@article{mbs:/content/journal/micro/10.1099/00221287-148-11-3405, author = "Warner, Jessica B. and Lolkema, Juke S.", title = "Growth of Bacillus subtilis on citrate and isocitrate is supported by the Mg2+–citrate transporter CitM", journal= "Microbiology", year = "2002", volume = "148", number = "11", pages = "3405-3412", doi = "https://doi.org/10.1099/00221287-148-11-3405", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-148-11-3405", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", keywords = "promoter fusion", keywords = "exchange", keywords = "TCA, tricarboxylic acid", keywords = "membrane vesicles", keywords = "TCA cycle intermediate", keywords = "FCCP, carbonylcyanide p-trifluormethoxy-phenylhydrazone", keywords = "divalent metal ion–citrate complex", keywords = "RSO, right-side-out", keywords = "MSMYE, minimal salts medium/0·05% yeast extract", abstract = " Bacillus subtilis 168 was assayed for its growth on tricarboxylic acid (TCA) cycle intermediates and related compounds as the sole carbon sources. Growth of the organism was supported by citrate, D-isocitrate, succinate, fumarate and L-malate, whereas no growth was observed in the presence of cis-aconitate,2-oxoglutarate, D-malate, oxaloacetate and tricarballylate. Growth of the organism on the tricarboxylates citrate and D-isocitrate required the presence of functional CitM, an Mg2+–citrate transporter, whereas its growth on succinate, fumarate and L-malate appeared to be CitM-independent. Interestingly, the naturally occurring enantiomer D-isocitrate was favoured over L-isocitrate by the organism. Like citrate, D-isocitrate was shown to be an inducer of citM expression in B. subtilis. The addition of 1 mM Mg2+ to the growth medium improved growth of the organism on both citrate and D-isocitrate, suggesting that D-isocitrate was taken up by CitM in complex with divalent metal ions. Subsequently, the ability of CitM to transport D-isocitrate was demonstrated by competition experiments and by heterologous exchange in right-side-out membrane vesicles prepared from E. coli cells expressing citM. None of the other TCA cycle intermediates and related compounds tested were recognized by CitM. Uptake experiments using radioactive 63Ni2+ provided direct evidence that D-isocitrate is transported in complex with divalent metal ions.", }