List Headline Image
Updated by Philasande Christine Cele on Nov 14, 2023
 REPORT
9 items   2 followers   7 votes   49 views

Adopt a bacterium- Shewanella oneidensis (it's ability to generate electricity)

there have been a plethora of memes, talks, jokes over load shedding in South Africa. Most of them were hilarious but I wasn't laughing when the lights went off after I poured oil into the frying pan. when we were given the task of choosing a species of bacteria I stopped scrolling when i saw the title " Bacteria eat pollution and generate electricity ". I was shocked, pun intended ; ) , and I had to know more about the bacterium Shewanella oneidensis and share what I found

1

Lets get to know these electrifying bacteria

Lets get to know these electrifying bacteria

The above image is of unstained Shewanella oneidensis bacteria under a scanning electron microscope (photo credit: Amedea B Seabra). The scientific name of these bacteria is Shewanella oneidensis. Their scientific classification is kingdom bacteria, phylum Proteobacteria, class Gamma Proteobacteria, order Alteromonadales, family shewanellaceae, and genus Shewanella (1). They (S.oneidensis) are facultative anaerobes meaning they will survive with or without oxygen, they use organic and inorganic compounds for respiration, it is this trait that makes these bacteria intriguing (2). Based on a study done by Venkateswaran and colleagues the main characteristic of these gram-negative rod shaped bacteria which have one unsheathed polar flagellum was sulfur reduction and halophilicity (2). The study showed that S.oneidensis does not form spores (2). When grown on LB agar plates the colonies appeared circular and approximately 1 to 4 mm in diameter, the colonies were smooth, convex in shape with regular edges (2). The pigmentation of the bacterial colonies was pinkish, they grew in temperatures of 40 ⁰C (2). The study also revealed the bacteria can tolerate high concentrations of salt, when NaCl concentration was 0.0 to 0.3 M the bacteria were able to grow and the growth increased when the concentration was 0.2 M of NaCl (2).
https://microbewiki.kenyon.edu/index.php/Shewanella_oneidensis_MR-1:_Background_and_Applications
Venkateswaran K, Moser D.P, Dollhopf M.E, Lies D.P, Saffarini D.A, Ma~Gregor B.J, Rigelberg D.B, White D.C, Nihijirna M, San H, Burghardt J, StackebrandP E, Nealsonl K.H.1999,Polyphasic taxonomy of the genus Shewanella and description of Shewanella oneidensis sp.International journal of systematic bacteriology,49,705-724.

2

Shewanella oneidensis grown on LB agar plates

Shewanella oneidensis grown on LB agar plates

Photo courtesy of B. Conley

6

So what makes these bacteria so exciting? Get comfortable because there is more than one reason.

So what makes these bacteria so exciting? Get comfortable because there is more than one reason.

Firstly Iron is important for every living organism and in the environments that the S.oneidensis inhabit iron is available in the form of raw minerals like ferrihydrite, goethite and hematite (1). Humans can't access this iron but with the aid of S.oneidensis the iron can be made available (1). In iron reduction, the bacteria donate negatively charged electrons to positively charged iron ions this makes the iron soluble in water and available for other organisms (1). Iron is not the only metal that Shewanella can alter physically, Uranium which is a heavy metal is radioactive and is used to fuel nuclear reactions and is used as a nuclear weapon (2). Uranium won't harm an individual by touching it but breathing in high concentrations could result in lung cancer, ingesting uranium could result in kidney damage (2). Uranuim contaminates the the environment and is a health concern when dissolved in water but Shewanella is capable of reducing uranium in the water and making it more insoluble this allows for the uranium to be extracted from the water and prevent further contamination, these bacteria will be useful in dustries such as mining and nuclear plants (2). Shewanella also reduce other metals and when you have time I encourage you to research further. From personal opinion S.oneidensis bacteria are awesome and its their ability to generate electricity that makes them so, how do they do this? well lets get into it. These facultative anaerobes use solid materials from outside their cell to generate electricity, they are able to respire on a variety of metals using them as a final electron accepter (3). The bacteria start by forming biofilms on the metal this is advantageous for the bacteria in that it is easier access the metal (4). The strategy is that they grow laterally so that they can gain as much ground as possible then they proceed to grow vertically forming biofilms (4). Using nanowires (very thin appendages) the bacteria connect with the metal and transport their electrons out the cell for respiration (3). These bacteria have caught the attention of NASA for its potential use in future space missions, these bacteria can be used in waste water treatment to generate electricity when the bacteria consume the organic waste (4).
Nyberg L,2014, Our hidden bacterial friends keep us all alive- shewanella oneidensis

Fredrickson J, Marshall M, 2006, Shewanella Uranium Reduction role described in PLoS article, Biological Science division research highlights Pacific Northwest national laboratory, 492.

Kouzuma A, Kasai T, Hirose A, Watanabe K, Catabolic and regulatory systems in Shewanella oneidensis MR-1 involved in electricity generation in microbial fuel cells.

Cheung C.L, Tabor A, 2018,Could Electricity-Producing Bacteria Help Power Future Space Missions?

8

Shewanella oneidensis growing on hematite

Shewanella oneidensis growing on hematite

Photo from Oak Ridge National Laboratory

The process of generating electricity

Shewanella oneidensis viewed under a microscope

4

Where are the Shewanella oneidensis bacteria found

Where are the Shewanella oneidensis bacteria found

The S.oneidensis bacteria are found free-living in fresh water and often in marine sediments (1). They are also found in soil sediments (2).
Conley B, 2019, Microbial extracellular electron transfer is a far out metabolism,American society for microbiology
Nyberg L,2014, Our hidden bacterial friends keep us all alive- shewanella oneidensis

5

Shewanella oneidensis are found in marine sediments

Shewanella oneidensis are found in marine sediments

scource by Lyle Nyberg