Microbio exam 3
- Destruction or removal of all forms of microbial life, including endospores but with the possible exception of prions
- (usually done by steam under pressure or a sterilizing gas such as ethylene oxide)
- destruction of vegetative pathogens
- ( may make use of physical or chemical methods)
- treatment is intended to lower microbial counts on eating and drinking utensils to safe public health levels
- (may be done with high-temperature washing or by dipping into a chemical disinfectant)
- removal of microbes from a limited area, such as the skin around an injection site
- (mostly a mechanical removal by an alcohol-soaked swab)
- destruction of vegetative pathogens on living tissue
- (treatment is almost always by chemical antibacterials)
- sufficient heat treatment to kill endospores of Clostridium botulinum in canned food
- (more-resistant endospores of thermophilic bacteria may surevive, but they will not germinate and grow under normal conditions)
What factors influence the effectiveness of antimicrobial treatments?
- the # of microbes: more microbes = longer to eliminate entire population
- environmental influences: presence of organic matter (ex. blood, vomit, feces) often inhibits antimicrobial and influences the selection of disinfectants.
- microbial characteristics
Why do we express bacterial death rate logarithmically?
- Bacterial populations usually die at a constant rate when heated or when treated with antimicrobial chemicals.
- EX: a population of 1 million microbes treated for 1 minute, 90% of the poplation die, now we're left with 100,000 microbes
understand concepts in regards to the microbial death curve
In what ways do control treatments act on microbes?
- Alteration of membrane permeability: damage to the lipids or proteins of the plasma membrane by antimicrobial agents causes cellular contents to leak into the surrounding medium and interferes with the growth of the cell
- Damage to proteins & nucleic acids: denaturation of proteins by heat or certain chemicals by breaking/attacking chemical (H) bonds of amino acids that give protein its shape; damage to nucleic acids (DNA&RNA) by heat, radiation, or chemicals=lethal to cell--->can not replicate, carry out normal metabolic functions
Thermal death point (TDP)
- the lowest temperature at which all the microorganisms in a particular liquid suspension will be killed in 10 minutes
Thermal death time (TDT)
- the minimal length of time for all bacteria in a particular liquid culture to be killed at a given temperature
Decimal reduction time (DRT or D Value)
- DRT is the time in minutes in which 90% of a population of bacteria at a given temperature will be killed
Moist heat in the means of controlling microbial growth
- moist heat kills microorganism by coagulating proteins (denaturation) which is caused by breakage of the hydrgen bond that hold the proteins in their 3D shape
- types of moist heat sterilization boiling(not very reliable), autoclave (more reliable)
- sterilizing the surface of a solid requires that steam actually come in contact with it
Boiling or flowing steam
- MOA: protein denaturation
- kills vegetative bacterial & fungal pathogens and some viruses within 10 min, less effective on endospores & other viruses ( some viruses can survive up to 30+ minutes of boiling; some endospores can resist boiling for 20+ hrs )
- uses: dishes, basin, pitchers, various equipment
- MOA: protein denaturation
- Very effect method of steriliztion; @ about 15 psi of pressure (121 C), all vegative cells and their endospores are killed in 15 min
- disadvantage: steam under pressure fails to sterilize when the air is not completely exhausted
- uses: microbiological media, solutions, linens, utensils, dressings, equipment
dry heat as a means of controlling microbial growth
- kills by oxidation effects
- methods include: direct flaming, incineration & hot-air sterilization
- takes longer & requires higher temperatures (vs moist heat)
- MOA: burning contaminats to ashes
- very effective method of sterilization
- uses: inoculating loops--->effectively>heat the wire to a red glow
- MOA: burning to ashes
- very effective method of sterilization
- uses: paper cups, contaminated dressings, animal carcasses, bags, wipes
- MOA: oxidation
- very effected method of sterilization but requires temp of 170 C for about 2 hr
- uses: empty glassware, instruments, needles , glass syringes
pasteurization as a means for control of microbial growth
- mild heating to food products, that sufficiently kills microbes that cause spoilage and pathogenic microbes without changing the taste of the product too much.
