Animal degradation of microbial storage polyhydroxyalkanoates

Area of Science:

• Biochemistry
• Microbiology
• Evolutionary Biology

Background:

• Microorganisms produce polyhydroxyalkanoates (sPHAs) as carbon and energy reserves.
• Polyhydroxyalkanoate depolymerases (PHADs) are enzymes typically found in bacteria and fungi for sPHA degradation.

Purpose of the Study:

• To investigate the presence and function of PHADs in animals and protists.
• To understand the evolutionary origin and ecological significance of PHADs in non-microbial organisms.

Main Methods:

• Discovery and characterization of a PHAD in the marine worm Olavius algarvensis.
• Enzyme assays and mass spectrometry to confirm sPHA degradation.
• Phylogenetic analysis and functional assays across diverse animal and protist species.

Main Results:

• A functional PHAD was identified in Olavius algarvensis, degrading sPHAs into usable monomers.
• PHADs were found in over 66 animal species and 19 protist species, indicating ancient origins.
• PHADs from various lineages effectively degrade sPHAs, demonstrating conserved function.

Conclusions:

• Animals and protists possess a previously unrecognized enzymatic pathway for degrading microbial sPHAs.
• The widespread distribution of PHADs suggests their presence in the last common ancestor of metazoans.
• This finding broadens our understanding of carbon cycling and nutrient acquisition in ecosystems.