Working little by little: the note taking habits of the historian François Louis Ganshof

The Belgian mediaevalist François Louis Ganshof (1895–1980) was in the habit of approaching his research topics with the help of large numbers of small slips of paper. The present examination explores his note taking practice in detail, and from different angles. The aim is to show, within the limits of a case study, how strongly material, methods, practice, and concepts were intertwined, and how different tradi- tions and customs were interwoven in Ganshof’s everyday work. The examination of this complex state of affairs can help broaden our perspective on how historical knowledge is produced and suggests that this production must itself be seen as the result of contingent, historical constellations.  The Belgian mediaevalist François Louis Ganshof (1895–1980) was in the habit of approaching his research topics with the help of large numbers of small slips of paper. The present examination explores his note taking practice in detail, and from different angles. The aim is to show, within the limits of a case study, how strongly material, methods, practice, and concepts were intertwined, and how different tradi- tions and customs were interwoven in Ganshof’s everyday work. The examination of this complex state of affairs can help broaden our perspective on how historical knowledge is produced and suggests that this production must itself be seen as the result of contingent, historical constellations

Chromosomal Gene Inactivation in the Green Sulfur Bacterium Chlorobium tepidum by Natural Transformation

Conditions for inactivating chromosomal genes of Chlorobium tepidum by natural transformation and homologous recombination were established. As a model, mutants unable to perform nitrogen fixation were constructed by interrupting nifD with various antibiotic resistance markers. Growth of wild-type C. tepidum at 40°C on agar plates could be completely inhibited by 100 μg of gentamicin ml(−1), 2 μg of erythromycin ml(−1), 30 μg of chloramphenicol ml(−1), or 1 μg of tetracycline ml(−1) or a combination of 300 μg of streptomycin ml(−1) and 150 μg of spectinomycin ml(−1). Transformation was performed by spotting cells and DNA on an agar plate for 10 to 20 h. Transformation frequencies on the order of 10(−7) were observed with gentamicin and erythromycin markers, and transformation frequencies on the order of 10(−3) were observed with a streptomycin-spectinomycin marker. The frequency of spontaneous mutants resistant to gentamicin, erythromycin, or spectinomycin-streptomycin was undetectable or significantly lower than the transformation frequency. Transformation with the gentamicin marker was observed when the transforming DNA contained 1 or 3 kb of total homologous flanking sequence but not when the transforming DNA contained only 0.3 kb of homologous sequence. Linearized plasmids transformed at least an order of magnitude better than circular plasmids. This work forms a foundation for the systematic targeted inactivation of genes in C. tepidum, whose 2.15-Mb genome has recently been completely sequenced

Microbial Thiocyanate Utilization under Highly Alkaline Conditions

Three kinds of alkaliphilic bacteria able to utilize thiocyanate (CNS(−)) at pH 10 were found in highly alkaline soda lake sediments and soda soils. The first group included obligate heterotrophs that utilized thiocyanate as a nitrogen source while growing at pH 10 with acetate as carbon and energy sources. Most of the heterotrophic strains were able to oxidize sulfide and thiosulfate to tetrathionate. The second group included obligately autotrophic sulfur-oxidizing alkaliphiles which utilized thiocyanate nitrogen during growth with thiosulfate as the energy source. Genetic analysis demonstrated that both the heterotrophic and autotrophic alkaliphiles that utilized thiocyanate as a nitrogen source were related to the previously described sulfur-oxidizing alkaliphiles belonging to the gamma subdivision of the division Proteobacteria (the Halomonas group for the heterotrophs and the genus Thioalkalivibrio for autotrophs). The third group included obligately autotrophic sulfur-oxidizing alkaliphilic bacteria able to utilize thiocyanate as a sole source of energy. These bacteria could be enriched on mineral medium with thiocyanate at pH 10. Growth with thiocyanate was usually much slower than growth with thiosulfate, although the biomass yield on thiocyanate was higher. Of the four strains isolated, the three vibrio-shaped strains were genetically closely related to the previously described sulfur-oxidizing alkaliphiles belonging to the genus Thioalkalivibrio. The rod-shaped isolate differed from the other isolates by its ability to accumulate large amounts of elemental sulfur inside its cells and by its ability to oxidize carbon disulfide. Despite its low DNA homology with and substantial phenotypic differences from the vibrio-shaped strains, this isolate also belonged to the genus Thioalkalivibrio according to a phylogenetic analysis. The heterotrophic and autotrophic alkaliphiles that grew with thiocyanate as an N source possessed a relatively high level of cyanase activity which converted cyanate (CNO(−)) to ammonia and CO(2). On the other hand, cyanase activity either was absent or was present at very low levels in the autotrophic strains grown on thiocyanate as the sole energy and N source. As a result, large amounts of cyanate were found to accumulate in the media during utilization of thiocyanate at pH 10 in batch and thiocyanate-limited continuous cultures. This is a first direct proof of a “cyanate pathway” in pure cultures of thiocyanate-degrading bacteria. Since it is relatively stable under alkaline conditions, cyanate is likely to play a role as an N buffer that keeps the alkaliphilic bacteria safe from inhibition by free ammonia, which otherwise would reach toxic levels during dissimilatory degradation of thiocyanate

Proposal of Histophilus somni gen. nov., sp nov for the three species incertae sedis 'Haemophilus somnus', 'Haemophilus agni' and 'Histophilus ovis'

Earlier investigations have shown that 'Haemophilus somnus', 'Haemophilus agni' and 'Histophilus ovis' represent the same species. In the present investigation, the taxonomic position of this species is explored further by sequencing the 16S rRNA and rpoB genes of strains that were investigated previously by DNA-DNA hybridization. These results clearly support the allocation of this species to a novel genus within the family PASTEURELLACEAE: The phenotypic separation of Histophilus somni gen. nov., sp. nov. from other members of the family can, for most strains, be based on capnophilia, yellowish pigmentation and indole production. However, due to phenotypic variation, the use of a species-specific PCR test based on the 16S rRNA gene is included in the species description. This is justified by the high sequence similarity of the 16S rRNA gene within the species and the fact that the highest sequence similarity to any other taxon within the family is 93.4 %. The type strain, 8025(T)=ATCC 43625(T)=CCUG 36157(T), was isolated in the USA from a bovine brain with lesions of thromboembolic meningoencephalitis