## 2 Results and Discussion
### Applications of TAs  
#### 2.10.1 The Potential of TAs as Antibacterial Agents--Pharmaceutical Industry  
Toxins of the TA systems constitute an attractive source of antibacterial drugs due to their bacteriostatic and bactericidal effects [5]. They could most likely be used as \"standalone\" antibacterial agents or combined with one of the conventional antibiotics to generate a synergistic antibacterial effect [5]. In either case, this will require a thorough understanding of the functionality of the toxin to make it druggable, including the interaction between the multiple copies of the same toxins, as well as understanding the interaction between the closely related antitoxins harbored by the strain [5]. As is the case with developing any novel drug, there are certain requirements that the combination of the toxin and conventional antibiotic, or the toxin to be drugged must meet (for details, the reader is referred to [5; 133]. Engineering the toxin protein might be a successful approach to enhance its antibacterial activity, eliminate its harmful effects on human cells, and increase its stability in the human serum, as was demonstrated by [PERSON] et al., 2015 [134]. Since _Geobacillus_ strains have several TA pairs, it could be of interest to investigate their potential as a source of thermostable antibacterial drug candidates.  
10.2 The Potential of _Geobacillus_ TAs as Antibacterial Agents and Antibacterial Targets--Food Industry  
Toxins of _Geobacillus_ strains could represent potential antibacterial candidates that antagonize the growth of geobacilli which cause problems in the food industry. The thermophilic _G. stearothermophilus_ is a known food-spoiling bacterium. The cells create biofilms on the stainless steel of the processing lines in dairy and food factories, and thus spoil the final product [135]. In a previous study, we demonstrated that _Geobacillus_ sp. ZGt-1 antagonized the growth of a strain of _G. stearothermophilus_ via the production of antibacterial proteins [27]. Similarly, TA system toxins of strain ZGt-1 or any other _Geobacillus_ strains could be exploited as antibacterial agents to antagonize the growth of _G. stearothermophilus_ in dairy and food factories.  
On the other hand, TA systems could be a target for toxin-activating molecules. By running a quick search for type II TA genes of _G. stearothermophilus_ DSM 458, using the TA finder tool, we found the strain harbors many TA pairs belonging to different type II TA families. As mentioned above, cells of _G. stearothermophilus_ form biofilms, and this feature could be due to the harbored TA genes (reviewed in [47]). Deletion of the strain TA genes could solve the problem of biofilm formation, as was shown for _E. coli_ (reviewed in [5]).  
Accordingly, in a factory where _G. stearothermophilus_ is causing problems, sequencing the genome of the strain and identifying the putative TA genes using bioinformatic tools, followed by identifying the functional ones experimentally, then choosing the TA to be targeted and selecting or designing one or more molecules that can activate the toxin, inactivate the antitoxin or disrupt the TA complex could be an effective approach for eliminating the strain capability of forming biofilms.  
An overview of the several potential applications of TA systems is available in [136].