SECRETION OF AN ANTIBACTERIAL FACTOR DURING RESUSCITATION OF DORMANT CELLS IN MICROCOCCUS-LUTEUS CULTURES HELD IN AN EXTENDED STATIONARY-PHASE

A high proportion of Micrococcus luteus cells in cultures starved for 3-6 months in spent medium following growth to stationary phase in bat ch culture lost the ability to grow and form colonies on agar plates, but could be resuscitated from dormancy by incubation in liquid medium containing supernatant taken from the late log phase of viable cultur es of the same organism (Kaprelyants et al. 1994). In the present work , we found that during the first 50-70 h of such resuscitation the dor mant cells actually divide for 10-17 generations in lactate minimal me dium containing yeast extract whilst remaining nonculturableon agar pl ates. Further incubation results in a decrease in the total cell numbe r in liquid medium. The addition of viable (culturable) Micrococcus lu teus cells in concentrations of up to 10(4) ml(-1) to test tubes conta ining either resuscitating cells or supernatant from these cultures re vealed the excretion of a factor or factors which inhibited the prolif eration of otherwise viable cells. The maximum production of this fact or took place after some 96 h of incubation of starved cells in resusc itation medium. Supernatant from late logarithmic phase batch cultures of M. luteus abolished the antibacterial effect of starved cultures i ncubated in resuscitation medium. It is concluded that the stimulating effect of viable cells, and of supernatant taken from batch cultures, on the resuscitation of dormant cells might be connected in part with overcoming the activity of an antibacterial factor causing self-poiso ning of dormant cells during their resuscitation.