Study Guide

Prokaryotes Terms

Advertisement - Guide continues below

Prokaryotes Terms


Type of Gram-positive bacterium that notably grows in threadlike structures called filaments.


Agar is a substance derived from seaweed that is used to make the media in petri dishes solid. Scientists originally used gelatin (the ingredient that makes Jell-O solid), but agar’s solidity at higher temperatures and inertness have made it the preferred hardener to this day.


Ammonia is a simple nitrogen-containing compound. Its formula is NH3. It is the product of nitrogen-fixing bacteria. Nitrogen is essential for life, and most organisms can’t use N2, which in the atmosphere, but can use ammonia to grow.


An antibiotic is a chemical compound that kills microbes or inhibits their growth.


Archaea is one of the three domains of life. They are single-celled organisms that, like bacteria, lack the nuclei and other organelles that eukaryotes have. Archaea, however, have different cell walls from bacteria, and have some enzymes for central processes that resemble eukaryotic proteins more than bacterial ones.


Bacillus means "little rod" and can be used either to refer to rod-shaped bacteria, generally, or the genus Bacillus, specifically. Like Bacillus anthracis (anthrax), a pretty scary little rod.


Bacteria are a domain of life, along with archaea and eukaryotes. Bacteria, like archaea, are single celled organisms that lack nuclei. Bacteria and archaea have some differences in central processes, notably transcription and translation, as well as different cell walls.


Antibiotics that kill bacteria are called bacteridical.


A virus that infects bacteria. It’s the turducken of infectious diseases.


Bacteriostatic antibiotics work by blocking growth rather than killing bacteria directly.


A biofilm is a community of cells held together by a slippery goo called EPS (see EPS definition below).

Broad-Spectrum Antibiotic

This is an antibiotic that targets many different species of bacteria.


A capsule is polysaccharide level that surrounds some prokaryotic cells.

Cell wall

The cell wall is the protective layer that surrounds cells. A bacterial cell wall is composed of peptidoglycan, while archaeal and eukaryotic cells, which have cells walls, used different materials.


Cellulase is an enzyme that is released by cells and degrades cellulose.


Cellulose is a major structural material in plant cell walls. It is a complex material made up of a lot of individual glucose (or sugar) molecules.


A painless skin lesion that occurs during the early stages of the disease syphilis. Syphilis is transmitted by contact between an uninfected person and a chancre on an infected person.


Chemoautotrophs are organisms that live off of the chemicals around them. Unlike photoautotrophs, chemoautotrophs cannot perform photosynthesis. Unlike chemoheterotrophs, chemoautotrophs can use carbon dioxide as a carbon source.


A community of microbes that has grown and divided into enough cells to be seen without requiring a microscope.


The term coccus (plural cocci) is used for cells with a spherical shape.


Commensal refers to a symbiotic relationship that is different from mutualism in that one species benefits while the other is unaffected.


Act of bringing something together

Class of verbs with same base

Conjugation Bridge

The conjugation bridge is a structure formed between mating bacteria.

Cytoplasmic Membrane

The cytoplasmic membrane is the inner membrane of Gram-negative bacteria, and the only membrane of Gram-positive bacteria and archaea. The cytoplasmic membrane is composed of phospholipids and keeps all the cellular goo inside the cell.


While spores (see spore below) are made by several branches of life, an endospore specifically refers to a bacterial spore.


The term endotoxin refers to lipopolysaccharide (see its definition below), the outer part of the outer membrane of Gram-negative bacteria. It is called endotoxin because it is a part of the cell, rather than secreted by it.

Enteric bacteria

Enteric bacteria live in the intestines.

Eubacterium Eubacterium

Eubacterium is an older term for bacterium.


Eutrophication refers to the excessive growth of algae in a water system after an influx of nutrients. The resulting oxygen depletion is often harmful to other life forms, including fish.

Earnings Per Share (EPS)

Imagine a lemonade stand. 20 grand in sales and 16 grand in gross profits. And yeah, we’ll spare you the “gross” jokes. The customer asked the lemonade-ista what the fly was doing in his lemonade, and yes, of course she said "the backstroke."

After gross profits on the income statement, there are operating expenses...and then operating profits. Then there are taxes. Yeah, there are always taxes. And then finally net income, a.k.a. earnings. But then, below earnings, you’ll see that there are a hundred shares in this little company.

