Unit 2 Microbiology.

Unit 2 Microbiology

Lesson 1 – Evolution of Microbes
View the video “Microbial Evolution” and respond to student worksheet. Lecture: Species Concept and Evolutionary Domains. Respond to handout questions.

Video: Microbial Evolution
4 parts of video

Species Concept What is a species?
A species is defined as a population that can naturally interbreed and produce fertile offspring, and that is reproductively isolated from other species. Right! Well, maybe not……..

Species Concept A bacterial species is a prokaryote whose 16S ribosomal RNA sequence differs by no more that 3%. rs/tools-of-the-trade/genetic-tools- and-techniques/16s-rrna 16S rRNA is part of the small subunit (SSU) of the ribosome; used to classify prokaryotes.

Species Concept Prokaryotes do not fit the biological species concept because they - Are haploid and reproduce asexually. - Cannot produce “fertile offspring” like plants and animals can. In microbiology, evolutionary (molecular)chronometers measure evolutionary change. - Chronometers are nucleotide or amino acid sequences that are homologous in different species. - The greater the number of differences in the sequence the more distantly related the two species are.

Species Concept Molecular Chronometers
Chronometer must be present in all groups being classified and it must be functionally homologous (not many sequence differences). The following genes and proteins are most frequently used to classify bacteria. - ribosomal RNA - ATPase proteins (synthesize ATP)  - RecA (enzyme facilitates genetic recombination) - Certain translation proteins.

Species Concept Ribosomal RNA is the most widely used chronometer for identifying bacterial species : - It is relatively large. - Universally distributed - Has many nucleotide sequences that are conserved.

Evolution of Microbes

Evolutionary Domains - Bacteria
Prokaryotic organisms At least 40 phyla Have little in common phenotypically In terms of phylogenetics, most are genetically related.

Evolutionary Domains - Archaea
Prokaryotic organisms 4 phyla in this domain Contain extremophiles - Hyperthermophiles: live in high temperatures. - Methanogenic : produce methane. - Extreme halophiles: live in high salt environments.

Evolutionary Domains - Eukarya
rRNA phylogeny based on 18S rRNA. Four kingdoms: Protista, Fungi, Plant, and Animal. Range from single cell to complex multi-cell organisms. Rapid diversification of Eukarya was tied to changes in oxygen levels on earth.

Lesson 1 –What You Need to Know
Questions for Speciation and Microbial Domains How is a bacterial species defined? What is an evolutionary (molecular) chronometer? What are 4 commonly used molecular chronometers? Why is 16S rRNA used to define bacterial species? What are the 3 domains in which microorganisms are found? Which domains contain prokaryotic organisms? Define hyperthermophiles, methangenic bacteria, and halophiles. What 4 kingdoms are contained in Eukarya

Lesson 2 – Phenotypic Identification of Bacteria
Working microbiologists use phenotypic commonality in identifying bacteria. Most frequently these phenotypes are: Cell shape Cell wall structure Cell respiration Growth factors Colony morphology

Phenotypic Identification
Cell Shape There are 4 bacterial shapes: - Cocci (coccus s.) or round - Bacilli (bacillus s.) or rod shaped - Spirillum or cork screw shaped - Filamentous or like jelly beans in straw

Phenotypic Identification – Cell Shape
Cocci Round shape Examples -Staphlococcus  (in clusters) -Streptococcus (in chains) 

Bacilli Rod shaped Examples - Bacillus anthracis  (agent in anthrax) - Escherichia coli  (used in biotechnology)

Spirillum Cork screw shape Example - Treponema pallidum (agent of syphilis)

Filamentous Jelly beans in straw Example -Leptothris discophora (aquatic bacteria uses iron the way we use oxygen).

Phenotypic Identification – Cell Wall Structure
Composition of Cell Walls Difference in cell wall structure becomes clear when a technique called the Gram stain is used. Bacteria on a glass slide are stained first with a purple dye; the slide is rinsed with ethanol, and then a red counter stain is applied. If bacteria remain purple = Gram positive. If bacteria turn red = Gram negative. related

Gram positive cocci Gram negative rods

Gram + organisms have a cell membrane and a cell wall made of peptidoglycan which gives the cell structure.

