science

Rhodospirillum rubrum

Rhodospirillum rubrum is a science 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 Rhodospirillum rubrum rather than just read about it. In short: Rhodospirillum rubrum (R. rubrum) is a Gram-negative bacterium, with a size of 0.8-1 μm. It is phylogenetically classified as a purple nonsulfur bacterium.

Key takeaways

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

Reference excerpt

Rhodospirillum rubrum (R. rubrum) is a Gram-negative bacterium, with a size of 0.8-1 μm. It is phylogenetically classified as a purple nonsulfur bacterium. It is a facultative anaerobe with a large set of possible metabolisms depending on the conditions of its environment. It's capable of using oxygen for aerobic respiration under aerobic conditions, or an alternative terminal electron acceptor for anaerobic respiration under anaerobic conditions. Alternative terminal electron acceptors for R. rubrum include dimethyl sulfoxide or trimethylamine oxide. Under aerobic growth photosynthesis is genetically suppressed and R. rubrum is then colorless. After the exhaustion of oxygen, R. rubrum immediately starts the production of photosynthesis apparatus including membrane proteins, bacteriochlorophylls and carotenoids, i.e. the bacterium becomes photosynthesis active. The repression mechanism for the photosynthesis is poorly understood. The photosynthesis of R. rubrum differs from that of plants as it possesses not chlorophyll a, but bacteriochlorophylls. While bacteriochlorophyll can absorb light up to a maximum wavelength of 800 to 925 nm, chlorophyll absorbs light having a maximum wavelength of 660 to 680 nm. R. rubrum is a spiral-shaped bacterium (spirillum, plural form: spirilla). R. rubrum is also a nitrogen fixing bacterium, i.e., it can express and regulate nitrogenase, a protein complex that can catalyse the conversion of atmospheric dinitrogen into ammonia. When the bacteria are exposed to ammonia, darkness, and phenazine methosulfate, nitrogen fixation stops. Due to this important property, R. rubrum has been the test subject of many different groups, so as to understand the complex regulatory schemes required for this reaction to occur. It was in R. rubrum that, for the first time, post-translational regulation of nitrogenase was demonstrated. Nitrogenase is modified by an ADP-ribosylation in the arginine residue 101 (Arg101) in response to the so-called "switch-off" effectors - glutamine or ammonia - and darkness. R. rubrum has several potential uses in biotechnology:

Quantitative accumulation of PHB (polyhydroxybutyrate) precursors in the cell for the production of bioplastic. Production of biological hydrogen fuel. Model system for studying the conversion from light energy to chemical energy and regulatory pathways of the nitrogen fixation system.

References

External links Type strain of Rhodospirillum rubrum at BacDive - the Bacterial Diversity Metadatabase

Illustrations

Worked examples

Example 1 — a first encounter with Rhodospirillum rubrum

Start with the simplest possible case. Write down what Rhodospirillum rubrum claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Rhodospirillum rubrum 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 Rhodospirillum rubrum 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 Rhodospirillum rubrum

In research: Rhodospirillum rubrum appears in science 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 Rhodospirillum rubrum 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: Rhodospirillum rubrum is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bacteria described in 1887, Phototrophic bacteria, Rhodospirillales, so understanding it makes those chapters shorter.
In everyday life: Look for Rhodospirillum rubrum 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 Rhodospirillum rubrum in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rhodospirillum rubrum 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 Rhodospirillum rubrum out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rhodospirillum rubrum in simple terms?

Rhodospirillum rubrum (R. rubrum) is a Gram-negative bacterium, with a size of 0.8-1 μm. It is phylogenetically classified as a purple nonsulfur bacterium.

Why does Rhodospirillum rubrum matter?

Because it connects several science 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 Rhodospirillum rubrum?

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 Rhodospirillum rubrum.