Mobile genetic elements of Fusobacterium nucleatum

Area of Science:

• Microbiology
• Genetics
• Oral Biology

Background:

• Fusobacterium nucleatum is a key gram-negative anaerobic bacterium in human oral flora.
• It significantly impacts oral cavity ecology, particularly in subgingival plaque, due to its adhesive properties.
• Understanding its genetic elements is crucial for developing biotechnological tools.

Purpose of the Study:

• To identify and characterize plasmids and transposons in Fusobacterium nucleatum.
• To explore their potential as tools for genetic manipulation (cloning, transformation, mutagenesis) of oral F. nucleatum isolates.

Main Methods:

• Analysis of laboratory strains for plasmids and transposons.
• Cloning of plasmid species in Escherichia coli for restriction mapping.
• Tetracycline resistance screening.
• Genomic fingerprinting for strain distinctness.

Main Results:

• A homologous family of small cryptic plasmids (6.0–6.6 kb) was identified in 18% of examined strains (n=74).
• Homologous plasmid sequences were found in two of three F. nucleatum subspecies.
• Five strains, belonging to subsp. polymorphum, showed tetracycline resistance due to a TetM determinant within a Tn916-like transposon.
• The transposon and a plasmid co-resided in one strain, with identical transposon hybridization patterns across resistant strains, despite genomic distinctness.

Conclusions:

• Fusobacterium nucleatum harbors cryptic plasmids and a Tn916-like transposon conferring tetracycline resistance.
• These genetic elements, particularly plasmids, show potential for developing genetic tools for F. nucleatum.
• Further research can leverage these findings for genetic engineering of oral bacteria.