Pushing the Envelope: Defining a Cytoskeletal-like Protein Required for Spore Development

Cell shape is an important feature of living organisms, linked to their function and ability to survive in the environment. In bacteria, the maintenance of cell shape is governed by the assembly and remodelling of their external layers, known as the cell envelope. Known antibiotics target the bacterial cell envelope and affect bacterial cell shape, leading to reduced bacterial survival and death. Thus, understanding the mechanisms underlying bacterial cell shape and cell envelope assembly can lead to new opportunities in drug development. In this project we focus on a new molecular process that controls the cell shape and cell envelope assembly of bacterial endospores (spores), one of the toughest cell types on Earth.

Spores are highly-resistant, dormant cells produced by some bacteria to survive starvation stress. Spore can persist in the environment for extended periods of time. In response to nutrient availability, or other signals, spores "reactivate" into growing bacteria through a process called germination. Spores have a defined shape and harbor a complex, multilayered cell envelope that contributes to their resistance properties and persistence in the environment. Some bacteria produce spores that underlie recurring and often deadly infections in humans, animals and pollinator insects. Spores can also contaminate food, compromise food safety and lead to food poisoning. Importantly, spores are not affected by current antibiotics and they resist common sterilisation strategies that kill growing bacteria.

While multiple studies have contributed to defining the complex composition of the spore envelope, less is known about the molecular mechanisms that regulate spore shape and the assembly of the spore envelope, which appear to be connected. By bringing together a team of experts in molecular genetics, biochemistry, cell biology and structural biology methods, this project expects to define a novel molecular process required for the assembly of the spore envelope and the maintenance of spore shape. Preliminary data suggest this mechanism employs a protein that may function like a structural scaffold on the inside of the spore and contributes to spore shape and assembly of an important spore envelope layer, the cortex. The cortex not only contributes to spore resistance properties but also plays a critical role in their exit from dormancy through germination.

The project's primary expected outcome is new knowledge of how bacteria transform into spores. The benefit of this new knowledge is that it will deepen and grow our understanding of bacterial spores and how bacteria build the highly-resistant spore cell envelope. This knowledge may provide a platform from which biotechnology industries could explore innovative strategies for controlling spore-forming bacteria. This project will also provide training to the next generation of microbiologists, securing Britain's future in Microbiology, a field that is critical to animal, human and environmental health, as well as food safety.

Cellular morphology is an important attribute linked to cell function and environmental adaptation. In bacteria, the maintenance of cellular morphology is governed by assembly and remodelling of the cell envelope and cytoskeletal-like proteins. In this project we focus on new biology controlling the morphology and envelope assembly of bacterial endospores (spores), one of the most resistant cell types on Earth.

Spores are highly resistant, dormant cells produced by some bacteria to survive starvation stress. Known pathogens (e.g. Bacillus anthracis, Clostridioides difficile, Paenibacillus larvae and Bacillus cereus) produce spores that underlie recurring and often deadly infections in humans, animals and pollinator insects and cause food poisoning. Spores have a defined shape and a complex, cell envelope, composed of multiple proteins and peptidoglycan, that contributes to their resistance to chemicals, heat and digestion by immune cells. By utilizing approaches in genetics, biochemistry, cell biology and structural biology, this project expects to reveal a new molecular mechanism regulating the assembly of the spore envelope and maintenance of spore shape. Preliminary data in genetics, cell biology and biochemistry suggest this mechanism employs a poorly-defined, cytoskeletal-like protein and a known signalling protease, to maintain spore shape and efficient assembly of the spore cortex - a thick layer of specialised peptidoglycan that contributes to spore resistance properties and germination.

The expected outcome is new knowledge of how bacteria develop into spores and how bacteria build their cell envelope. This new knowledge may provide a platform from which industry could explore innovative strategies for controlling spore-forming bacteria. This project will also provide training to the next generation of microbiologists, securing Britain's future in Microbiology, a field that is critical to animal, human and environmental health, as well as food safety.