- MOA: protein denaturation
- lowers microbial numbers
- many thermoduric bacteria survive pasteurization but they are unlikely to cause disease
- high temperature short-time (HTST) pasteurization: common pasteurizing method; temp typically 72 C for 15 sec; applied as milk continuously passes a heat exchange; lowers total bacterial counts
- ultra high temperature (UHT) treatments: means of commercial sterilization of milk
- MOA: separation of bacteria from suspending liquid
- removes microbes by passage of liquid or gas through a screen like material; most filters in use consist of cellulose acetate or nitrocellulose
- Uses: sterilizing liquids (enzymes, vaccines) that are destroyed by heat
- MOA: plasmolysis
- results in loss of water from microbial cells
- uses: food preservation
- gamma rays have a short wavelength (less than 1 nm) so it holds more energy
- MOA: destruction of DNA
- not widespread in rountine sterilization
- uses: sterilizing pharmaceuticals, medical & dental supplies
- wavelength between 1 nm & 380 nm
- example: UV light(260 nm) -damages the DNA of exposed cells by causing bonds to form between adjacent pyrimidine bases which inhibit correct replication
- disadvantage: the radiation is not very penetrating=organisms must be directly exposed to the rays
- uses: control of closed environments with UV (germicidal) lights: hospital rooms, nurseries, operating rooms, cafeterias
how are chemical controls' effectiveness evaluated?
- Use-dilution test (current standard for testing)
- disk-diffusion method
- serial dilutions
- preformed in lab
- consists of paper disks soaked with chemical to be tested placed in agar plate with test organism
- if clear zone around disk is seen, chemical is effective
- method of evaluating disinfectants & antiseptics
- metal or glass cylinders are dipped in cultures of test bacteria, removed & dried at 37 C. They are placed in a in a solution of disinfectant for 10 minutes @ 20 C. the cylinders are then transferred to a medium that permits the growth of surviving bacteria.
- current standard of testing
What is the genetic code?
(using a copy know how to go back & forth between mRNA codons, amino acids & DNA)
- set of "rules" that determines how a nucleotide sequence is converted into the amino acid sequence of a protein
- protein synthesis & signaling start & stop in the process
- consists of 64 codons that correspond with 20 amino acids
Describe the process of protein synthesis.
- Transcription: RNA polymerase binds to promoter site, DNA unwinds
- RNA is synthesized by complementary base pairing of nucleotides with nucleotide bases on the template strand of DNA
- the site of synthesis move along DNA;DNA rewinds after being transcribed
- transcription reaches the terminator.
- RNA & RNA polymerase are released and the DNA helix re-forms
- Translation: ribosomal units come together; tRNA carrying the first amino acid is matched with the start codon on mRNA
- The ribosome moves along mRNA, as tRNA continues to match the anticodon with the codons, the ribosome joins the amino acids with a peptide bond.
- this continues on until the ribosome reaches a stop codon they the polypeptide chain of amino acids ribosome comes apart.
- the polypeptide is the newly formed protein.
Role of DNA in protein synthesis
- DNA acts as a template of genetic information in which is transcribed in to a complementary base sequence of RNA
Role of RNA polymerase in protein synthesis
- enzyme that synthesizes RNA from the DNA template
role of mRNA in protein synthesis
- carries coded information for making specific proteins from DNA to ribosomes
role of ribosomes & rRNA in protein synthesis
- site at which translation occurs
- functions: to direct the orderly binding of tRNAs to codons & to assemble the amino acid brought there into a chain, ultimately producing a protein
- cellular machinery of the protein synthesis
role of tRNA in protein synthesis
recognizes the specific codons of mRNA and transport the required amino acids
- groups of 3 nucleotides
- each codon " codes" for a particular amino acid (genetic code)
- the sequence of codons on an mRNA molecule determine the sequence of amino acides that will be in the protein being synthesized
a sequence of 3 bases pairs on the tRNA molecule
what is transcription?
