Chapter 19 Flashcards
Bacteria and Archaea
Prokaryotes; superficially similar in appearance, but striking structural and biochemical differences that reveal ancient evolutionary separation between the two groups.
Which organisms are members of the domains Archaea and Bacteria?
Earth’s first organisms were prokaryotes, single-cell organisms that lack organelles such as nucleus, chloroplasts, and mitochondria. For the first 1.5 billion years, all life was prokaryotic. Predominant form of life.
Peptidoglycan Molecules
Contained in cell walls of bacterial cells, a polysaccharide that also incorporates some amino acids, which helps strengthen the cell wall. Unique to bacteria, archaea does not have it on their cell walls.
What is a structural and compositional differences between Archaea and Bacterial cells?
Their plasma membranes, ribosomes, and RNA polymerases, as well as mechanics of basic processes such as transcription and translation.
Clades
Groups of species linked by descent from a common ancestor.
Appearance of Colonies
Groups of individuals that descended from a single cell.
The Gram Stain
A staining technique that distinguishes two types of cell-wall construction in bacteria. Depending on the results of the stain, these bacteria are classified as either gram-positive or gram-negative. Used as means of clade classification.
How big are bacteria and archaea?
very small, ranging from .02 to 10 micrometers in diameter. (in comparison, the diameters of eukaryotic cells range from about 10 to 100 micro meters).
Largest Known bacterium.
Thiomargarita namibiensis is 700 micrometers in diameter, visible to the naked eye.
Cell wall that surround prokaryotic cells most common shapes are:
Spherical, rodlike, and corkscrew-shaped.
How do prokaryotes survive and reproduce?
they adapt and both domains to inhabit and exploit a wide range of environments.
Some prokaryotes are motile. What does this mean?
They can move about. - Many of these motile prokaryotes have Flagella and it may appear at one end of a cell, in pairs (one at each end of the cell), as a tuft at one end of the cell, or scattered over the entire cell surface.
Flagella
Hair-like motile extension of the plasma membrane; it contains microtubules arranged in a 9+2 pattern. Propels some cells through fluids and allows to disperse into new habitats, migrate towards nutrients, and leave unfavorable environments.
Anatomic differences between gram positive prokaryotes and gram negative prokaryotes
gram positive bacteria lack the outermost “wheels”
Differences between bacterial flagella and archaeal flagella.
In bacterium flagella, a unique wheel-like structure embedded in the bacterial membrane and cell wall allows the flagellum to rotate. Archaeal flagella are thinner than bacterial and are constructed of different proteins. Archaeal flagella is still not well understood.
Biofilms
Sticky layer of protective slime, composed of polysaccharide or protein, which protects the cells and helps them adhere to surfaces. Slime-secreting prokaryotes of one or more species aggregate in colonies to form communities known as biofilms. ex. Dental plaque, formed by bacteria that inhabits the mouth.
Biofilms protection
Helps defend the embedded bacteria against a variety of attacks, including those launched by antibiotics and disinfectants. They are harmful to humans and very difficult to eradicate. Many infections of the body take the form of biofilms, including tooth decay, gum disease, and ear infections.
Endospores
Rod-shaped protective structure bacteria that forms inside a bacterium that contains genetic material and a few enzymes encased within a thick protective coat that protects the bacteria. After an endospore is formed, the bacterial cell that contains it breaks open, and the spore is released to the environment. All metabolic activity ceases until the spore encounters favorable conditions, at which time metabolism resumes and the spore develops into an active bacterium.
Prokaryotes are specialized for specific habitats
Even though they can occupy virtually every habitat, including extreme conditions, no single species of prokaryotes, however, is as versatile. Some stop growth at a specific temperature , and others survive for longer periods of time in other habitats.
Prokaryotes have diverse metabolisms.
Able to colonize diverse habitats partly because they have evolved diverse methods of acquiring energy and nutrients from environment. ex anaerobic respiration.
Anaerobs
an organism that can live and grown in the absence of oxygen. Some anaerobes are opportunists, engaging in anaerobic respiration when oxygen is lacking and switching back when oxygen becomes available. Many prokaryotes are strictly aerobic.
Energy sources for prokaryotes.
Can extract energy from an array of substances. Not only the sugars, carbs, fats and proteins, but also on compounds that are inedible or even poisonous to humans including petroleum, methane (natural gas) and solvents such as benzene and toluene.
Cyanobacteria
They use photosynthesis to capture energy directly from sunlight. -like green plants, photosynthetic bacteria possess chlorophyll. Most species produce oxygen as a by product of photosynthesis, but some known as the sulfur bacteria, use hydrogen sulfide instead of water in photosynthesis, releasing sulfur instead of oxygen. NO PHOTOSYNTHETIC ARCHAEA ARE KNOWN.
How do prokaryotes reproduce?
Most prokaryotes reproduce asexually by Binary Fission, a form of cell division that is much simpler than mitotic cell division. Produces genetically identical copies of the original cell. Under optimal conditions, they can divide about once every 20 minutes.