Gram – organisms have a cell membrane and a cell wall with a thinner layer of peptidoglycan plus an outside layer of lipopolysaccharides. The lipopolysaccharides make Gram – organisms more virulent.

Phenotypic Identification – Cell Respiration
There are 3 types of cell respiration( synthesis of ATP): - Aerobic: Use oxygen for cell respiration. - Anaerobic: Cannot tolerate oxygen. Use fermentation - Facultative anaerobes: Can use or not use oxygen depending on availability.

Phenotypic Identification – Growth Factors
Nutrient Source - Heterotroph: Consume energy from outside source. - Autotroph: Make and consume energy. Energy Source (Autotrophs) - Chemoautotroph : Use chemicals as energy source. - Phototrophs: Use light as energy source

Phenotypic Identification – Colony morphology
A single bacteria put onto a solid agar plate, if given sufficient nutrients, optimal temperature and pH, will multiply and form a colony. All members of the colony are genetically identical. Bacterial colonies of different species differ from one another.

Phenotypic Identification – Colony Morphology
To identify a colony, the following basic elements are noted. Form- What is the basic shape of the colony? Elevation - What is the cross sectional shape of the colony? Margin - What is the magnified shape of the edge of the colony? Surface - How does the surface of the colony appear? Opacity – Is the colony translucent, transparent, iridescent? Chromogenesis – pigmentation.

Phenotypic Classification- Colony Morphology
Form

Elevation – Cross sectional shape

Phenotypic Identification-Colony Morphology
Margin – Shape of colony edge

Phenotypic Identification- Colony Morphology
Opacity – Clear, Opaque, Iridescent Iridescent

Chromogenesis – pigmentation

Lesson 2 – What You Need to Know
Name and identify cell shapes Describe the similarity and difference between Gram positive and Gram negative cell walls. Explain the Gram stain procedure. Why is cell wall morphology important in clinical treatments? Define 3 types of cell respiration in bacteria. Describe 4 ways in which microbes produce and/or use energy? How are chemoautotrophs and photoautotrophs alike and different? What basic elements are noted in colony identification? Name and identify the colony forms. Name and identify the colony elevation. Name and identify the colony margin. Define chromogenesis.

Lesson 3 – Prokaryotic Structure
Webquest: Visit the 3 websites noted on your handout to learn about prokaryotic structures and function. Respond to all questions on the Webquest handout. Next read the Powerpoint slides on additional prokaryotic structures Respond to all questions on the handout. Class review and discussion

Prokaryotic Structure - Webquest
Complete your handout

Prokaryotic Structures - Additional
DNA in prokaryotes is found in the - Nucleoid Region - Plasmids A typical prokaryote has one chromosome containing most of the genes in the cell. A few species of Bacteria & Archaea contain two chromosomes. The DNA is a double stranded circular molecule. Bacterial genomes contain from 500,000 base pairs to about 4 million base pairs, depending on the species..

Plasmids Plasmids are DNA Exist and replicate separately from the chromosome. Most are circular, some are linear. Prokaryotes contain one or more plasmids. Range in size from 100 to 1,000 base pairs. Plasmid DNA can be exchanged among bacteria. Genes for antibiotic resistance are found on plasmids and one bacteria can transfer these genes to another bacteria. Bacterial plasmids play a role in recombinant DNA technology.

The differences between a bacterial chromosome and a plasmid: - Chromosomes carry many more genes than plasmids and the genes are essential to cellular function. Essential genes are called housekeeping genes. - Plasmids carry far fewer genes and are expendable because the genes are not necessary for growth under all conditions.

Restriction Endonucleases Are enzymes naturally found in bacteria. Have the ability to cut up the foreign viral DNA if a virus is invading a bacterial cell. The possibility of viral infection plummets. Can be thought of as a bacterial immune system because the role of restriction endonucleases is to protect the bacteria. Are of several types . Play a role in recombinant DNA technology

Be able to define all prokaryotic structures and their functions; as listed in the Webquest. Be able to locate the structures on a diagram. Be able to answer the following questions from your Powerpoint slides Where is DNA found in bacteria? Describe the typical bacterial genome with respect to structure, location, and size. Describe a plasmid with respect to size, location, and function. Contrast bacterial chromosomal and plasmid DNA. How do restriction endonucleases work?

