biology

Photobacterium damselae subsp. damselae

Photobacterium damselae subsp. damselae 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 Photobacterium damselae subsp. damselae rather than just read about it. In short: Photobacterium damselae subsp. damselae (previously known as Vibrio damsela) is a halophilic gram-negative rod-shaped bacterium. Commonly found in marine environments, P.d. subsp. damselae can cause disease in many species of marine wildlife and is an emerging threat in aquaculture.

Key takeaways

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

Reference excerpt

Photobacterium damselae subsp. damselae (previously known as Vibrio damsela) is a halophilic gram-negative rod-shaped bacterium. Commonly found in marine environments, P.d. subsp. damselae can cause disease in many species of marine wildlife and is an emerging threat in aquaculture. In humans Photobacterium damselae subsp. damselae can cause severe infections. The type strain of Photobacterium damselae subsp damselae is ATCC 33539T.

Taxonomy In 1971 a novel marine bacterium was isolated from a patient with an infected wound. The same organism was recovered in 1981 from the skin ulcers of a blacksmith damselfish and it was subsequently named Vibrio damselae after the fish from which it was first isolated. It was briefly reclassified as Listonella damsela based on 5S RNA sequencing. The name Photobacterium damselae was proposed in 1991 when researchers found that the microbe shared several key phenotypic traits with members of the genus Photobacteria, namely the absence of a flagellar sheath and accummulation poly-β-hydroxybutyrate. Further phylogenetic studies found that Photobacterium damselae shared 80% DNA relatedness with Pasteurella piscida suggesting that both strains belonged to the same species. The two organisms were reclassified as Photobacterium damselae subsp. damselae and Photobacterium damselae subsp. piscida respectively.

Characteristics

Culture P. damselae grows readily on media used in clinical laboratories, including TCBS agar. On media supplemented with blood, P. damselae produces beta-hemolytic colonies. The degree of hemolysis can vary significantly between isolates.

Virulence factors P. damselae subsp. damselae's virulence in mammals and fish is determined by a large virulence plasmid called pPHDD1, which encodes two toxins, damselysin (Dly) and HlyApl. P. damselae subsp. damselae produces a heat-labile cytolytic toxin called damselysin (Dly). Dly is a phospholipase D with activity against sphingomyelin. This toxin exerts strong hemolytic activity in the erythrocytes across a variety of animal species. Dly and its gene (dly) are considered to play an important role in the virulence of this organism. This species also produces a small β-pore-forming-toxin called phobalysin (PhlyP). Multiple PhlyP come together as oligomers to form small pores on cells that cause potassium leakage. In vitro studies suggest that P. damselae subsp. damselae can utilize heme, hemoglobin, and ferric ammonium citrate as sole iron sources.

Pathogenicity

In humans Photobacterium damselae subsp. damselae infections most commonly manifest as sepsis and soft tissue infections, especially when wounds are exposed to marine water. Soft tissue infections can progress into severe disease such as necrotizing fasciitis over a matter of hours. In one case reported in 1996, a 64-year-old man reported to a hospital with a swollen red hand 14 hours after sustaining an injury while unhooking a saltwater perch. Despite extensive debridement and the initiation of empiric antibiotic therapy the man was later found responseless in his room. The man was pronounced deceased 36 hours after the initial injury.

In marine animals Photobacterium damselae subsp. damselae has been isolated from numerous marine animals including bigeye trevally and rainbow trout. In vitro studies have found that the bacterium can be transmitted through the water.

References

Illustrations

Worked examples

Example 1 — a first encounter with Photobacterium damselae subsp. damselae

Start with the simplest possible case. Write down what Photobacterium damselae subsp. damselae 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 Photobacterium damselae subsp. damselae 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 Photobacterium damselae subsp. damselae 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 Photobacterium damselae subsp. damselae

In research: Photobacterium damselae subsp. damselae 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 Photobacterium damselae subsp. damselae 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: Photobacterium damselae subsp. damselae is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bacterial diseases of fish, Gram-negative bacteria, Marine microorganisms, so understanding it makes those chapters shorter.
In everyday life: Look for Photobacterium damselae subsp. damselae 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 Photobacterium damselae subsp. damselae in 20 minutes

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

Frequently asked questions

What is Photobacterium damselae subsp. damselae in simple terms?

Why does Photobacterium damselae subsp. damselae 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 Photobacterium damselae subsp. damselae?

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 Photobacterium damselae subsp. damselae.