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 measu red during the growth of Salmonella enteritidis and Salmonella typhimu rium as submerged colonies in agarose gel and gelatin gel, and as plan ktonic cells in broth. Growth in all three systems showed similar tren ds 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, (approximate to 0.66), but did r ise slightly during stationary phase. The large proportion of dead cel ls during early exponential phase may have contributed to the adenosin e diphosphate and adenosine monophosphate pools, through cell lysis or excretion, and it. is suggested that this was likely to account for t he low values of AEC. In agarose and gelatin gelled cultures the perce ntage of adenosine triphosphate (ATP) in relation to the total adenyla tes showed random fluctuations. This was contrary to the broth culture where percentage ATP was highest after 12 h and the data formed a smo oth curve. These data demonstrated that considerable physiological het erogeneity 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. (C) 1998 Elsevier Science B.V. All rights reserved.