Proline utilization system is required for infection by the pathogenic α-proteobacterium Brucella abortus

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Proline utilization (Put) systems are known in bacteria but unexplored in Brucella abortus.
• The Put system typically involves proline dehydrogenase (PutA) and its activator (PutR).

Purpose of the Study:

• To investigate the role and functionality of the Put system in Brucella abortus.
• To elucidate the genetic regulation and biochemical activity of the Put system in this pathogen.

Main Methods:

• Gene deletion studies (ΔputR) to assess bacterial survival and replication.
• Oxidative stress assays using hydrogen peroxide.
• Quantitative reverse transcription-PCR and reporter gene assays (putA-lacZ).
• Electrophoretic mobility shift assays (EMSA) to confirm protein-DNA binding.
• Biochemical analysis of purified PutA protein activity.

Main Results:

• putA and putR genes are critical for chronic Brucella abortus infection in mice.
• These genes are not essential for survival in naive macrophages.
• putR is necessary for resistance to oxidative stress (hydrogen peroxide).
• PutR directly activates putA transcription in Brucella.
• Purified PutA protein exhibits proline dehydrogenase activity, converting proline to glutamate.

Conclusions:

• The Put system plays a significant role in Brucella abortus host replication and survival.
• PutR acts as a transcriptional activator for putA in Brucella.
• The study details the genetic regulation and biochemical function of the Put system in Brucella.