Please enable JavaScript.
Coggle requires JavaScript to display documents.
Chapter 27 (Transformation and Transduction (In transformation, the…
Chapter 27
-
-
-
In Eukaryotes that have cell walls, such as plants and fungi, the walls are usually made of cellulose or chitin.
In contrast, most bacterial cell walls contain peptidoglycan, a polymer composed of modified sugars cross-linked by short polypeptides.
Most prokaryotes are unicellular, although the cells of some species remain attached to each other after cell division.
Prokaryotic cells typically have diameters of 0.5-5, much smaller than the 10-100 diameter of many eukaryotic cells.
Prokaryotes are well-organized, achieving all of an organism's life functions within a single cell, although they are unicellular and small cell-surface structure.
-
Nitrogen Metabolism
-
Whereas eukaryotes can obtain nitrogen only from a limited group of nitrogen compounds, prokaryotes can metabolize nitrogen in many forms.
Ex: Some cyanobacteria and some methanogens( a group of archaea) convert atmospheric nitrogen(N2) to ammonia (NH3), a process called nitrogen fixation.
-
-
Ex: nitrogen-fixing prokaryotes can increase the nitrogen available to plants, which cannot use atmospheric nitrogen but can use the nitrogen compounds that the prokaryotes produce form ammonia.
Metabolic Cooperation
Cooperation between prokaryotic cells allows them to use environmental resources they could not use as individual cells.
In some cases, this cooperation takes place between specialized cells of a filament.
Metabolic cooperation between different prokaryotic species often occurs in surface-coating colonies known as biofilms.
Most cells in a filament carry out only photosynthesis, while a few specialized cells called heterocysts(sometimes called heterocytes) carry out only nitrogen fixation.
Each heterocyst is surrounded by a thickened cell wall that restricts entry of O2 produced by neighboring photosynthetic cells.
Cells in biofilm secrete signaling molecules that recruit nearby cells, causing the colonies to grow.
Biofilm are common in nature, but they can cause problems by contaminating industrial products and medical equipment and contributing to tooth decay and more serious health problems.
Gram Stain
Developed by the 19th century Danish physician Hans Christian Gram, scientists can categorize many bacterial species according to differences in cell wall composition.
-
The walls of gram-negative bacteria have less peptidoglycan and are structurally more complex, with an outer membrane that contains lipopolysaccharides(carbohydrates bonded to lipids).
Gram staining is a valuable tool in medicine for quickly determining if a patient's infection is due to gram-negative or gram-positive bacteria.
The lipids portions of the lipopolysaccharides in the walls of many gram-negative bacteria are toxic, causing fever or shock.
-
-
-
Reproduction
-
By binary fission, a single prokaryotic cell divides into 2 cells, which then divides into 4,8,16, and so on.
Under optimal conditions, many prokaryotes can divide every 1-3 hours; some species can produce a new generation in only 20 minutes.
Motility
Unlike eukaryotes, prokaryotes lack a nucleus; their chromosome is located in the nucleoid, a region of cytoplasm that is not enclosed by a membrane.
In addition to its single chromosome, a typical prokaryotic cell may also have much smaller rings of independently replicating DNA molecules called plasmias, most carrying only a few genes
The genome of a prokaryote is structurally different from a eukaryotic genome and in most cases has considerably less DNA.
Conjugation and Plasmids
In a process called Conjugation, DNA is transferred between two prokaryotic cells(usually of the same species) that are temporarily joined.
The ability to form pili and donate DNA during conjugation results from the presence of a particular piece of DNA called the F factor(f for fertility).
The F factor of E. coli consists of about 25 genes, most required for the production of pili.
-