Niche-directed evolution modulates genome architecture in freshwater Planctomycetes

Area of Science:

• Microbiology
• Evolutionary Biology
• Genomics

Background:

• Freshwater bacteria are diverse but poorly represented in culture collections and genomic databases.
• Understanding the evolutionary ecology of dominant freshwater bacterial groups, such as Planctomycetes, is challenging due to cultivation difficulties.

Purpose of the Study:

• To investigate the evolutionary history of freshwater Planctomycetes.
• To understand the genome architecture drivers in these aquatic lineages.
• To overcome cultivation-dependent limitations using ecogenomic approaches.

Main Methods:

• Ecogenomic analysis of freshwater Planctomycetes.
• Phylogenetic inference to reconstruct evolutionary trajectories.
• Comparative genomics to analyze genome architecture and functional adaptations.

Main Results:

• Planctomycetes have transitioned from soil/sediment to freshwater environments, diversifying into aquatic-specific clades.
• The most abundant freshwater lineage exhibits a specialized lifestyle, including enhanced regulatory circuits and a metabolism adapted for aggregate mineralization.
• This lineage possesses the smallest genomes, indicating niche-directed genome streamlining through gene loss.

Conclusions:

• Ecogenomics provides a powerful alternative to cultivation for studying uncultured microbes.
• Freshwater bacterial genomes are shaped by adaptation to specific aquatic niches, favoring streamlined architectures.
• Evolutionary transitions from terrestrial to aquatic habitats drive significant diversification and specialization in microbial lineages.