Search PubMed⌕ Search

Biomedical subjects

R B Webb

Publications and source records attributed to R B Webb.

At least 55 records · Page 3Linked to original sources
PubMed1972

High-intensity vapor lamp for biological research.

A vapor arc light source has been adapted to the study of the lethal action on bacteria of near-ultraviolet (UV) and visible light. Its use makes possible much shorter exposure times than could be obtained from previously available sources. The output of radiant energy is sufficient to provide a fairly detailed action spectrum for lethality in the long-UV and visible region without the addition of exogenous sensitizers. Populations of cells of Escherichia coli WP2 were inactivated through five log(10) cycles with light at 460 nm. Significant inactivation also was obtained with light at 550 and 650 nm.

Bacteria↗
PubMed1972

Toxicity of irradiated medium for repair-deficient strains of Escherichia coli.

Nutrient agar medium is made highly toxic to certain repair-deficient strains of Escherichia coli by exposure of the uninoculated plates to radiation from cool-white fluorescent lamps or black-light fluorescent lamps. This sensitivity is associated with the genetic deficiencies, fil, phr, and recA. Repair-sufficient and uvr strains are only slightly affected by the irradiated media. The poor growth and reduced plating efficiency frequently associated with BPhr and recA strains are very likely caused by inadvertent exposure of the medium to fluorescent light.

Agar↗
PubMed1968

Electronically controlled continuous culture device.

A photocell-controlled continuous culture device, a Nephelostat, is described that maintains a wide variety of cultures of microorganisms in balanced growth. This Nephelostat controls concentrations of bacteria within +/-3% over a cell concentration range of 10(6) to 10(9) cells per ml. Growth rates are recorded so that changes in the growth rate are observed over small increments of time. Spontaneous and caffeine-induced mutation rates of two strains of Escherichia coli were compared under Nephelostat and chemostat conditions.

Automation↗
PubMed1967

Mutagenesis in Escherichia coli by visible light.

Mutation to resistance to bacteriophage T5 in continuous cultures of Escherichia coli was induced by visible light (wavelength longer than 408 nanometers) and by black light (300 to 400 nanometers). Mutation rates more than 18 times greater than the spontaneous rate (no light) were obtained with moderate, nonlethal intensities of visible light. Mutation rates for both visible and black light were proportional to irradiance.

Coliphages↗