Novel integrative elements and genomic plasticity in ocean ecosystems.

Area of Science:

• Microbiology
• Genetics
• Marine Biology

Background:

• Microbial evolution is accelerated by horizontal gene transfer.
• The marine picocyanobacterium Prochlorococcus shows high genomic plasticity, but the mechanisms are not well understood.

Purpose of the Study:

• To identify and characterize novel mobile genetic elements in Prochlorococcus.
• To understand the role of these elements in microbial evolution and adaptation.

Main Methods:

• Discovery and characterization of a new family of DNA transposons, termed tycheposons.
• Analysis of tycheposon hallmark genes, including a site-specific tyrosine recombinase.
• Investigation of tycheposon excision and integration at tRNA genes.
• Selection experiments to observe tycheposon dynamics and host adaptation.
• Detection of tycheposons in environmental samples (vesicles and phage particles).

Main Results:

• A novel family of DNA transposons, tycheposons, was identified in Prochlorococcus.
• Tycheposons possess unique mobile-lifecycle-linked genes and can carry cargo genes, such as those for nutrient acquisition.
• Tycheposons integrate at tRNA genes, driving the remodeling of genomic islands.
• Tycheposons were dynamically gained and lost in a selection experiment, promoting adaptation.
• Tycheposons are dispersed via vesicles and phage particles in seawater.
• Similar elements were found in co-occurring microbes, suggesting widespread importance.

Conclusions:

• Tycheposons are key drivers of genetic variability and adaptation in Prochlorococcus.
• Tycheposons contribute to the remodeling of bacterial genomes and the diversification of microbial communities.
• The discovery of tycheposons provides insights into microbial evolution and adaptation in oligotrophic oceans.