@article{huang_suyemoto_garner_cicconi_altier_2008, title={Formate acts as a diffusible signal to induce Salmonella invasion}, volume={190}, ISSN={["1098-5530"]}, DOI={10.1128/JB.00205-08}, abstractNote={ABSTRACT To infect an animal host, Salmonella enterica serovar Typhimurium must penetrate the intestinal epithelial barrier. This process of invasion requires a type III secretion system encoded within Salmonella pathogenicity island I (SPI1). We found that a mutant with deletions of the acetate kinase and phosphotransacetylase genes ( ackA-pta ) was deficient in invasion and SPI1 expression but that invasion gene expression was completely restored by supplying medium conditioned by growth of the wild-type strain, suggesting that a signal produced by the wild type, but not by the ackA-pta mutant, was required for invasion. This mutant also excreted 68-fold-less formate into the culture medium, and the addition of sodium formate to cultures restored both the expression of SPI1 and the invasion of cultured epithelial cells by the mutant. The effect of formate was pH dependent, requiring a pH below neutrality, and studies in mice showed that the distal ileum, the preferred site of Salmonella invasion in this species, had the appropriate formate concentration and pH to elicit invasion, while the cecum contained no detectable formate. Furthermore, we found that formate affected the major regulators of SPI1, hilA and hilD , but that the primary routes of formate metabolism played no role in its activity as a signal.}, number={12}, journal={JOURNAL OF BACTERIOLOGY}, author={Huang, Yanyan and Suyemoto, Mitsu and Garner, Cherilyn D. and Cicconi, Kellie M. and Altier, Craig}, year={2008}, month={Jun}, pages={4233–4241} }
 @article{huang_leming_suyemoto_altier_2007, title={Genome-wide screen of Salmonella genes expressed during infection in pigs, using in vivo expression technology}, volume={73}, ISSN={["1098-5336"]}, DOI={10.1128/AEM.01481-07}, abstractNote={ABSTRACT Pigs are a food-producing species that readily carry Salmonella but, in the great majority of cases, do not show clinical signs of disease. Little is known about the functions required by Salmonella to be maintained in pigs. We have devised a recombinase-based promoter-trapping strategy to identify genes with elevated expression during pig infection with Salmonella enterica serovar Typhimurium. A total of 55 clones with in vivo-induced promoters were selected from a genomic library of ∼10,000 random Salmonella DNA fragments fused to the recombinase cre , and the cloned DNA fragments were analyzed by sequencing. Thirty-one genes encoding proteins involved in bacterial adhesion and colonization (including bcfA, hscA, rffG , and yciR ), virulence ( metL ), heat shock ( hscA ), and a sensor of a two-component regulator ( hydH ) were identified. Among the 55 clones, 19 were isolated from both the tonsils and the intestine, while 23 were identified only in the intestine and 13 only in tonsils. High temperature and increased osmolarity were identified as environmental signals that induced in vivo-expressed genes, suggesting possible signals for expression.}, number={23}, journal={APPLIED AND ENVIRONMENTAL MICROBIOLOGY}, author={Huang, Yanyan and Leming, Christopher L. and Suyemoto, Mitsu and Altier, Craig}, year={2007}, month={Dec}, pages={7522–7530} }