Searching for new targets for natural transformation of E. coli

Now it is clear that my transformation does not use any competence homologue components. Others have reported another transformation mechanism (in which components of type IV secretion system are required) related to conjugation. We tried to search for these type IV secretion system homologue in E. coli K-12, but nothing was found. To our knowledge, only three form of HGT events: transformation, conjugation and transduction. The candidates for the former two forms of HGT can be excluded. The only linkage that we can refer to is transduction. First of all, we need to find porins which are conserved and required for double strand DNA phage binding or passing through the outer membrane. Then we will test their effect on our cryptic transformation.

Two candidates were screened out——tsx gene and ompA.

The reasons are as following
tsx:
1. involved with the permeation of ribo- and deoxy-nucleosides across the outer membrane of E. coli.
2. serves as a receptor for bacteriophages and colicins.
3. part of its protein has nucleotide affinity.

ompA:
1. non-specific diffusion channel
2. phage receptor
3. mediator of F-factor dependent conjugation (we have the phenotype indicating that cell density is important for transformation and this implies that cell-cell contact might be involved in transformation)
4. rpoS regulated. (rpoS is the only gene which has been identified to be required)