Researchers Study Thermotolerant Genes in Zymomonas mobilis

High-temperature fermentation (HTF) technology is expected to reduce the cost of bioconversion of biomass to fuels or chemicals. For stable HTF, the development of a thermotolerant microbe is indispensable. However, understanding the molecular mechanisms of thermotolerance in microbes needs to be improved. Kannikar Charoensuk from the Rajamangala University of Technology in Thailand aimed to study genes from the thermotolerant Zymomonas mobilis, an efficient ethanologenic microbe.

Thermotolerant genes essential for survival at a critical high temperature (CHT) were identified via transposon mutagenesis in Z. mobilis TISTR 548. Products of these genes were classified into nine categories, namely metabolism, membrane stabilization, transporter, DNA repair, tRNA modification, protein quality control, translation control, cell division, and transcriptional regulation.

Cells with transposon insertion in these identified genes showed a defect in growth at 39°C but grew normally at 30°C. Among those, more than 60% were found to be sensitive to ethanol at 30°C, indicating that thermotolerance partially overlaps with ethanol tolerance in the organism.

The thermotolerant genes from Escherichia coli and Acetobacter tropicalis can also be classified into 9 categories according to the classification of those of Z. mobilis. Analysis showed that there are 7 conserved thermotolerant genes that are shared by these microbes.