MircroBiology Quiz 2study Guide

Generation time

the time it takes for a population to double, Varies among species • Environmental conditions,

Exponential growth

growth whose rate becomes ever more rapid in proportion to the growing total number or size.predictable doublings of the population, where 1 cell become 2 cells, becomes 4, becomes 8 etc.

biofilms

Colonies of bacteria that adhere together and adhere to environmental surfaces.Cause slipperiness of rocks in stream bed, slimy "gunk" in sink drains, scum in toilet bowls, dental plaque

Pure culture

defined as population of cells derived from a single cell • Allows study of single species

aseptic technique

A procedure performed under sterile conditions. Obtains a pure culture (population from a single cell). Minimizes potential contamination

culture medium

A nutrient material prepared for the growth of microorganisms in a laboratory. Contains nutrients dissolved in water • Can be broth (liquid) or solid gel

Streak-plate method

Simplest, most commonly used method for isolating • Spreads out cells to separate • Obtain single cells so that individual colonies can form

stock culture

Often stored in refrigerator as agar slant • Cells can be frozen at -70°C for long-term storage • Requires solution that prevents ice crystal formation • Can be freeze-dried

Closed systems

systems that can sustain themselves without interacting with their environments. Nutrients not renewed; wastes not removed

batch cultures

yields characteristic growth curve

Open system

required to maintain continuous growth • Termed continuous culture • Nutrients added, wastes removed continuously

Lag phase

is defined as the initial period in the life of a bacterial population when cells are adjusting to a new environment before starting exponential growth.

Exponential (log) phase

This is when cells divide by binary fission and the doubling of each generation creates the exponential growth for which the phase is named

Stationary phase

the stage when growth ceases but cells remain metabolically active. Nutrient levels too low to sustain growth • Total numbers remain constant • Some die, release contents; others grow

Death phase

As waste builds up and nutrient-rich media is depleted, is the point where the living cells stop metabolic functions and begin the process of death.Total number of viable cells decrease • Cells die at constant rate • Exponential, but usually much slower than cell growth

Phase of prolonged decline

Some fraction may survive • Adapted to tolerate worsened conditions

Psychrophile

-5° to 15°C • Found in Arctic and Antarctic regions

Psychrotroph

20° to 30°C • Important in food spoilage

Mesophile

25° to 45°C • Pathogens 35° to 40°C

Thermophiles

45° to 70°C • Common in hot springs

Hyperthermophiles

70° to 110°C • Usually members of Archaea • Found in hydrothermal vents

Catalase

An enzyme produced in all cells to decompose hydrogen peroxide, a by-product of cell respiration

Superoxide dismutase (SOD)

An enzyme that destroys superoxide: O2- + O2- + 2H+ --> H2O2 + O2

neutrophiles

Range of pH 5 to 8; optimum near pH 7

Acidophiles

grow optimally at pH below 5.5

Alkaliphiles

grow optimally at pH above 8.5

Halotolerant

able to survive at high salt concentrations but do not require these conditions for growth.withstand up to 10%

Halophiles

require high salt concentrations • Marine bacteria ~3% • Extreme halophiles ≥ 9%

Heterotrophs

organisms that cannot make their own food, use organic carbon

Autotrophs

Organisms that make their own food, use inorganic carbon as CO2

Nitrogen fixation

Process of converting nitrogen gas into ammonia

carbon fixation

The incorporation of carbon from carbon dioxide into an organic compound by an autotrophic organism.

growth factors

Amino acids, vitamins, purines, pyrimidines

fastidious

requires numerous growth factors, : have complicated nutritional requirements

Photoautotrophs

energy from sunlight; carbon from inorganic CO2

Photoheterotrophs

energy from sunlight; carbon from organic compounds

Chemolithoautotrophs

(also termed chemoautotrophs, chemolithotrophs): energy from inorganic compounds; carbon from CO2

Chemoorganoheterotrophs

energy and carbon from organic compounds

Complex media

contains variety of ingredients • Exact composition highly variable • Often a digest of proteins

Chemically defined media

composed of exact amounts of pure chemicals • Used for specific research experiments • Usually buffered

Selective media

inhibits growth of certain species

Differential media (Blood Agar)

contains substance that microbes change in identifiable way

Anaerobic containers

useful if microbe can tolerate brief O2 exposures. useful if microbe can tolerate brief O2 exposures; can also use semisolid culture medium containing reducing agent (e.g., sodium thioglycolate) • Reduce O2 to water

Anaerobic chamber

used to provide an oxygen free atmosphere for work with oxygen sensitive organisms.

Robert Koch (1843–1910)

Developed methods of cultivating bacteria • Worked on methods of solid media to allow single bacteria to grow and form colonies • Tried potatoes, but nutrients limiting for many bacteria

Joseph Lister

revolutionized surgery: introduced methods to prevent infection of wounds,

Sterilization

a process that destroys or eliminates all forms of microbial life

Disinfection

involves the destruction of microorganisms, but not usually spores, on inanimate surfaces or objects

Disinfectants

used on inanimate objects – May be called biocides, germicides, bactericides

Antiseptics

used on living tissues to fight off microoganisms

Pasteurization

involves heating liquids at high temperatures for short amounts of time. Pasteurization kills harmful microbes in milk without affecting the taste or nutritional value

Decontamination

the technique or process of removing, inactivating, or killing pathogens to make an environment clean and safe

Sanitized

Reduces the microbial population, but does not kill or destroy bacteria

Preservation

process of delaying spoilage of foods and other perishable products • Adjust conditions • Add bacteriostatic (growth-inhibiting) preservatives

Cryptosporidium parvum

a protozoan that infects a wide variety of vertebrates, including humans, causes diarrhea

Bacterial endospores

only extreme heat or chemicals completely destroys

Protozoan cysts and oocysts

resistant to disinfectants; excreted in feces; causes diarrheal disease if ingested

Mycobacterium species

Gram-positive, catalase positive, non-motile, non-spore forming rod-shaped bacteria waxy cell walls makes resistant to many chemical treatments

Pseudomonas species

resistant to and can actually grow in some disinfectants

Naked viruses

ack lipid envelope; more resistant to disinfectants

Critical items

Medical devices that have contact with sterile body tissues or fluids, High risk of contamination

Semicritical instruments

those that come into contact with mucous membranes or non-intact skin

Non-critical instruments

those that come in contact with intact skin but not mucous membranes, Low risk of contamination.

