MicroBio Exam 2

Psychrophiles

Microbes that thrive in cold environments (at around 0-15 degrees C)

Psychrotrophs

Microbes that can grow at 0 degrees C but thrive around 20-30 degrees C. Cause food spoilage in refrigerators.

Mesophiles

Microbes that have best growth around 25-40 degrees C. Normal microbiota & pathogens of animals.

Thermophiles

Microbes that grow best around 50-60 degrees C. Found in hot springs and Organic composts.

Hyperthermophiles

Microbes that grow best at higher than 80 degrees C.

What keeps hyperthermophiles living in the oceanic depths

The pressure of the water stops water from boiling at temps higher than 100 degrees C.

Ideal pH for most bacteria

Most bacteria grow best between pH 6.5 and 7.5

Ideal pH for molds and yeasts

Molds and yeasts grow between pH 5 and 6

Acidophiles are what?

Microbes that grow in acidic environments

Define Osmotic Pressure

The tendency for water to move from low concentration areas of a solute to high concentration areas

Hypertonic environment

higher in solute concentration outside the cell than inside the cell

plasmolysis

shrinkage of the cell’s cytoplasm

Extreme or obligate halophiles require what?

High salt concentrations sometimes as high as 30%

Facultative halophiles are?

Microbes that tolerate high salt concentrations around (2–10% NaCl)

Before the development of modern food-preservation techniques

such as pasteurization and canning, why might people have used

techniques that rely on osmotic pressure?

By removing water from food it also removed the water from the cells preventing growth of most food spoiling bacteria.

Why is Carbon required for microbial growth

Backbone for structure of organic molecules

Chemoheterotrophs use organic molecules as both carbon and energy sources

Autotrophs use2CO as their carbon source

Why is Nitrogen required for microbial growth

Required for building proteins, DNA, and ATP

Most bacteria decompose protein-containing material for the nitrogen source

Some bacteria use NH4+ or NO3- from organic material

A few bacteria use N2 in nitrogen fixation

How does anaerobic respiration use nitrogen

Nitrate is the terminal electron acceptor

Why is sulfur required for microbial growth

Used in amino acids, thiamine, and biotin

Most bacteria decompose protein for the sulfur source

Some bacteria use SO4(2-) or H2S

Why is Phosphorus needed for microbial growth

Used in DNA, RNA, and ATP

Found in membranes (phospholipids)

PO4(3+) is a source of phosphorus

What are the 4 chemical elements needed for microbial growth

Nitrogen, Carbon, Sulfur, Phosphorus

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 but cannot use

oxygen

Microaerophiles

require oxygen concentration lower

than air

Biofilm communication

cell-to-cell via quorum sensing

biofilm role

Share nutrients

• Shelter bacteria from harmful environmental factors

Biofilm formation

Migrating clump of bacteria, —> adheres to a surface

Biofilm infection abilities

grow inside medical tools/tubing, resistant to microbicide

Deep-freezing

-50 C - -95 C

Lyophilization (freeze-drying)

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

Bacterial growth

is represented by an increase in number

of cells, not cell size

Binary fission

cell division process used by most

bacteria

Budding

used by a few bacterial species

Binary fission results

Binary fission doubles the number of cells each

generation

• Total number of cells = 2^number of generations

Bacterial growth curve

A few bacteria are inoculated into a liquid growth medium

– The population of bacteria is counted at intervals

– The log(10) of the number of bacteria (y-axis) is plotted

versus time (x-axis)

Lag Phase

No or little increase in number

– Intense metabolic activity, “tooling up” for rapid growth

Log Phase (Exponential growth phase)

Rapid reproduction, minimum constant generation time

Stationary Phase

Growth slows as carrying capacity is approached

– Cell deaths balances number of new cells

– Diminished nutrients, accumulating wastes

Death Phase

Deaths exceed production of new cells

– Population is decreasing logarithmically

Sepsis

refers to bacterial contamination

Asepsis

is the absence of significant

contamination

– Aseptic surgery techniques prevent the

microbial contamination of wounds

Sterilization

removing and destroying all

microbial life

Commercial sterilization:

killing Clostridium

botulinum endospores in canned goods

Clostridium botulinum

Food borne disease-botulism Often via contaminated canned food

Disinfection

destroying harmful microorganisms

on inanimate surfaces or environments

Antisepsis

destroying harmful microorganisms

from living tissue

Degerming

the mechanical removal of microbes

from a limited area

Sanitization

lowering microbial counts on eating

utensils to safe levels

Biocide (germicide)

treatments that kill

microbes

Bacteriostasis:

inhibiting, not killing, microbes

Effectiveness of treatment depends on:

Number of microbes

– Environment (organic matter, temperature,

biofilms)

– Time of exposure

– Microbial characteristics (endospores, cell wall)