Lesson 4 - Hand washing Lab (Effectiveness of antimicrobial soap vs
Lesson 4 - Hand washing Lab (Effectiveness of antimicrobial soap vs. hand sanitizer) Day 1: Hand washing and agar plate inoculation Day 2: Review plate streaking for colony isolation video, collect data, and streak plates for isolation. Day 3: Collect data, study colony morphology, and gram stain organisms.

Lesson 4 – Hand washing Lab
Video Resources for Lab Pouring agar plates. Dilutions and spread plating Streaking plates Aseptic transfer Making smears Gram stains

Lesson 5 – E. coli Lecture : E. coli and its use in biotechnology. Pathogenic E.coli Reading: Pathogenic E. coli. Respond to handout questions. Case Study: Microbial Pie Activity: Track the Epidemic

E.coli Escherichia coli Gram negative rod Facultative anaerobe
Found in the intestines of warm blooded animals as normal flora. Benefits its host by producing vitamin K Reduces numbers of pathogenic bacteria in the intestine.

E. coli E.coli is a hardy organism that is easy to culture and easy to manipulate in the lab. It is a model organism in biotechnology. Model organisms are extensively studied to understand biological phenomena and the information can be applied to other organisms. E.coli genome was one of the first to be sequenced in 1997

E.coli Most economically robust area in biotechnology is production of human proteins. E.coli has played a major role in production of these proteins. Human genes for proteins can be cloned and inserted into plasmids in E.coli through recombinant DNA technology

E. coli E.coli is then grown in large bioreactors and it produces the protein of interest. Purification methods separate the target protein from the biological molecules in which it was produced. The proteins can then be used by humans.

E. coli The following proteins are manufactured via this technique:
Insulin For diabetes Human Growth Hormone For growth hormone deficiency Factor VIII For hemophilia Erythropoietin For stimulation RBC growth

E.coli Pathogenic vs. Non-pathogenic E.coli. Most E.coli strains live commensally in the intestines of warm blooded animals. These strains are non-pathogenic. Non-pathogenic strains of E.coli strains are used in biotechnology research. Some E.coli strains are virulent and produce gastrointestinal disease. These strains are pathogenic.

E.coli Causes of virulence Toxicity - Ability to cause disease by a preformed toxin. Toxin inhibits host cell function and kills host cell. Invasiveness - Ability of organism to grow in host cell tissue in such large numbers that pathogen inhibits host cell activity.

E.coli E.coli virulence Due to an enterotoxin, a type of exotoxin.
The enterotoxin is secreted by the bacteria and affects the cell membrane of intestinal cells. It makes the host cell membrane more permeable to chloride ions. As chloride enters the host cells, sodium and water leave the host cells. This causes diarrhea and abdominal pain. Virulent E.coli is acquired by eating contaminated food

Where does nonpathogenic E.coli normally reside? What is a benefit of having E.coli as normal microbial flora? Explain the term “model organism”. Describe how E.coli is used to produce a protein such as insulin. Describe the 2 factors that can make E.coli a virulent organism. What are the 3 antigens used to type E.coli and where are these antigens located on the organism? What types of diseases can be caused by E.coli? What is the mode of transmission for gastrointestinal diseases? How do enterotoxins work?

Lesson 6- Gene Transfer and Recombination
Lecture: Natural gene transfer and recombination. Whole class lecture: Gene transfer in prokaryotic organisms. Pantomime of gene transfer Case Study: Antibiotic resistance

Gene Transfer and Recombination
Bacteria pass on their DNA to the next generation asexually through binary fission. Many bacteria, however, have the capacity to physically exchange DNA with other bacteria. There are 3 DNA exchange processes in Transformation Transduction Conjugation These 3 process are collectively referred to as lateral or horizontal gene transfer.

Transformation Transformation
Process by which free DNA is incorporated into a recipient cell and brings about genetic change.

