CHANGES IN CELLULAR-STATES OF THE MARINE BACTERIUM DELEYA-AQUAMARINA UNDER STARVATION CONDITIONS

In this study, we have used different fluorescent dyes and techniques to characterize the heterogeneity and changes of the physiological sta tes encountered by the marine bacterium Deleya aquamarina during a 92- day starvation survival experiment at 20 and 5 degrees C. Changes of p hysiological states were investigated on a single-cell basis by flow c ytometry and epifluorescence microscopy in conjunction with fluorescen t dyes specific for various cellular functions and constituents, Heter ogeneities within populations with regard to functions (respiration, s ubstrate responsiveness, enzymatic activity, and cytoplasmic membrane permeability), constituent (DNA), and cell volume (light scatter) were compared to the evolution of viable plate counts (CFU), At 20 degrees C, CFU changes were divided into three stages corresponding to stabil ity up to day 13 followed by a rapid drop between days 13 and 32 and t hen by stabilization at a level of 10 to 20% during the remaining surv ival period, Most of the cellular fractions showing a metabolic activi ty were close to the evolution of the culturable cells, suggesting the absence of viable but nonculturable cells, On the other hand, cells w ith selective cytoplasmic membrane permeability but without any metabo lic activity were observed, and this stage was followed by DNA alterat ion occurring at different rates after the loss of membrane cytoplasmi c permeability. We observed a greater maintenance of culturability, ph ysiological functions, DNA, and cellular volume at the lower temperatu re, These results have different ecological implications from both met hodological and conceptual viewpoints.