{"doi":"10.1101/2025.02.12.637803","title":"Stimulation of the <i>Caulobacter crescentus</i> surface sensing pathway by deletion of a specialized minor pilin-like gene","abstract":"Abstract Bacteria colonize surfaces through complex mechanisms of surface sensing. Pili are dynamic bacterial appendages that play an important role in this process. In Caulobacter crescentus , tension on retracting, surface-bound pili triggers the rapid synthesis of the adhesive holdfast, which permanently attaches cells to surfaces. However, the detailed mechanisms of pilus-mediated surface sensing are unclear. In this study, we used a genetic screen to isolate mutants with altered pilus activity to identify genes that may be involved in pilus-mediated surface-sensing. This screen identified cpaL , whose deletion led to reduced piliation levels, and surprisingly, a threefold increase in surface adhesion due to increased holdfast production. To understand this finding, we compared holdfast synthesis in wild-type and cpaL mutant cells under conditions that block pilus retraction. While this treatment increased holdfast production in wild-type cells by triggering the surface-sensing pathway, no increase was observed in the cpaL mutant, suggesting that mutation of cpaL maximally stimulates surface-sensing. Furthermore, when the cpaL mutant was grown in a medium that blocks the surface sensing pathway, cells exhibited decreased surface attachment and holdfast production, consistent with a role for CpaL in pilus-dependent surface sensing in C. crescentus . To better understand the function of CpaL, we analyzed its predicted structure, which suggested that CpaL is a minor pilin fused to a mechanosensitive von Willebrand factor type A (vWA) domain that could be accommodated at the pilus tip. These results collectively position CpaL as a strong candidate for a mechanosensory element in pilus-mediated surface sensing. Importance Surface sensing is a crucial mechanism that allows bacteria to change their behaviors to adapt to life on a surface. Surface recognition by bacteria is the initial step toward surface colonization and biofilm formation. In Caulobacter crescentus , tight adherence (Tad) pili play a key role in surface recognition and adaptation. However, the mechanism of pilus-mediated surface sensing and the proteins that influence this process remain unknown. Here, we demonstrate that CpaL, a potential pilus tip mechanosensory protein, could be the major element of Tad pilus-mediated surface attachment and colonization in C. crescentus . CpaL plays an important role in the regulation of holdfast synthesis and production upon surface contact. By identifying CpaL as a key player in the process of surface recognition, our work offers valuable insights into the mechanisms of bacterial adhesion.","journal":"bioRxiv (Cold Spring Harbor Laboratory)","year":2025,"id":561959,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":0,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9478,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2025-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":347999,"name":"Gregory B. Whitfield","orcid":"0000-0003-0274-8402","position":1,"is_corresponding":false},{"id":278675,"name":"Courtney K. Ellison","orcid":"0000-0003-3259-079X","position":2,"is_corresponding":false},{"id":278676,"name":"Yves V. Brun","orcid":"0000-0002-9289-1909","position":3,"is_corresponding":false},{"id":1464105,"name":"Farah Obeid Charrouf","orcid":"0000-0003-0176-0901","position":0,"is_corresponding":true}],"reference_count":61,"raw_metadata":null,"created_at":"2026-07-19T02:56:01.883848Z","pmid":"40027758","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}