Spore formation in C. difficile is governed by small RNAs - a twist on the classic model of sporulation initiation
Using a suite of RNA-sequencing-based technologies, our lab has recently demonstrated that, in C. difficile, the Hfq chaperone binds to and facilitates the regulatory activities of most small RNAs in this gram-positive bacterium. We leveraged this Hfq dependence and performed Hfq RIL-seq in bacterial cultures undergoing sporulation to identify potential RNA regulators of spore formation. These analyses identified numerous sRNAs that base-pair with mRNAs encoding central regulators of spore formation, suggesting that they interfere with this morphogenic process at multiple stages. In particular, we identified a network of ten sRNAs that appear to regulate the initiation of sporulation directly via the spo0A mRNA. Our findings not only provide novel mechanistic insights into the control of sporulation initiation in C. difficile but also offer an opportunity to identify the environmental signals that regulate this process. Therefore, current research efforts focus on understanding how these sRNAs are integrated into transcriptional regulons and whether they are uniformly expressed across populations or correlate with distinct cellular states and/or sporulation stages. Latest work from our group identifies a stress-responsive mechanism in which a small RNA acts as a molecular switch, favoring a reversible stress response over irreversible differentiation into a spore. I will also highlight how we aim to exploit these regulatory principles to gain a better understanding how non-coding RNAs contribute to the spatiotemporal regulation of spore formation.