Distribution, Function and Regulation of Type 6 Secretion Systems of Xanthomonadales

Area of Science:

• Bacteriology
• Microbial Pathogenesis
• Genomics

Background:

• Xanthomonadales bacteria, including Xanthomonas spp., are significant agricultural plant pathogens.
• Type 6 secretion systems (T6SSs) are sophisticated nanomachines employed by bacteria for inter-bacterial and host interactions.
• The T6SS in Xanthomonas citri is known to confer resistance to amoeba predation, highlighting its anti-eukaryotic role.

Purpose of the Study:

• To investigate the distribution and phylogenetic classification of T6SSs within the Xanthomonadales order.
• To identify potential T6SS effectors in Xanthomonadales species through in silico analysis.
• To explore the functional diversity of T6SSs, including both anti-prokaryotic and anti-eukaryotic activities.

Main Methods:

• In silico analysis of 35 Xanthomonadales genomes.
• Phylogenetic classification of identified T6SSs.
• Prediction of putative T6SS effector proteins based on known toxic domains.

Main Results:

• T6SSs are widely distributed across the Xanthomonadales order.
• Phylogenetic analysis revealed three major groups of T6SSs.
• In silico predictions identified numerous putative effectors, suggesting diverse anti-prokaryotic and anti-eukaryotic functions.

Conclusions:

• T6SSs are a common feature in Xanthomonadales, contributing to their ecological roles.
• The identified putative effectors suggest a broad functional repertoire for T6SSs in this order.
• Xanthomonadales T6SSs likely play roles in both bacterial competition and host interactions, with functions varying by phylogenetic group and species.