Influence of qseC and sdiA gene in biofilm formation by atypical enteropathogenic Escherichia coli

Author(s)

Hebert Fabricio Culler

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2015-01-20

Examining board members

Marcelo Palma Sircili; Marcelo Brocchi; Viviane Nakano; Bruna Leite; Monica Aparecida Midolli Vieira

• Advisor: Marcelo Palma Sircili

Abstract

Atypical enteropathogenic Escherichia coli are capable to form biofilm on biotic and abiotic surfaces. Several E. coli mechanisms are regulated by Quorum Sensing, including expression of virulence factors and biofilm formation. Quorum Sensing is a signaling system that confers bacteria the ability to respond to chemical molecules known as autoinducers. SdiA and QseC are Quorum Sensing receptors found in several bacteria, including aEPEC. SdiA detects type 1 autoinducer molecules (AI-1) known as N-acil homoserin lactones. However, Escherichia coli do not produce this kind of molecules and SdiA detects AHLs produced by other bacteria. QseC receptor detects type 3 autoinducer molecules and the human hormones adrenalin and noradrenaline. In this study the influence of the sdiA and qseC deletion in the biofilm formation and architecture, pellicle and ring-like structure formation and transcription of some genes (bcsA, csgA, csgD, fliC, fimA and rpoS) in two strains of aEPEC (O55:H7 and ONT:H25) was verified. The results of the analysis of the two aEPEC strains were distinct, confirming the heterogeneity reported by other studies in the same patotypes. The strain ONT:H25?sdiA formed a thick biofilm in 96-well plates and thick ring-like structure on the tube wall compared with the wild type and complemented strains. Furthermore, the sdiA mutant strain was capable to form pellicle on both surfaces, while the wild type and complemented strains were negative. The strain O55:H7?sdiA did not show a significant difference on the formation of these structures compared to the wild type and complemented strains. qRT-PCR analysis demonstrated an enhance on the transcription of csgA, csgD and fimA in the deleted sdiA ONT:H25 strain, suggesting that a relative increase of biofilm formation in ONT:H25 strain could be related to the increase of the expression of type 1 and curli fimbriae. The addition of AHLs to the wild type strain ONT:H25 decreased the biofilm formation and the transcriptional levels of csgD and fimA, but not in the mutant strain, indicating that sdiA plays a role in the regulation of biofilm formation in aEPEC. AHLs also increased the repressor efects of this receptor in biofilm related genes. The mutant qseC strains showed a decrease in biofilm formation when compared to wild type and complemented strains, but there was no difference in the pellicle formation in the air-liquid interface, as in the ring-like structure formation in the tube wall. The ONT:H25?qseC strain was negative to curli fimbriae expression in congo red plates and displayed an increase in the transcription of bcsA and fimA genes, while a decrease was verified in the csgA, csgD and fliC genes compared to the wild type strain. The addition of adrenalin increased the biofilm formation and motility in both mutant strains, possibly indicating the presence of other receptor in aEPEC involved in the detection of these hormones in the absence of QseC. In conclusion, these two Quorum Sensing receptors are related with biofilm formation in aEPEC (AU)

• FAPESP's process: 10/13782-9 - QseC and SdiA involvment in atypical EPEC biofilm formation.
• Grantee: Hebert Fabricio Culler
• Support Opportunities: Scholarships in Brazil - Doctorate