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Bacteria and Archaea Chapter 27 (Structural and functional adaptions…
Bacteria and Archaea Chapter 27
Diverse nutritional and metabolic adaptions have evolved in prokaryotes
Nitrogen Metabolism
For example: some cyanobacteria and some methanogens ( a group of archaea ) convert atmospheric nitrogen ( N2) to ammonia (NH2) a process called nitrogen fixation.
Nitrogen is essential for the production of amino acids and nucleic acids in all organisms.
Metabolic Cooperation
Heterocysts: (hereocytes cells that carry out only nitrogen fixation.
Biofilms: The metabolic cooperation between different prokaryotic species often occurs in surface - coating colonies.
Cooperation between prokaryotic cells allows them to use environmental sources they could not use as individual cells.
The role of oxygen in metabolism
Anaerobis respiration: is respiration using electron acceptors other than O2, such as nitrate ions ( NO3^-) or sulfate ions (SO4^2-).
Facultative anaerobes use O2 f it is present but can also carry out fermentation or anaerobic respiration in an anaerobic respiration in an anaerobic environment.
Obligate aerobes: must use O2 for cellular respiration and can not grow without it, but are also poisoned by it.
Prokaryotes have both beneficial and harmful impacts on humans
Pathogenic Bacteria
Example: More than 1 million people die each year of lung disease tuberculosis, caused by Mycobacterium turberculosis.
Exotoxins- are proteins secreted by certain bacteria and other oranisms (Vibrio cholerae).
Pathogenic prokaryotes are bacteria that have a negative reputation. ( Bacteria cause about half of all human disease)
Endotaxins- are lipopolysaccharide components of the outer membrane of gram-negative bacteria (Salmonella).
Prokaryotes in Research and technology
The prokaryotic CRISPR-Cas system helps bacteria and archaea defend against attack by viruses.
CRISPRs- short DNA repeats that interact with proteins known as the Cas proteins.
Bioremediation--the use of organism to remove pollutants from soil, air or water. ( Attack prokaryotes)
Structural and functional adaptions contribute to prokaryotic success
Motility
Example: Prokaryotes that exhibit chemotaxis change their movement pattern in response to chemicals.
Taxis- a directed movement toward or away from stimulus.
Cell- Surface Structures
Peptidoglycan- a polymer composed of modified sugars cross-linked by short polypeptides.
Gram Stain- categorize many bacterial species according to differences in the cell wall composition.
Gram-positive bacterla have relatively simple walls composed of a thick layer of peptidoglycan .
Capsule- a sticky, slimy layer that surrounds the cell wall of many prokaryotes.
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).
Endospores- are resistant cells in bacteria when they lack water or essential nutrients.
Fimbriae- are hair like appendages that prokaryotes attach to. Its usually shorter and more than pili.
Pili (singlar pilus)- appendages that pulls two cells together prior to DNA transfer from one cell to the other ; pili are sometimes referred to as sex pili.
Internal Organization and DNA
Eukaryotes have linear chromosomes. Have a nueclus.
Plasmids- are replicating DNA molecules.
Prokaryotes have cicular chromosomes. NO nucleus; their chromosome is located in the nucleoid,a region of cytoplasm that is not enclosed by a membrane.
Reproduction
Prokaryotic populations can consist of many trillions of individuals-- far more than population of Eukaryotes.
Example: Binary fission- a single prokaryotic cell that divides into 2 cells that keep dividing.
Rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotes
Transformation and Transduction
Example: A harmless strain of Streptococcus pneumoniae can be transformed into pneumonia causing cells if the cells are exposed to DNA from a pathogenic strain.
Transduction- phages (from" bacteriophages", the viruses that infect bacteria) carry prokaryotic genes from one host cell to another.
Transformation, the genotype and possibly phenotype of a prokaryotic cell are altered by the uptake of foreign DNA from its surroundings.
Genetic Recombination
Horizontal gene transfer is the movement of genes from one organism to another.
def. The combining of DNA from two sources.
Conjugation and Plasmids. F factor as a plasmid and in the chromosome.
F factor- The ability to form pili and donate DNA during conjugation results from the presence of a particular piece of DNA.
F factor can exist as a plasmid or as a segment of DNA within the bacterial chromosome.
Conjugation- is when DNA is transferred between two prokaryotic cells (usually of the same species) that are temporarily joined.
The F Factor in the Chromosome: Chromosomal genes can be transferred during conjugation when the donor cell's F factor is integrated into the chromosome (Hfr cell).
R plasmids- R for resistance to antibiotics or other bacterial growth inhibitors.
Rapid Reproduction and Mutation
The probability of mutation occurring in a given E.coli gene is about one in 10 million (1 x 10^-7) per cell division.
E. coli cells that arise each day in a person's intestine, approximately ( 2 x 10^10) x (1 x 10^-7)=2,000 bacteria that have a mutation in that gene.
Escherichia coli as it reproduces by binary fission in a human intestine.
The total number of new mutations when all 4,300 E.coli genes are 4,300 x 2000--more 8 million per day per human host.
Prokaryotes play crucial roles in the biosphere
Ecological Interactions
Commensalism- an ecological relationship in which one species benefits while the other is not harmed or helped in any significant way.
Parasitism- an ecological relationship in which a parasite eats the cell contents, tissues, or body fluids of its host.
Mutualism- an ecological interaction between two species in which both benefit.
Pathogens- are parasites that cause disease.
Host- is the larger organism in a symbiotic relationship (symbiont).
Symbiosis- an ecological relationship which two species live in close contact with each other.
