Determination of a Growth Advantage in Stationary Phase (GASP) in three strains of Arcobacter butzleri

Cultures exposed to long periods of starvation have demonstrated increased percentages of adaptive mutants that have undergone natural selection and have evolved survival mechanisms (Roszak and Colwell,1987). These survival mechanisms may allow survival in otherwise unfavourable environmental conditions that are exceed in their innate adaptations to cope with atypical condition. Mutations increasing fitness for lengthened periods of survival during nutrient deprivation are termed growth advantage in stationary phase (GASP) phenotype, which grow and displace their wild type parents (Zinser and Kolter, 2000). A phenomenon which has been described in a range of bacteria including Escherichia coli (Zinser and Kolter, 2000) and Campylobacter jejuni (Martinez-Rodriguez et al., 2004). This study demonstrates an unusual pattern of fluctuating numbers of viable cells for three strains of A. butzleri, whereby when stationary phase was reached there was a rapid loss of viability, later followed by an increase in the total number of cells (approximately 2 log). Similar findings were demonstrated in three different media (BHI, TSB and ASB). GASP phase cells have a greater tolerance to acid (pH3 for 10 min) and high temperature (75C for 30 min) treatments compared with stationary phase cells (2.031 and 2.532 compared with 1.014 and 65 cfu/ml) and exponential phase cells (2.014 and 2.362 compared with 60 and 95 cfu/ml) respectively. The net result is that an equilibrium population is established that is better adapted to longer-term survival than cells present on the entry into stationary phase, which may pose a significant fitness advantage to environmental stress agents. To our knowledge this is the first time that this phenomenon has been demonstrated in A. butzleri.