Exam 2 Microbiology essay

The Lytic Cycle (T-even phages)

Phage causes lysis and death of the host cell

Chemical methods of microbial control

Phenol, Phenolics, Bisphenols, Biguanides, Halogens and alcohols.

Catabolic energy supply

Replication, transcription, translation

Pre-transcriptional control

Repression inhibits gene expression and decreases enzyme synthesis

Transcription in molecular process

Synthesis of a complementary mRNA strand from a DNA template. Transcription begins with RNA polymerase binds to the promoter sequence on DNA. Transcription proceeds in the 5'→ 3' direction; only one of the two DNA strands is transcribed. Transcription stops when it reaches the terminator sequence on DNA.

Molecular processes

replication, transcription, translation

operator

segment of DNA that controls transcription of structural genes

Describe the general morphology of several different viral type (helical, complex, enveloped, etc)

-Helical viruses— cylindrical capsid, rod shaped. -Polyhedral viruses—roughly spherical shaped with multiple flat faces. -Enveloped viruses- Envelope is made of lipids, proteins, and carbohydrates. - Complex viruses—complicated structures. irregular shapes with structures like tails or fibers.

Biguanides of Chemical Methods of Microbial Control

Chlorhexidine -Used in surgical hand scrubs -Disrupt plasma membranes

bacterial conjugation

the method of transfer of genetic material from one bacteria to another placed in contact -how plasmids spread-the sharing of DNA between bacteria of the same generation -Requires cell-to-cell contact via sex pili

DNA replication

the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules. Replication is an essential process because, whenever a cell divides, the two new daughter cells must contain the same genetic information, or DNA, as the parent cell.

Regulation of Bacterial Gene Expression

Constitutive genes are expressed at a fixed rate Other genes are expressed only as needed Inducible genes ( can be turned on) Repressible genes( can be turned off) Catabolite repression (nutritional sources)

Bisphenols of Chemical Methods of Microbial Control

Contain two phenol groups connected by a bridgeHexachlorophene and triclosanDisrupt plasma membranes

Biosynthesis of DNA viruses

DNA viruses replicate their DNA in the nucleus of the host using viral enzymes Synthesize capsid in the cytoplasm using host cell enzymes Examples- HERPESVIRIDAE PAOVAVIRIDAE -cellular enzyme transcribes viral DNA in nucleus POXVIRIDAE-viral enzyme transcribes viral DNA in virion, in cytoplasm

DNA structure

Double-stranded. It has two nucleotide strands which consist of its phosphate group, five-carbon sugar (the stable 2-deoxyribose), and four nitrogen-containing nucleobases: adenine, thymine, cytosine, and guanine.

rate of microbial death

Effectiveness of treatment depends on: Number of microbes Environment (organic matter, temperature, biofilms) Time of exposure Microbial characteristics

Physical methods of microbial control

Heat: Pasteurization reduces spoilage organisms and pathogens. Thermoduric organisms survive. Dry heat sterilization(kills by oxidation) flaming. Filtration: Passage of substance through a screenlike material. Low Temperatures: Refrigeration- Deep-freezing- Lyophilization (freeze drying) High Pressure: denatures protein Desiccation: absence of water prevents metabolism. Osmotic Pressure: uses salts and sugars to create hypertonic environment; causes plasmolysis. Radiation: ionizing radiation, nonionizing radiation, microwaves.

horizontal gene transfer

Horizontal transfer refers to the passage of a plasmid from donor to any recipient cell outside of cell division, often through conjugation .-transfer of genes between cells of the same generation

Translation of mRNA begins at the start codon:

AUG

DNA and RNA containing animal viruses

DNA- Adenoviridae: tumors in animals Lyssavirus- Rabies Herpes Hepadnavirus RNA- hepatitis delta virus Borna disease virus picornaviruses nodaviruses tetraviruses

Describe the process of viral multiplication

For a virus to multiply: - It must invade a host cell - It must take over the host's metabolic machinery - One-step growth curve

Operon model of gene expression

In an inducible operon, structural genes are not transcribed unless an inducer is present example- in the absence of lactose, lactose inducer binds to the operator, preventing transcription. In the presence of lactose, lactose binds to the repressor, the repressor cannot bind to the operator and trinscription occurs

Genetic transfer and recombination

In conjugation, the donor bacterium transfers DNA to the recipient by mating. Recombination is the rearrangement of donor and recipient genomes to form new, hybrid genomes. Transposons are mobile DNA segments that move from place to place within or between genomes.

