Micro Exam #3
Terms in this set (59)
Destruction/removal all microbial life, including endospores (not prions)
Destruction of vegetative pathogens
Destruction of vegetative pathogens on living tissue
removal of microbes from a limited area (i.e. skin around injection site)
Treatment intended to lower microbe counts on eating & drinking utensils to safe public health levels
Kills microbes (i.e. fungicide)
Inhibit microbial growth
absence of significant bacterial contamination
What are the 4 factors that influence the effectiveness of treatment?
1. Number of microbes
3. Time of exposure
4. Microbial characteristics
What are the 2 major effects that microbial control agents have on cellular structures
1. Alteration of membrane permeability
2. Damage to proteins and nucleic acids
List the physical methods of controlling microbial growth discussed
3. Low temperature
4. High pressure
6. Osmotic pressure
Compare the modes of moist heat (autoclave) and dry heat (hot-air) treatments to control growth.
Autoclaving is a moist heat sterilization, its steam under pressure and is the most effective. Dry heat sterilization kills by oxidation for example direct flaming, the items are placed in an oven with takes longer.
Describe how filtration suppress microbial growth
Passage of liquid/gas through filter with pores small enough to trap microbes. High-efficiency particulate air (HEPA) removes microbe from air. Membrane filters remove bacteria, viruses, large proteins
Describe how low temperatures suppress microbial growth.
Low temperature inhibits microbial growth
Refrigeration (0oC - 7oC)
Describe how high pressure suppress microbial growth.
High pressure denatures proteins
Describe how desiccation suppress microbial growth.
Desiccation prevents metabolism
Microbes without water can survive but not grow
Viruses & endospores can resist
Describe how osmotic pressure suppress microbial growth.
Osmotic pressure causes plasmolysis
Microbes in [high] salts, sugars
Molds & yeasts more capable than bacteria at growing in low moisture/high osmotic pressure
Explain how radiation kills cells
Effect depends on its wavelength, intensity & duration
-Ionizing radiation (X rays, gamma rays)
High degree of penetration
Ionizes water to release OH• that react with DNA
-Non-ionizing radiation (UV, 260 nm)
Low degree of penetration
Makes thymine dimers in DNA that interfere with replication.
Microwaves kill microbes indirectly as materials get hot.
Inducers induce transcription of a gene. Default OFF.
List the factors related to effective disinfection.
Careful attention to properties and concentration to use at.
Presence of organic matter.
Degree of contact with microbe.
Identify the methods of action and preferred uses of chemical disinfectants.
Bisphenols- antibacterial soap
Chlorine- bleach surface cleaner
Gaseous- denatures proteins on hospital beds
Supercritical fluids- medial implants
Identify chemical sterilizers.
-Gaseous: Ethylene oxide penetrates most material to denature proteins. Use: heat sensitive materials (i.e. mattresses in hospitals)
-Supercritical fluids: CO2 compressed into 'supercritical state' with gaseous (lowered surface tension) and liquid (increased solubility) propertiesUse: Medical implants - bone, tendons, ligaments from donors
Any material prepared for growth of bacteria in a lab
Microbes introduced into culture medium to initiate growth
Microbes growing in/on culture medium
Solidifying agent added to medium when we want to grow bacteria on solid medium
Microbes that grow better in high Co2
An increase in bacterial numbers
Even division to produce 2 new cells
Begins with outgrowth from parent that grows to be daughter cell
Fragments of bacteria initiate growth of new cells
Time required for a cell to divide/population to double
Study if what genes are, how they carry information, how information is expressed, and how genes are replicated
Segment of DNA that encodes a functional product, usually a protein
Structures containing DNA and regulatory proteins that physically carry hereditary information. Chromosomes contain the gene.
All genetic information in a cell
Set of rules that determines how a sequence of DNA is converted to a protein sequence (amino acids)
Genes of an organism, genetic makeup is what we can't see
Expression of genes, what we can see
Set of promoter and operator and structural genes they control
Region of DNA where RNA polymerase initiates transcription
Traffic light. Stop/go signal for transcription.
Repressors block ability of RNA polymerase to initiate transcription. Default ON
Occasional mistakes made during DNA replication
Agent that causes mutations
Base substitution resulting in substitution. Ex: sickle cell disease
Base substitution resulting in nonsense (stop) codon. Incomplete protein.
Insertion/deletion of one or more nucleotide pairs.
Molecules structurally similar to normal nitrogenous bases but with different base-pairing properties.
Vertical gene transfer
When genes are passed from an organism to its offspring. Plants, animals, bacteria.
Horizontal gene transfer
Genes are passed laterally to other microbes of the same generation. Bacteria only!!
Process if joining pieces of DNA from different sources
Portion of one chromosome is exchanged with a portion of another chromosome.
Occurs naturally. Horizontal transfer.
Bacteriophage! Horizontal transfer.
Quick and efficient. Horizontal transfer. Bacterial and sex pili.
What are plasmids?
Small, circular, double stranded DNA molecules. Replicate independently of bacterial chromosome.
Carries genes for sex pili and transfer of plasmid during conjugation.
Carries plasmids and kills bacteria.