Tubulation and dispersion of oil by growth of marine bacteria on oil droplets

The activity of bacteria on surfaces exhibits collective behaviors such as active turbulence and active stresses, which result from motility or growth and interactions with the local surroundings. Here, we describe experimental observations on the emergence of tubular structures resulting from the growth and division of rod-shaped bacteria on the liquid interface of oil droplets. Using microfluidics and time-lapse microscopy, we quantify the dimensions and growth rates of individual tubular structures as well as the bulk biofilm formation on hundreds of droplets over 72 hours. We find that the length of tubular structures is comparable to the initial droplet radius and that they are composed of an outer shell of bacteria that stabilize an inner filament of oil. The oil filament undergoes breakup into smaller microdroplets dispersed within the bacterial shell, where the average radius of the dispersion is described by the most unstable Plateau-Rayleigh wavelength. This work provides insight into active stresses at deformable interfaces and improves our understanding of microbial oil biodegradation and its potential influence on the transport of oil droplets in the ocean water column.