ON RESUSCITATION FROM THE DORMANT STATE OF MICROCOCCUS-LUTEUS

It has been found previously that a significant number of Micrococcus luteus cells starved in a prolonged stationary phase (up to 2 months) and then held on the bench at room temperature without agitation for p eriods of up to a further 3-7 months can be resuscitated in liquid med ia which contained (statistically) no initially-viable (colony-forming ) cells but which were fortified with sterile supernatant from the lat e logarithmic phase of batch growth. Here it was found that such resus citation can be done only within a defined time period after taking th e first sample from such cultures, necessarily involving agitation of the cells. The duration of this period depends on the age of the starv ed culture: cells kept on the bench for 3 months possess a 2 month per iod of resuscitability while cells starved for 6 months can be resusci tated only within 10 days after the beginning of sampling. It is sugge sted that the input of oxygen to the starved cultures while they are a gitated may exert a negative influence on the cells, since cultures st ored in anaerobic conditions (under nitrogen) had a more prolonged 'su rvival' time. The cells which experienced between 10 and 60 days of st arvation on the bench could be resuscitated, although the number of re suscitable cells depended strongly on the concentration of yeast extra ct in the resuscitation medium. This concentration for cells stored on the bench for more than 2 months was 0.05% while '1-month-old' cells displayed a maximum resuscitability in the presence of 0.01% of yeast extract. Application of the fluorescent probe propidium iodide reveale d the formation of cells with a damaged permeability barrier if resusc itation was performed by using concentrations of yeast extract of 0.1% and above. Thus the successful resuscitation of bacterial cultures un der laboratory conditions may need rather strictly defined parameters if it is to be successfully performed for the majority of cells in a p opulation.