Halogens of Chemical Methods of Microbial Control

Iodine- Tincture: solution in aqueous alcohol- Iodophor: combined with organic molecules - Impairs protein synthesis and alters membranes Chlorine- Oxidizing agents; shut down cellular enzyme systems Bleach: hypochlorous acid (HOCl)- Chloramine: chlorine + ammonia

Compare and contrast the effectiveness of moist heat and dry heat sterilization. Give an example for each.

Moist heat and dry heat sterilization both kill bacteria. Dry heat sterilization takes place at high temperature under dry air while moist heat sterilization takes place at high temperature and pressure generated by the steam of water. Moist heat sterilization is used with an autoclave and dry heat is used by flaming and hot air-sterilization.

Lysogenic cycle of bacteriophage lambda

Phage DNA is incorporated in the host -Lysogeny: phage remains latent - Phage DNA incorporates into host cell DNA - Inserted phage DNA is known as a prophage - When the host cell replicates its chromosome, it also replicates prophage DNA - Results in phage conversion —the host cell exhibitsnew properties-Specialized transduction - Specific bacterial genes transferred to another bacterium via a phage - Changes genetic properties of the bacteria

Describe how proteins can be infectious

Prion= infectious protein. Mammals make "normal" proteins called cellular PrP with alpha helix folding. Disease causing proteins called prion PrP is beta pleat folded. If an abnormal prion protein PrP^Sc enters a cell, it changes a normal prion protein to PrP^Sc, which now changes another normal prion, resulting in an accumulation of the abnormal PrP^Sc. Ex: Mad cow disease.

Translation (catabolic energy supply)

Process by which mRNA is decoded and a protein is produced, where proteins are synthesized from amino acids using the genetic information present in mRNA

Operon systems: induction and repression; negative feedback

Repression is a decrease in gene expression. Induction is an increase in gene expression due to the presence of an inducer.Negative feedback loops are common motifs in gene networks that reduce expression noise and intercellular variability in protein levels

Transcription in Prokaryotes

Synthesis of a complementary mRNA strand from aDNA template- begins when RNA polymerase binds to the promoter sequence on DNA- proceeds in the direction; only one of the two DNA strands is transcribed- stops when it reaches the terminator sequence on DNA

Translation ends at nonsense codons

UAA, UAG, UGA

Differentiate a virus from a bacterium

Virus- smaller than bacteria, piece of nucleic acid surrounded by protein coats, can't be classified as living, multiply inside living cells by using the synthesizing machinery of the cell. Contains either DNA or RNA.Bacteria- living, contains DNA and RNA, organelles, reproduce by binary fission.

Describe the general structure of a virus

Viruses are classified by their nucleic acid and by differences in the structures of their coat (capsid) Viruses have few or no enzymes of their own for metabolism. - may possess structural proteins, matrix proteins (if enveloped), viral enzymes (if applicable) and attachment proteins on their surface. - Viruses are very small and require the electron microscope to be seen. Much smaller than bacteria and red blood cells. Normally 20 to 1000 nm in length.

transposons

are segments of DNA that can move from one region of DNA to another • Contain insertion sequences (IS) that code for transposase that cuts and reseals DNA • Complex transposons carry other genes (e.g, inantibiotic resistance)

plasmids

are self-replicating circular pieces of DNA • 1 to 5% the size of a bacterial chromosome • Often code for proteins that enhance the pathogenicity of a bacterium - is a small, circular, double-stranded DNA molecule that is distinct from a cell's chromosomal DNA. Plasmids provide a mechanism for horizontal gene transfer within a population of microbes -fertility genes (help bacteria to shape DNA) -virulence genes (bacteria infection)

Replication (catabolic energy supply)

consumes energy and precursors for faithfully copying genomes, propagating the genetic material from generation to generation

Describe the general characteristics of a virus

contain DNA or RNA -contain a protein coat -obligate intracellular parasites -Require living host cells to multiply -no ribosomes, cytoplamic membran, cytosol, organelles They are extremely small in size and simpler than bacteria. They are ultra-microscopic, which are visible only with an electron microscope. They are considered to be the organisms that live at the edge of living and non-living things.

