???? Hydrocarbon Eating Bacteria Attack Oil Droplets

2023-08-25 06:00:04

Alcanivorax bacteria proliferate following oil spills and contribute to the degradation of oil in the oceans. In a study, published in the journal Science, a collaboration of scientists isolated specimens of Alcanivorax borkumensis bacteria in the laboratory, fed them crude oil (Crude oil comes from the operation of a well, after treatments of…) and then observed how they worked together to eat the oil as quickly and efficiently as possible. This discovery makes it possible to better understand the processes of biodegradation (Biodegradation is the decomposition/degradation of organic matter by…) of spilled hydrocarbons.

Amoco Cadiz, Exxon Valdez, Deepwater Horizon (Deepwater Horizon was an oil rig leased by the company…)… During these oil spills, disastrous for aquatic life, the bacteria (Bacteria (Bacteria) are prokaryotic unicellular living organisms, characterized…) Alcanivorax borkumensis. The Latin name Alcanivorax means “alkane devourer”; these bacteria break down the long carbon chains produced by living organisms, and as such play a role in the carbon cycle. These bacteria are found en masse in oil spills and it has been shown that they can degrade oil slicks before they reach the coast.

As part of an international collaboration between the University of Tsukuba (Japan), the Center for Theoretical Physics (Theoretical physics is the branch of physics that studies the aspect…) (CPT, CNRS / Aix-Marseille University / University of Toulon), the laboratory Activation process (Activation may refer to:) selective by uni-electronic or radiative energy transfer (PASTEURCNRS / ENS-PSL / Sorbonne University), the Pierre-Gilles de Gennes Institute (Pierre-Gilles de Gennes (October 24, 1932 in Paris – May 18, 2007 in Orsay, France) is a…) (PSL University) and the Curie physical-chemistry laboratory (PCC, CNRS / Institut Curie (The Institut Curie is a foundation, whose main activities are on the one hand…) / Sorbonne University), the authors immobilized in a microfluidic chip (Microfluidics is science and technology systems manipulating fluids and including…) oil droplets gradually devoured by these bacteria, and monitoring under a confocal microscope (A confocal microscope is an optical microscope which has the property of…) their evolution during the time. The team was thus able to observe and quantify the entire process, from initial colonization to complete consumption of the oil droplets. The conclusions of this work were published in the journal Science on August 18, 2023. Terry McGenity and Pierre Philippe Laissue, of the University of Essex, published in the same issue of the journal a perspective article describing this work.

While bacteria that have been exposed for a short time to an insoluble carbon source form biofilms growing in volume keeping the droplet spherical, bacteria that have been exposed to oil for a longer time form thin biofilms or appear from many dendrites. In this study, the authors show that the rate at which bacteria degrade droplets depends on the morphology of the biofilm: due to their larger contact surface between the bacterial biofilm and the water/oil interface, dendritic biofilms are much more effective for rapid oil degradation. However, rather than being caused by an increase in individual metabolic rate, this acceleration is the consequence of the collective organization (An organization is) of the biofilm at the interface.

Under the microscope, the bacteria appear as elongated rods along the surface between the oil and the water. Just before forming a tube, the bacteria gradually move towards a central point, which will become the heart of the tube. This star pattern is known in liquid crystal theory as the +1 charge topological defect. Once the water/oil surface has been deformed, the formation of these tubes with a well-controlled radius is made possible both by a reduction in the interfacial tension of the oil during the time of exposure to the hydrocarbons, and by a increase in the hydrophobicity of bacteria, which induces the appearance of a preferential curvature of the water-oil interface. The authors have developed a model that explains this phenomenon.

Finally, the researchers focused on studying the presence of surfactants in the culture medium, so as to simulate the use of dispersants massively spilled into the sea during the Deep Water Horizon accident. In the context of their experiments, the authors show that surfactants decrease the adhesion of bacteria to oil drops, preventing the formation of tubes and thus compromising the degradation of oil by these bacteria. However, further work is still needed before definitive conclusions can be drawn on the effect of surfactants in the management of oil spills, in particular due to the great diversity in the composition of ocean waters.

The study authors also envision fundamental applications in understanding a key carbon cycle process called sea snow, where bacteria – including Alcanivorax borkumensis – devour organic matter (Organic matter (OM) is the carbonaceous matter produced in general by …) in suspension. This degradation process then contributes to the trapping of carbon dioxide in the depths of the ocean.


Alcanivorax borkumensis Biofilms Enhance Oil Degradation By Interfacial Tubulation,
Manoj Prasad, Nozomu Obana, S.-Z. Lin, Ken Sakai, Carles Blanch-Mercader, Jacques Prost, Nakao Nomura, Jean-François Rupprecht, Jacques Fattaccioli, AS Utada, published August 18, 2023 in Science.
Doi: 10.1126/science.adf3345

Open archive: bioRxiv

#Hydrocarbon #Eating #Bacteria #Attack #Oil #Droplets

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