Unveiling multiple copies of MlaC highlights its multifaceted nature

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Physiology

Background:

• The maintenance of lipid asymmetry (Mla) system is crucial for phospholipid transport in Gram-negative bacteria.
• In E. coli, the Mla system comprises MlaA-OmpF/C (outer membrane), MlaC (periplasm), and MlaFEDB (inner membrane) proteins.
• The presence and role of MlaA, MlaB, and MlaC in diderm bacteria beyond E. coli are not well understood.

Purpose of the Study:

• To investigate the distribution and genetic organization of Mla components, particularly MlaC, in diverse bacterial genera.
• To explore the evolutionary mechanisms shaping the mla operon.
• To understand the substrate promiscuity of MlaC within the Mla system.

Main Methods:

• Bioinformatic analysis to identify Mla components across 63 genera of Proteobacteria and related phyla.
• Comparative genomics to analyze the genetic arrangements of the mla operon.
• Phylogenetic analysis to infer evolutionary relationships and processes.

Main Results:

• Multiple copies of MlaC were identified in 63 distinct genera, confirming its widespread presence.
• The mla operon exhibits varying genetic arrangements, categorized into four distinct groups, indicating evolutionary diversification.
• The study reveals MlaC's substrate promiscuity, suggesting a broader role in lipid transport.

Conclusions:

• MlaC is a conserved and mobile component of the Mla system across a wide range of Gram-negative bacteria.
• The observed variations in mla operon organization are likely due to evolutionary processes like gene duplication, loss, and rearrangement.
• MlaC's substrate promiscuity offers new insights into the functional plasticity and evolutionary potential of the Mla system.