Biology subjects

Santin, Y. G.

Publications and source records attributed to Santin, Y. G..

3 recordsLinked to original sources

bioRxiv2023

Distinct dynamics and proximity networks of hub proteins at the prey-invading cell pole in a predatory bacterium

In bacteria, cell poles function as subcellular compartments where proteins localize during specific lifecycle stages, orchestrated by polar "hub" proteins. Whereas most described bacteria inherit an "old" pole from the mother cell and a "new" pole from cell division, polarizing cells at birth, non-binary division poses challenges for establishing cell polarity, particularly for daughter cells inheriting only new poles. We investigated polarity dynamics in the obligate predatory bacterium Bdellovibrio bacteriovorus, proliferating through filamentous growth followed by non-binary division within prey bacteria. Monitoring the subcellular localization of two proteins known as polar hubs in other species, RomR and DivIVA, revealed RomR as an early polarity marker in B. bacteriovorus. RomR already marks the future anterior poles of the progeny during the predators growth phase, in a define time window closely following the onset of divisome assembly and the end of chromosome segregation. In contrast to RomRs stable unipolar localization in the progeny, DivIVA exhibits a dynamic pole-to-pole localization. This behaviour changes shortly before division of the elongated predator cell, where DivIVA accumulates at all septa and both poles. In vivo protein interaction networks for DivIVA and RomR, mapped through endogenous miniTurbo-based proximity labeling, further underscore their distinct roles in cell polarization and the importance of the anterior "invasive" cell pole in prey-predator interactions. Our work emphasizes the strict spatiotemporal coordination of cellular processes underlying B. bacteriovorus proliferation, offering insights into the subcellular organization of bacteria with filamentous growth and non-binary division.

microbiology↗

bioRxiv2023

Lifecycle of a predatory bacterium vampirizing its prey through the cell envelope and S-layer

Predatory bacteria feed upon and kill other bacteria in various natural environments. Obligate epibiotic predators like Bdellovibrio exovorus consume their prey whilst remaining attached to the outside of the prey. How these predators achieve epibiotic feeding through the prey cell envelope has not been explored previously. Whereas the S-layer is the only proposed defensive structure against predatory bacteria, it remains unclear how this thin outer layer of the envelope might prevent epibiotic attacks. Similarly, the lifecycle of B. exovorus during the predator-prey interaction is poorly understood, with current models suggesting a binary division. Here we imaged the entire predatory lifecycle of B. exovorus and the fate of its Caulobacter crescentus prey by time-lapse microscopy and cryo-electron microscopy to monitor predator attack, growth and division and assess the impact of the S-layer on epibiotic predation. Our data reveal that B. exovorus uses non-binary division in a novel proliferation pattern that mainly generates three progenies. Moreover, we found that B. exovorus predates regardless of the presence of an S-layer, calling for revisiting its protective role against predators. Finally, our results indicate that epibiotic predation relies on the establishment of a secured junction between the prey and predator outer membranes, which must be resolved unilaterally to maintain cellular integrity of the predator departing from the prey surface.

microbiology↗

bioRxiv2022

Modulation of prey size reveals adaptability and robustness in the cell cycle of an intracellular predator

Despite the remarkable diversity of bacterial lifestyles, the sophisticated regulatory networks underlying bacterial replication have only been investigated in a limited number of model species so far. In bacteria that do not rely on canonical binary division for proliferation, the coordination of major cellular processes is still mysterious. Moreover, bacterial growth and division remain largely unexplored within spatially confined niches where nutrients are limited. This includes the lifecycle of the model endobiotic predatory bacterium Bdellovibrio bacteriovorus, which grows by filamentation within its host or prey cells and produces a variable number of daughter cells. Here, we examined how the size of the micro-compartment in which predators replicate (i.e., the prey bacterium) impacts their cell cycle progression at the single-cell level. Using Escherichia coli with genetically encoded size differences, we show that the duration of the predator cell cycle scales with prey size. As a result, the size of the prey determines the number of predator offspring, through a relationship that is maintained across prey species. Strikingly, the nutritional quality of the prey cell determined the specific growth rate of predators regardless of prey size, reminiscent of the effect of medium composition on the growth of other bacteria. Tuning the predatory cell cycle by modulating prey dimensions also allowed us to reveal invariable temporal connections between key cellular processes. Altogether, our data uncover adaptability and robustness shaping the enclosed replication of B. bacteriovorus. Consequently, predators optimally exploit the finite prey resources and space while ensuring a strict cell cycle progression. This study opens the way to explore diverse cell cycle control strategies by extending their characterization to intracellular lifestyles, beyond canonical models and growth conditions.

microbiology↗