The founder owns 60 of them. Mom owns 10. The new step-dad owns 20. He was guilted into it by the divorce lawyer. And Enrique the gardener, who has cleverly weaseled his way into the family’s hearts and minds, owns the last 10. It’s annual report time, and the investors want to know what their earnings per share that they can all compare relative performance on their investments.

So...the total earnings of the company was $5,250. Which means that the earnings per share were that 5,250 figure divided by 100...or $52.50. That’s what each share earned if you divvied the company into 100 little pie slices, or parts. So yeah…earnings per share equals earnings per slice o’ pie.

Wait—“lemonade pie”…has that been done yet? Hm…time for a new business venture…


Exotoxin is a toxic protein that is secreted by a microorganism.


An extremophile is an organism that prefers to live in harsh environments. Examples of harsh environments include high and low temperate and high and low pH, like a hydrothermal vent in the ocean or the inside of a cow’s stomach.

Facultative Anaerobe

This refers to an organism that grows well in both the presence and absence of oxygen.


The flagellum is a whip-like appendage that enables cells to swim.


The polysaccharide coat that surrounds some bacterial cells. If rigid, it is called a capsule; if not, it is referred to as a "slime layer".


In Gram-negative bacteria the cytoplasm is surrounded by two membrane layers. By contrast, Gram-positive bacteria only have one membrane layer. The extra space Gram-negative bacteria have between their membranes is called the periplasm. Gram-negative bacterial cell walls are relatively thin and are located in the periplasm. They are called Gram-negative because they are not colored by the Gram-stain test.


Gram-positive bacteria differ from Gram-negative bacteria in that they have one, rather than two, membrane layers surrounding their cytoplasm. Their thick cell wall appears outside this membrane. Gram-positive bacteria are stained by the Gram-stain test.

Gram Stain

Gram stain is the dye crystal violet, which is used in a test to differentiate Gram-positive from Gram-negative bacteria.


The characteristic of having one set of unpaired chromosomes. Gametes (eggs and sperm) in a sexually reproducing organism are haploid.


Cyanobacteria that can fix nitrogen, but cannot perform photosynthesis.


The outer part of the outer membrane of Gram-negative bacteria is composed of lipopolysaccharide (LPS). LPS is made up of fatty acids that go into the membrane and polysaccharide that sticks out. LPS helps maintain the integrity of Gram-negative cells, which have thin cell walls.


Media is a mix of compounds concocted for growing cells in a laboratory, aka a "science factory."


A membrane is the bilayer of lipids (fats) that surrounds cells. Proteins such as transporters and pores are inserted in membranes.


A mesophile is an organism that grows at moderate temperatures. Mesophiles are contrasted with thermophiles, which prefer warm temperatures, and psychrophiles, that prefer cold temperatures.


A methanogen is an archaea that produce the greenhouse gas methane.

Miasma Theory

Miasma Theory is an outdated theory based on the idea that disease comes from bad vapors in the air.

Nitrogen fixation

Nitrogen fixation is a process by which certain microorganisms transform atmospheric nitrogen, N2, into the nitrogen-containing compound NH3.

Obligate aerobe

An organisms that can only grow in the presence of oxygen.

Obligate anaerobe

An organism that can only grow in the absence of oxygen.

Opportunistic pathogen

An opportunistic pathogen is a strain that is normally commensal, but becomes pathogenic under certain conditions, e.g. compromised immune system or access to the bloodstream.


An organelle is a cellular compartment. Organelles are a hallmark of eukaryotes; they are non-existent in prokaryotes.

Outer Membrane

This refers to the outer of the two membranes that surround Gram-negative cells. The outer layer of the outer membrane is composed of LPS while the inner layer is composed of phospholipid.


A pathogen is an organism that can cause disease.


Pathology can mean two things. (I) Deviation from a normal, healthy condition. (II) The study of disease.


Antibiotics derived from the mold Penicillium.


Peptidoglycan is a compound made up of two sugars bound to a short peptide (3-5 amino acids). It is the basic unit of the bacterial cell wall.


The space between (Dave Matthews, anyone?) the cytoplasmic (inner) membrane and outer membrane in Gram-negative bacteria.


