In crowded spaces like the inside of a human cell, depletion interactions are essential. Our study uses duplex DNA as depletants, whereas spherical depletants, such as polyethylene glycol (PEG), have been utilized extensively to cause depletion. We describe an unexpected phase separation in a Bacillus subtilis suspension that causes aggregation at micromolar DNA concentrations. On the other hand, at millimolar concentrations, the common depletant polyethylene glycol causes the bacterium cells to aggregate and phase separate. We provide straightforward explanations for these startling findings, demonstrating that rods are far more potent depletants than spheres. The aggregation kinetics and structural organization of bacterial suspensions under different depletant concentrations are also measured by optical microscopy, dynamic light scattering (DLS), and turbidity measurements. We discover that bacterial clustering, phase behavior, aggregate morphology, and movement are significantly impacted by the depletant form. Overall, these discoveries broaden our knowledge of how bacteria organize themselves in response to depletion and emphasize the critical function that depletant shape plays in regulating bacterial interactions. Importantly, since DNA is found in vivo and in the majority of situations where bacteria are present, our findings can be used to describe phenomenology related to bacterial systems.
