Search PubMed⌕ Search

Biomedical subjects

C R Robertson

Publications and source records attributed to C R Robertson.

77 records · Page 5Linked to original sources
PubMedDate not supplied

Physiological and genetic strategies for enhanced subtilisin production by Bacillus subtilis.

Defined minimal media conditions were used to assess and subsequently enhance the production of subtilisin by genetically characterized Bacillus subtilis strains. Subtilisin production was initiated by the exhaustion or limitation of ammonium in batch and fed-batch cultures. Expression of the subtilisin gene (aprE) was monitored with a chromosomal aprE::lacZ gene fusion. The beta-galactosidase production driven by this fusion reflected subtilisin accumulation in the culture medium. Subtilisin gene expression was temporally extended in sporulation-deficient strains (spoIIG), relative to co-genic sporogenous strains, resulting in enhanced subtilisin production. Ammonium exhaustion not only triggered subtilisin production in asporogenous spoIIG mutants but also shifted carbon metabolism from acetate production to acetate uptake and resulted in the formation of multiple septa in a significant fraction of the cell population. Fed-batch culture techniques, employing the spoIIG strain, were investigated as a means to further extend subtilisin production. The constant provision of ammonium resulted in linear growth, with doubling times of 11 and 36 h in each of two independent experiments. At the lower growth rate, the responses elicited (subtilisin production, glucose metabolism, and morphological changes) during the feeding regime closely approximated the ammonium starvation response, while at the higher growth rate a partial starvation response was observed.

Bacillus subtilis↗
PubMedDate not supplied

Specificity analysis of antibodies to single-stranded micrococcal DNA in the sera of normal human subjects and patients with systemic lupus erythematosus.

To evaluate the properties of antibodies to bacterial DNA in the sera of normal human subjects (NHS) and patients with systemic lupus erythematosus (SLE), the effects of ionic strength and pH on their binding to single-stranded DNA (ssDNA) from Micrococcus lysodeikticus (MC) were measured. By ELISA, antibodies to MC ssDNA in NHS showed greater activity at high ionic strength (0.2-1.0 M) than antibodies in lupus sera. Similarly, antibodies in NHS had higher activity at pH 9 than lupus anti-DNA. Competition binding assays indicated, moreover, that NHS anti-DNA showed greater inhibition by DNA than lupus anti-DNA at comparable inhibitor concentrations. Together, these results suggest that antibodies to MC ssDNA in NHS and SLE sera may differ in their mode of interaction with bacterial DNA and that NHS can generate high avidity antibodies to at least certain DNA determinants.

Animals↗