A spacesuit for bacteria
Chemists from the University of California at Berkeley, working under the guidance of Professor Peidong Yang, have developed a protective shell that allows bacteria to survive in conditions unsuitable for their existence. The purpose of creating this shell is to increase the duration of the functioning of a unique system in which living bacteria are combined with light-absorbing semiconductors. This combination allows you to capture carbon dioxide and convert it into chemical compounds suitable for use in industry or, if you dream up, in the conditions of space colonies of the future.
Organometallic structures cover bacteria, forming a soft shell that stretches as bacteria grow and divide and protects bacteria from oxygen and its active forms.
This system simulates the process of photosynthesis in plants. However, while plants absorb carbon dioxide and use the energy of sunlight to convert it into carbohydrates, including those we eat, the hybrid system absorbs carbon dioxide and light to produce various carbon-containing compounds that differ depending on the type of bacteria.
The bacteria used in the experiments are anaerobic, that is, adapted to life in conditions depleted of oxygen. Usually, in order to maintain their vital activity, such microorganisms absorb electrons from the environment. In his first study in 2016, devoted to the combination of bacteria with solid silicon oxide nanowires, Professor Yang found that when adding cadmium to the nutrient medium, anaerobic bacteria cover themselves with a natural semiconductor shell of cadmium sulfide, effectively absorbing light and supplying the bacteria with electrons.
Increasing the efficiency of electron capture by bacteria increases the activity of biochemical processes occurring in them and, accordingly, the synthesis of useful carbon-containing products. However, this process is accompanied by the production of reactive oxygen species, which have a detrimental effect on bacteria.
To solve this problem, as part of their latest study, the authors developed a protective shell formed on the surface of bacteria by fragments of organometallic structures based on zirconium added to the nutrient medium. The resulting flexible mesh metal-organic structure, one nanometer thick, covers the surface of the bacterial cell in places and, unlike solid metal-organic nanowires that prevent the normal course of the process of bacterial growth and division, allows bacteria to increase in size and divide. At the end of the division process, the free areas of the bacterial cell surface are covered with new organometallic structures contained in the solution.
Impervious to molecular oxygen and its active forms, the organometallic shell at normal oxygen concentrations (about 20% by volume) increases the life expectancy of bacteria by five times, which in most cases exceeds the life expectancy in their normal habitat. The lifespan of such microorganisms varies from several weeks to several months, after which they can be removed from the system and replaced with new ones.
A hybrid system can be a winning approach for both industry and the environment. It is able to absorb carbon dioxide emitted into the atmosphere by power plants and convert it into useful products. In addition, it can be used to synthesize the necessary chemical compounds in an artificial environment, such as inside spacecraft.
When cadmium is added to the nutrient medium, the bacteria Moorella thermoacetica are coated with light-absorbing particles of cadmium sulfide, resulting in a hybrid artificial system that converts sunlight and carbon dioxide into valuable chemical products.
In their experiments, the researchers used the bacteria Morella thermoacetica and Sporomusa ovata, synthesizing acetic acid – an important raw material for the chemical industry. These microorganisms were chosen because the product they produce is always 100% acetic acid. However, the authors note that, if necessary, it is always possible to pick up bacteria that synthesize methane, ethanol or another carbon-containing compound.
To date, the authors continue to work on improving the properties of the system, such as the efficiency of light absorption, electron transfer and the production of specific compounds. They expect that combining these optimized properties with new metabolic mechanisms will allow the production of more complex molecules with the help of bacteria.
Article by Zhe Ji et al. Cytoprotective metal-organic frameworks for anaerobic bacteria is published in the journal Proceedings of the National Academy of Sciences.
Evgenia Ryabtseva, portal "Eternal Youth" http://vechnayamolodost.ru according to University of California, Berkeley: 'Spacesuits' protect microbes destined to live in space.