Heat treatment

useful for microbial control • Reliable, safe, relatively fast, inexpensive, non-toxic • Can be used to sterilize or disinfect • Methods include moist heat, dry heat

Moist heat

destroys microorganisms by the irreversible coagulation and denaturation of enzymes and structural proteins

Autoclave

a machine that uses steam under pressure to kill harmful bacteria, viruses, fungi, and spores on items that are placed inside a pressure vessel

Dry heat

kills microorganism by oxidizing molecules. The essential cell constituents are destroyed and the organism dies.

Membrane filters

a technique for testing water samples Small pore size (0.2 µm) – Thin

Depth filters

use a porous filtration method to retain particles throughout the entire depth of the medium, rather than just holding them on the surface

Filtration of air

is the physical removal of microorganisms from the air by filters of appropriate retention efficiency

Electromagnetic radiation

radio waves, microwaves, visible and ultraviolet light, X rays, and gamma rays • Energy travels in waves; no mass • Wavelength inversely proportional to frequency • High frequency has more energy than low frequency

Ionizing radiation

can inactivate microorganisms either directly or indirectly by production of free radicals

Ultraviolet radiation

destroys microbes directly • Damages DNA • Used to destroy microbes in air, water, and on surfaces • Poor penetrating power

Microwaves

kill by generated heat, not directly

High Pressure

Used in pasteurization of commercial foods, Avoids problems with high temperature pasteurization • Employs high pressure up to 130,000 psi • Destroys microbes by denaturing proteins and altering cell permeability • Products maintain color, flavor associated with fresh food

Sterilants

destroy all microorganisms

High-level disinfectants

destroy viruses, vegetative cells • Do not reliably kill endospores • Semi-critical instruments

Intermediate-level disinfectants

destroy vegetative bacteria, mycobacteria, fungi, and most viruses • Disinfect non-critical instruments

Low-level disinfectants

destroy fungi, vegetative bacteria except mycobacteria, and enveloped viruses • Do not kill endospores, naked viruses • Disinfect furniture, floors, walls

Alcohols

60–80% aqueous solutions of ethyl or isopropyl alcohol • Kills vegetative bacteria and fungi • Not reliable against endospores, some naked viruses

Aldehydes

Glutaraldehyde, formaldehyde, and orthophthalaldehyde • Inactivates proteins and nucleic acids • 2% alkaline glutaraldehyde common sterilant • Immersion for 10–12 hours kills all microbial life

Formaldehyde

used as gas or as formalin (37% solution) • Effective germicide that kills most microbes quickly • Used to kill bacteria and inactivate viruses for vaccines • Used to preserve specimens

Biguanides

Chlorhexidine most effective • Extensive in antiseptics • Stays on skin, mucous membranes • Relatively low toxicity • Destroys vegetative bacteria, fungi, some enveloped viruses • Common in many products: skin cream, mouthwash

Ethylene oxide

Useful gaseous sterilant • Destroys microbes including endospores and viruses

Halogens

oxidize proteins, cellular components: Chlorine & Iodine

Chlorine

Destroys all microorganisms and viruses • Used as disinfectant

Iodine

Kills vegetative cells, unreliable on endospores • Commonly used as iodophore, Some Pseudomonas species can survive in stock solution

Metal Compounds

Silver still used as disinfectant: creams, bandages • Silver nitrate eyedrops were required to prevent Neisseria gonorrhoeae infections acquired during birth – Antibiotics have largely replaced

Ozone

O3 : unstable form of oxygen • Decomposes quickly, so generated on-site • Powerful oxidizing agent • Used as alternative to chlorine • Disinfectant for drinking and wastewater

Peroxygens

powerful oxidizers used as sterilants • Readily biodegradable, no residue • Less toxic than ethylene oxide, glutaraldehyde

Hydrogen peroxide

effectiveness depends on surface • Aerobic cells produce enzyme catalase – Breaks down H2O2 to O2 , H2O • More effective on inanimate object • Doesn’t damage most materials

Peracetic acid

more potent than H2O2 • Effective on organic material • Useful on wide range of material

Phenolic Compounds (Phenolics)

Phenol one of earliest disinfectants • Has unpleasant odor, irritates skin • kill most vegetative bacteria • Mycobacterium at high concentrations • Not reliable on all virus groups,

Cationic

(positively charged) detergents • Nontoxic, used to disinfect food preparation surfaces • Charged hydrophilic and uncharged hydrophobic regions

Nitrate and nitrite

used in processed meats • Inhibit endospore germination and vegetative cell growth • Stops growth of Clostridium botulinum • Higher concentrations give meats pink color

Low-Temperature Storage

Refrigeration inhibits growth of pathogens and spoilage organisms by slowing or stopping enzyme reactions

Barbara McClintock

Observed that kernel colors in corn not inherited in a predictable manner • Concluded segments of DNA moved in and out of genes involved in color

Staphylococcus aureus

Gram-positive coccus; commonly called Staph • Frequent cause of skin and wound infections

auxotroph

Growth factor required

Prototroph

does not require growth factors