Genome-wide effects on Escherichia coli transcription under climatic stress conditions

Abstract

Climate change is global, and its impacts are affecting all the Earth’s environment, where it has indirect effects such as the altering of the genome of bacteria. Effects on bacteria may involve mutations that make them better adapted to warmer and more acidic conditions, leading to changes in ecosystems. Regulation of CO2 levels is carried out by the oceans, however, if levels of CO2 continue to rise, the oceans will start to acidify, thus disrupting marine and algae life. The acidic ions can be actively taken up by bacteria cells, such as Escherichia coli found in the same environment, thus making the cytoplasm of the cell acidic. This study was carried out by primarily determining the bacterial growth curves of E. coli for 6 different conditions of varying temperature and carbon dioxide concentrations. The 3 different temperatures used were of 37°C, 32°C and 27°C, of which both atmospheric and 6% CO2 were used. E. coli was acclimated to the afore mentioned conditions through 10 generations and the obtained results were recorded. End of the exponential growth phase cells underwent RNA extraction, followed by cDNA synthesis from which qPCR could be performed to detect and quantify the target genes in the acid stress (rpoS, gadA, gadC, gadW and gabD) and heat shock (hdeA, dnaK, dnaJ, rpoH, groES and groEL) pathways. The growth curves indicated that only for the conditions of 37°C both atmospheric and 6% CO2, the 10th generation growth curves showed a shorter exponential phase when opposed to the 1st generation ones. With varying in temperature, there was a great decrease in the exponential phase of both 32°C and 27°C when compared to the control. It could be concluded that an increase in temperature will cause an increase in growth rate of the tested bacterium, however an increase in CO2 concentration will likely have little to no effect on the growth rate. Detection and quantification of the cDNA was performed through qPCR, where 9 different primers were tested on E. coli to identify any difference in genome expression. The condition for 32°C 6% CO2 showed significant difference than the other tested conditions meaning that the E. coli strain tested was adapting to the implemented conditions.