Photoautotrophs are organisms that perform photosynthesis and can use carbon dioxide as a carbon source. Contrast with chemoautotrophs.


The pilus (plural: pili) is a small appendage that bacteria use in order to stick to other bacteria or to various surfaces. Special pili, called sex pili, are used to transfer DNA between bacteria. Each pilus is made up of lots of many interlinked units of a protein called pilin.


A plasmid is a small piece of DNA, maintained separately from the chromosome. Plasmids are common in prokaryotes, but rare in eukaryotes.

Population bloom

Rapid increase in the population of certain species.


A reservoir is a place where something is stored.

Restriction enzyme

A restriction enzyme is an enzyme which cuts DNA at a specific site.


A saprophyte is an organism that lives off dead matter.

Septic shock

Septic shock is a dangerous immune system overreaction, typically in response to bacterial endotoxin.


Serotype is a classification of microorganisms that is based on how antibodies interact with them. Antibodies are proteins from multicellular organisms—rabbit and mouse antibodies are most commonly used—that specifically recognize different features of microorganisms. For example, some antibodies recognize the LPS or the proteins that make up flagella.


Spirillum (plural spirilla) is the term for bacteria with a rigid spiral or corkscrew-like shape, like uncooked rotini.


Spirochetes, like spirilla, are spiral-shaped bacteria. Unlike spirilla, however, they are bendable, like cooked rotini. Is it dinnertime yet?

Spontaneous Generation

This refers to an incorrect theory that life sprang from nowhere. For example, people believed that under the right conditions, mud would transform itself into earth worms.


A single haploid cell that contains the genetic information necessary to make a new plant.


These are bacteria that are widespread on skin and in the soil. They are sphere-shaped (cocci) that group in grape-like clusters. MRSA (methicillin-resistant Staphylococcus aureus) is an antibiotic-resistant form of a Staphylococcus species.


These are sphere shape cocci that grow in a chain. Certain Streptococcus species cause strep throat as well as rheumatic and scarlet fever.


Something that is sterile has no living things (cells or spores) in it. (Sterile can also mean unable to produce bear children.)

Sulfa drugs

The first antibiotics ever developed. Their name comes from sulfonamide, a chemical group they all contain.


Symbiosis is an interaction between different species that is beneficial to at least one species. Symbiotic relationships include mutualism, commensalism, and parasitism.


An antibiotic originally identified in Streptomyces bacteria. It works by targeting protein synthesis.


Thermoacidophiles are archaea that thrive in hot, acidic conditions.


Thermophilic means prefers hot conditions.


A toxin is a poisonous substance.


Transduction is the transfer of genetic material by a virus.


Transformation is the introduction of DNA into an organism directly from the outside environment. Transformation is in contrast with transduction, in which the DNA is inserted by a virus, and conjugation, in which the DNA is donated by another, attached cell.


A mathematical structure that has both magnitude and direction, represented by an ordered pair of components.

Roots of Common Terms in Prokaryotes

(L - Latin, G - Greek)


bacillus = small rod or staff (L)


bacterion = staff (G) (* this is because the first bacteria seen had this shape)


bacterion = staff (G); cida = slayer (L)


bacterion = staff (G); phagos = eating (G)


bacterion = staff (G); stasis = stopping (G)


Chemo = of chemical (L); auto = by oneself (G); trophikos = nourishment (G)


kokkos = grain, seed, berry (G)


Com = together with (or sharing) (L); mensa = a table (L)


extremus = outermost (L); philos = loving (G)


flagellum = whip (L)


haploos = single (G)


lipos = fat (G); poly = much (G); saccharum = sugar (L)


meso = middle (G); philos = loving (G)


stain, defilement (G)


organ = tool, instrument (G); ella = diminutive form (L)


pathos = suffering, disease (G); genes = producer of (G)


peptos = cooked, digested (G); glykys = sweet (G)

Periplasm peri

= going around (G); something molded (G)


pilus = hair (L)


plasma = something molded (G)


spira = coil (L)


spira = coil (L); chaite = hair (G)


spora = seed (G)

Symbiosis symbiosis

= living together, companionship (G)


vector = carrier, bearer (L)

This is a premium product

Tired of ads?

Join today and never see them again.

Please Wait...