Discovery of a novel antibacterial protein CB6-C to target methicillin-resistant Staphylococcus aureus

Haipeng Zhang,Jingrui Chen,Yuehua Liu,Hongxia Ma,Yu Jia,Muhammad Inam,Lingcong Kong,Qijun Xu,Xiuyun Jiang,Chengguang He

doi:10.1186/s12934-021-01726-9

Haipeng Zhang, Jingrui Chen + Show 8 more

Open Access

https://doi.org/10.1186/s12934-021-01726-9

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Abstract

Given a serious threat of multidrug-resistant bacterial pathogens to global healthcare, there is an urgent need to find effective antibacterial compounds to treat drug-resistant bacterial infections. In our previous studies, Bacillus velezensis CB6 with broad-spectrum antibacterial activity was obtained from the soil of Changbaishan, China. In this study, with methicillin-resistant Staphylococcus aureus as an indicator bacterium, an antibacterial protein was purified by ammonium sulfate precipitation, Sephadex G-75 column, QAE-Sephadex A 25 column and RP-HPLC, which demonstrated a molecular weight of 31.405 kDa by SDS-PAGE. LC–MS/MS analysis indicated that the compound was an antibacterial protein CB6-C, which had 88.5% identity with chitosanase (Csn) produced by Bacillus subtilis 168. An antibacterial protein CB6-C showed an effective antimicrobial activity against gram-positive bacteria (in particular, the MIC for MRSA was 16 μg/mL), low toxicity, thermostability, stability in different organic reagents and pH values, and an additive effect with conventionally used antibiotics. Mechanistic studies showed that an antibacterial protein CB6-C exerted anti-MRSA activity through destruction of lipoteichoic acid (LTA) on the cell wall. In addition, an antibacterial protein CB6-C was efficient in preventing MRSA infections in in vivo models. In conclusion, this protein CB6-C is a newly discovered antibacterial protein and has the potential to become an effective antibacterial agent due to its high therapeutic index, safety, nontoxicity and great stability.

Highlights

Multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) etc. are remarkable foodborne bacteria of nosocomial and community-acquired bacterial infections around the world and have been spreading at alarming rates globally [1]
In summary, we used a series of protein purification methods to identify the antimicrobial protein obtained from Bacillus velezensis CB6 as antibacterial protein CB6-C, which was shown to have the minimum inhibitory concentration (MIC) of 16 μg/ mL for MRSA
Analysis of the biological characteristics showed that antibacterial protein CB6-C had good stability and safety and demonstrated an additive effect with conventional antibiotics and metal ions such as C o2+, Ni+ and K+

Summary

Introduction

Multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) etc. are remarkable foodborne bacteria of nosocomial and community-acquired bacterial infections around the world and have been spreading at alarming rates globally [1]. Through 40% ammonium sulfate precipitation, purification and mass spectrometry identification, we had purified a protein with an antibacterial activity against MRSA. Recent study discovered that crude protein precipitated with 100% saturated ammonium sulfate leads to a better antibacterial effect against MRSA. A series of protein purification methods were used to identify the antibacterial protein as antibacterial protein CB6C, which was shown to be stable and safe against MRSA and exhibited effective antibacterial activity both in vitro and in vivo. These characteristics make the antibacterial protein CB6-C more likely to become a potential candidate as an antibacterial agent

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