Poster Presentation Society for Molecular Biology and Evolution Conference 2016

Overexpression of overlapping ORFs in Escherichia coli O157:H7 reveals growth phenotype (#616)

Barbara Zehentner 1 , Richard Landstorfer 1 , Svenja Simon 2 , Daniel A. Keim 2 , Siegfried Scherer 1 , Klaus Neuhaus 1
  1. Technical University Munich, Freising, GERMANY, Germany
  2. Lehrstuhl für Datenanalyse und Visualisierung, Fachbereich Informatik und Informationswissenschaft, Universität Konstanz, Konstanz

The existence of overlapping genes is commonly accepted for viruses but not generally in other organisms. Bacterial genomes seem to contain a number of overlapping open reading frames (ORFs) which could be a coding reserve for future adaptation. Antiparallel ORFs which show transcriptional and translational signals were found in the genome of Escherichia coli O157:H7 (EHEC). However, the potential function of such ORFs remains unknown.

A high-throughput phenotyping method was developed to investigate the effect of overlapping ORFs on bacterial growth. Therefore, the candidate ORFs were cloned and simultaneously overexpressed in 20 different growth conditions. To detect phenotypes within the different growth conditions, the fraction of each clone before and after growth was analyzed using next-generation sequencing. For each overlapping ORF tested, a ‘phenotypic signature’ across all stress conditions was determined. In two biological repeats several of the tested candidates showed clear growth disadvantages or advantages. At least two candidates were found to improve growth under acidic conditions. Single competitive assays verified this phenotype. However, most overlapping ORFs do not influence the bacterial growth significantly under the conditions tested. Thus, these sequences might be useful in specific habitats only, despite their formerly detectable expression, which would corroborate the hypothesis that such genes may form a coding reserve potentially useful under stress conditions.