Biology subjects

Kysela, D. T.

Publications and source records attributed to Kysela, D. T..

3 recordsLinked to original sources

bioRxiv2018

Diverse spatial organization of photosynthetic membranes among purple nonsulfur bacteria

In diverse bacteria, proper cellular physiology requires the utilization of protein- or membrane-bound compartments that afford specific metabolic capabilities. One such compartment is the light-harvesting intracytoplasmic membrane (ICM) of purple nonsulfur bacteria (PNSB). Here we reveal that ICMs are subject to differential spatial organization among PNSB. We visualized ICMs in live cells of fourteen PNSB species by exploiting the natural autofluorescence of the photosynthetic machinery. We then quantitatively characterized ICM localization using automated computational analysis of autofluorescence patterns within single cells across the population. Our studies revealed that ICMs are localized in distinct subcellular patterns that differ between species; some PNSB elaborate ICMs throughout the cell, while others spatially restrict ICM to varying degrees. The most highly-restricted ICMs were localized in a specific pattern corresponding to progression of cell growth and division. An identical pattern of ICM restriction was conserved across at least two genera. Phylogenetic and phenotypic comparisons established that ICM localization and ICM architecture are not strictly interdependent and that neither trait fully correlates with the evolutionary relatedness of the species. This discovery of new diversity in bacterial cell organization has implications for understanding both the mechanisms underpinning spatial arrangement of bacterial compartments and the potential benefits of adopting different spatiotemporal patterns.

microbiology↗

bioRxiv2017

Obstruction of pilus retraction stimulates bacterial surface sensing

Surface association provides numerous fitness advantages to bacteria. Thus, it is critical for bacteria to recognize surface contact and to consequently initiate physiological changes required for a surface-associated lifestyle (1). Ubiquitous microbial appendages called pili are involved in sensing surfaces and mediating downstream surface-associated behaviors (2-6). The mechanism by which pili mediate surface sensing remains unknown, largely due to the difficulty to visualize their dynamic nature and to directly modulate their activity without genetic modification. Here, we show that Caulobacter crescentus pili undergo dynamic cycles of extension and retraction that cease within seconds of surface contact, and this arrest of pilus activity coincides with surface-stimulated holdfast synthesis. By physically blocking pili, we show that imposing resistance to pilus retraction is sufficient to stimulate holdfast synthesis in the absence of surface contact. Thus, resistance to type IV pilus retraction upon surface attachment is used for surface sensing.\n\nOne Sentence SummaryBacteria use the tension imparted on retracting pilus fibers upon their binding to a surface for surface sensing.

microbiology↗

bioRxiv2017

ComM is a hexameric helicase that promotes branch migration during natural transformation in diverse Gram-negative species

Acquisition of foreign DNA by natural transformation is an important mechanism of adaptation and evolution in diverse microbial species. Here, we characterize the mechanism of ComM, a broadly conserved AAA+ protein previously implicated in homologous recombination of transforming DNA (tDNA) in naturally competent Gram-negative bacterial species. In vivo, we found that ComM was required for efficient comigration of linked genetic markers in Vibrio cholerae and Acinetobacter baylyi, which is consistent with a role in branch migration. Also, ComM was particularly important for integration of tDNA with increased sequence heterology, suggesting that its activity promotes the acquisition of novel DNA sequences. In vitro, we showed that purified ComM binds ssDNA, oligomerizes into a hexameric ring, and has bidirectional helicase and branch migration activity. Based on these data, we propose a model for tDNA integration during natural transformation. This study provides mechanistic insight into the enigmatic steps involved in tDNA integration and uncovers the function of a protein required for this conserved mechanism of horizontal gene transfer.

microbiology↗