Transformation Do you remember the Griffith experiment?
hapter8/videos_animations/griffith.html

Transformation Transformation Bacterial cell is lysed. DNA pours out
Bacterial chromosome breaks into 10 gene fragments genes. Other competent bacterial cells take up the DNA from the environment. Competency is genetically determined. DNA enters the cell & is escorted through the cytoplasm by competence specific proteins to prevent degradation. DNA is recombined (integrated) into bacterial chromosome. hill.com/sites/ /student_view0/chapter13/animation_qui z_1.html

Transformation

Transformation Transformation in Biotechnology
In biotechnology procedures, the term transformation has a slightly different meaning. E.coli are poorly transformed under natural conditions. If you treat the organism with calcium ions and chill it, it becomes easily transformed (DNA from other source enters the cell). Transformation of this organism generally occurs in the plasmid.

Transduction Transduction
DNA is transferred from cell to cell by a virus. Virus can transfer host cell DNA along with its own genetic material.

Transduction In transduction, any gene on a donor bacterial chromosome can be transferred to a recipient. A phage (virus for bacteria) enters the host cell & during a lytic infection enzymes responsible for packaging viral DNA sometimes package the host DNA accidentally. The resulting virus with a piece of the donor DNA is called a transducing particle. This transducing particle cannot go on to cause infection in a new cell. The DNA released is incorporated into a recipient bacterial cell chromosome. hill.com/sites/ /student_view0/chapter13/animation_qui z_2.html

Transduction

Plasmids Plasmids revisited
Are genetic elements that replicate independently of the host chromosome. Are unessential, do not control vital cell functions. Are double stranded, mostly circular (some linear), structures with fewer genes than the bacterial chromosome. Of different types may be present in a cell and numbers of these types can vary. Called episomes can integrate into the bacterial chromosome.

Plasmids Types of plasmids
F (fertility) plasmid - most studied, results in the expression of sex pili. R (resistance) plasmids - contain genes that can build a resistance against antibiotics Col plasmids - which contain genes that code for bacteriocins that can kill other bacteria. Degradative plasmids, which enable the digestion of unusual substances. Virulence plasmids- which turn the bacterium into a pathogen.

Conjugation Conjugation
Process of genetic transfer that involves cell to cell contact. Conjugative plasmid uses this process to transfer a copy of itself to a new host. Process involves a donor cell and a recipient cell.

Conjugation

Conjugation Conjugation (using the F plasmid as an example)
The F+ cell has the plasmid and is the donor. The F- cell is the recipient. F+ cell synthesizes a sex pillus. Sex pillus makes specific contact with the F- cell; pulling it toward the F+ cell. The DNA (plasmid) is transferred from the F+ to the F- cell through the sex pillus.

Conjugation Depending on the species, the plasmid can be replicated first in the F+ cell & then transmitted to F-. Other times, the 2 DNA strands are separated in F+ and one strand is transferred to F-. Both cells will then make a complimentary strand.. The original F- cell turns into an F+ cell & can conjugate with other bacteria. Conjugative plasmids spread rapidly through populations much like infectious agents. If plasmids contain genes that offer a selective advantage (like an antibiotic resistance gene), this can ensure survival of that population. hill.com/sites/ /student_view0/chapter13/animation_qui z_3.html

Gene Transfer and Recombination Activity
First, work with a partner. Explain the processes of transformation, transduction, and conjugation. Next, have your partner explain the same to you. Next, create 6 groups. We will create pantomimes of horizontal gene transfer. 2 groups – Transformation 2 groups- Transduction 2 groups - Conjugation

Be able to explain the process of transformation. Be able to explain the process of transduction. Be able to explain the process of conjugation. ( Use a good level of detail in your explanation and be sure to include appropriate vocabulary words) Describe plasmids. What are the different types of plasmids and their functions.