RNA function

create proteins via translation RNA carries genetic information that is translated by ribosomes into various proteins necessary for cellular processes. mRNA, rRNA, and tRNA are the three main types of RNA involved in protein synthesis

Phenol and Phenolics

injure lipids of plasma membranes, causing leakage

How does radiation effectively kill microbes? Provide a specific example.

ionizing radiation kills microbes by ionizing water to create reactive hydroxyl radicals and damage DNA by causing lethal mutations. Non-ionizing radiation damages DNA by creating thymine dimers and microwaves killed by heat, not especially antimicrobial.

Lac operon

is an inducible operon that is normally turned off. The lac operon is an example of inducible control because the presence of lactose turns on transcription of the genes for its own metabolism. example: ecoli

transduction in horizontal gene transfer

is the process by which DNA is transferred from one bacterium to another by a virus. It also refers to the process whereby foreign DNA is introduced into another cell via a viral vector -involves the transfer of either a chromosomal DNA fragment or a plasmid from one bacterium to another by a bacteriophage.

transformation in horizontal gene transfer

is the specific process where exogenous genetic material is directly taken up and incorporated by a cell through its cell membrane. -gives genes to others -donor cell contributes a part of the genome to recipient cell - genes transferred from one bacterium to another as "naked" DNA

Translation in molecular process

mRNA is translated into the "language" of proteins. Codons of mRNA are "read" sequentially. Codons are groups of three mRNA nucleotides that, code for a particular amino acid, 61 sense codons encode the 20 amino acids, the genetic code involves degeneracy, meaning each amino acid is coded by several codons.

RNA structure

made up of nucleotides, which are ribose sugars attached to nitrogenous bases and phosphate groups.The nitrogenous bases include adenine, guanine, uracil, and cytosine. RNA mostly exists in the single-stranded form, but there are special RNA viruses that are double-stranded

Transcription (catabolic energy supply)

(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA, a central mechanism by which cells respond to physiological cues to generate the energy required for anabolic pathways, transport of molecules and mechanical work.

Promoter

segment of DNA where RNA polymerase initiates transcription of structural genes.

operon

set of operator and promoter sites and the structural genes they control

DNA function

stores an organism's genetic material in the nuclei. replicates itself when dividing. provides code or template for the particular sequencing of amino acids that bond together and make a protein.

replication in molecular process

supplied by nucleotides, Hydrolysis of two phosphate groups on ATP provides energy, Most bacterial DNA replication is bidirectional, each offspring cell receives one copy of the DNA molecule, replication is highly accurate due to the proofreading capability of DNA polymerase

Trp operon

tryptophan binds to the repressor protein and enables it to repress gene transcription, an example is repressible control because it uses proteins bound to the operator sequence to physically prevent the binding of RNA polymerase example: e. coli

Vertical gene transfer

vertical gene transfer is the transfer of genetic material from parent to offspring. -transfer of genes from anorganism to its offspring

Discuss the relationship between DNA and RNA containing viruses and cancer

~ 10% of cancers are caused by viruses Several DNA viruses are retroviruses and oncogenic. The genetic material of oncogenic viruses become integrated into the host cells DNA. DNA viruses include HPV and Hep B. Among the RNA viruses only the retroviruses seem to oncogenic. HTLV-1&2 have been found to cause cancer. -Activated oncogenes transform normal cells into cancerous cells*Transformed cells have increased growth, loss of contact inhibition, tumor-specific transplant antigens, and T antigens The genetic material of oncogenic viruses becomes integrated into the host cell's DNA

Biosynthesis of RNA viruses that use DNA

• Single-stranded RNA, produce DNA • Use reverse transcriptase to produce DNA from the viral genome • Viral DNA integrates into the host chromosome as a provirus Examples- • Retroviridae • Lentivirus (HIV) • Oncoviruses