MICROBIO EXAM II

Psychrophiles

Cold-loving, live in deep ocean and polar regions

Mesophiles

Moderate temperature loving, normal microbiota and pathogens of animals

Thermophiles

Heat loving, found in hot springs and organic compost piles

Psychrotophs

Cause food spoilage

Ideal pH for most bacteria

6.5-7.5

Acidophilus

Grow best in acidic environments

Plasmolysis

The shrinkage of the cells cytoplasm

Occurs in hypertonic environments

Extreme/obligate halophiles

Requires high salt concentration

Facultative halophiles

Tolerate high salt concentrations

Carbon

Structural backbone of organic molecules

Nitrogen

Component of proteins, DNA and ATP

Bacteria’s tend to break down protein containing material for sourcing nitogen

Sulfur

Used in amino acids, thiamine and biotin

Bacteria tends to decompose protein for sourcing sulfur

Phosphorus

Used in DNA, RNA, ATP

Found in phospholipid membranes

Obligate aerobes

Require oxygen

Facultative anaerobes

Able to grow with or without oxygen

Grow via fermentation or anaerobic respiration when oxygen is not available

Anaerobes

Unable to use oxygen and most are harmed by it

Aerotolerant anaerobes

Tolerate oxygen but cannot use it

Microaerophiles

Requires oxygen concentration lower than air

Singlet oxygen

Toxic form of oxygen that has been boosted to a higher energy state

Extremely reactive

O2-

Superoxide radicals

Toxic form of oxygen, highly reactive

Superoxide dismutase

An enzyme found in cells which use or tolerate oxygen to remove superoxide radicals

Peroxide anion

Toxic form of oxygen which is the active component in hydrogen peroxide ad benzoyl peroxide

Catalase

Enzyme made by some microbes to remove peroxide by converting hydrogen peroxide to water and oxygen

Hydroxyl radical

Most reactive free radical

Peroxidase

Enzyme made by some microbes to remove peroxides by converting hydrogen peroxide to 2 water molecules

Organic growth factors

Organic compounds obtained from he environments like vitamins, amino acids, purines and pyrimidines

Biofilms

Microbial community which form slime or hydrogels that adhere to surfaces and protect bacteria from harmful environmental factors

Quorum sensing

How bacteria in biofilms communicate cell-to-cell

Bacteria secrete an inducer (signaling chemical) to attract other bacterial cells

Culture medium

Nutrients prepared for microbial growth

Sterile

No living microbes

Inoculum

Introduction of microbes into a medium

Culture

Microbes growing in or on a culture medium

Agar

Complex polysaccharide used as a solidifying agent for culture media

Chemically defined media

Exact chemical composition is known

Complex media

Extracts and digests of yeasts, meat, or plant

Reducing media

Used for the cultivation of anaerobic bacteria

Contain chemicals that combine with oxygen to deplete it

Heated to drive of oxygen

Mycobacterium leprae

Bacteria which can’t be grown on lab media

Grown in armadillos

Rickettsia and chlamydia

Bacteria cant be grown on lab media

Grown in tissue culture

Capnophiles

Microorganisms which require higher CO2 for growth

Selective media

Suppress unwanted microbes and encourage desired ones

Selective media for salmonella typhi

Bismuth sulfite agar, inhibits gram positive and most gram negative bacteria

Sabourauds dextrose agar

Inhibits bacteria, fungi can grow

Differential media

Allow distinguishing of colonies of different microbes on the same plate

Enrichment culture

Encourages growth of a desired microbe by increasing very small number of a desired organism to detectable levels

Bio safety level 1

No special precautions

Bio safety level 2

Lab coat, gloves, eye protection

Bio safety level 3

For work with highly infectious airborne pathogens

Bio safety level 4

Sealed, negative pressure, “hot zone”

Binary fission

Cell division process used by most bacteria

Cell elongates and DNA is replicated —> plasma membrane begins to constrict and new wall is made—> cross wall forms separating the two dna copies —> cell separates

