Submitted to: American Society for Microbiology Branch Meeting
Publication Type: Abstract Only
Publication Acceptance Date: September 24, 2005
Publication Date: September 24, 2005
Citation: Winter, K., Houghton, J.O., Bearson, B.L. 2005. Characterization of genes involved in norepinephrine-enhanced growth of salmonella enterica serovar typhimurium. American Society for Microbiology Branch Meeting. p. 66. Technical Abstract: The iron-binding protein transferrin sequesters iron in serum as part of the mammalian innate immune system and prevents bacterial growth. The catecholamine norepinephrine (NE) enhances growth of Escherichia coli and Salmonella enterica serovar Typhimurium in a nutritionally-poor medium (SAPI) containing 30% serum. In E. coli the catecholate siderophore enterobactin is required for norepinephrine-enhanced growth in SAPI-serum medium. However, in S. Typhimurium enterobactin is converted into salmochelin by glucosylation. S. Typhimurium strains with mutations in iron utilization genes were analyzed to determine if norepinephrine enhances growth of S. Typhimurium by providing iron via salmochelin. Growth rates of wild-type and mutant strains were determined in SAPI-serum in the presence or absence of norepinephrine, and with or without 10% medium preconditioned by growth of the wild-type. The salmochelin precursor enterobactin is required for norepinephrine-enhanced growth since entA mutants did not grow in SAPI-serum medium containing norepinephrine. The iroCDE mutant, deficient in salmochelin uptake and degradation but proficient in salmochelin synthesis, does not grow in SAPI-serum medium containing norepinephrine, suggesting that salmochelin uptake and/or breakdown is required. Growth of the iroCDE mutant was restored with addition of 10% norepinephrine-preconditioned medium to SAPI-serum indicating that a salmochelin breakdown product from wild-type cultures enhances growth. A model is proposed in which norepinephrine provides iron to salmochelin. Salmochelin with bound iron is subsequently metabolized and the resulting salmochelin breakdown products can also provide iron to the cell for growth.