Biology subjects

Dudley, C. E.

Publications and source records attributed to Dudley, C. E..

3 recordsLinked to original sources

bioRxiv2026

Polyphosphate acts as an architectural regulator of carbon fixation and nucleoid structure in cyanobacteria

Polyphosphate (polyP) is a conserved inorganic polymer traditionally viewed as a stress-induced phosphate and energy reserve. In cyanobacteria, however, polyP granules are constitutively present and frequently observed in proximity to carboxysomes, the bacterial microcompartments that mediate CO2 fixation. Here we show that polyP functions as a spatially organized regulator of the photosynthetic cytoplasm in Synechococcus elongatus. PolyP granules localize to the nucleoid and are periodically arranged along the cell axis, independently of the McdAB carboxysome positioning system. Despite this independence, polyP and carboxysomes associate non-randomly, and this association is enhanced when active carboxysome positioning by the McdAB system is disrupted. Loss of polyP synthesis leads to nucleoid expansion, an increased number of smaller carboxysomes with high mobility, and severe defects in growth under ambient CO2. Perturbation of polyP turnover further reveals structural connections to both carboxysomes and thylakoid membranes. Together, these findings identify polyP as an architectural integrator that couples chromosome organization, metabolic compartmentalization, and photosynthetic fitness.

microbiology↗

bioRxiv2025

Nucleoid Compaction Influences Carboxysome Localization and Dynamics in Synechococcus elongatus PCC 7942

The bacterial nucleoid is not just a genetic repository--it serves as a dynamic scaffold for spatially organizing key cellular components. ParA-family ATPases exploit this nucleoid matrix to position a wide range of cargos, yet how nucleoid compaction influences these positioning reactions remains poorly understood. We previously characterized the Maintenance of Carboxysome Distribution (Mcd) system in the cyanobacterium Synechococcus elongatus PCC 7942, where the ParA-like ATPase McdA binds the nucleoid and interacts with its partner protein, McdB, to generate dynamic gradients that distribute carboxysomes for optimal carbon fixation. Here, we investigate how nucleoid compaction impacts carboxysome positioning, particularly during metabolic dormancy when McdAB activity is downregulated. We demonstrate that a compacted nucleoid maintains carboxysome organization in the absence of active McdAB-driven positioning. This finding reveals that the nucleoid is not merely a passive substrate for positioning, but an active player in spatial organization. Given the widespread role of ParA-family ATPases in the positioning of diverse cellular cargos, our study suggests that nucleoid compaction state is a fundamental, yet underappreciated, determinant of mesoscale organization across bacteria.

microbiology↗

bioRxiv2022

Cell Surface-localized CsgF Condensate is a Gatekeeper in Bacterial Curli Subunit Secretion

Curli are functional amyloids present on the outer membrane of E. coli. Cell-surface aggregation of CsgA, the major subunit of curli, is a well-orchestrated process. CsgB, the minor subunit of curli, nucleates the aggregation of CsgA while CsgF, a curli accessory protein, ensures proper anchoring of CsgB to the cell surface. The molecular basis of the interactions between CsgF and curli subunits is unclear. Here, we show that CsgF undergoes phase separation in vitro and that the ability of CsgF variants to phase separate tightly correlated with CsgF function in cells during curli biogenesis. Substitution of phenylalanine residues in the CsgF N-terminus both reduced the propensity of CsgF to phase-separate and impaired curli biogenesis. Exogenous addition of purified CsgF complemented csgF - cells. This exogenous addition assay was used to assess the ability of CsgF variants to complement csgF - cells. The presence of CsgF on the cell surface modulated the secretion of CsgA to the cell surface. We also found that the CsgB nucleator protein is a CsgF client. CsgB can form SDS-insoluble aggregates within the dynamic CsgF condensate, and we propose that these multi-component CsgF-B condensates form a nucleation-competent complex that templates CsgA amyloid formation on the cell surface. Together, our study provides insight into the ability of CsgF to phase separate, regulate CsgA secretion, and promote CsgB aggregation in curli assembly.

biochemistry↗