Doubles number of cells each generation (2^#of gen = cells)

Phases of growth

Lag, log, stationary, death

Lag phase

No or little increase in number, intense metabolic activity prepping for rapid growth

Log phase

Exponential growth, rapid reproduction

Stationary phase

Growth slows as carrying capacity is approached, cell deaths balance number of new cells, diminished nutrients

Death phase

Dying cells exceed new cell production

direct measurements

counting micorbial cells

plate count

performed on pour plate or spread plate method, for plates with 30-300 colonies

pour plate method

bacteria mixed into a dish with agar

spread plate method

bacteria spread on the surface of a plate

serial dilution

inoculum is diluted multiple times to isoloate distinguishable colonies

filtration

solution is passed through a filter that collects bacteria then transferred to a petri dish containing nutrients to allow colony growth on the surface

most probable number (MPN) method

statistical technique used to estimate the concentration of a microorgs in a sample without directly counting individual colonies directly

direct microscopic count

average number of bacteria per viewing field is calculated

number of cells counted/volvume of area counted = sumber of bacteria per ml

turbidity

measurement of cloudiness with a spectrophometer

metabolic activity

amount of metabolic activity product is proportional to the number of bacteria

dry weight

bacteria are filtered, dried, weighed

used for filamentous orgs

generation time

time required for a cell to divide

lyophilization

method to preserve cultures

frozen and dehydrated in a vacuum (-54 to -72 C)

deep-freezing

method to preserve cultures (-50 t o -95 C)

nitrogen fixation

coversion of atmospheric nitrogen to ammonia

trace element

inorganic elements required in small amounts by cells as enzyme cofactors

include iron, copper, molybdenum and zinc

often found in the tap water in the lab

sepsis

refers to bacterial contamination

asepsis

absence of significant contamination

sterilization

removing and destroying all microbial

clostridium botulinum

endospore found in canned goods killed by commerical sterilization

disinfection

destroying harmful microorganisms on inanimate surface or enviornment

antisepsis

destroying harmful microorgs from living tissue

degerming

mechancical removal of microbes from a limited area

sanitization

lowering microbial cout to safe levels

biocide (germicide)

treatments that kill microbes

bacteriostasis

inhibiting, not killing, microbes

methods for micorbial control

damage to plsama membrane, damage to proteins, damage to nucleic acids

treatment effectiveness dependent on

number of micorbes, enviornment, time and charecteristics

thermal death point

lowest temperature at which all cells in a liquid culture are killed in 10 minutes

thermal death time

minimal time for all bacteria in a liquid culture to be killed at a particular temeprature

decimal reduction time

minutes to kill 90% of a specifc population of bacteria at a given temperature

moist heat sterilization

denatures proteins

ex. autoclave

kills all orgs and endospores except prions

pasteurization

reduces spoilage orgs and pathogens in milk and juices

high tem short time (HTST)

72 C for 15 seconds

thermoduric

organisms survive but unlikely to cause disease or to spoil refrigerated milk

dry heat sterilization

kills by oxidation

inlcudes flaming, incineration, hot air sterilization

filtration

passage of substance through a screenlike material

used for heat sensitive materials

HEPA filter

removes microbes greater than 0.3 um in diameter

membrane filters

remove microbes greater than 0.22 um

desiccation

absence of water prevents metabolism

bacteriostatic

stops bacteria from reproducing and growing without killing them outright

can occur with low temerature treatments

ionizing raditation

ionizes water to create reactive hydroxyl radicals, damage dna by causing lethal mutations

(xrays, gamma rays, electron beams)

gamma rays

ionizing radiation used to penetrate deeply but requires hours to sterilize

high energy electron beam

ionizing radiation with short sterilization time but less penetration

nonionizing radiation (UV)

damage dna by creating thymine dimers

good for surfaces as less penetration

visible blue light

kills wide range of bacteria due to the formation of singlet oxygen (toxic)