prokaryotes

(noun)

( /proʊkæri.oʊts/, pro-kah-ree-otes or /proʊkæriəts/, pro-kah-ree-əts) a group of organisms whose cells lack a cell nucleus (karyon), or any other membrane-bound organelles. Most prokaryotes are unicellular organisms, although a few such as myxobacteria have multicellular stages in their life cycles.

Related Terms

Examples of prokaryotes in the following topics:

  • Bacterial Chromosomes in the Nucleoid

    • A genophore is the DNA of a prokaryote.
    • It is commonly referred to as a prokaryotic chromosome.
    • The genophore is circular in most prokaryotes, and linear in very few.
    • These organelles are very similar to true prokaryotes.
    • Prokaryote cell (right) showing the nucleoid in comparison to a eukaryotic cell (left) showing the nucleus.

  • Common Bacterial Traits

    • Bacteria are a subset of prokaryotes and while very different, they still have some common features.
    • Bacteria constitute a large domain of prokaryotic microorganisms.
    • Bacteria as prokaryotes share many common features, such as:
    • The term "bacteria" was traditionally applied to all microscopic, single-cell prokaryotes, having the similar traits outlined above.
    • It should be noted that Bacteria and Archaea are similar physically, but have different ancestral origins as determined by DNA of the genomes that encode different prokaryotes.

  • Prokaryotic Transcription and Translation Are Coupled

    • Prokaryotic transcription occurs in the cytoplasm alongside translation and can occur simultaneously.
    • Prokaryotic transcription is the process in which messenger RNA transcripts of genetic material in prokaryotes are produced, to be translated for the production of proteins.
    • Prokaryotic transcription occurs in the cytoplasm alongside translation .
    • Prokaryotic transcription and translation can occur simultaneously.
    • Transcription is controlled by a variety of regulators in prokaryotes.

  • Chemical Analysis of Microbial Cytoplasm

    • Prokaryotes may sometimes contain an extra chromosomal piece of DNA referred to as the plasmid.
    • Unlike eukaryotes, prokaryotes, specifically bacteria, typically contain one cytosol-specific ribosome.
    • In prokaryotes, for example, lipid droplets are plentiful in cells which require lipid storage mechanisms.
    • These lipid droplets store molecules such as fatty acids which are present in the cytoplasmic membrane of prokaryotes.
    • Structure of a typical prokaryotic cell.

  • Inhibiting Nucleic Acid Synthesis

    • Antimicrobial drugs inhibit nucleic acid synthesis through differences in prokaryotic and eukaryotic enzymes.
    • The antimicrobial actions of these agents are a result of differences in prokaryotic and eukaryotic enzymes involved in nucleic acid synthesis.
    • Prokaryotic transcription is the process in which messenger RNA transcripts of genetic material are produced for later translation into proteins.

  • Antibiotics from Prokaryotes

    • Most of the currently available antibiotics are produced by prokaryotes mainly by bacteria from the genus Streptomyces.
    • Explain the role of Streptomyces and other prokaryotes in antibiotic production

  • Ribosomes

    • In prokaryotes, ribosomes can be found in the cytosol as well.
    • This protein-synthesizing organelle is the only organelle found in both prokaryotes and eukaryotes, asserting the fact that the ribosome is a trait that evolved early on, most likely present in the common ancestor of eukaryotes and prokaryotes.
    • All prokaryotes have 70S (where S=Svedberg units) ribosomes while eukaryotes contain larger 80S ribosomes in their cytosol.
    • Compare and contrast ribosome structure and function in prokaryotes and eukaryotes

  • ABC Transporters

    • ATP-binding cassette transporters (ABC-transporters) are members of a protein superfamily that is one of the largest and most ancient families with representatives in all extant phyla from prokaryotes to humans.
    • ABC transporters are involved in tumor resistance, cystic fibrosis and a range of other inherited human diseases along with both bacterial (prokaryotic) and eukaryotic (including human) development of resistance to multiple drugs.
    • In prokaryotes, importers mediate the uptake of nutrients into the cell.
    • Exporters or effluxers, which are both present in prokaryotes and eukaryotes, function as pumps that extrude toxins and drugs out of the cell.
    • Summarize the function of the three major ABC transporter categories: in prokaryotes, in gram-negative bacteria and the subgroup of ABC proteins

  • Shared Features of Bacteria and Archaea

    • Within prokaryotes, archaeal cell structure is most similar to that of Gram-positive bacteria, largely because both have a single lipid bilayer and usually contain a thick sacculus of varying chemical composition.
    • In phylogenetic trees based upon different gene/protein sequences of prokaryotic homologs, the archaeal homologs are more closely related to those of Gram-positive bacteria.
    • Gupta's proposal is also supported by other work investigating protein structural relationships and studies that suggest that Gram-positive bacteria may constitute the earliest branching lineages within the prokaryotes.

  • Cell Inclusions and Storage Granules

    • This is often true when large evolutionary distances are crossed; for example, a cDNA isolated from Eukarya and expressed as a recombinant gene in a prokaryote, risks the formation of the inactive aggregates of protein known as inclusion bodies.
    • For example, eukaryotic systems for carbohydrate modification and membrane transport are not found in prokaryotes.
    • The internal microenvironment of a prokaryotic cell (pH, osmolarity) may differ from that of the original source of the gene.
    • In addition, the fine controls that may keep the concentration of a protein low will also be missing in a prokaryotic cell, and overexpression can result in filling a cell with ectopic protein that, even if it were properly folded, would precipitate by saturating its environment.