Thermophilic Bacteria have the Toxin-Antitoxin System too: Type II Toxin-Antitoxin System Composites in Geobacillus

The toxin-antitoxin (TA) systems play a significant role in regulating stress responses in prokaryotes and they also have a biotechnological potential. Thus, they have been attracting research attention. While considerable recognition has been given to type II TA system of mesophiles, thermophiles have received limited attention. Here, we are presenting the putative type II TA families encoded on the genomes of four thermophilic strains belonging to the Geobacillus genus. We employed the TA finder tool to mine for TA-coding genes and manually curated the results using protein domain analysis tools. We also used the NCBI BLAST, Operon Mapper, ProOpDB, and sequence alignment tools to reveal the geobacilli TA features. We identified 28 putative TA pairs, distributed over eight TA families. Among the identified TAs, 15 represent putative novel toxins and antitoxins, belonging to the MazEF, MNT-HEPN, ParDE, RelBE, and XRE-COG2856 TA families. We also identified a potentially new TA composite, AbrB-ParE. Furthermore, we are proposing a Geobacillus acetyltransferase TA (GacTA) family, which potentially represents one of the unique TA families with a reverse gene order. This study aims for highlighting the significance of studying TAs in thermophiles, in general, and in Geobacillus, in particular, and facilitating future experimental research.