Paralogization and New Protein Architectures in Planctomycetes Bacteria with Complex Cell Structures
Mayank Mahajan1, Benjamin Yee1, Emil Hägglund1
1Molecular Evolution, Department of Cell and Molecular Biology, Science for Life Laboratory, Biomedical Centre, Uppsala University, Uppsala, Sweden.
Molecular Biology and Evolution
|December 7, 2019
Summary
Planctomycetes bacteria possess complex cell structures resembling eukaryotes. Genomic analysis reveals novel protein families and convergent evolution, blurring the lines between prokaryotes and eukaryotes.
Area of Science:
- Microbiology
- Evolutionary Biology
- Genomics
Background:
- Planctomycetes bacteria exhibit unique cellular complexity, including intracellular membranes, reminiscent of eukaryotic cells.
- The evolutionary origins of these complex bacterial cell architectures remain a subject of debate.
- Understanding the genomics of Planctomycetes can shed light on the evolution of cellular complexity.
Purpose of the Study:
- To investigate the evolutionary genomics of bacteria with complex cell architectures, specifically within the Planctomycetes phylum.
- To analyze the genomes of Gemmata obscuriglobus, G. massiliana Soil9, CJuql4, and Tuwongella immobilis to understand gene flux and protein evolution.
- To compare protein domain composition and length in Planctomycetes with other prokaryotes and eukaryotes.
Main Methods:
- Whole-genome sequencing of four Planctomycetes species: Gemmata obscuriglobus, G. massiliana Soil9, CJuql4, and Tuwongella immobilis.
- Gene flux analysis to identify the emergence of novel protein families within the Gemmataceae family.
- Comparative analysis of protein domain architecture, length, and distribution profiles between Planctomycetes and other prokaryotic and eukaryotic organisms.
Main Results:
- Massive emergence of novel protein families was observed in the Gemmataceae family.
- Expanded protein families contain unique multidomain architectures, combining prokaryotic and eukaryotic-associated domains.
- Proteins in Gemmataceae are longer with longer linkers, suggesting ancestral presence in Planctomycetales.
- Significant overlap exists between the longest prokaryotic proteins and shortest eukaryotic proteins.
Conclusions:
- The similarities between Planctomycetes and eukaryotes are attributed to convergent evolution, not direct ancestry.
- Genomic and protein analyses challenge a strict boundary between prokaryotes and eukaryotes regarding gene paralogy, protein length, and domain composition.
- Planctomycetes provide a model for studying the evolution of complex cellular features and the continuum between prokaryotic and eukaryotic life.
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