biology

Gloeobacter

Gloeobacter 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 Gloeobacter rather than just read about it. In short: Gloeobacter is a genus of cyanobacteria. It is the sister group to all other photosynthetic cyanobacteria.

Key takeaways

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

Reference excerpt

Gloeobacter is a genus of cyanobacteria. It is the sister group to all other photosynthetic cyanobacteria. Gloeobacter's order, Gloeobacterales, is unique among cyanobacteria in not having thylakoids, which are characteristic for all other cyanobacteria and chloroplasts. Instead, the light-harvesting complexes (also called phycobilisomes), that consist of different proteins, sit on the inside of the plasma membrane (among the cytoplasm). Subsequently, the proton gradient in Gloeobacter is created across the plasma membrane, whereas it forms across the thylakoid membrane in cyanobacteria and chloroplasts. The whole genome of G. violaceus (strain PCC 7421) and of G. kilaueensis have been sequenced. Many genes for photosystem I and II were found missing, likely related to the fact that photosynthesis in these bacteria does not take place in the thylakoid membrane as in other cyanobacteria, but in the plasma membrane. There is also a genome for G. morelensis.

Description Gloeobacter violaceus produces several pigments, including chlorophyll a, β-carotene, oscillol diglycoside, and echinenone. The purple coloration is due to the relatively low chlorophyll content. G. kilaueensis grows with a few other bacteria as a purple-colored biofilm around 0.5 mm thick. Cultivated colonies are dark purple, smooth, shiny, and raised. G. kilaueensis is mostly unicellular, capsule-shaped, about 3.5×1.5 μm, and embedded in mucus. They divide over the width of the cell. Cells color gramnegative, and lack vancomycin resistance. They are not motile and do not glide. Growth ceases in complete darkness, so Gloeobacter is very likely obligatory photoautotrophic.

Species and distribution Gloeobacter violaceus was found on a limestone rock in the Swiss canton Obwalden. G. kilaueensis occurred within a lava cave at the Kilauea-caldera on Hawaii. It grew there at a temperature around 30 °C at very high humidity, with moisture condensing and dripping off the biofilm. Gloeobacter could have split off from the other cyanobacteria between 3.7 and 3.2 billion years ago. The species of Gloeobacter may have branched 280 million years ago.

Phylogeny

Notes:

GTDB has three more metagenome-only genera under Gloeobacteraceae, each with one species containing one genome. Aphanocapsa lilacina was published in 2016 to genus Aphanocapsa. The protologue is found in a copyrighted book, with no free online copies as of May 2025.

Related groups Anthocerotibacter panamensis, found in a sample of hornwort from a rainforest in Panama, also lacks thylakoids. It has very few of the genes that are required to perform photosynthesis, but is still able to perform it, very slowly. It may have been split from Gloeobacter about 1.4 Ga ago. This genus is officially a member of family Anthocerotibacteraceae within order Gloeobacterales. GTDB RS226 concurs in assigning Anthocerotibacter to Gloeobacterales, but is not yet aware of the name "Anthocerotibacteraceae" for the family; it instead calls the family "FY9".

See also List of bacteria genera List of bacterial orders

References

Illustrations

Worked examples

Example 1 — a first encounter with Gloeobacter

Start with the simplest possible case. Write down what Gloeobacter 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 Gloeobacter 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 Gloeobacter 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 Gloeobacter

In research: Gloeobacter 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 Gloeobacter 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: Gloeobacter is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cyanobacteria, Cyanobacteria genera, so understanding it makes those chapters shorter.
In everyday life: Look for Gloeobacter 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Gloeobacter” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Gloeobacter in 20 minutes

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

Frequently asked questions

What is Gloeobacter in simple terms?

Gloeobacter is a genus of cyanobacteria. It is the sister group to all other photosynthetic cyanobacteria.

Why does Gloeobacter 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 Gloeobacter?

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 Gloeobacter.