Identification and characterization of Bacillus anthracis spore-associated proteins

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Bacillus anthracis is a Gram-positive, rod-shaped, spore-forming bacterium and the etiological agent of anthrax. Spore formation is essential for persistence in soil and for subsequent infection of animals. The sporulation process has been studied extensively in Bacillus subtilis, but little is known about sporulation in B. anthracis. Additionally, B. anthracis spores contain an outer balloon-like layer (the exosporium) which is not found on spores of B. subtilis. Consequently, very little is understood about the biosynthesis as well as function of the exosporium. BclA is a major spore surface glycoprotein which comprises the hair-like nap layer on the exosporium. We are examining BclA assembly into the exosporium and if other spore proteins serve as binding partners to BclA. We have identified several proteins that affect BclA incorporation. One of these proteins was found to interact with an additional collagen-like protein, BclB. Another was found to affect levels of both BclA and BxpB. As such, BxpB was also studied in regards to its complex formation. This is the first evidence of a protein whose incorporation occurs after BclA. Host-cell spore interactions may not be solely based on interactions with BclA, but may involve additional spore-associated proteins missing in a BclA mutant. This spore-associated protein was found to be surface exposed on the exosporium. We are currently investigating how this structural defect affects spore biology and virulence.