Journal of Microbiology

Research Support, U.S. Gov't, Non-P.H.S.

Phenotypic Diversity of Escherichia coli O157:H7 Strains Associated with the Plasmid O157: Ji Youn Lim , Joon Bae Hong , Haiqing Sheng , Smriti Shringi , Rajinder Kaul , Thomas E. Besser , Carolyn J. Hovde; J. Microbiol. 2010;48(3):347-357. Published online June 23, 2010; DOI: https://doi.org/10.1007/s12275-010-9228-4

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Abstract: Escherichia coli O157:H7, a food-borne pathogen, causes hemorrhagic colitis and the hemolytic-uremic syndrome. A putative virulence factor of E. coli O157:H7 is a 60-MDa plasmid (pO157) found in 99% of all clinical isolates and many bovine-derived strains. The well characterized E. coli O157:H7 Sakai strain (Sakai) and its pO157-cured derivative (Sakai-Cu) were compared for phenotypic differences. Sakai-Cu had enhanced survival in synthetic gastric fluid, did not colonize cattle as well as wild-type Sakai, and had unchanged growth rates and tolerance to salt and heat. These results are consistent with our previous findings with another E. coli O157:H7 disease outbreak isolate ATCC 43894 and its pO157-cured (43894-Cu). However, despite the essentially sequence identical pO157 in these strains, Sakai-Cu had changes in antibiotic susceptibility and motility that did not occur in the 43894-Cu strain. This unexpected result was systematically analyzed using phenotypic microarrays testing 1,920 conditions with Sakai, 43894, and the plasmid-cured mutants. The influence of the pO157 differed between strains on a wide number of growth/survival conditions. Relative expression of genes related to acid resistance (gadA, gadX, and rpoS) and flagella production (fliC and flhD) were tested using quantitative real-time PCR and gadA and rpoS expression differed between Sakai-Cu and 43894-Cu. The strain-specific differences in phenotype that resulted from the loss of essentially DNA-sequence identical pO157 were likely due to the chromosomal genetic diversity between strains. The O157:H7 serotype diversity was further highlighted by phenotypic microarray comparisons of the two outbreak strains with a genotype 6 bovine E. coli O157:H7 isolate, rarely associated with human disease.

Reversible function of RapA with the C-terminus of RapC in Dictyostelium: Dongju Kim , Wonbum Kim , Taeck Joong Jeon; J. Microbiol. 2021;59(9):853-848.; DOI: https://doi.org/10.1007/s12275-021-1400-5

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Rap small GTPases are involved in diverse signaling pathways associated with cell growth, proliferation, and cell migration. There are three Rap proteins in Dictyostelium, RapA, RapB, and RapC. RapA is a key regulator in the control of cell adhesion and migration. Recently RapA and RapC have been reported to have opposite functions in the regulation of cellular processes. In this study, we demonstrate that the C-terminus of RapC, which is not found in RapA, is essential for the opposite functions of RapC and is able to reverse the functions of RapA when fused to the tail of RapA. Cells lacking RapC displayed several defective phenotypes, including spread morphology, strong adhesion, and decreased cell migration compared to wild-type cells. These phenotypes were rescued by full-length RapC, but not by RapC missing the C-terminus. Furthermore, recombinant RapA fused with the C-terminus of RapC completely recovered the phenotypes of rapC null cells, indicating that the functions of RapA were modified to become similar to those of RapC by the C-terminus of RapC with respect to cell morphology, cell adhesion and migration, cytokinesis, and development. These results suggest that the C-terminal residues of RapC are able to suppress and change the functions of other Ras proteins in Ras oncogenic signaling pathways.

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RapB Regulates Cell Adhesion and Migration in Dictyostelium, Similar to RapA
Uri Han, Nara Han, Byeonggyu Park, Taeck Joong Jeon
Journal of Microbiology.2024; 62(8): 627. CrossRef
Adhesion of Dictyostelium Amoebae to Surfaces: A Brief History of Attachments
Lucija Mijanović, Igor Weber
Frontiers in Cell and Developmental Biology.2022;[Epub] CrossRef

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