We are examining the long-term effects of bacterial infection on host cell characters. We observed a dose-dependent increase in the efficiency of ExoS54-Cre-mediated recombination, which peaked around 30% at a MOI of 50 for R26R-EYFP mESC. The subsequent decline in recombination is clearly not due to insufficient protein delivery, but more likely (+)-JQ1 distributor resultant of excess protein translocation or bacterial cytotoxicity. Deletion of the P. aeruginosa type III secreted exotoxins resulted in a considerable decrease in cytotoxicity, as compared to that of wild-type PAK-J strain, which allowed cells to remain viable and undergo gene expression changes after infection. However, P. aeruginosa possesses additional virulence factors that contribute to cytotoxicity. Efforts are currently underway to further reduce the toxicity of this strain in an attempt to enhance cell viability and the efficacy of protein delivery. In addition to reduction of cytotoxicity, we are also in the process of engineering a strain which is more sensitive to antibiotics. Currently, gentamicin and ciprofloxacin are used to eradicate any residual bacteria after infection. While bacterial survival assays have indicated that these conditions are sufficient to destroy lingering intracellular and extracellular bacteria, it will be more convenient to infect with a strain that is sensitive to antibiotics commonly used in cell culture, such as penicillin and streptomycin. Alternatively, an auxotrophic mutant can also be utilized in which specific nutrient withdrawal will result in inhibition of the bacterial growth. These studies serve as a foundation for the bacterial delivery of transcription factors to efficiently modulate concentration-dependent and temporal activation of gene expression to direct cell fate switch without jeopardizing genomic integrity which is critical for future clinical translation. The ability of few exogenous transcription factors to completely redirect endogenous gene expression is epitomized by the discovery of nuclear reprogramming. Induction of pluripotency, while almost exclusively achieved by transgene expression, has been documented to occur with recombinant protein transduction as well, albeit at extremely low efficiency . Having demonstrated the ability to deliver large quantities of nuclear targeting protein directly into eukaryotic cells, efforts are currently underway to harness the power of the type III secretion system to deliver nuclear reprogramming factors to efficiently induce pluripotency and lineage specific differentiation. Antimicrobial peptides, an innate immune component ubiquitous among plants and animals, are variously active against a wide range of pathogens, such as gram-positive bacteria, gramnegative bacteria, fungi and protozoa. They are therefore proposed as one of the most likely substitutes for common antibiotics, to confront an increasingly serious threat to human health caused by antibiotic-resistant bacterial infection.