biology

Shewanella

Shewanella is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Shewanella rather than just read about it. In short: Shewanella is the sole genus included in the marine bacteria family Shewanellaceae. Some species within it were formerly classed as Alteromonas.

Key takeaways

Shewanella belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Shewanella to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Shewanella from memory before moving on to harder problems.

Reference excerpt

Shewanella is the sole genus included in the marine bacteria family Shewanellaceae. Some species within it were formerly classed as Alteromonas. Shewanella consists of facultatively anaerobic Gram-negative rods, most of which are found in extreme aquatic habitats where the temperature is very low and the pressure is very high. Shewanella bacteria are a normal component of the surface flora of fish and are implicated in fish spoilage. Shewanella chilikensis is a species of the genus Shewanella commonly found in the marine sponges of Saint Martin's Island of the Bay of Bengal, Bangladesh. Shewanella oneidensis MR-1 is a widely used laboratory model to study anaerobic respiration of metals and other anaerobic extracellular electron acceptors, and for teaching about microbial electrogenesis and microbial fuel cells.

Biochemical characteristics of Shewanella species Colony, morphological, physiological, and biochemical characteristics of Shewanella species are shown in the Table below.

Note: + = Positive; – =Negative

Metabolism Currently known Shewanella species are heterotrophic facultative anaerobes. In the absence of oxygen, members of this genus possess capabilities allowing the use of a variety of other electron acceptors for respiration. These include thiosulfate, sulfite, or elemental sulfur, as well as fumarate. Marine species have demonstrated an ability to use arsenic as an electron acceptor as well. Some members of this species, most notably Shewanella oneidensis, have the ability to respire through a wide range of metal species, including manganese, chromium, uranium, and iron. Reduction of iron and manganese through Shewanella respiration has been shown to involve extracellular electron transfer through the employment of bacterial nanowires, extensions of the outer membrane.

Applications The discovery of some of the respiratory capabilities possessed by members of this genus has opened the door to possible applications for these bacteria. The metal-reducing capabilities can potentially be applied to bioremediation of uranium-contaminated groundwater, with the reduced form of uranium produced being easier to remove from water than the more soluble uranium oxide. Scientists researching the creation of microbial fuel cells, designs that use bacteria to induce a current, have also made use of the metal reducing capabilities some species of Shewanella possess as a part of their metabolic repertoire.

Significance One of the roles that the genus Shewanella has in the environment is bioremediation. Shewanella species have great metabolic versatility; they can reduce various electron acceptors. Some of the electron acceptors they use are toxic substances and heavy metals, which often become less toxic after being reduced. Examples of metals that Shewanella are capable of reducing and degrading include uranium, chromium, and iron. Its ability to decrease toxicity of various substances makes Shewanella a useful tool for bioremediation. Specifically, Shewanella oneidensis strain MR-1 is often used to clean up contaminated nuclear weapon manufacturing sites. Shewanella also contributes to the biogeochemical circulation of minerals. Members of this genus are widely distributed in aquatic habitats, from the deep sea to the shallow Antarctic Ocean. Its diverse habitats, coupled to its ability to reduce a variety of metals, makes the genus critical for the cycling of minerals. For instance, under aerobic conditions, various species of Shewanella are capable of oxidizing manganese. When conditions are changed, the same species can reduce the manganese oxide products. Hence, since Shewanella can both oxidize and reduce manganese, it is critical to the cycling of manganese.

See also Shewanella haliotis Electric bacteria List of bacterial genera named after personal names

References

External links Shewanella Genome Projects (from Genomes OnLine Database) Comparative Analysis of Shewanella Genomes (at DOE's IMG system)

Illustrations

Worked examples

Example 1 — a first encounter with Shewanella

Start with the simplest possible case. Write down what Shewanella claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Shewanella before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Shewanella ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Shewanella

In research: Shewanella appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Shewanella in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Shewanella is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alteromonadales, Bacteria genera, Gram-negative bacteria, so understanding it makes those chapters shorter.
In everyday life: Look for Shewanella outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Shewanella in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Shewanella means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Shewanella out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Shewanella in simple terms?

Shewanella is the sole genus included in the marine bacteria family Shewanellaceae. Some species within it were formerly classed as Alteromonas.

Why does Shewanella matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Shewanella?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Shewanella.