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Ch 19 Viruses and Ch 27 Bacteria and Archaea - Coggle Diagram
Ch 19 Viruses and Ch 27 Bacteria and Archaea
Virus Structure
Viral Genomes
they contain DNA or RNA
SS for single stranded DNA or RNA
DS for double stranded DNA or RNA
is either DNA or RNA based on the nucleic acid in the genome
viruses are smaller than bacteria
a provirus is a viral genome that is permanently inserted into a host genome
Capsids and Envelopes
the protein shell enclosing the viral genome is called a capsid
the protein shell enclosing the viral genome is called a capsid
capsids are built from a large number of protein subunits called capsomeres
many of the most complex capsids are found among the viruses that infect bacteria, called bacteriophages, or simply phage
a membrane, derived from membranes of the host cell, that cloaks the capsid, which in turn encloses a viral genome
What a Virus is
viruses cannot reproduce or carry out metabolic activities outside of a host cell
a virus is an infectious particle consisting of little more than genes packaged in a protein coat
viruses are non-living
a prion is an infectious agent that is a misfolded version of a normal cellular protein, prions appear to increase in number by converting correctly folded versions of the protein to more prions
Viral Replication
Host Cells
viruses are obligate intracellular parasites so they can replicate only within a host cel
host range is the limited number of species whose cells can be infected by a particular virus
viruses usually identify host cells by a “handshake” fit between viral surface proteins and specific receptor molecules on the outside of cells
Lytic Cycle
lytic cycle is a type of phage replicative cycle resulting in the release of new phages by lysis (and death) of the host cell
each of these phages can then infect a healthy cell, and a few successive lytic cycles can destroy an entire bacterial population in just a few hours
virulent phage is a phage that replicates only by a lytic cycle
has a shorter duration but has more severe symptoms
Lysogenic Cycle
lysogenic cycle is a type of phage replicative cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage, is replicated along with the chromosome, and does not kill the host
a temperate phage is a phage that is capable of replicating by either a lytic or lysogenic cycle
prophage is a phage genome that has been inserted into a specific site on a bacterial chromosome
the term lysogenic signifies that prophages are capable of generating active phages that lyse their host cells
Structure and Function of Archaea
Gram Staining
peptidoglycan is a type of polymer in bacterial cell walls consisting of modified sugars cross-linked by short polypeptides
gram staining is a staining method that distinguishes between two different kinds of bacterial cell walls; may be used to help determine medical response to an infection
gram positive have lots of peptidoglycan making it purple
gram negative have less peptidoglycan making it pink
Cell Surface Structures
the cell wall of many prokaryotes is surrounded by a sticky layer of polysaccharide or protein, which is called a capsule
endospores are thick-coated, resistant cell produced by some bacterial cells when they are exposed to harsh conditions
fimbriae is a short, hairlike appendage of a prokaryotic cell that helps it adhere to the substrate or to other cells
pili is a structure that links one cell to another at the start of conjugation; also called a sex pilus or conjugation pilus
Motility
taxis is an oriented movement toward or away from a stimulus
chemotaxis change their movement pattern in response to chemicals
prokaryotes may move toward nutrients or oxygen (positive chemotaxis) or away from a toxic substance (negative chemotaxis)
Genetic Diversity in Prokaryotes
Genetic Recombination
transduction is bacteria can take in foreign DNA from the environment and the 2 bacteria must be in close proximity
transformation is when bacteria can take in foreign DNA from the environment
conjugation is when one bacteria donates DNA (F positive) and one receives DNA (F negative)
F Factor
f factor (fertility) bacteria that have F factor receive the designation F +
If F negative obtains the allele for the F factor from an F positive the F negative will become F positive
if only a portion of DNA is given to F negative the F negative is now a recombinant and we recognize that with Hfr
Hfr stands for high frequency of recombination and functions as donors during conjugation
Diverse Adaptations
organisms that obtain energy from light are called phototrophs
those that obtain energy from chemicals are called chemotrophs
nitrogen fixation is nitrogen N2 to ammonia NH3
heterocyst are specialized cell that engages in nitrogen fixation in some filamentous cyanobacteria; also called a heterocyte
extremophiles are organisms that lives in environmental conditions so extreme that few other species can survive there