PMID:23377937

Citation	Sharma, VK and Bearson, BL (2013) Hha Controls Escherichia coli O157:H7 Biofilm Formation by Differential Regulation of Global Transcriptional Regulators FlhDC and CsgD. Appl. Environ. Microbiol. 79:2384-96
Abstract	Although molecular mechanisms promoting adherence of enterohemorrhagic Escherichia coli (EHEC) O157:H7 on epithelial cells are well characterized, regulatory mechanisms controlling biofilm formation are not fully understood. In this study, we demonstrate that biofilm formation in EHEC O157:H7 strain 86-24 is highly repressed compared to that in an isogenic hha mutant. The hha mutant produced large quantities of biofilm compared to the wild-type strain at 30°C and 37°C. Complementation of the hha mutant reduced the level of biofilm formation to that of the wild-type strain, indicating that Hha is a negative regulator of biofilm production. While swimming motility and expression of the flagellar gene fliC were significantly reduced, the expression of csgA (encoding curlin of curli fimbriae) and the ability to bind Congo red were significantly enhanced. The expression of both fliC and csgA and the phenotypes of motility and curli production affected by these two genes, respectively, were restored to wild-type levels in the complemented hha mutant. The csgA deletion abolished biofilm formation in the hha mutant and wild-type strain, and csgA complementation restored biofilm formation to these strains, indicating the importance of csgA and curli in biofilm formation. The regulatory effects of Hha on flagellar and curli gene expression appear to occur via the induction and repression of FlhDC and CsgD, as demonstrated by reduced flhD and increased csgD transcription in the hha mutant, respectively. In gel shift assays Hha interacted with flhDC and csgD promoters. In conclusion, Hha regulates biofilm formation in EHEC O157:H7 by differential regulation of FlhDC and CsgD, the global regulators of motility and curli production, respectively.
Links	PubMed Online version:10.1128/AEM.02998-12
Keywords
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECO57:HHA		GO:1900191: negative regulation of single-species biofilm formation	ECO:0000315:		P		Figure 2 shows when you have a hha mutant, biofilm formation increases but when you complement the mutant with hha+, biofilm formation goes down, as hha is a negative regulator of biofilm production	complete CACAO 7511
ECO57:HHA	involved_in	GO:1900191: negative regulation of single-species biofilm formation	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

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