Applications of microbial bioplastic polyhydroxyalkanoates as biosignatures for astrobiological detection

Determining a reliable method to detect life on another planet is an essential first step in the pursuit of discovering extraterrestrial life. Polyhydroxyalkanoates (PHAs), bioplastic polymers created by microorganisms, are strong candidates for defining the presence of extraterrestrial life due to their water insolubility, strong ultraviolet resistance, high melting points and high crystallinity, amongst other qualities. PHAs are abundant on Earth, and their chemical properties can easily be distinguished from non-biological matter. Their widespread distribution and conferred resistance to astrobiologically relevant extreme environments render PHAs highly favourable candidates for astrobiological detection. Integrating detection of PHA biosignatures into current and future life-detection instruments would be useful for the planetary search for life. PHAs are analysed and characterized in laboratories by gas chromatography-mass spectrometry, infrared spectroscopy, Raman spectroscopy and immunoassay analysis in addition to other methods. We outline a path forward to integrate PHA detection in astrobiology missions to aid the search for extraterrestrial life.