Test 3 Flashcards by Jacey Golden

what does genetics explore (4)

traits from parent to offspring
expression and variation
structure and function of genetic material
how the material changes

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genome

sum total of genetic material of a cell / all of the genes constitute the genetic makeup

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chromosome

single molecule of DNA complexed with protein

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3 basic categories of genes

-structural genes that code for proteins
-genes that code for RNA
-regulatory genes that control gene expression

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genotype

All the genes in the genome and the specific version of each gene

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phenotype

The expression of the genotype creates observable traits

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Parts of a nucleotide

5 carbon sugar =deoxyribose
phosphate group
nitrogenous base - AGTC

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3 mechanism of horizontal gene transfer

conjugation
transformation
transduction

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Conjugation

Transfer of a plasmid or chromosomal fragment from a donor cell to a recipient cell via a direct connection/ transfers genetic information through pilus

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Transduction

Random fragments of disintegrating host DNA are picked up by the phage during assembly

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Transformation

Uptake of naked DNA from the environment and its incorporation into the genome of the recipient cell

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microorganisms causing infection or spoilage

vegetative bacterial cells and endospores
fungal hyphae and spores, yeast
protozoan trophozoites and cysts
worms
viruses
prions

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highest resistance microbes

prions, bacterial endospores

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moderate resistance microbes

pseudomonas sp.
mycobacterium tuberculosis
staphylococcus aureus
protozoan cysts

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least resistance microbes

most bacterial vegetative cells
fungal spores and hyphae, yeast
enveloped viruses
protozoan trophozoites

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sterilization

Everything is dead. All microorganisms are dead including endospores

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Disinfection

Applies to inanimate surfaces and objects. Endospores are likely to survive, most vegetative pathogens are dead

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antisepsis

Same as disinfection but applies to living tissue. Cleaning a wound to prevent infection is antisepsis, not disinfection

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sanitization

Reducing the number of microorganisms to an acceptable and safe level. Cleaning with the realization that tougher microbes might survive

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degerming

Mechanical removal of germs from a defined area. Washing your hands or brushing your teeth are examples

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factors that affect death rate

Number of microbes
Nature of microbes in the population
Temperature and pH of environment
Concentration or dosage of agent
Mode of action of the agent
Presence of solvents, organic matter, or inhibitors

Practical Concerns in Microbial Control

-Does the application require sterilization?
-Is the item to be reused?
-Can the item withstand heat, pressure, radiation, or chemicals?
-Is the method suitable?
-Will the agent penetrate to the necessary extent?
-Is the method cost- and labor-efficient and is it safe?

Antimicrobial Agents’ Modes of Action - cell wall

cell wall becomes fragile and cell lyses; some
antimicrobial drugs, detergents, and alcohol

Antimicrobial Agents’ Modes of Action - cell membrane

loses integrity; detergent surfactants

Antimicrobial Agents’ Modes of Action - protein and nucleic acid synthesis

prevention of replication, transcription, translation, peptide bond formation, protein synthesis; chloramphenicol, ultraviolet radiation, formaldehyde

Antimicrobial Agents’ Modes of Action - proteins

disrupt or denature proteins; alcohols, phenols, acids, heat

methods of physical control

1. Heat – moist and dry 2. Cold temperatures 3. Desiccation 4. Radiation 5. Filtration

moist heat

Lower temperatures and shorter exposure time / Coagulation and denaturation of proteins

dry heat

Moderate to high temperatures / Dehydration, alters protein structure; incineration

Thermal death time (TDT)

shortest length of time required to kill all test microbes at a specified temperature

thermal death point

Lowest temperature required to kill all microbes in a sample in 10 minutes

boiling water

boiling at 100C for 30 mins / Destroys non-spore-forming pathogens Disinfection

pasteurization

Heat is applied to kill potential agents of infection and spoilage without destroying the food flavor or value

microbiostatic

slows the growth of microbes

Desiccation

gradual removal of water from cells

lyophilization

freeze drying, preservation

Ionizing radiation

deep penetrating power / sufficient energy to cause electrons to leave their orbit

what is used to sterilize medical supplies and food products

gamma, x-ray, and cathode rays

non-ionizing radiation

little penetrating power / must be directly exposed

filtration

physical removal of microbes by passing a gas or liquid through filter (HEPA)

High-level germicides

kill endospores = sterilants

intermediate level germicides

kill fungal spores (not endospores) tubercle bacillus, and viruses

Low-level germicides

Eliminate only vegetative bacteria, vegetative fungal cells, and some viruses

Germicidal categories (11)

1. Halogens 2. Phenolics 3. Chlorhexidine 4. Alcohols 5. Hydrogen peroxide 6. Aldehydes 7. Gases 8. Detergents & soaps 9. Heavy metals 10. Dyes 11. Acids and Alkali

Halogens

chlorine and iodine

Chlorine exs

hypochlorites (chlorine bleach), Cl2, chloramines

Iodine exs

I2, Iodophors (betadine)

Phenolics

Disrupt cell walls and membranes and precipitate proteins, low to intermediate) lysol and triclosan

Chlorhexidine

Hibiclens, Hibitane. low to intermediate A surfactant and protein denaturant with broad microbicidal properties

Alcohols

Ethyl, isopropyl in solutions of 50-95% intermediate level

Hydrogen peroxide

Produce highly reactive hydroxyl-free radicals that damage protein and DNA while also decomposing to O2 gas – toxic to anaerobes Antiseptic at low concentrations; strong solutions are sporicidal