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Chapter 27 Bacteria and Archaea (Rapid reproduction mutation and genetic…
Chapter 27
Bacteria and Archaea
Masters of adaption
Halobacterium species are among the most Salt tolerant organisms on earth they thrive in salinities that hydrate and kill other cells
Halobacterium cell compensates for water lost through osmosis by pumping potassium ions into the cell until the ionic concentration inside the cell matches the concentration outside
Halobacterium many other prokaryotes can tolerate extreme conditions examples include Deinococcus radiodurans which can survive 3 million rads of radiation and picrophilus oshimae which can grow at a pH of 0.03
Structural and functional adaptations contribute to prokaryotic success
In a hypertonic environment most prokaryotes lose water and shrink away from their wall
In eukaryotes that have so walls such as plants and fungi the walls are usually made up of cellulose or chitin
And contrast most bacterial cell walls contain peptidoglycan a polymer composed of modified sugars cross-linked by short polypeptides
Using a technique called the Gram stain developed by the 19th century danish precision Hans Christian grandpa scientist conduct categorize many bacterial species according to the differences in cell wall composition
Gram-positive bacteria have relatively simple was composed of a thick layer of peptidoglycan
The walls of gram-negative bacteria have less Peptidogglycan and are structurally more complex with an outer membrane that contains lipopolysaccharides
Gram staining is a valuable tool and medicine for quickly determining if a patient infection is due to gram-negative or two gram-positive bacteria
However Certain gram-positive species have viral and strains that are resistant to one or more anabiotic’s for example methicillin resistant is staphylococcus aureus or MRSA which can cause lethal skin infections
The cell wall of many prokaryotes is surrounded by sticky layer of polysaccharide or protein this layer is called a capsule if it is dense and will define or he slime layer if it is not as well organized
In another way of withstanding harsh conditions certain bacteria develop resistance cells called endospores when they lack water or essential nutrients
Finally some prokaryotes stick to their substrate or to one another by means of hair like appendages called fimbriae
Fimbriae are usually shorter and more numerous than pili appendages that pull two cells together prior to DNA transfer from one cell to the other pili are sometimes referred to as a sex pili
Motility
About half of all prokaryotes are capable of Taxis a directed movement toward or away from a stimulus
Prokaryotes that exhibit chemo taxis change their movement pattern in response to chemicals
Flagellate may be scattered over the entire surface of the cell or concentrated at one or both ends prokaryotic flagella differ greatly from eukaryotic flagella
Internal organization and DNA
Unlike eukaryotes and prokaryotes lack a nucleus their chromosome is located in the nucleotide
In addition to its single chromosome a typical prokaryotic cell may also have much smaller rings up independently replicating DNA molecules called plasmids most caring only a few jeans
Reproduction
Many prokaryotes can reproduce quickly and favorable environment
By binary fission a single prokaryote cell divides into two cells which then divide into 4,8,16 and so on
In reality of course this does not occur the cells eventually exhauster nutrients supply toys in them selves with metabolic waste these competitions from other microorganisms or are consumed by other organisms still many prokaryotic species potential for rapid population growth emphasizes three key features of their biology they are small they were produced by binary fission and they often have short generation times
Rapid reproduction mutation and genetic recombination promote genetic diversity in prokaryotes
And transformation the genotype and possibly phenotype of a prokaryotic cell or altered by the uptake of foreign DNA from its surrounding
In transduction phages Carrie prokaryotic genes from one host cell to another
In a process called conjugation DNA is transferred between two prokaryotic cells that are temporarily joined
The ability to form a pili and donate do you need during conjugation results from the presence of a particular piece of DNA called the F factor
Mutation in a different gene may alter the intra-cellular target protein for an antibiotic molecule reducing its inhibitory effect
In other cases bacteria have resistance jeans which code for enzymes that specifically destroyer otherwise hinder the effectiveness of certain anabiotic‘s such as tetracycline and ampicillin search resistance genes are often carried by plasmids known as R plasmids
Chromosomal genes can be transferred during conjugation when the donor cells a factor is integrated into the chromosome
