Exosporium and interspace assembly remains largely mysterious.
Tyler J. Boone, Michael Mallozzi, Alex Nelson, Brian Thompson, Mark Khemmani, DörteLehmann, Alexis Dunkle, Paul Hoeprich, Amy Rasley, George Stewart, Adam Driks 2018, 'Coordinated Assembly of the Bacillus anthracis Coat and Exosporium during BacterialSpore Outer Layer Formation', mBiohttps://doi.org/10.1128/mBio.01166-18. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
The exosporium may also be involved in spore adherence, protection and germination.
Rebecca Rabi, Sarah Larcombe, Rommel Mathias, Sheena McGowan, Milena Awad, Dena Lyras 2018, 'Clostridium sordellii outer spore proteins maintain spore structural integrity andpromote bacterial clearance from the gastrointestinal tract.', PLoS Pathogenshttp://europepmc.org/articles/PMC5927469?pdf=render. Retrieved from PLOS CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
In a few strains, crystals are produced inside the exosporium and are associated with the spores after sporulation.
Yiguang Zhu, Fang Ji, Hui Shang, Qian Zhu, Pengxia Wang, Chengchen Xu, Yun Deng, DonghaiPeng, Lifang Ruan, Ming Sun 2011, 'Gene clusters located on two large plasmids determine spore crystal association (SCA)in Bacillus thuringiensis subsp. finitimus strain YBT-020.', PLoS ONEhttp://europepmc.org/articles/PMC3208593?pdf=render. Retrieved from PLOS CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
In this work, we explore the contribution of both cysteine-rich proteins in exosporium integrity, spore biology and pathogenesis.
Paulina Calderón-Romero, Pablo Castro-Córdova, Rodrigo Reyes-Ramírez, Mauro Milano-Céspedes,Enzo Guerrero-Araya, Marjorie Pizarro-Guajardo, Valeria Olguín-Araneda, Fernando Gil,Daniel Paredes-Sabja 2018, 'Clostridium difficile exosporium cysteine-rich proteins are essential for the morphogenesisof the exosporium layer, spore resistance, and affect C. difficile pathogenesis.',PLoS Pathogenshttp://europepmc.org/articles/PMC6101409?pdf=render. Retrieved from PLOS CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
Nonetheless, the mechanisms directing exosporium assembly into a shell surrounding the spore are still very poorly understood.
Tyler J. Boone, Michael Mallozzi, Alex Nelson, Brian Thompson, Mark Khemmani, DörteLehmann, Alexis Dunkle, Paul Hoeprich, Amy Rasley, George Stewart, Adam Driks 2018, 'Coordinated Assembly of the Bacillus anthracis Coat and Exosporium during BacterialSpore Outer Layer Formation', mBiohttps://doi.org/10.1128/mBio.01166-18. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)