Actinomycete-like proteasomes in a Gram-negative bacterium

Area of Science:

• Microbiology
• Molecular Biology
• Genomics

Background:

• Proteasomes are essential protein-degrading complexes previously identified only in Actinobacteria.
• Mine-drainage biofilms host diverse microbial communities adapted to extreme environments.
• Understanding prokaryotic proteasome presence offers insights into bacterial evolution and function.

Purpose of the Study:

• To investigate the presence and origin of proteasomes in acidophilic mine-drainage microbial communities.
• To explore the evolutionary relationship between proteasomes and other proteases in prokaryotes.
• To determine if proteasomes and HslVU coexist within the same prokaryotic organisms.

Main Methods:

• Cultivation-independent proteogenomic analysis of mine-drainage biofilm.
• Phylogenetic analysis to trace the origin of proteasome genes.
• Comparative genomics to assess the co-occurrence of proteasome and HslVU genes.

Main Results:

• Proteasomes were identified in Gram-negative bacteria belonging to the Nitrospirae phylum (Leptospirillum group II).
• Evidence suggests that proteasome genes were acquired by these bacteria from Actinobacteria via horizontal gene transfer.
• The study confirmed that proteasomes and the related ATP-dependent protease HslVU are not mutually exclusive in prokaryotes.

Conclusions:

• The discovery of proteasomes in Nitrospirae expands the known bacterial hosts for these complexes.
• Horizontal gene transfer is a significant mechanism for the dissemination of proteasome genes in prokaryotes.
• Prokaryotic cells can harbor both proteasomes and HslVU, indicating functional or regulatory coexistence.