The TA System Gene HipBA In Escherichia Coli Affects Biofilm Formation And DNA Release

The majority of bacteria live in surface-associated communities called biofilms while singular, free floating organisms are comparatively uncommon. Microorganisms attach via appendages such as fimbriae and flagella, accumulating until microcolonies are formed, further stimulated by the production of the microbial matrix containing polysaccharides, glycoproteins, and DNA. This multicellular behavior is crucial for effective host colonization, since80%of human bacterial chronic inflammatory and infectious diseases involve biofilms. Biofilm formation is also disadvantageous for industrial fermentation due to several problems. Biofilm production-deficient E. coli strain as a host for biotechnological applications has been developed.The E. coli Toxin-antitoxin systems are known as a role in biofilm formation. Within TA systems, one gene encodes stable toxin protein while another gene encodes unstable anti-toxin protein. Rescent studies have reported that cell death and lysis have an important role in the process of biofilm formation. But the known function of TA system in biofilm formation is limited and debated. Kim et al reported that TA system genes could affect the production of fimbriae by regulating the expression of YjgK, the fimbriae has a key role in both biofilm attachment and dispersal. Meanwhile, Kolodkin-Gal et al found that TA system affected bacterial cell death differently during biofilm formation. In addition, the TA system is a key resistance factor. So the relationship between the cell lysis and biofilm formation is still unknown.In our research, we used hip gene to research the relationship between TA system and biofilm formation. Initially, we obtained and constructed the hip mutants JW1500and BWH2to find some differences of biofilm development between the BW25113wide type and hip mutants. To our best knowledge, this is the first report shows hip mutants had significant decrease biofilm without antibiotic supplement. In static conditions and flow chamber, hip mutants had a notable decrease on biofilm formation and structure. DNA is widely considered as an important structural component in bacterial biofilm. Our work extracted extracellular DNA from E. coli biofilm. Additionally, the amount of extracellular DNA in BW25113and its hip mutant were different. Furthermore, treatment of the BW25113biofilm with DNase I caused a reduction in biofilm formation, whereas similar treatment of the hip mutants biofilm had only a minor effect. These results, together with eDNA presence within biofilms of BW25113and HipBA mutants, demonstrate that HipBA plays a significant role during biofilm development and that eDNA is an important structural component of E. coli BW25113biofilms. So we summarized that HipBA can influence E. coli biofilm formation and the TA system can affect biofilm formation by reducing the amount of eDNA present in the biofilm. Measurement of β-Galactosidase activity in culture supernatants showed that there were more cell lysis in BW25113wide type than hip mutant. Therefore, we hypothesize that HipA can influence the DNA release by mediating the cell lysis. Finally, it is the first report hipA can significantly decrease biofilm formation without antibiotic supplement. Meanwhile, we provide a novel mechanism that TA system may affect biofilm formation by reducing the amount of eDNA present in the biofilm.