Loss of salt-tolerance and transformation efficiency in Escherichia coli associated with sub-lethal injury by centrifugation

Sub-lethal injury of Escherichia coli has been detected following centrifugation at g -forces between 5 and 30 kg. The extent of injury was measured either as a reduction in colony forming ability when plated onto NaCl-containing plates (2% w/v), or as a reduction in transformation efficiency associated with plasmid pBR322 encoding ampicillin resistance. In both cases, the extent of sub-lethal injury was found to increase with increasing centrifugal force and probably reflects structural damage to the cell envelope.