The observation that A. salmonicida contains the spf gene (which encodes Spot 42), but lacks the galK operon (the natural Spot 42 target in E. coli), have inspired scientists to study the role of Spot 42 in this fish pathogen. A. salmonicida is unable to utilize galactose (lacks gal operon) in minimal medium and addition of galactose has little effect on the growth rate.
The observation that A. salmonicida possesses the spf gene (which encodes Spot 42) but lacks the galK operon (the natural target of Spot 42 in E. coli) has sparked scientific interest in understanding the role of Spot 42 in this fish pathogen. Furthermore, A. salmonicida's inability to utilize galactose and its minimal response to galactose supplementation highlight important aspects of its metabolic capabilities.