Adenylates and adenylate-energy charge in submerged and planktonic cultures of Salmonella enteritidis and Salmonella typhimurium

Adenine nucleotide values and adenylate energy charge (AEC) were measured during the growth of Salmonella enteritidis and Salmonella typhimurium as submerged colonies in agarose gel and gelatin gel, and as planktonic cells in broth. Growth in all three systems showed similar trends with a ten-fold decrease in total adenylate pool during exponential growth, before attaining a fairly stable value throughout stationary phase. AEC values were generally low, (≈0.66), but did rise slightly during stationary phase. The large proportion of dead cells during early exponential phase may have contributed to the adenosine diphosphate and adenosine monophosphate pools, through cell lysis or excretion, and it is suggested that this was likely to account for the low values of AEC. In agarose and gelatin gelled cultures the percentage of adenosine triphosphate (ATP) in relation to the total adenylates showed random fluctuations. This was contrary to the broth culture where percentage ATP was highest after 12 h and the data formed a smooth curve. These data demonstrated that considerable physiological heterogeneity exists within a colony of bacteria growing in a gel matrix and by analogy a food material also, and that AEC is a poor indicator of cell viability in such systems.