Lesson 7 – Microbial Biotechnology
Products of microbial biotechnology Read and familiarize yourself with the Powerpoint. Read each article on the website at the bottom of each slide and make a copy of it for your notes. Write a synopsis of each article

Food Biotechnology Food Biotechnology - fermentation
Scientists are currently working on ways to improve use of microorganisms in food production. - Developing virus resistant organisms through recombinant DNA technology to prevent economic losses in the dairy industry. - Developing bacteria to produce chemicals to kill contaminating organisms in food making processes. - Produced a microbial enzyme used to make cheese. compass.org/eng/grocery_shopping/processed_foods/29.dairy_prod ucts_eggs_genetic_engineering.html

Enzymes, Antibiotics, and Human Proteins
Recombinant DNA technology has enabled production of new enzymes, antibiotics, and human proteins from microbial fermentation. Prourokinase is an enzyme which helps heal wounds infected with E.coli. New and novel antibiotics with two pathways for treatment are being developed. Tissue plasminogen activator, a protein which dissolves blood clots is being produced. Article/Biotechnology-in-the-Manufacturing-of-Detergents-159.html

Fuels and Biopolymers Fuels and Biopolymers
Hydrogen power is a fuel of the future. Biotechnologists are looking at Clostridium species as generators of hydrogen. Plastics worldwide are polluters because they are not biodegradable. Several organisms are being studied as producers of bioplastics. These biodegradable plastics will have several applications in the industrial and medical fields. Bioplastic shtml

Agriculture Agriculture
A Pseudomonas bacteria has been bioengineered with B. thuringiensis toxin . The bacteria colonizes plants and acts as a biopesticide to kill insect larvae. Baculoviruses are used to contaminate plant material. Insects ingest the plant and develop a lethal viral infection Biotechnologists are working on ways to bioengineer the Baculovirus to enhance its ability as a biopesticide.

Bioremediation Bioremediation
Microorganisms with hydrocarbon oxidizing enzymes clean oil spills. Microorganisms are used in waste water treatment facilities to purify water. Bacteria are being studied which have the capacity to remove heavy metals such as arsenic, copper, tin, and mercury from the environment. save-lives-and-clean-mines

Lesson 7 - What You Need to Know
Discuss the relationship between renin and chymosin. What are the 4 types of enzyme based detergents? How do enzyme based detergents work vs. conventional detergents? Why are enzyme based detergents preferable? Explain how bacteria convert fruits and vegetables into plastics? Describe how Baculoviruses act as an insecticide? What are the advantages and disadvantages of using this approach? Why does the bacterium NT-26 hold such promise in cleaning up mining areas?

Lesson 8 – Debate: Are GMOs beneficial or harmful to society.
What are GMOs? GMOs, or “genetically modified organisms,” are plants or animals that have been genetically engineered with DNA from bacteria, viruses or other plants and animals. These experimental combinations of genes from different species cannot occur in nature or in traditional crossbreeding. Visit the following websites for debate research htm hp

Refer to your handout for debate information and rubrics. You need to be able to: - Provide 3 arguments in favor of GMOs. - Provide 3 arguments against GMOs. - Take a position for or against GMOs and support the argument.

Lesson 9 – Microbial Eukaryotic Cells Fungi
Reading: Fungal Biotechnology Lecture: Yeasts, Filamentous Fungi and Molds Video: The Biology of Fungi (16 min)

Fungi Fungi – General Characteristics
Fungi are composed of eukaryotic cells. Some are unicellular and some are multicellular. Habitats: Most are terrestrial and some are aquatic Energy : Fungi are heterotrophic decomposers. (A few are parasitic) Cell Walls: Resemble plants architecturally but are made of chitin not cellulose. Reproduction: Many reproduce asexually and sexually using spores. Recent molecular evidence suggests fungi are probably more closely related to animals than to plants or protists.

Fungi - Why are they important in biotechnology?
Reading: Fungal Biotechnology Visit the following website: Activity Provide 4 examples of why fungi are important in biotechnology and explain their use.

Fungi There are 3 basic types of fungi Unicellular fungi - Yeast
Filamentous fungi – Mold and fungi Macroscopic fungi – Mushrooms We will limit our discussion to the first two types

Yeast Yeast - 1,500 species of yeast - not part of a single taxon.
Cells - typically spherical, oval, or cylindrical - usually 3-4 microns in size - most are unicellular - some multicellular: a string of connected yeast cells connected by psuedohyphae.

