# Identification of Antimicrobial Peptides from Nibribacter radioresistens, a UV and Gamma Radiation Tolerant Bacterium

## TL;DR

This paper identifies antimicrobial peptides from a radiation-tolerant bacterium and shows they can kill both Gram-negative and Gram-positive bacteria.

## Contribution

The study is the first to identify and characterize AMPs from Nibribacter radioresistens.

## Key findings

- The genome of N. radioresistens contains 11 AMP gene candidates (NB_AMP1 to NB_AMP11).
- Synthetic NB_AMP2 showed strong antibacterial activity against E. coli and S. aureus.
- Most cloned AMPs, except NB_AMP5 and NB_AMP7, exhibited antibacterial activity in E. coli.

## Abstract

Background: Nibribacter radioresistens, a UV and gamma radiation-tolerant bacterium, was reported to have superior antibacterial activities against a variety of pathogenic bacteria through the production of antimicrobial peptides (AMPs), but nothing is known about its AMPs. Methods/Results: In this study, our genomic and transcriptomic data showed that the N. radioresistens genome contains 11 AMP gene candidates, designated as NB_AMP1 to NB_AMP11, which are expressed differently in logarithmic growth and stationary phase. Moreover, the cell-free supernatant of all Escherichia coli DH5α strains containing cloned AMPs except for NB_AMP5 and NB_AMP7 exhibited antibacterial activities against both Gram-negative and Gram-positive bacteria such as E. coli and Staphylococcus aureus. Synthetic AMPs supported the antibacterial activities of cloned AMPs, and, in particular, the synthetic NB_AMP2 showed superior antibacterial activities against both E. coli and S. aureus. Conclusions: Altogether, these results suggest that the AMP candidates from N. radioresistens may function as antimicrobial peptides, effectively causing cellular lysis through pore formation in the bacterial membrane.