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ROS Mediated Stress Response in Illuminated Cattle Feces Derived DOM
Citation:
Oladeinde, A., E. Lipp, C. Chen, AND M. Molina. ROS Mediated Stress Response in Illuminated Cattle Feces Derived DOM. Interscience Conference of Antimicrobial Agents and Chemotherapy, San Diego, CA, September 17 - 21, 2015.
Impact/Purpose:
Presented at ASM's Interscience Conference of Antimicrobial Agents and Chemotherapy.
Description:
Bacterial exposure to exogenous reactive oxygen species (ROS) is known to increase theexpression of oxidative stress related genes and has been linked to acquisition of antibioticresistance (AR). ROS, including hydrogen peroxide (H202), singlet oxygen e o 2), andhydroxyl radicals (OH) are known to be produced from dissolved organic matter (DOM)photolysis. In surface waters impacted by agriculture, livestock manure has beenimplicated as a major contributor of DOM from runoff producing rain events. Weperformed whole transcriptome sequencing (WTS) on a fecal indicator, E. colic3ooo and apathogenic surrogate, E. coli 0157:H7s69I4 during growth in irradiated cattle fecal extract(CFE) to compare the expression of ROS and antibiotic resistance related genes. Freshcattle feces were made into a liquid extract through a series of dilution, filtration andcentrifugation steps to eliminate all pathogens and indicators. The resulting CFE wasexposed to artificial sunlight for 12hr and then inoculated with the bacteria of interest.Bacterial growth was monitored for 72hr, and triplicate samples were collected at 0, 6, 12,24 and 48hr for WTS using the Illumina NextSeq 500 platform. The production of ROSwas monitored using a combination of ROS quenching and spectrophotometric assays.Photolysis of CFE for 12hr resulted in the production of H20 2 and 10 2. There wassignificant differential expression of genes between bacteria grown in irradiated CFE andnon-irradiated control. However, the expression of these transcripts seems to be regulateddivergently between the two bacteria. After 48hr of growth under aerobic conditions, 33%of oxyR-regulated genes were divergently expressed, including the fur gene, known for itsinterplay in iron and AR regulation, which showed a 5-fold increase in E. coli and a 7-folddecrease in E. coli 0157:H7. Among SoxRS regulated genes, 38% of the genes weredivergently expressed. These included several genes related to antibiotic resistance suchas members of the MarRAB operon, which showed an increase in expression in E. coli0157, while for E. coli, there was no detectable expression in the marR gene after 48hr.Our results support the notion that exogenous ROS production from DOM photolysisinduces oxidative and antibiotic resistance related genes in bacteria of public healthinterest.