- synthesis of a complementary strand of RNA from a DNA template
What is translation?
- process in which the mRNA is decoded and and protein synthesis occurs
what is a polyribosome?
chain of ribosome on mRNA that reads one strand of mRNA simultaneously, helping to synthesize the same protein at different spots on the mRNA
what are exons, introns?
- exons: regions of DNA expressed
- Introns: the intervening regions of DNA that do not encode the protein
What is a mutation?
- a permanent change in the base sequence of DNA
- know that mutations occur spontaneously and by the action of mutagens, which broadly speaking, may be chemical agents or radiation
- most common type of mutation in which a single base at one point in the DNA is replaced with a different base.
- changes in DNA in which one or few nucleotide pairs are deleted or inserted in DNA
What is aflatoxin and what does it do?
- Aflaxtoxin is a frameshift mutagen, that results in a mold that grows on peanuts and grain and is know to be a toxin that causes cancer
How might a UV caused thymine dimer to repair?
- UV can cause repair in a thymine dimer through a process called nucleotide excision repair.
- This involves an enzyme called Photolyases in which bacteria & organisms have.
- Enzymes cut out the incorrect base and fill the gap with newly synthesized DNA that is complementary to the correct strand.
Differentiate between horizontal and vertical gene transfer.
- Vertical gene transfer occurs during reproduction when genes are passed from an organism to its offspring
- Horizontal gene transfer in bacteria involves a portion of the cell's DNA being transferred from donor to recipient.
Transformation in bacteria
- genes are transferred from one bacterium to another as "naked" DNA in solution
- process occurs naturally in some genera of bacteria
Conjugation in Bacteria
- process requires contact between living cells
- on type of genetic done cell is F+; recipient cells are F-. F cells contain plasmids called F factors; these are transferred to the F- cells during conjugation
- when the plasmid becomes incorporated into the chromosome, the cell is called an Hfr (high frequency of recombination) cell
- During conjugation an Hfr cell can transfer chromosomal DNA to an F- cell.
transduction in bacteria
- bacterial DNA is transferred from a donor cell to a recipient cell inside a virus that infects bacteria
self repilcating circular molecules of DNA carrying genes that enhances cell's survival
- when a recipient cell is in a phsiologcal state in which it can take up the donor DNA
- results from alterations in the cell wall that make it permeable to large DNA molecules
What does it mean when a plasmid confers resistance? pathogenicity?
- plasmid that confer resistance are a know as resistance factors (r factors) it is the gene that makes a pathogen resistant to antibiotics; acquired through the spread of genes from one organism to another
- plasmid that confer pathogenicity are the genes that make the bacteria pathogenic
know the plasmid types
- conjugative plasmids -pieces of DNA that carry genes for sex pili and for the transfer of plasmid ex. f facter
- dissimulation plasmids- code for enzymes that trigger the catabolism of certain unusual sugars and hydrocarbons
- resistance factors (R factors)- gene that makes a pathogen resistant to antibiotics
- plasmids carrying genes for toxins or bacteriocins
What are transposons and why do they matter?
- small segments of DNA that can move from one region to another region of the same chromosome or to a different chromosome or a plasmid
- provide a natural mechanism for the movement of genes from one chromosome to another
- maybe carried between cells on plasmids or viruses; spread from one organism or even species to another
- potentially powerful mediator of evolution in organism
How do plant viruses enter their hosts and spread?
Plasmodesmata (small channels connecting cell walls of plant cells), wounds and insects bites
Which viral families are known to cause cancer in humans?
Retroviruses, Hepednaviruses, herpesviruses, human papillomavirus
Differentiate between biotechnology and recombinant DNA technology
Biotechnology is the use of microorganisms, cell, or cell parts to manufacture a product ex. penicillin
Recombinant DNA technology is the inserting of genes into cells to add or enhance certain traits, such as penicillin production
are a special class DNA-cutting enzymes that exist in bacteria
When the double stranded helix of DNA is cut halfway through one spot and then the rest of the way through in a separate area, this creates a staggered end instead of a clean, blunt, cut through both single strands of DNA. A sticky end then is easier to recombine with another piece of DNA with similar cuts.
cDNA (complementary DNA)
- In genetics, complementary DNA (cDNA) is double-stranded DNA synthesized from a messenger RNA (mRNA) template in a reaction catalysed by the enzyme reverse transcriptase. cDNA is often used to clone eukaryotic genes in prokaryotes.
