Evidence for Potential Horizontal Gene Transfer Between Escherichia coli and STX1-Converting Bacteriophages: APhylogenetic and Sequence Alignment Analysis

Abstract

Horizontal Gene Transfer (HGT) plays a crucial role in the evolutionary dynamics of prokaryotes and their associated bacteriophages, facilitating the acquisition of new traits such as virulence factors. This study aimed to investigate the evolutionary relationship between Escherichia coli (E. coli) and Shiga toxin 1 (STX1)-converting bacteriophages, with a specific focus on evaluating potential HGT events between them. Phylogenetic trees were constructed to analyze their evolutionary relatedness, and sequence alignment analyses were conducted using bioinformatics tools, including BLAST (forward and reverse searches), MUSCLE, and MEGA. Phylogenetic analysis revealed that E. coli and STX1-converting bacteriophages clustered within the same clade, a result consistent with the HGT hypothesis. However, the bootstrap value of this clade was only 40%-50%, which is below the generally accepted high-confidence threshold of 80%, limiting the reliability of the conclusion. Additionally, alignment of the top 10 sequences obtained from forward and reverse BLAST searches showed sequence similarity with offsets. Given the inherent evolutionary differences between bacteria (E. coli) and viruses (STX1-converting bacteriophages), such sequence similarity cannot be explained by vertical inheritance, thus providing supplementary evidence for potential HGT. In conclusion, the data from this study suggest that HGT may exist between E. coli and STX1-converting bacteriophages, but further verification with a larger sample size and higher-resolution phylogenetic analysis is required to improve the confidence of the conclusion.