Within host selection for faster replicating bacterial symbionts

Area of Science:

• Microbiology
• Genetics
• Evolutionary Biology

Background:

• Wolbachia are intracellular symbionts in arthropods, influencing host reproduction and immunity.
• The wMelPop strain of Wolbachia causes pathogenicity in Drosophila melanogaster due to genomic amplification of the Octomom region.
• Octomom copy number varies within and between hosts, suggesting potential for selection.

Purpose of the Study:

• To investigate if Octomom copy number changes within individual Drosophila melanogaster during their lifespan.
• To determine if within-host selection acts on Wolbachia populations with varying Octomom copy numbers.

Main Methods:

• Time course analysis of Octomom amplification in Drosophila melanogaster.
• Controlled maternal Octomom copy number to establish baseline.

Main Results:

• Octomom copy number showed a slight increase throughout the adult lifespan of individual Drosophila.
• This indicates selection acting on intra-host variation of Octomom copy number.
• Faster-replicating bacterial symbionts are favored within hosts.

Conclusions:

• Within-host selection favors faster-replicating Wolbachia strains with higher Octomom copy numbers.
• This intra-host selection may be counteracted by selection against highly pathogenic Wolbachia at the between-host level.