ABSTRACT
If rapid growth (rap) mutants of Escherichia coli could be obtained, these might prove a valuable contribution to fields as diverse as growth rate control, biotechnology and the regulation of the bacterial cell cycle. To obtain rap mutants, a dnaQ mutator strain was grown for four and a half days continuously in batch culture. At the end of the selection period, there was no significant change in growth rate. The result means that selecting rap mutants may require an alternative strategy and a number of such alternatives are discussed.
Subject(s)
Cell Division/genetics , Escherichia coli/genetics , Mutation/genetics , Bacteriological Techniques , Cell Cycle/genetics , DNA Replication/genetics , Gene Expression Regulation, Bacterial/physiology , Selection, GeneticABSTRACT
A colorimetric assay utilising Neutral Red (C.I. 50040), a nuclear stain, was developed to determine the cellular viability of hybridoma cells in microtitre plates. A linear correlation (r = 0.99) was found to exist between the uptake of Neutral Red by viable cells and the viable cell count determined by Trypan blue exclusion test. The linearity stretched over the range of cell concentrations normal in batch cultures (2-30 x 10(4)/0.2 ml) with as little as +/- 6% intra-plate well-to-well variation and +/- 10.2% inter-assay variation. Microscopical examinations of viable hybridoma cells stained with Neutral Red showed that it was located in the nucleus. The possible bifunctional activity of the Neutral Red assay as a test for cellular viability and estimating the DNA content of hybridoma cells is discussed along with its application in a drug screening programme.