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Transcriptome Changes of Escherichia coli, Enterococcus faecalis, and Escherichia coli O157:H7 Laboratory Strains in Response to Photo-Degraded DOM
Citation:
Oladeinde, A., E. Lipp, C. Chen, R. Muirhead, T. Glenn, K. Cook, AND M. Molina. Transcriptome Changes of Escherichia coli, Enterococcus faecalis, and Escherichia coli O157:H7 Laboratory Strains in Response to Photo-Degraded DOM. Frontiers in Microbiology. Frontiers, Lausanne, Switzerland, 9:882, (2018). https://doi.org/10.3389/fmicb.2018.00882
Impact/Purpose:
Survival of bacteria in the environment is dictated by their ability to grow or persist under diverse abiotic and biotic stressors. In aquatic ecosystems, resource availability, sunlight, temperature, pH, and competition have been shown to be important drivers of bacterial population dynamics (Bradford et al., 2013, 2015; Pachepsky et al., 2014). To understand the role of photo-produced ROS on the survival of specific laboratory bacterial strains, we attempted to isolate the effect of H2O2 using controlled microcosms of natural water spiked with cattle feces-derived DOM exposed to a solar simulator prior to inoculation with bacteria. Following bacterial inoculation, microcosms were incubated in the dark for up to 24 h. We employed high throughput RNA-seq and qRT-PCR to investigate the expression of transcripts required for H2O2 detoxification and oxidative stress. In addition, we used the RNA-seq data to identify Single Nucleotide Variants (SNVs) acquired following inoculation into water amended with DOM. We provide insights into the different survival mechanisms used by two important fecal indicator strains for water quality monitoring, and a zoonotic pathogen of public health interest.
Description:
In this study, we investigated gene expression changes in three bacterial strains (Escherichia coli C3000, Escherichia coli O157:H7 B6914, and Enterococcus faecalis ATCC 29212), commonly used as indicators of water quality and as control strains in clinical, food, and water microbiology laboratories. Bacterial transcriptome responses from pure cultures were monitored in microcosms containing water amended with manure-derived dissolved organic matter (DOM), previously exposed to simulated sunlight for 12 h. We used RNA sequencing (RNA-seq) and quantitative real-time reverse transcriptase (qRT-PCR) to compare differentially expressed temporal transcripts between bacteria incubated in microcosms containing sunlight irradiated and non-irradiated DOM, for up to 24 h. In addition, we used whole genome sequencing simultaneously with RNA-seq to identify single nucleotide variants (SNV) acquired in bacterial populations during incubation. These results indicate that E. coli and E. faecalis have different mechanisms for removal of reactive oxygen species (ROS) produced from irradiated DOM. They are also able to produce micromolar concentrations of H2O2 from non-irradiated DOM, that should be detrimental to other bacteria present in the environment. Notably, this study provides an assessment of the role of two conjugative plasmids carried by the E. faecalis and highlights the differences in the overall survival dynamics of environmentally-relevant bacteria in the presence of naturally-produced ROS.
URLs/Downloads:
DOI: Transcriptome Changes of Escherichia coli, Enterococcus faecalis, and Escherichia coli O157:H7 Laboratory Strains in Response to Photo-Degraded DOM
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