A novel class of polymorphic toxins in Bacteroidetes

Area of Science:

• Microbiology
• Bacterial Genetics
• Molecular Biology

Background:

• Bacteroidetes are abundant Gram-negative bacteria found in diverse environments and animal gut microbiota.
• Many Bacteroidetes species possess large proteins with an N-terminal domain of unknown function, termed TANFOR.
• These TANFOR proteins are suspected to play significant roles in bacterial interactions and survival.

Purpose of the Study:

• To characterize the function and nature of TANFOR-containing proteins in Bacteroidetes.
• To identify novel toxin families within these bacterial proteins.
• To elucidate the secretion mechanism and biological relevance of TANFOR-containing proteins.

Main Methods:

• Bioinformatic analysis of bacterial protein domains and gene neighborhoods.
• Prediction of protein function based on sequence homology and structural motifs.
• Investigation of gene co-occurrence patterns with secretion system components.

Main Results:

• TANFOR-containing proteins possess polymorphic C-terminal toxin domains with predicted antibacterial and anti-eukaryotic activities.
• A novel family of antibacterial DNase toxins, named BaCT (Bacteroidetes C-terminal Toxin), was identified within TANFOR proteins.
• TANFOR-encoding gene clusters are frequently associated with genes for type IX secretion system (T9SS) substrates.

Conclusions:

• TANFOR-containing proteins represent a newly identified class of polymorphic bacterial toxins.
• The BaCT domain is a novel antibacterial toxin family found in Bacteroidetes.
• TANFOR-containing proteins are hypothesized to be substrates of the type IX secretion system (T9SS).