The F factor in the deposit form is called the F possum in cells containing the F plasmid designated cells function as DNA donor during conjugation
Diverse nutritional and metabolic adaptations have a evolved in prokaryotes
The role of oxygen in metabolism
Prokaryotic metabolism also varies with respect to oxygen
Obligate aerobes must use oxygen for cellular respiration and cannot grow without it
Obligate anaerobes on the other hand are poison by oxygen
some obligate anaerobes live exclusively by fermentation others extra chemical by anaerobic respiration
Fuck called to tell if anaerobes use oxygen if it is present but can also carry out for mentation or anaerobic respiration in an anaerobic environment
Nitrogen metabolism some cyanobacteria and some methanogens convert atmospheric nitrogen into ammonia a process called nitrogen fixation
Metabolic cooperation
The cyanobacterium Anabaena how’s genes that encode proteins for photosynthesis and for nitrogen fixation
Most cells in a filament carry out only photosynthesis while a few specialize cells called heterocyst carry out only nitrogen fixation
Metabolic cooperation between different prokaryotic species often ochers in surface coating colonies known as biofilms
Prokaryotes have radiated into a diverse set of lineages
These adaptations have enabled prokaryotes to inhabit every environment known to support life if there are organisms in a particular place some of those organisms are prokaryotes
One lesson from studying prokaryotic phylogeny is that the genetic diversity of Love prokaryotes is immense
Another important lesson from the molecular systematics is that horizontal gene transfer has played a key role in the evolution of Prokaryotes
Bacteria
Every major mode of nutrition and metabolism is represented among bacteria and even a small taxonomic group of bacteria may contain species exhibiting many different nutritional modes
Archaea
Archaea share certain traits with bacteria and other trade with eukaryotes
The first prokaryotes assigned to domain Archaea living environment so extreme that a few other organisms can survive there such organisms are called extremophiles meaning lovers of extreme conditions and include extreme halophiles and extreme thermophiles
Extreme halophiles live in highly Celine environments such as the great Salt Lake in Utah the dead sea in Israel and the Spanish Lake.
Extreme thermophiles thrive in very hot environment
Many other Archaea living more moderate environments consider the methanogens Archaea that release methane as a byproduct of their unique ways to obtain energy
Prokaryotes play crucial roles in the biosphere
Prokaryotes are so important to the biosphere that if they were to disappear the prospects of survival for many other species would be dim
Chemical recycling
The Adams that make up the organic molecules in all living things were at one time part of inorganic substances in the soil air in water
Some chemo hetero traffic prokaryotes function as decomposers breaking down dead organisms as well as waste products in there by unlocking supplies of carbon nitrogen and other elements
Prokaryotes also convert other molecules to form that can be taken up by other organisms
Ecological interactions
Consider symbiosis an ecological relationship in which two species live in close contact with each other
In general the larger organisms in a symbiotic relationship is known as the host and the smaller is known as the symbiont
There are many cases in which A prokaryote and its host participate in mutualism and ecological interaction between two species in which both benefit
Other interactions take the form of commensalism and ecological relationship in which one species benefits while the other is not harmed or help in any significant way
Finally some prokaryotes engage in parasitism and ecological relationship with which a parasite eats the cell contents tissues or body fluids in its host
Parasites that causes these are known as pathogens many of which are prokaryoti
Prokaryotes have both beneficial and harmful impacts on humans
Mutualistic bacteria
Different species live in different portions of the intestines and they may vary in their ability to process different foods
Many of the species are mutualist digesting food that our own intestines cannot break down
Bacteroids thetaiotaomicron includes a large array of jeans involved in synthesizing carbohydrate vitamins and other nutrients needed by humans
Pathogenic bacteria
Exotoxins are proteins secreted by certain bacteria and other organisms
Endotoxins are lipopolysaccharide components of the outer membrane of gram-negative bacteria
Among other applications this CRISPR – CAS9 system has already open new lines of research on HIV the virus that causes AIDS
Another way to harness prokaryotes is bioremediation the use that organisms to remove pollutants from soil air or water
