to ensure their physiological state without causing any considerable deterioration of synchrony.     

Studies on the Heat Resistance of Bacteria, with Particular Reference to the Genus Microbacterium: I. A New Technique using Solid Media

Summary: The new technique depends upon spreading bacterial cells over the surface of an agar medium in a Petri dish. The cells are heated, cooled, grown and counted in situ . The plates are preheated on the surface of a water bath and held for the required time on the surface of a second bath at the desired temperature. They are cooled by cold water jetted on to the base. The experimental control of factors affecting the accuracy of the method are discussed and applications suggested.     

Raman spectroscopy of blood and urine liquid biopsies for ovarian cancer diagnosis: identification of chemotherapy effects

Blood plasma and serum Raman spectroscopy for ovarian cancer diagnosis has been applied in pilot studies, with promising results. Herein, a comparative analysis of these biofluids, with a novel assessment of urine, was conducted by Raman spectroscopy application in a large patient cohort. Spectra were obtained through samples measurements from 116 ovarian cancer patients and 307 controls. Principal component analysis identified significant spectral differences between cancers without previous treatment (n = 71) and following neo-adjuvant chemotherapy (NACT), (n = 45). Application of five classification algorithms achieved up to 73% sensitivity for plasma, high specificities and accuracies for both blood biofluids, and lower performance for urine. A drop in sensitivities for the NACT group in plasma and serum, with an opposite trend in urine, suggest that Raman spectroscopy could identify chemotherapy-related changes. This study confirms that biofluids' Raman spectroscopy can contribute in ovarian cancer's diagnostic work-up and demonstrates its potential in monitoring treatment response.