Name: prokaryote chromosomes and plasmids
Uploaded: 2025-08-06T09:37:52.000Z
Duration: 46 s
Channel: JoVE

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North Carolina K-12 Science Standard Course of Study

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Biology

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From Molecules to Organisms- Structures and Processes

LS.Bio.2.1

Genomic DNA in Prokaryotes

- [Istruttore] Come gli
organismi più complessi,

i procarioti usano DNA a doppio filamento

come materiale genetico.

Tuttavia, questi organismi
unicellulari organizzano

e conservano il DNA in modo diverso.

La cellula procaritoide

non ha un vero nucleo
legato alla membrana.

Invece, un'area del
citoplasma, il nucleoide,

ospita l'intero genoma in un cromosoma

arrotolato e a doppio filamento.

Il DNA qui e' profondamente intaccato,

super arrotolato per una
conservazione efficiente.

Oltre al genoma completo,

molecole di DNA a doppio filamento
più piccole, le plasmidi,

esistono nel citoplasma.

Si replicano indipendentemente
dalla cellula

e possono contenere geni

che conferiscono la
sopravvivenza delle cellule

come la resistenza agli
antibiotici se esposta

ad un antibiotico come l'ampicillina.

Millan, Alvaro San. "Evoluzione della resistenza agli antibiotici mediata da plasmidi nel contesto clinico". Trends in Microbiology 26, n. 12 (1 dicembre 2018): 978–85. <a href="https://doi.org/10.1016/j.tim.2018.06.007" target="__blank">https://doi.org/10.1016/j.tim.2018.06.007</a>.

dna genomico nei procarioti

Il genoma della maggior parte degli organismi procacariotici è costituito da DNA a doppio filamento organizzato in un cromosoma circolare in una regione di citoplasma chiamata nucleoide. Il cromosoma è strettamente avvolto, o supercoiled, per una conservazione efficiente. I procati contengono anche altri pezzi circolari di DNA chiamati plasmidi. Questi plasmidi sono più piccoli del cromosoma e spesso portano geni che conferiscono funzioni adattive, come la resistenza agli antibiotici.

<h4>Diversità genomica nei batteri</h4>

Sebbene i genomi batterici siano molto più piccoli dei genomi eucarioti, variano notevolmente in termini di dimensioni e contenuto genico. Uno dei più piccoli genomi batterici conosciuti è quello del Mycoplasma genitalium, un patogeno trasmesso sessualmente che causa infezioni delle vie urinarie e genitali negli esseri umani. Il genoma di M. genitalium è lungo 580.076 coppie di basi ed è costituito da 559 (476 codifica e 83 non codificanti). All'altra estremità dello spettro si trova un particolare ceppo di cellulosum di srangio, un batterio che abita il suolo. Il genoma della cellulosa S. è enorme per un batterio lungo 14.782.125 coppie di basi, codificando 11.599 geni.

<h4>I batteri possono acquisire resistenza agli antibiotici da Plasmidi</h4>

Prima della scoperta di antibiotici, lesioni minori potrebbero diventare mortali a causa dell'incapacità di fermare semplici infezioni batteriche. La scoperta della penicillina nel 1928 ha fatto dante all'era degli antibiotici, caratterizzata dalla rivoluzione dei trattamenti medici e dall'aumento dell'aspettativa di vita. Tuttavia, l'uso eccessivo di antibiotici nell'uomo e negli animali agricoli ha causato l'evoluzione della resistenza agli antibiotici da parte di alcuni batteri, rendendoli meno efficaci o inefficaci. I geni di resistenza agli antibiotici possono essere portati su plasmidi, il che è problematico perché molti batteri possono scambiare plasmidi con specie imparentate lontanamente attraverso un processo chiamato coniugazione batterica. La resistenza agli antibiotici può quindi diffondersi rapidamente attraverso le popolazioni batteriche, evidenziando l'urgente necessità di sviluppare nuovi antibiotici.

DNA genomico nei procarioti

The genome of most prokaryotic organisms consists of double-stranded DNA organized into one circular chromosome in a region of cytoplasm called the ...

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prokaryote chromosomes and plasmids

Most prokaryotes store their DNA in one circular chromosome inside the nucleoid, a region of cytoplasm. This chromosome is double-stranded and tightly wound, or supercoiled, so it fits efficiently inside the cell. Prokaryotes also carry smaller circular DNA pieces called plasmids.

Plasmids often carry genes that give bacteria helpful traits. One important example is antibiotic resistance. Bacteria can gain these plasmids and the traits they carry, which can help them adapt to changing conditions.

Bacterial genomes can differ a lot in size and gene content. Mycoplasma genitalium has one of the smallest known bacterial genomes. It is 580,076 base pairs long and contains 559 genes, including 476 coding genes and 83 noncoding genes.

At the other extreme, a strain of Sorangium cellulosum has a much larger genome for a bacterium. Its genome is 14,782,125 base pairs long and encodes 11,599 genes. These examples show how much prokaryotic genomes can vary.

Plasmids also matter because they can spread antibiotic resistance. Before antibiotics were discovered, even minor injuries could become deadly bacterial infections. Penicillin, discovered in 1928, helped start the antibiotic era and greatly improved medical treatment and life expectancy.

Overuse of antibiotics in people and agricultural animals has helped some bacteria evolve resistance. Resistance genes can move on plasmids, and many bacteria can exchange plasmids with distantly related species through bacterial conjugation. This can spread resistance quickly through bacterial populations and shows why new antibiotics are still needed.

Prokaryote Chromosomes and Plasmids

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genomic dna in prokaryotes

Most prokaryotes store their DNA in one circular chromosome inside the nucleoid, a region of cytoplasm. This chromosome is double-stranded and tightly wound, or supercoiled, so it fits efficiently inside the cell. Prokaryotes also carry smaller circular DNA pieces called plasmids. Plasmids often carry genes that give bacteria helpful traits. One important example is antibiotic resistance. Bacteria can gain these plasmids and the traits they carry, which can help them adapt to changing...

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cancer

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Cancer develops when mutations affect genes that control cell division. Those changes can remove the normal brakes on growth and lead to uncontrolled cell proliferation. Modern science and medicine have improved how cancer is understood and treated, and some patients can now be cured. There is still no single cure for cancer because cancer is not one disease. It is a large group of many diseases. Even when two people have the same mutation in an oncogene or a tumor suppressor gene, their...

key terms and concepts

Learn how prokaryotes package DNA in a circular chromosome and plasmids, and how plasmids can spread antibiotic resistance between bacteria.

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Prokaryote Chromosomes and Plasmids

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