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 discovery 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 prompted researchers to investigate the function of Spot 42 in this fish pathogen. A. salmonicida is unable to utilize galactose (lacks gal operon) in minimal medium, and adding galactose has a negligible impact on its growth rate.