Heat

denatures enzymes

Thermal death point (TDP)

owest

temperature at which all cells in a liquid culture

are killed in 10 min

Thermal death time (TDT)

the lowest temperature required to kill all microorganisms in a liquid suspension within a set time, usually 10 minutes

Decimal Reduction Time

the time or dose needed under specific conditions to reduce a living microbial population by 90%

Moist Heat Sterilization

coagulates/denatures proteins, steam under pressure

121 C at 15 psi for 15 minutes

Kills all organisms (except prions) and endospores

Steam must contact the item’s surface

Preferred method for sterilization in health care

environments

Pasteurization

reduces spoilage organisms and pathogens in

milk and juices

High-temperature short-time (HTST)

72 C for 15 sec

Ultra-high-temperature (UHT)

Will sterilize milk, creamer, and juice which can then be stored

without refrigeration

• Rapidly heated to 140 C for 4 seconds, followed by rapid

cooling

Dry Heat Sterilization

Kills by oxidation

– Flaming

– Incineration

– Hot-air sterilization

Oven 170 C, 2 hours

Filtration

Passage of substance through a screenlike material

• Used for heat-sensitive materials

Desiccation

absence of water prevents metabolism

Osmotic pressure

uses high concentrations of salts and

sugars to create hypertonic environment; causes

plasmolysis

Ionizing radiation (X-rays, gamma rays, electron

beams)

Ionizes water to create reactive hydroxyl radicals

– Damages DNA by causing lethal mutations

Gamma rays

penetrate deeply but require hours to

sterilize

High-energy electron beams

less penetration, but

fast (seconds)

Nonionizing radiation

(ultraviolet, 260 nm)

– Damages DNA by creating thymine dimers, Effective, but doesn’t penetrate; good for surfaces

– Must avoid contact with eyes and skin

Microwaves

kill by heat; not especially antimicrobial

Phenol and Phenolics

Injure lipids of plasma membranes, causing leakage

• Remain active in the presence of organic matter

Bisphenols

Contain two phenol groups connected by a bridge

• Disrupt plasma membranes

Biguanides

Effective against gram-positive bacteria, many gram-

negative bacteria, and enveloped viruses

• Disrupt plasma membranes

Essential Oils

Microbial action primarily due to phenolics and terpenes

• Stronger activity against gram-positive bacteria

Alcohols

Denatures proteins and dissolves lipids

• No effect on endospores and nonenveloped viruses

Nitrites and nitrates

Prevent endospore germination (Clostridium botulinum)

– Primarily used with meat products

– Nitrites preserve the red color of meat

Aldehydes

Inactivate proteins by cross-linking with functional groups

Gaseous Chemosterilants

Gaseous sterilants cause alkylation-replacing hydrogen atoms of a

chemical group with a free radical (Proteins are alkylated)

Ethylene oxide

Must be used in a sealed chamber

Can sterilize large pieces of equipment and furniture,

depending on chamber size

Chlorine dioxide

Used in enclosed building areas or water treatment

Can also be used as an aqueous solution for surface

disinfection

Plasma

Fourth state of matter, consisting of electrically excited gas

• Free radicals destroy microbes

• Will sterilize

• Used for tubular instruments (arthroscopic and laparoscopic

surgical instruments)

Differences between bacteria and fungi

Fungi

-Eukaryotic

-Chitin cell wall

-Reproduces by spores

Bacteria

-Prokaryotic

-No spores present

-Peptidoglycan cell wall

Molds and fleshy fungi

vegetative structure,

he fungal thallus (body) consists of hyphae filaments; a

mass of hyphae is a mycelium

• Vegetative hyphae obtain nutrients while aerial hyphae are

involved with reproduction

Yeasts

vegetative structure

Nonfilamentous and unicellular

• Budding yeasts divide unevenly

• Fission yeasts divide evenly

Dimorphic fungi

vegetative structure

Yeastlike at 37C

moldlike at 25C

Asexual spores

Produced via mitosis and cell division; formed by the

hyphae of one organism

Sexual spores

Fusion of nuclei from two opposite mating strains

Plasmology (phase 1)

haploid donor cell nucleus (+)

penetrates cytoplasm of recipient cell (-)

Karyogamy phase 2

+ and - nuclei fuse and form

diploid zygote

Meiosis phase 3

diploid nucleus produces haploid nuclei

(sexual spores)

Mycosis

fungal infection

Systemic mycoses:

deep within the body, affect a number of tissues and organs

Subcutaneous mycoses:

beneath the skin

Cutaneous mycoses

affect hair, skin, and nails

Also known as dermatomycoses

Superficial mycoses

localized (e.g., hair shafts)

Opportunistic mycoses

fungi harmless in normal habitat but pathogenic in a

compromised host

economic productions of fungi

fermenting food and drink, producing citric acid, killing termites, statins, hep b vaccine, cellulase and taxol

Lichens

Symbiosis between fungi and algae (or cyanobacteria)

Crustose

encrusted on the substratum

Foliose

leaflike