Thursday 13 April 2023

Cultivating microbial communities in a permanently stable manner


The capabilities of complex microbial communities are used for numerous biotechnological processes. This requires special compositions of the microbial communities. However, these are often unstable and susceptible to disruption.


Scientists from Helmholtz Centre for Environmental Research have developed a so-called 'mass transfer method with a loop' that can stabilize microbial communities in the long term.


A minor random event can give rise to a completely different microbial community. This can happen rather quickly when microorganisms grow exponentially. In addition, there is constant flow or mass transfer in bioreactors, which can be disastrous for some microorganisms.


In microbial communities, there are also microorganisms that are present only in comparatively small numbers and which multiply slowly. For example, the methane-forming microorganisms used in biogas production. These organisms have slower growth rates and come into play only at later stages.


If the crucial microorganisms are inadvertently lost from the system, everything ultimately comes to a standstill.


In order to prevent this, a research team has proposed a new method called "mass transfer with a loop". This would be the type of loop is built into the bioreactor system in order to stabilise the microbial community and prevent microbial groups from being lost from the system altogether.


The researchers created five bioreactors, each with identical microbial communities. They then investigated whether and to what extent the composition of these communities changed over time. To do this, they used high-throughput flow cytometry to quickly examine single cells and characterise them in detail.


Various parameters of the bacteria such as cell size, cell density, and DNA content can be determined. A sample with 200,000 bacterial cells can thus be displayed as precisely as a fingerprint within just a few minutes.


Using special computer methods, the research team analysed the huge amounts of data generated and was thus able to detect changes in the microbial composition. It was found that the microbial communities in the five bioreactors developed quite differently despite the identical conditions.


The researchers then introduced a loop into the system. This sixth bioreactor was connected to each of the five reactors via inflow and outflow. As a result, a constant exchange or mass transfer took place between the bioreactors


This showed that the microbial communities in the bioreactors were synchronised with each other by the loop and that their composition and functions were permanently stabilised. In addition, the survival probability of micro-organisms with a low growth rate was considerably increased. This rescue effect can be crucial for many biotechnological processes.


The microbiologists were able to show for the first time that the principle of mass transfer with a loop can stabilise microbial communities in the long term.


See:  Shuang Li, Nafi'u Abdulkadir, Florian Schattenberg, Ulisses Nunes da Rocha, Volker Grimm, Susann Müller, Zishu Liu. Stabilizing microbial communities by looped mass transfer. Proceedings of the National Academy of Sciences, 2022; 119 (17) DOI: 10.1073/pnas.2117814119

 Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (

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