ABSTRACT
Just as the development of the first light microscopes uncovered a new microbial frontier, the use of high-throughput sequencing and metagenomics has uncovered a new frontier of unculturable microorganisms, often referred to as “microbial dark matter”. The biology of these organisms, which have been found in many environmental and human microbiomes, profoundly impacts our understanding of evolution. However, many of these organisms are difficult to culture, genetically intractable, and rely on other microbes within their niche to proliferate.

CryoET is an ideal method to study genetically intractable microbial communities as it can determine high-resolution cellular details and macromolecular structures in situ without recombinant expression systems. We used electron cryo-ET to observe the intercellular interactions of microbes from Shark bay stromatolites. We embark on “microbial safari”, observing the fascinating biology of Asgard archaea. Tomographic reconstructions combined with 3D segmentation cast light on the diverse plethora of microbes in microbial dark matter and reveal cellular features such as intercellular nanotubes and enormous attachment organelles that facilitate the interactions between microbial cells.

Our work shows the vast the resources that microbial communities commit to intercellular interactions and provides mechanistic insights into the primordial nature of symbiosis, and eukaryogenesis.

BIOGRAPHY

Dr Matt Johnson completed his PhD from the University of Birmingham, UK in molecular microbiology, where he used high throughput sequencing technologies to investigate lab-based evolution. After his PhD Matt moved to Monash University where he characterised secreted bacterial toxins using structural biology. In 2016 Matt joined Dr Leyton’s laboratory at the Australian National University to study the folding and secretion of autotransporter toxins. Matt returned to Melbourne to work in A/Prof Ghosal’s laboratory at the University of Melbourne where he has been using electron cryo-tomography and cryoFIB-SEM to investigate intercellular interactions in situ.