Further Elucidation of Galactose Utilization in MG1363.

Since the 1970s, galactose metabolism in has been in debate. Different studies led to diverse outcomes making it difficult to conclude whether galactose uptake was PEP- or ATP- dependent and decide what the exact connection was between galactose and lactose uptake and metabolism. It was shown that some strains possess two galactose-specific systems - a permease and a PTS, even if they lack the lactose utilization plasmid, proving that a lactose-independent PTS exists. However, the PTS transporter was never identified. Here, with the help of transcriptome analyses and genetic knock-out mutants, we reveal the identities of two low-affinity galactose PTSs. A novel plant-niche-related PTS component Llmg_0963 forming a hybrid transporter Llmg_0963PtcBA and a glucose/mannose-specific PTS are shown to be involved in galactose transport in MG1363.