- an enzyme that catalyzes the formation of DNA from an RNA template in reverse transcription.
- In molecular cloning, a vector is a DNA molecule used as a vehicle to artificially carry foreign genetic material into another cell, where it can be replicated and/or expressed. A vector containing foreign DNA is termed recombinant DNA.
The basic tool of DNA analyses is a fragment of DNA called the DNA probe. A DNA probe is a relatively small, single-stranded fragment of DNA that recognizes and binds to a complementary section of DNA in a complex mixture of DNA molecules. The probe mingles with the mixture of DNA and unites with the target DNA much like a left hand unites with the right. Once the probe unites with its target, it emits a signal such as radioactivity to indicate that a reaction has occurred.
- A Ti or tumour inducing plasmid is a circular plasmid that often, but not always, is a part of the genetic equipment that Agrobacterium tumefaciens and Agrobacterium rhizogenes use to transduce its genetic material to plants.
- In RFLP analysis, the DNA sample is broken into pieces and (digested) by restriction enzymes and the resulting restriction fragments are separated according to their lengths by gel electrophoresis.
Is a technique by which small samples of DNA can be quickly amplified, that is, increased to quantities that are large enough for analysis
Ways to insert foreign DNA into cells
1. DNA transformation
1. A process in which cells can take up DNA from the surrounding environment by using a plasmi
2. Uses an electrical current to form microscopic pores in the membranes of the cells. DNA then enters the cells through the pores
Some cells need their cell walls to be changed to protoplasts in order to be be able to use electroporation. Protoplasts are made by enzymatically removing the cell wall.
3. Protoplast Fusion.
process that also takes advantage of the properties of protoplasts. In a solution protoplasts diffuse at a low, but significant rate. Two protoplasts can fuse creating one new recombinant cell.
glass micropipette with diameter smaller than the cell is used to puncture cell and insert DNA
pro and cons of rDNA technology
Pros- medically we can synthesize human insulin for diabetes patients etc. agriculturally we can engineer plants to resist bugs, or extreme weather.
Cons- health concerns like recombinant DNA has resulted in the inadvertent production of toxic substances in genetically engineered bacteria, yeast, plants and animals it could similarly cause these problems in humans. Also ethical concerns arise if human DNA is inserted into tomato crops to hasten growth is eating these tomatoes, cannibalism. Similar ethical debates can be found on biotechnology.
- Fungi are chemoautotrophs
- They typically are multicellular
- Typically can both sexually or asexually reproduce
- Sterols present in membrane
- no peptidogylcan in cell wall
- limited to heterotrophic, aerobic, and facultative anaerobic
- obtain nutrients by diffusion
- sometimes multicellular
- rarely produce toxins
- Generally chemoautotrophic (some photoautotrophic)
- nutrients through absorption or ingestion
- parasitic protozoans form resistant cysts
Are segmented and have spores and septums
continuous, no pores or septum, only cell walls and nuclei
Symbiotic fungi that many plants depend on to help their roots absorb minerals and water from soil
any fungal infection is called a mycosis
When environmental conditions are suitable hyphae grow to form a filamentous mass called mycelium.
- Mycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae.
Fungal Pathogen of Candida albicans
(This is the paragraph question so I just gave more than adequate information to pick and choose from)
Its asexual spore types are Chlamydoconidia. Its habitat is human normal microbiota. The type of mycosis is cutaneous, systemic, and mucocutaneous. It belongs Ascomycota phylum. Overgrowth of of fungus in mucous membranes from suppression bacterial micrioflora are called Candidiasis. In the form of pseudohyphae Candida is resistant to phagocytosis. Infected areas become bright red with lesions on the border.
