**Abbreviations of substances**

*The Universe of Escherichia coli*

O2 generation.

with strong binding affinities.

**Acknowledgements**

**Conflict of interest**

**Abbreviations**

*A*<sup>F</sup> PDI activity (in μM<sup>−</sup><sup>1</sup>

*B*<sup>0</sup> initial amount of bacteria CFU colony formation unit *C*<sup>W</sup> water solubility

*ε* molar absorption coefficient LB Luria-Bertani medium

PDI photodynamic inactivation RPy *N*-alkylpyridinium group

*t* irradiation time

*m* number of ethylene glycol unit

*n* carbon number of the alkyl chain on the Ap [*P*] minimum effective concentrations of sensitizer

*Z* valence number of the porphyrin complex

*T*1/2 half-life time required to reduce *B* from *B*0 to 0.5*B*<sup>0</sup>

*B* mount of bacteria

Miyazaki.

**5. Conclusion**

via <sup>1</sup>

sensitizers passed through the cell wall may reach biogenic proteins, lipids,

these molecules to induce cell death. Although E-type porphyrins generate <sup>1</sup>

close as possible to the target molecules. The P type porphyrins with amphiphilic characters, which can be incorporated inside *E. coli*, will be advantageous to PDI

PDI of *E. coli* K-12 (IFO 3301) was examined using 19 kinds of cationic porphyrin sensitizers. In conclusion, (1) *E. coli* has high drug-resistance toward the hydrophobic and monocationic porphyrins such as Type E. (2) However, *E. coli* has low drug-resistance toward polycationic porphyrins such as Type P. (3) Especially, *E. coli* has low drug-resistance toward polycationic porphyrins with moderately long alkyl chain, for example, (HeptPy3)2P(Tpp)3+ and (EtPy5)2P(Tpp)3+. Alkyl chains might result in moderate hydrophobicity to take advantage of interaction between hydrophobic parts of cell membranes. (4) Polycationic porphyrins can interact with the anionic outer membrane at the first step and DNA and proteins inside the cells

We thank Mr. Tomohiko Shinbara, Mr. Hiroki Kanemaru, Mr. Yusaku Suemoto,

Miyamoto, and Hidekazu Uezono for their efforts on PDI of *E. coli* at University of

h<sup>−</sup><sup>1</sup>

): *A*F = 60/([*P*] × T1/2)

Mr. Kyosuke Takemori, Mr. Masato Shigehara, Mr. Kou Suzuki, Ms. Akari

The authors declare that they have no competing interests.

O2 was generated near to

O2 should be generated as

O2 in aqueous medium

O2

and DNA. Under irradiation, reactive oxygen such as <sup>1</sup>

is very short (~3 μs) [40]. Thus, for efficient PDI, <sup>1</sup>

efficiently under visible light irradiation, the lifetime of <sup>1</sup>

**132**

