Hegde, O. | Search bioRxiv

bioRxiv2022

Physics of Self-Assembly and Morpho-Topological Changes of Klebsiella Pneumoniae in Desiccating Sessile Droplets

We have investigated the flow and desiccation-driven self-assembly of Klebsiella Pneumoniae in the naturally evaporating sessile droplets. Klebsiella Pneumoniae exhibits extensive changes in its morphology and forms unique patterns as the droplet dries, revealing hitherto unexplored rich physics governing its survival and infection strategies. Self-assembly of bacteria at the droplet contact line is characterized by order-to-disorder packing transitions with high packing densities and excessive deformations (bacteria deforms nearly twice its original length scales). In contrast, thin-film instability-led hole formation at the center of the droplet engenders spatial packing of bacteria analogous to honeycomb weathering. The varying physical forces acting on bacteria based on their respective spatial location inside the droplet cause an assorted magnitude of physical stress. Self-assembly favors the bacteria at the rim of the droplet, leading to enhanced viability and pathogenesis on the famously known "coffee ring" of the droplet compared to the bacteria present at the center of the droplet residue. Mechanistic insights gained via our study can have far-reaching implications for bacterial infection through droplets, e.g., through open wounds.

microbiology↗

bioRxiv2021

Vapor mediation as a tool to control micro-nano scale dendritic crystallization and preferential bacterial distribution in drying respiratory droplets

Deposits of biofluid droplets on surfaces (such as respiratory droplets formed during an expiratory event fallen on surfaces) are composed of the water-based salt-protein solution that may also contain an infection (bacterial/viral).The final patterns of the deposit formed are dictated by the composition of the fluid and flow dynamics within the droplet. This work reports the spatio-temporal, topological regulation of deposits of respiratory fluid droplets and control of motility of bacteria by tweaking flow inside droplets using non-contact vapor-mediated interactions. When evaporated on a glass surface, respiratory droplets form haphazard multiscale dendritic, cruciform-shaped precipitates--using vapor mediation as a tool to control these deposits at the level of nano-micro-millimeter scales. Wemorphologically control dendrite orientation, size and subsequently suppress cruciform-shaped crystals. The nucleation sites are controlled via preferential transfer of solutes in the droplets; thus, achieving control over crystal occurrence and growth dynamics. The active living matter like bacteria is also preferentially segregated with controlled motility without attenuation of its viability and pathogenesis. For the first time, we have experimentally presented a proof-of-concept to control the motion of live active matter like bacteria in a near non-intrusive manner. The methodology can have ramifications in biomedical applications like disease detection, controlling bacterial motility, and bacterial segregation.

bioengineering↗