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Genome-Wide Analysis of the Response of Brucella melitensis NI to Polymyxin B
Zhen Wang1, Jiawei Wang1, Jie Cheng1
1Beijing Key Laboratory of Traditional Chinese Veterinary Medicine, Animal Science and Technology College, Beijing University of Agriculture, Beijing 102206, China.
Background:
The ability of pathogenic bacteria to survive Antimicrobial Peptides (AMPs) in various host niches may contribute to their virulence. Polymyxin B is a cationic AMP, and polymyxin drugs are considered to be the "last line of defense" in the clinical treatment of bacterial infections.
Objective:
The objectives of this study were to comprehensively study the response of Brucella melitensis strain NI to polymyxin B treatment and to identify the target genes in Brucella induced by polymyxin B stimulation.
Methods:
Following treatment with polymyxin B, differentially expressed genes in Brucella were detected using RNA-seq and validated using qRT-PCR.
Results:
In total, 874 differentially expressed genes were identified, including 560 up-regulated and 314 down-regulated genes. Functional annotation and KEGG pathway analysis revealed that many of these genes are involved in metabolism, two-component systems, transcriptional regulation, transport/ membrane proteins, and virulence factors. Expression of genes involved in T4SS and flagellar biosynthesis and assembly, which are important virulence factors in Brucella, were up-regulated by polymyxin B treatment.
Discussion:
Additionally, genes encoding the ABC transporters YejABEF and the cold-shock protein CspA were also up-regulated. These genes confer resistance to AMPs and contribute to the virulence of Brucella. The NIΔsufC, NIΔsufD, NIΔompW, NIΔexbB, NIΔtetR, and NIΔcspA mutants were also more sensitive than B. melitensis NI to polymyxin B.
Conclusion:
The results of this study provide important insights into the comprehensive response of Brucella in response to polymyxin B stimulation.
Insights
Brucella melitensis up-regulates genes for resistance and virulence when exposed to Polymyxin B, a last-resort antibiotic. This response is crucial for bacterial survival and infection.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Antimicrobial Resistance
Background:
- Pathogenic bacteria survival of Antimicrobial Peptides (AMPs) contributes to virulence.
- Polymyxin B is a critical last-line defense antibiotic against bacterial infections.
Purpose of the Study:
- To investigate the response of Brucella melitensis strain NI to Polymyxin B.
- To identify genes in Brucella induced by Polymyxin B.
Main Methods:
- Differential gene expression analysis using RNA-sequencing (RNA-seq).
- Validation of gene expression using quantitative reverse transcription PCR (qRT-PCR).
Main Results:
- Identified 874 differentially expressed genes (560 up-regulated, 314 down-regulated).
- Key genes involved in metabolism, two-component systems, transport, and virulence factors were affected.
- Up-regulation of Type IV Secretion System (T4SS) and flagellar genes, crucial virulence factors.
Conclusions:
- Polymyxin B treatment up-regulates genes conferring AMP resistance and virulence, including ABC transporters and CspA.
- Mutants lacking specific genes (e.g., sufC, ompW, cspA) showed increased sensitivity to Polymyxin B.
- The study provides insights into Brucella's comprehensive response to Polymyxin B.
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