Chromosomal organization governs the timing of cell type-specific gene expression required for spore formation in Bacillus subtilis.

During the early stages of spore formation in Bacillus subtilis, asymmetric division precedes chromosome segregation, such that the forespore transiently contains only about one-third of the genetic material surrounding the origin of replication. Shortly after septum formation, the transcription factor sigmaF initiates forespore-specific gene expression that is essential for the proteolytic activation of pro-sigmaE in the neighbouring mother cell. Moving the sigmaF-dependent spoIIR gene from its original origin-proximal position to an ectopic origin-distal site caused a delay in spoIIR transcription, as well as delays and reductions in the proteolytic activation of pro-sigmaE and sigmaE-directed gene expression. These defects correlated with the accumulation of disporic sporangia, thus reducing sporulation efficiency in a manner that depended upon the distance that spoIIR had been moved from the origin-proximal third of the chromosome. A significant proportion of disporic sporangia exhibited sigmaE activity in their central compartment, indicating that delays and reductions in sigmaE activation can lead to the formation of a second septum at the opposite pole. These observations support a model in which chromosomal spoIIR position temporally regulates sigmaE activation, thereby allowing for the rapid establishment of mother cell-specific gene expression that is essential for efficient spore formation. The implications of these findings for cell type-specific gene expression during the early stages of spore formation in B. subtilis are discussed.

Detection of cell-surface antigens of bovine ocular squamous cell carcinoma.

A serologic study was conducted to identify surface antigens on cultured cells of bovine ocular squamous cell carcinoma. Sera from cattle with various stages of disease were tested for reactivity with surface antigens of cultured autologous and allogeneic cells. Radioiodine-labeled protein A assays were conducted to determine the presence of antibodies for tumor cells. It was found that all sera tested had antibodies at a high level to autologous cells, whereas the reactivity of allogeneic serum to cultured cells varied. Furthermore surface reactivity was not observed in these sera in tests for reactivity with normal epithelial cells. Reactive sera were analyzed by absorption tests with autologous and allogeneic cells. Absorbed sera showed no reactivity to surface antigens on autologous or allogeneic cells. Also, results of quantitative absorption studies indicated that absorption with precarcinoma cells eliminated the reactivity of sera from carcinoma- (cancer-) bearing animals toward cultured tumor cells. This indicates that there might be a shared antigen among the cells from precarcinoma and carcinoma lesions.

Cryopreservation of bovine mononuclear leukocytes.

A technique of cryopreservation of bovine mononuclear leukocytes for use in lymphocyte stimulation tests and cell identification studies has been developed. Dimethyl sulfoxide was used as the cryopreservation agent. Cells were frozen to --40 C at a controlled rate of --1 C/minute and then to --80 C at a rate of --4 C/minute, and were subsequently stored in liquid nitrogen (--109 C). The cells were than recovered by rapid thawing in a 37-C water bath, diluted with tissue culture media, washed, and used for lymphocyte stimulation and cell identification tests. The magnitude of the lymphocyte blastogenic responses of frozen and thawed mononuclear leukocytes was similar to that seen with freshly collected cells. Additionally, percentages of T cells, B cells, and monocytes were similar between frozen and thawed cells and freshly collected cells.