micro lecture 5-9

cell envelope

structure surrounding bacterial cells, includes multiple layers

glycocalyx

polysaccharide layer outside some bacteria, not essential

slime layer

loose glycocalyx protecting against water loss

capsule

tightly bound glycocalyx, thick and gummy

peptidoglycan

polysaccharide polymer forming bacterial cell walls

lysozyme

enzyme breaking bonds in peptidoglycan, found in secretions

teichoic acid

component of gram-positive cell wall, reinforces structure

periplasm

space between cytoplasmic and outer membranes in gram-negative bacteria

lipopolysaccharide

complex molecule in gram-negative outer membrane, includes polysaccharides

porins

protein channels in outer membrane allowing molecule passage

chemotaxis

movement towards attractants or away from repellents

bacterial motility

movement driven by flagella in bacteria

endospore germination

process of endospore returning to vegetative state

germ theory

theory that microorganisms cause dieases

defined media

media with known chemical composition

undefined media

media with complex, unknown chemical composition

selective medium

media that inhibits the growth of certain microorganisms

differential medium

media that differentiates microorganisms based on reactions

chemoorganotroph

organisms that use organic chemicals for energy

chemolithotroph

organisms using inorganic chemicals for energy

exoenzymes

enzymes secreted by prokaryotes for digestion

simple diffusion

movement of molecules from high to low concentrations

facilitated diffusion

passive transport requiring no energy input

active transport

energy-requiring movement of molecules against gradient

binary fission

asexual reproduction method in prokaryotes

generation time

time for population to double in size

total cell count

direct microscopic counting of all cells

viable count

counting only living cells via colony formation

turbidity

cloudiness of a liquid indicating cell density

sterilization

removal or destruction of all viable microorganisms

disinfection

removal or destruction of pathogens (but not spores) from non-biological areas

antisepsis

destruction or inhibition of vegetative cells (not spores) from external areas of the body

sanitization

any cleansing technique that mechanically removes microorganisms, usually soaps

cide

killing

static

prevents growth

decimal reduction time

time for a 10x reduction in population size

factors determining effectiveness of a control agent

includes the number of microorganisms, temperature and pH of the environment, concentration of the agent, mode of action, and presence of interfering compounds

moist heat

includes hot water, boiling water, and steam, typically at 60-135C

dry heat

includes ovens and bunsen burners, typically at 160-1000C

pasteurization

heating to a temperature below boiling to kill specific pathogens and increase shelf time

flash method

71.6C for 15 seconds, resulting in killing most viruses and 97-99% reduction in vegetative stages of bacteria and fungi

ionizing radiation

knocks electrons off atoms to form ions, damaging DNA and proteins by breaking bonds

non-ionizing radiation

excites atoms but doesn’t ionize, damages DNA by creating T-T dimers

UV light

type of non-ionizing radiation caused for surface disinfection and water treatment

sonication

disruption of microorganisms using sound waves

lag phase

no increase in number of living bacterial cells

log phase

exponential increase in number of living bacterial cells

stationary phase

plateau in number of living bacterial cells; rate of cell division and death roughly equal

death or decline phase

exponential decrease in number of living bacterial cells

psychrophile

grows at below freezing temperatures

mesophile

grows at moderate temperatures

thermophile

grows at high temperatures

hyperthermophiles

grows at extremely high temperatures

bacterial tumbling

clockwise rotation of flagella

bacterial running

counter-clockwise rotation of flagella

first postulate

suspected causation agent must be absent from all healthy organisms but present in all diseased organisms

second postulate

causative agent must be isolated from diseased organism and grown in pure culture

third postulate

cultured agent must cause the same disease when inoculated into a healthy susceptible organism

fourth postulate

same causative agent must be reisolated from inoculated, diseased organism

halogen

chlorine. destroys by oxidation

phenol and phenolics

denature proteins, disrupt cell membranes, aromatic with hydroxide

alcohol

ethanol and isopropyl. dehydrate membrane

hydrogen peroxide

forms oxygen free radicals

gases

chlorine dioxide and certain oxides. disrupt proteins. oxides are effective sterilants

surfactants

lower surface tensions of water. ionic and non-ionic

cationic

most effective ionic detergent. solubilize membrane and disrupt proteins

heavy metals

silver and copper. form ions that complex with cell components. attach to proteins filling active site