microbio unit 3 test

Sterilization

The removal of all microorganisms, including endospores. Sterilant - sterilizing agent

disinfection

Any treatment used on inanimate objects to kill or inhibit the growth of pathogenic microorganisms

a chemical used is called a disinfectant.

antisepsis

A chemical method to reduce pathogenic microorganisms of the skin or mucous membranes

the chemical is called an antiseptic

sanitization

The removal of microbes from eating utensils and food preparation areas.

biocide/germicide

A substance capable of killing microorganisms.

bacteriostasis

A treatment capable of inhibiting bacterial growth.

Bacteriocidal

agents that kill bacterial cells

asepsis

The absence of contamination by unwanted organisms.

thermal death point (TDP)

The temperature required to kill all the bacteria in a liquid culture in 10 minutes.

thermal death time (TDT)

The length of time required to kill all bacteria in a liquid culture at a given temperature.

decimal reduction time (DRT)

The time (in minutes) required to kill 90% of a bacterial population at a given temperature; also called D value.

autoclave

Equipment for sterilization by steam under pressure, usually operated at 15 psi and 121°C., denatures proteins

pasteurization

The process of mild heating to kill particular spoilage microorganisms or pathogens. (not sterilization, remaining organisms are not pathogenic)

high-efficiency particulate air (HEPA) filter

A screenlike material that removes particles larger than 0.3 μm from air.

membrane filter

A screenlike material with pores small enough to retain microorganisms; a 0.45-μm filter retains most bacteria.

desiccation

The removal of water.

ionizing radiation

High-energy radiation with a wavelength less than 1nm; causes ionization. X rays and gamma rays are examples.

nonionizing radiation

Short-wavelength radiation that does not cause ionization; ultraviolet (UV) radiation is an example.

use-dilution test

A method of determining the effectiveness of a disinfectant using serial dilutions.

disk-diffusion method

An agar-diffusion test to determine microbial susceptibility to chemotherapeutic agents; also called Kirby-Bauer test.

alcohol

An organic molecule with the functional group—OH.

Kills bacteria & fungi but not endospores or nonenveloped viruses.

Denatures proteins & disrupts membranes, most effective concentration 70%

oligodynamic action

The ability of small amounts of a heavy metal compound to exert antimicrobial activity. Metal ions combine with sulfhydryl groups and denature proteins.

surface-active agent (surfactant)

Any compound that decreases the tension between molecules lying on the surface of a liquid; also called surfactant. Soaps

Penicillin

Discovered by Fleming in 1928, produced by Penicillium

Narrow Spectrum

Drugs affecting a limited range of microbial types

Broad-spectrum Antibiotics

Affect a wide range of gram-positive or gram-negative bacteria

Cell Wall Synthesis Inhibition

Penicillins prevent peptidoglycan synthesis

Protein Synthesis Inhibition

Drugs like chloramphenicol target bacterial 70S ribosomes

Plasma Membrane Injury

Polypeptide antibiotics alter membrane permeability

Nucleic Acid Synthesis Inhibition

Interferes with DNA replication and transcription

Essential Metabolite Synthesis Inhibition

Antimetabolites compete with normal substrates (PABA) for enzymes

Enzymatic Destruction

Resistance mechanism involving drug inactivation by enzymes

Prevention of Penetration

Resistance mechanism preventing drug entry to target site

Alteration of Drug's Target Site

Resistance mechanism changing the drug's target within the microbe

Rapid Efflux

Resistance mechanism involving quick ejection of the antibiotic

Antibiotic Misuse

Includes using outdated antibiotics and not completing prescribed regimen

psychrophiles

live at very cold temperatures, freezers, arctic

Psychrotrophs

Grow between 0°C and 20-30°C

Cause food spoilage

mesophiles

moderate temperature loving microbes (20-40C), most microbes grow at these temps

thermophiles

growth at higher temps, 50-60oC, hot springs

hyperthermophiles

Archaea, optimum growth temperature >80*C, volcanic vents, deep ocean vents

acidophiles

grow in acidic environments, 5.5 , pump out excess protons; or lower, most fungi and algae

Alkaliphiles (alkalophiles)

growth optimum between pH 8.5 and pH 11.5, pump in protons

Neutrophiles

pH of 6.5-7.5, most organisms fall into this range

plasmolysis

A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.

obligate halophiles

salt-loving bacteria; require high osmotic pressure (dead sea)

facultative halophiles (osmotolerant)

tolerate high osmotic pressure

obligate aerobes

require oxygen

facultative anaerobes

can survive with or without oxygen, prefer to use aerobic respiration, however in the absence of oxygen, can use either fermentation or anaerobic respiration

obligate anaerobes

unable to use oxygen, and oxygen is toxic due to lack of enzymes to break down toxic byproducts

aerotolerant anaerobes

do not use oxygen but are not killed by it

microaerophiles

require oxygen concentration lower than air concentrations

biofilms in microbial growth

microbial communities; form slime or hydrogels that adhere to surfaces; bacteria communicate cell-to-cell via quorum sensing; share nutrients; shelter bacteria from harmful environmental factors

1000x resistant to microbicides; involved in 70% of infections in hospital (catheters, heart valves, contacts, dental caries)

CFU

population of cells arising from single cell or spore or from group of attached cells

often called colony-forming unit

bacterial division

do not go through mitosis; go through binary fission

increase number of cells, not size

budding

Conidiospores (actinomycetes)

Fragmentation of filaments

generation time

time required for cell to divide

20 minutes to 24 hours

binary fission doubles number of cells each generation

total number of cells = 2^number of generations

growth curves are represented logarithmically

lag phase of bacterial growth

organisms acclimate to their surrounding; they grow in size but do not increase in number

the first phase of the bacterial growth curve

Log phase of bacterial growth

cells divide at an exponential rate

the second of the four phases of bacterial growth

stationary phase of bacterial growth

new cells are produced at the same rate as the old cells die, leaving the number of live cells constant

the third of the four phases of the bacterial growth curve

death phase of bacterial growth

as resources become insufficient, bacteria die off

direct measurement of microbial growth

direct count of microbial cells; plate count; filtration; most probable number (MPN) method; direct microscopic count

direct microscopic count

Volume of a bacterial suspension placed on a slide

Average number of bacteria per viewing field is calculated

Uses a special Petroff-Hausser cell counter; live and dead bacteria are included

MPN (most probable number)

a statistical determination of the number of bacteria per 100ml , only live bacteria are included

turbidity method

- Indirect method

- Counts both live and dead cells

- uses spectrophotometer

serial dilution

take initial stock sample of bacteria, successive tubes, dilute down to smaller numbers

turbidity

measurement of cloudiness with a spectrophotometer

metabolic activity

amount of metabolic product is proportional to the number of bacteria

dry weight

bacteria are filtered, dried, and weighed; used for filamentous organisms