Development and population structure of mixed (S + M) Pseudomonas aeruginosa cultures in the late stationary growth phase

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Population growth, the ratio between dissociants, pH, and levels of reducing sugars in the medium were monitored during prolonged (375 h) batch cultivation of Pseudomonas aeruginosa S and M dissociants on mineral medium with glucose. During the stationary growth phase (100–375 h), two scenarios were possible. The first one included extensive cell autolysis coupled to alkalinization of the medium and an increased ratio of the M dissociant. In the second case, acidification of the medium was coupled to the oscillating secondary growth, mostly of the M dissociant; the dynamics of cell numbers of this dissociant correlated with the dynamics of the culture optical density. In this scenario, periodical appearance of reducing sugars in the medium was detected; it was in the opposite phase with the changes of the M dissociant cell numbers. The differences between scenarios of P. aeruginosa growth in the late stationary phase were probably due to the physiological and biochemical characteristics of the S and M dissociants, including different pathways of glucose utilization (respiration or fermentation), resistance to acidification, as well as synthetic (proteolytic) activity and productivity of autoinducers.

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