- Creamy white lesions on your tongue, inner cheeks, and sometimes on the roof of your mouth, gums and tonsils
- Slightly raised lesions with a cottage cheese-like appearance
- Redness or soreness that may be severe enough to cause difficulty eating or swallowing
- Slight bleeding if the lesions are rubbed or scraped
- Cracking and redness at the corners of your mouth (especially in denture wearers)
- A cottony feeling in your mouth
- Loss of taste
People with any suppressed microbiota or depressed immune systems are prone to candidiasis
The goal of any oral thrush treatment is to stop the rapid spread of the fungus, but the best approach may depend on your age, your overall health and the cause of the infection.
- Healthy adults and children. Your doctor may recommend antifungal medication. This comes in several forms, including lozenges, tablets, or a liquid that you swish in your mouth and then swallow.
- Infants and nursing mothers. If you're breast-feeding and your infant has oral thrush, you and your baby could pass the infection back and forth. Your doctor may prescribe a mild antifungal medication for your baby and an antifungal cream for your breasts. Ask your doctor about the best way to clean your breast nipples, bottle nipples, pacifiers and any detachable parts of a breast pump if you use one.
- Adults with weakened immune systems. Most often your doctor will recommend antifungal medication. But Candida albicans can become resistant to many antifungal medications, especially in people with late-stage HIV infection. So a drug called amphotericin B may be used, but only when other drugs aren't effective, as it can cause serious side effects.
long filaments of cells joined together
What "doe" (lol) reindeer and lichen have to do with the Chernobyl Nuclear Disaster
70,000 agriculturally raised reindeer had to be disposed of because they had high levels of radiation. Lichens are a common food source for all tundra herbivores. The lichen, fed on by the reindeer had absorbed cesium-137 which had been spread in the air by the nuclear disaster
What do sudden oak deaths in CA and the Irish potato famine have in common
The fungus that caused the great potato blight was Phytophthora infestans. Today many Phytophthora cause damage to crops and plants all over. Recently University of CA linked the sudden deaths of oak trees to a new species of Phytophthora. When in close proximity different types of Phytophthora can form a zygote together with the offspring inheriting genes from both parents.
What organism grows on the hair of sloths and polar bears?
Green algae grows on sloths and polar bears in warm climates
What acid-fast organism is a frequent cause of recreational waterborne diarrhea? to what group of eukaryotes does it belong?
Cryptosporidium is the most common cause of recreational waterborne diarrhea. It belongs to the apicomplexan protozoans group of eukaryotes.
Identify Parasite, its parts, and a disease it causes?
- characteristics include 1-4 nuclei
- this intestinal protozoan is known to be the cause of amoebic dysentery.
- infection occurs when human host ingests cysts either fecal-oral contact or contaminated food/water
- trophozoites parasitize the mucosa and submucosa of the colon causing ulcers. They feed on RBCs and bacteria
- symptoms include abdominal pain, diarrhea, blood & mucus in feces, nausea, vomiting and hepatitis
Identify Parasite, its parts, and a disease it causes?
- characteristics: diplomonad; 4 pairs of flagella and a sucking disc; multinucleate cysts lack flagella
- known to cause Giardisis; transmission typically involves fecal contaminated water or food
- symptoms include chronic diarrhea, dehydration, abdominal pain
Identify Parasite and a disease it causes?
- apicomplexan protozoan; asexual reproduction of parasite takes place in the liver and RBCs of human host, sexual reproduction occurs in the intestine of Anophele mosquito after ingesting gametocytes.
- Blood parasite that causes malaria; transmitted through the saliva of an infected mosquito to human host
- symptoms correspond with the rupture of RBCs & include chills, vomiting nausea, headache, fever
Identify Parasite and a disease it causes?
*this is from the slide in class; but to have a better idea there is another view attached
- blood parasite known to cause sleeping sickness(Africa) & Changas' disease (New World)
cell morphology : just know these