The Enigmatic Esx Proteins: Looking Beyond Mycobacteria

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• Bacteria utilize diverse protein secretion systems to transport molecules across cellular membranes.
• Type VII secretion systems (T7SSs) are a conserved family of protein transporters, initially identified in mycobacteria.
• Recent research has expanded the understanding of T7SSs beyond mycobacteria, revealing their presence in various bacterial lineages.

Purpose of the Study:

• To provide a comprehensive overview of non-mycobacterial Type VII secretion systems.
• To review the current knowledge on the phylogenetic distribution, structural components, and functional roles of T7SSs in diverse bacterial settings.
• To highlight recent advancements in understanding T7SS mechanisms and substrate functions.

Main Methods:

• Literature review and synthesis of existing research on Type VII secretion systems.
• Phylogenetic analysis to determine the distribution of T7SSs across bacterial phyla.
• Comparative analysis of T7SS components and mechanisms in different bacterial species.
• Functional characterization of T7SS substrates based on published studies.

Main Results:

• Type VII secretion systems are widely distributed across bacterial phyla, not limited to mycobacteria.
• Non-mycobacterial T7SSs exhibit variations in their protein components and structural organization.
• Substrates secreted by T7SSs are involved in diverse biological processes, including inter- and intra-species interactions.
• T7SSs play significant roles in the virulence and environmental adaptation of various bacteria.

Conclusions:

• Type VII secretion systems represent a critical and widespread mechanism for protein export in bacteria.
• Understanding non-mycobacterial T7SSs is essential for deciphering bacterial physiology, pathogenesis, and host-microbe interactions.
• Further research into T7SS structure and function will likely uncover novel roles and potential therapeutic targets.