Fructophilic lactic acid bacteria as a window into multi-scale convergent evolution

Area of Science:

• Microbiology
• Genomics
• Evolutionary Biology

Background:

• Fructophilic lactic acid bacteria (FLAB) are characterized by poor growth on glucose but enhanced growth with fructose or electron acceptors.
• FLAB inhabit fructose-rich environments, including flowers, fruits, and insects like honey bees.
• Representative genera include Apilactobacillus and Fructobacillus, which are phylogenetically distant.

Purpose of the Study:

• To investigate the unique genomic characteristics of FLAB.
• To understand the evolutionary processes driving FLAB adaptation to fructose-rich environments.
• To explore the convergent reductive evolution in FLAB and compare it with other organisms.

Main Methods:

• Comparative genomic analysis of FLAB.
• Investigation of gene loss patterns, particularly the adhE gene.
• Analysis of carbohydrate transport and metabolism genes.

Main Results:

• FLAB possess small genomes with reduced carbohydrate metabolism genes, reflecting adaptation to fructose.
• Independent gene loss occurred in Fructobacillus and Apilactobacillus, with similar orders of loss for many genes.
• The absence of an intact adhE gene was identified as the cause of poor glucose growth in FLAB.

Conclusions:

• FLAB exemplify habitat-driven convergent reductive evolution.
• Genome reduction in FLAB is a specific adaptation to fructose-rich environments.
• FLAB share evolutionary traits with eukaryotic yeasts inhabiting similar fructose-rich niches.