Yeast Yeast with pseudohyphae Pseudohyphae help yeast invade tissues.

Yeast Energy Yeast flourish in environments where sugar is present.
They are facultative aerobes; using aerobic cell respiration and fermentation. In a lab, yeast can be cultured with nutrient agar and grow colonies.

Yeast Reproduction Yeasts generally reproduce asexually by budding.
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Yeast Reproduction Yeast can sexually reproduce by mating.
Two different mating types fuse into a diploid cell. Diploid cell can bud to make additional diploid cells. Diploid cell undergoes meiosis and produces haploid cells called ascospores. Ascospores create new yeast cells.

Yeast Yeast containing ascospores

Yeast – What You Need to Know
What are the general characteristics of fungi? Name the 3 general types of fungi and provide an example. Describe the following: 1. Structure of a yeast cell 2. Energy use in yeast 3. Asexual and sexual reproduction of yeast

Filamentous Fungi Filamentous Fungi
Widespread in nature, usually seen on stale bread, cheese, or fruit. Called molds.

Filamentous Fungi Cell Structure
A filament called a hypha (hyphae p,) grows from a single terminal cell  The hyphae grow together across a surface and form compact tufts called mycelium. This compact mat represents many intertwined hyphae. 

Filamentous Fungi Cell Structure
From the mycelium, hyphae grow upward. At the end of the vertical hyphae are spores called conidia. Conidia are asexual spores and are often pigmented. esources/CAL/Microconcepts/Reprodu ction/fungiRepro.html

Filamentous Fungi Reproduction – Asexual
The function of the conidia is the dispersal of the fungus(via spores) to new habitats. When new conidia form they are white and eventually become pigmented.

Filamentous Fungi Fungi can reproduce sexually.
Reproduction - Sexual Fungi can reproduce sexually. An example is bread mold Rhizopus. Hyphae called stolons of opposite mating types (+ & -) fuse to form a structure called gametangia Dipoid zygospore is formed. Zygospore produces sporandia which undergo meiosis and release haploid spores.

Saccharomyces cerevisiae
Several yeasts, in particular Saccharomyces cerevisiae, have been widely used in biotechnology. S. cerevisiae is a simple eukaryotic cell, serving as a model organism for all eukaryotes. Fundamental cellular processes such as the cell cycle,, DNA replication, recombination, cell division, and metabolism have been studied. In 1996, S. cerevisiae was announced to be the first eukaryote to have its genome, consisting of 12 million base pairs, fully sequenced as part of the Genome project. S. cerevisiae as a model organism has improved our understanding of human disease genes.

Fungi – What You Need to Know
Describe the structure of a mold and the functions of each structure. Include the terms fungal cell, hyphae, mycelium, and conidia in your description. Explain filamentous fungal asexual and sexual reproduction. Include the terms conidia, stolon, gametangia, zygospore, and sporandia in your description. What is the role of S. cerevisiae?

Video: Biology of Fungi
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Lesson 10 - Viruses Homework: Review and understand powerpoint and videos on virus structure, replication, and vectors. Class: Create 4 work groups and develop review questions on assigned slides Class: Present your slides and review questions to the class. Write the review questions on the board; to be copied by students Work in groups of 4 to create a rap song involving virus content. Create and present a rap song about viruses.(See handout).

Virus – Use in biotechnology
Viruses as vectors Vector (in biotechnology) DNA that can be used to carry and replicate foreign DNA in biotechnology experiments. Viruses can serve as vectors. Genes of interest can be inserted into the viral genome and the genes of interest will replicate along with the virus.

Viruses – Use in Biotechnology
Viral vectors can be delivery system for gene therapy. ns/GeneTherapy/GeneTherapy.htm Viruses have potential as delivery systems in gene therapy because A. They naturally enter cells. B. They can integrate in the host cell genome. C. They are cell specific which would allow for targeted gene therapy.

Viruses General Properties
A minute particle containing nucleic acid, a protein coat, and sometimes other macromolecules. Can exist in extracellular or intracellular form. Extracellular –is metabolically inert. Intracellular – viral replication occurs.

