Mirco Bio Test 2

chapters 6-8 & 12

microbial growth

increase in number of cells

populations

the total number of bacterial cells in a given area

colonies

the same genetically identical bacteria mass

physical requirements for growth

temperature, pH, osmotic pressure

chemical requirements for growth

carbon, nitrogen, sulfur, phosphorus, elements, oxygen, organic growth factor

minimum growth temperature

the lowest temp the species can grow

optimum growth temperature

the temp at which the species best grows

maximum growth temp

the highest temp the species can grow

psychotrophs

cold living, grow between 0c and 20-30c, cause food spoilage in cold foods

mesophiles

moderate temperature, temp between 25-40c, include common disease organisms

thermophiles

heat loving

why refrigerate?

colder temps slow down growth rate of microbes

ideal pH for bacterial growth

6.5 - 7.5

acidophiles

grow in acidic enviroments

helicobacter pylori

survives in highly acidic stomach but isnt acidophile so it creates openings to release the stomach acid creating stomach ulcers

vaginal microbiota

is an acidic environment to prevent overgrowth of pathogens

halophiles

salt-loving, they require high osmotic pressure and hypertonic environments (salt or sugar)

facultative halophiles

tolerate high osmotic pressures but dont require the high salt

S. aureus

is salt tolerant and causes wound infections in sweaty or salty environments

obligate aerobes

require oxygen to grow, with the presence of enzymes

facultative anaerobes

greater growth in presence of oxygen but can growth without, presence of enzymes

obligate enzymes

growth stops with the presence of oxygen, lacks enzymes

aerotolerant anaerobes

growth is can occur without oxygen but oxygen has no impact, presence of one enzyme

micro-aerophiles

growth with just the right amount of oxygen (low concentration), no enzyme

chemicaly defined media

exact chemical composition is known

complex media

extracts and digests of yeasts, meats or plants

sterile

the culture will only contain the microbes one adds to the medium

agar

a complex polysaccharide used to solidify the culture

reducing media

is used to deplete the O2 in a medium for an anaerobic (no oxygen) culture

capnophiles

require a high concentration of CO2

biosafety levels

BSL-1 no precautions to BSL-4 sealed lab

selective media

killing unwanted microbes and encouraging wanted microbes

differential media

allows multiple microbes to grow but uses visible indicators to differentiate

know the different selective and differential medias

no answer

as cell divide the population increases ______

exponentially

generation time

used to find the time required for a cell to divide and for its population to double

LAG phase of growth

period of little to no division lasting 1hr to several days; undergo metabolic activity

LOG phase

cell reproduction is the most active and exponential growth phase

Stationary phase

the growth rate slows and the number of microbial deaths balances the new cells; population stabilized

death phase

the number of deaths exceeds the number of new cells formed

plate count

helps estimate the number of bacteria in the original broth by counting the colonies on the plate

sterilization

removing all microbial life

commercial sterilization

in food - enough heat to destroy C. botulinum endospores

disinfection

removing pathogens - usually the use of chemical to treat a surface or an object

antisepsis

removing pathogens from living tissue

degerming

removing microbes from a limited area

sanitization

lowering microbial counts on eating utensils to minimize chance of disease

biocide/germicide

kills microbes

bacteriostasic

inhibiting not killing microbes. once you remove the bacteriostatic agent the growth may resume

sepsis

microbial contamination

asepsis

the absence of significant contamination

aseptic technique

to reduce contamination

factors the influence antimicrobial treatments

number of microbes, environmental influence, time of exposure, microbial characteristics

what do microbial control agents do?

alter the membrane permeability of the membrane, damage to proteins, damage to nucleic acids

heat

the most common method for food preservation

thermal death point (TDP)

lowest temperature at which all cells in a liquid are killed

thermal death time (TDT)

the minimal length of time for all to be killed in a liquid at a given temperature

decimal reduction time (DRT)

minutes to kill 90% of a population at a given temperature. important in the food canning industry

boiling

not always a reliable sterilization technique

autoclave

steam under pressure with high heat; steam at 15psi at 121C and kills in 15 min

pasteurization

eliminates pathogenic microbes, to prolong milks good quality in refrigeration

dry heat sterilization

kills by oxidation: hot-air sterilization, flaming, incineration

HEPA filter

high efficiency particulate air filter removes microbes > 0.3

membrane filtration

removes microbes > 0.22

low temp

inhibits microbial growth by slowing the metabolic rate

high pressure

denatures proteins and carbohydrates

desiccation

prevents metabolism and growth but bacteria remain viable; completely drying out of water

osmotic pressure

causes plasmolysis - shrinking of cytoplasm and plasma; causes water loss

ionizing radiation

removes electrons to cause water to release OH and damages DNA; sterilize pharmaceuticals

non-ionizing radiation

damages DNA

microwaves

kills by heat

principles of disinfection impacts

concentration, nature of the material, pH, time

disinfection

removal of all pathogens usually on inanimate surfaces

dilution test

metal rings dipped in test bacteria then dried and placed in disinfectant then rings transferred to a culture to see if the bacteria survived

Kirby Bauer test

used to determine how effective specific antibiotics are against a particular bacterium

phenol

disrupt lipid-containing plasma membranes

phenol use

used for the control of surgical infection in the operating room, odor control in sewage, skin irritant

bisphenols

endocrine disrupting compounds; derived from phenol

hexachlorophene

used for surgical and hospital microbial control procedures; works to control infections

triclosan

disrupts plasma membranes by inhibiting lipids; in antibacterial soaps, cutting boards, cosmetics

chlorhexidine

used in surgical hand scrubs; disrupt plasma membranes, broad spectrum of impact against gram positive and negative and some viruses

chloramine

oxidizing agents that prevent the cellular enzyme from functioning - potent germicidal action; chlorine and ammonia

tinctures

plant or animal extract in aqueous alcohol; iodine

iodophors

inorganic molecule with iodine for slow release

betadine

commercial preparation, these don’t stain and are less irritating; alter protein synthesis and membranes

alcohols

ethanol and isopropanol; denatures proteins, dissolves lipids, coagulates proteins; kills bacteria not endospores, 70% concentration

oligodynamic action

denature proteins

silver nitrate

used to prevent ophthalmia neonatorum in newborns - replaced with antibiotics

silver sulfadiazine

used as a topical cream on burns; applied as wound dressings, release silver ion slowly

silver

nanoparticles in plastic containers and athletic apparel to minimize bacteria growth and odors

copper

sulfate is an algicide (pool, fish tank)

mercury

bacteriostatic activity used in control mildew in paints because of organic matter

soap

breaks apart oily film and lifts up oil and debris that floats away

degerming

removing microbes from a limited area

quaternary ammonium compounds (Quats)

positive charged cationic detergents disrupt plasma membrane causing loss of cytoplasm

bactericidal

found as antimicrobial in mouthwash (zephiran and cepacol)

sulfur dioxide

maintain food pH but interfere with microorganisms metabolism and their plasma membrane

sodium nitrate

prevents endospore germination and preserves the redness in the meat

antibiotics

use is restricted and prevent the growth of endospore forming bacteria that would spoil dairy products

aldehydes

very effective antimicrobials; inactivate proteins forming covalent cross links; used for embalming morticians (preserve after death)