Investigating proteins that influence membrane-associated germination processes in Bacillus subtilis spores

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Virginia Tech

Many endospore-forming bacteria cause diseases such as anthrax and food poisoning. Spores however also contribute to various agricultural and industrial processes. Spores possess extreme resistance properties, notably to chemical, et and dry heat, desiccation, and UV damage. For pathogenic spore formers, this poses an issue as spores are resistant to most decontamination methods currently in use. This work focuses on characterizing proteins thought to contribute to spore stability and efficient spore germination. Understanding how spores can remain stable for long periods of dormancy and against various insults and rapidly initiate germination could allow for the development of techniques that induce germination early and rapidly, promoting inexpensive decontamination. Physiological studies found that a family of spore-associated lipoproteins is needed for efficient spore germination and influences membrane fluidity in dormant spores. All the members of the lipoprotein family serve the same function, as each can fulfill the role of another. In vivo cross-linking was used to characterize protein-protein interactions found on the inner spore membrane. Glutaraldehyde crosslinking revealed that the four lipoproteins appear to interact. Bacterial two-hybrid analysis on individual protein domains further suggests the lipoproteins seem to interact through their predicted ring-building motif within their otherwise uncharacterized domains. Additionally, the absence of the spore lytic enzyme SleB seems to alter the crosslinking pattern of the lipoproteins, suggesting either it's interacting or helping facilitate lipoprotein interactions. Fluorescence microscopy reveals an unequal spatial distribution of the lipoproteins on the spore membrane, which seems to be supported by preliminary super-resolution microscopy studies. Further work aiming to characterize the entire inner spore membrane interactome is currently being conducted. The presented research used many methods and built many collaborations with the goal of providing insight to spore dormancy and efficient spore germination with an additional goal of understanding inner spore membrane protein behavior and how it leads to the highly resistant properties native to bacterial endospores.

Bacteria, Microbial Physiology, Spores, Membranes, Lipoproteins