Strain-specific transcriptional and posttranscriptional regulation of heat-labile toxin expression by enterotoxigenic Escherichia coli

• Published in: Brazilian journal of microbiology Vol. 51; no. 2; pp. 455 - 465
• Main Authors: Rodrigues, Juliana Falcão, Lourenço, Rogério Ferreira, Maeda, Denicar Lina Nascimento Fabris, de Jesus Cintra, Mariana, Nakao, Naomi, Mathias-Santos, Camila, Luiz, Wilson Barros, de Souza Ferreira, Luís Carlos
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.06.2020; Springer Nature B.V
• Subjects: Bacterial and Fungal Pathogenesis - Research Paper; Bacterial Toxins - genetics; Biomedical and Life Sciences; Developing countries; Diarrhea; E coli; Enterotoxigenic Escherichia coli - genetics; Enterotoxins; Enterotoxins - genetics; Escherichia coli; Escherichia coli Proteins - genetics; Etiology; Food Microbiology; Gene Expression Regulation, Bacterial; Gene regulation; Heat; LDCs; Life Sciences; Medical Microbiology; Microbial Ecology; Microbial Genetics and Genomics; Microbiology; mRNA stability; Mycology; Nucleotides; Operon; Polymorphism; Polymorphism, Genetic; Post-transcription; Regulatory sequences; Temperature; Thermal stability; Toxins; Transcription, Genetic; Heat-labile toxin; Enterotoxigenic; LT-specific mRNA; Transcriptional and posttranscriptional mechanisms; Biodiversity; Enterotoxigenic Escherichia coli
• ISSN: 1517-8382; 1678-4405
• DOI: 10.1007/s42770-020-00231-2

Enterotoxigenic Escherichia coli (ETEC) represents one of the most important etiological agents of diarrhea in developing countries and characteristically produces at least one of two enterotoxins: heat-labile toxin (LT) and heat-stable toxin (ST). It has been previously shown that the production and release of LT by human-derived ETEC strains are variable. Although the natural genetic polymorphisms of regulatory sequences of LT-encoding ( eltAB ) genes may explain the variable production of LT, the knowledge of the transcriptional and posttranscriptional aspects affecting LT expression among ETEC strains is not clear. To further understand the factors affecting LT expression, we evaluated the impact of the natural polymorphism in noncoding regulatory sequences of eltAB among clinically derived ETEC strains. Sequence analyses of seven clinically derived strains and the reference strain H10407 revealed polymorphic sites at both the promoter and upstream regions of the eltAB operon. Operon fusion assays with GFP revealed that specific nucleotide changes in the Pribnow box reduce eltAB transcription. Nonetheless, the total amounts of LT produced by the tested ETEC strains did not strictly correspond to the detected LT-specific mRNA levels. Indeed, the stability of LT varied according to the tested strain, indicating the presence of posttranscriptional mechanisms affecting LT expression. Taken together, our results indicate that the production of LT is a strain-specific process and involves transcriptional and posttranscriptional mechanisms that regulate the final amount of toxin produced and released by specific strains.