Viruses - Genomes Genomes
Viral genomes are very small (3 to 100 genes)and encode for those functions that they cannot adapt from their host. Viral genomes are categorized by the type of nucleic acid present. Double stranded DNA Single stranded DNA Double stranded RNA Single stranded RNA Single stranded RNA that replicates with a DNA intermediate. Viral genomes can be linear or circular.

Viruses - Structure Virus Structure Varies widely in size, shape,
and chemical composition. Commonalities of structure Nucleic acid (DNA or RNA) Capsid- made of one to several proteins which surrounds nucleic acid. Envelope –most animal viruses have an envelope. The envelope is composed of a phospholipid bilayer from the host and proteins which the virus makes. Viruses without an envelope are called naked viruses.

Viruses - Structure Enzymes Some viruses contain enzymes.
Bacteriophages have lysozyme to make a small hole in bacterial cell wall. Retroviruses have reverse transcriptase that transcribes DNA from their RNA. Viruses have enzymes because the cell would not be able to replicate the viruses with out them.

Viruses - Replication Viral Replication
Phases of replication process are Attachment Penetration Synthesis of nucleic acid &proteins Assembly Release

Viruses - Attachment Attachment
Viruses - specific for the host cells they infect. Proteins on the outside of naked or enveloped virus interact with specific cell membrane receptors on host. If a cell membrane is altered, the virus cannot infect the cell; host resistance. However, viruses protein mutation enable viruses to interact with changed receptors.

Viruses - Penetration Penetration
Three ways a virus can penetrate a cell membrane: Membrane Fusion : Viral envelope and cell membrane fuse. Viral capsid alone brought into cytoplasm Entry Pore formation: Endocytosis of virus. Membrane removed in cytoplasm Viral Penetration: The viral capsid is injected into the host cell's cytoplasm.

Viruses - Synthesis Synthesis of nucleic acids and proteins - DNA viruses How viruses synthesize nucleic acids in the cell depends on the type of nucleic acid present in the virus. Double stranded DNA virus- Incorporates its DNA into host genome & protein synthesis can begin. Single stranded DNA virus – Complimentary DNA strand must be synthesized in the host because RNA polymerase requires double stranded DNA.

Viruses - Synthesis Synthesis of nucleic acid and protein – RNA viruses RNA viruses need an RNA-dependent RNA-polymerase to replicate their RNA. Cells do not have this enzyme. RNA viruses need to code for an RNA-dependent RNA polymerase. No viral proteins can be made until viral messenger RNA is available . The nature of the RNA in the virus affects its replication strategy.

Viruses - Synthesis Synthesis of nucleic acids and proteins- RNA virus
Single stranded RNA virus – There are 2 types of single stranded RNA viruses. Plus-stranded RNA viruses -RNA is the same sense (direction) as mRNA and it functions as mRNA. This mRNA can be translated immediately upon infection of the host cell. Negative-stranded RNA viruses - RNA is negative sense (complementary to mRNA) and must therefore be copied into the complementary plus-sense mRNA before proteins can be made. The virus uses its own RNA polymerase to make the plus stranded m RNA. Double-stranded RNA virus - RNA is double stranded and can’t function as mRNA; Also need to package an RNA polymerase to make their mRNA after infection of the host cell.

Viruses - Synthesis Synthesis of nucleic acids and proteins – retrovirus. The single strand of retrovirus RNA serves as a template to make a single strand of DNA with the virus’ enzyme reverse transcriptase. A complimentary DNA strand is made and the double stranded DNA is then a template for mRNA synthesis. hill.com/sites/ /student_view0/chapter2 4/animation__hiv_replication.html

Viruses - Replication Synthesis of nucleic acids and proteins
Once mRNA is made proteins can by synthesized. Early proteins – are made first which are necessary for viral replication. Late proteins- are then synthesized such as the viral coat protein.

Viruses – Self Assembly
Viruses self assemble in cells. Virus self-assembly within host cells has implications for the study of the origin of life, as it lends credence to the hypothesis that life could have started as self-assembling organic molecule

All of the review questions you copied from the board.

Unit 2 Microbiology.

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