In and out: an analysis of epibiotic vs periplasmic bacterial predators

Area of Science:

• Microbiology
• Genomics
• Evolutionary Biology

Background:

• Bdellovibrio and like organisms (BALO) are Gram-negative bacterial predators.
• BALO exhibit two main predatory strategies: periplasmic and epibiotic.
• The genetic basis for these predatory strategies is largely unknown.

Purpose of the Study:

• To compare the genetic and phenotypic differences between epibiotic and periplasmic BALO.
• To elucidate the evolutionary origins of different BALO predatory strategies.

Main Methods:

• Comparative genomics of four BALO species: Bdellovibrio exovorus, Micavibrio aeruginosavorus (epibiotic), B. bacteriovorus, and Bacteriovorax marinus (periplasmic).
• Electron microscopy to observe predatory interactions.
• Analysis of antibiotic resistance genes and metabolic pathways.

Main Results:

• Epibiotic predators possess smaller genomes (approx. 2.5 Mbp) compared to periplasmic predators (approx. 3.5 Mbp).
• Periplasmic predators have significantly more proteins, peptidases, and rRNA operons.
• Epibiotic predators showed metabolic deficiencies and evolved via convergent evolution, with one species arising from a non-predatory ancestor.

Conclusions:

• Significant genomic and proteomic differences distinguish epibiotic and periplasmic BALO.
• Epibiotic BALO likely evolved through convergent evolution and gene loss.
• Understanding these differences provides insight into bacterial predation and evolution.