Ch. 6/9 Microbial Growth & Control

environmental factors that influence microbial growth

1. temperature

2. oxygen availability

3. pH

4. water availability

psychrophile

cold loving microbes

optimum tempreature between -5 - -15 degrees C

found in cold - oceans, arctic and antarctic regions

psychrotroph

cold eater - cold tolerant

optimum 15-25 degrees C

important in refrigerated food spoilage

mesophile

middle lover - human body temperature

optimum between 20 - 45 degrees C

pathogens!

thermophile

heat lover

found in hot springs & compost heaps

optimum temperature between 45 - 80 degrees C

hyperthermophile

high heat lover - can tolerate above boiling

archaea in hydrothermal vents - extremophiles

80+ degrees C

factors that determine organism's oxygen requirement & tolerance

1. energy harvesting mechanisms

2. ability to inactivate harmful ROS reactive oxygen species

obligate aerobes

requires oxygen

facultative anaerobes

grow best if oxygen is present, but can grow without it

obligate anaerobes

cannot grow in the presence of oxygen

microaerophiles

require small amounts of oxygen, but higher concentrations are inhibitory

aerotolerant anaerobe

obligate fermenter & indifferent to oxygen

mechanisms for living in pH extremes

pumping hydrogen ions into or out of the cell to maintain a near neutral pH

Helicobacter pylori

bacteria that causes gastritis & peptic ulcers

uses urease to neutralize stomach acid

Listeria monocytogenes

cause of Blue Bell recall

psychrotroph, osmotolerant & halophile and human pathogen

neutrophile

multiplies in range of pH 6-8

MOST bacteria

acidophile

grows optimally at a pH below 5.5

optimum 3

often archaea

alkalophile

grows optimally at a pH above pH 8

optimum 9

halotolerant

can grow in relatively high salt solutions, up to approximately 10% NaCl - but doesn't need it

example of halotolerant microbe

Staphylococcus aureus & Staphylococcus epidermidis

grow on salty skin

halophile

requires high levels of sodium chloride

example of halophile

marine bacteria or Archaea in the Dead Sea

boiling

Doing this for 5 minutes destroys MOST organisms & viruses.

Kills protists in drinking water (cause diarrheal disease)

Does NOT kill endospores.

endospores

reason we have to autoclave

pasteurization

Significantly decreases the numbers of heat-sensitive microorganisms, including spoilage microbes and pathogens. Does NOT kill endospores.

pasteurization

chosen methods to remove MOST microbes from food products: milk, juice & wine

boiling

Method used to remove MOST bacteria & viruses from water.

autoclaving

The MOST effective method of sterilization

autoclaving

uses heat, steam and pressure to destroy ALL microbes including endospores

autoclaving

121 degrees C, 15 p.s.i. for 15-20 minutes

incineration

burns cell components to ashes

incineration

method used when flaming an inoculating loop or destroying medical waste like animal carcasses

binary fission

A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size

bacterial growth

an increase in number of cells in the population

generation time

the span for a population to double

a.k.a. doubling time

cooperative or synergistic

type of interaction in mixed microbial population where one member helps the growth of another

competitive or antagonistic

type of interaction in a mixed microbial population where one member restricts the growth of another

lag phase

flat no growth period

bacteria adjusting to environment & making enzymes

lag phase

What does A represent on the growth curve?

exponential or log phase

What does B represent on the growth curve?

stationary phase

What does C represent on the growth curve?

death phase

What does D represent on the growth curve?

physical methods of microbial control

Heat, filtration, irradiation & mechanical removal

microbes resistant to disinfectants

Pseudomonas (cause HIAs)

Mycobacterium (T.B.)

non-enveloped viruses like polio-virus

exponential or log phase

rapid growth - population doubles at regular intervals

MOST metabolically active & MOST sensitive to antibiotics

stationary phase

# of new cells = # of dying cells

nutrients too low for growth

death phase

# of viable cells decrease - food is gone and waste is high

not as rapid as exponential or log phase

chemical methods of microbial control

1. denature proteins

2. alter DNA

3. damage cell membranes

sepsis

microbial contamination or clinically critical condition with pathogens in the blood stream.

aseptic

environment or procedure that is free from significant contamination

sterile

no living microbes (including endospores & viruses)

disinfectant

chemical agent that eliminates MOST or ALL pathogens on an OBJECT

used on a lab bench

antiseptic

elimination of MOST pathogens on LIVING TISSUE

used on a child

bactericidal

KILLS bacteria

bacteriostatic

INHIBITS growth of bacteria

effect of cold temperatures

bacteriostatic

slows down chemical reactions

effect of high temperatures

bactericidal

denatures proteins

capnophile

grows best at higher CO2 tensions than normally present in the atmosphere

Who can grow in a candle jar?

microaerophiles & canophiles

Streptococcus pyogenes

catalase

enzyme that breaks down hydrogen peroxide H2O2, a ROS reactive oxygen species

so oxygen WON'T kill cells

superoxide dismutase

converts superoxide, a ROS reactive oxygen species (free radicals) to lessen damaging substances, such as hydrogen peroxide - so oxygen WON'T kill cells

superoxide & hydrogen peroxide

toxic forms of oxygen - ROS

neutralized by the aerotolerant

obligate anaerobes

group killed by hydrogen peroxide & hyperbaric oxygen therapy

obligate aerobes

group killed by vacuum packaging

skin, stomach & vagina

acidic body regions that inhibit microbial growth

macronutrients

needed in large quantities

role in cell structure & metabolism

micronutrients

needed in trace amounts

role in enzyme function & protein shape

growth factors

organic molecules that an organism can't synthesize and must be provided - reflect biosynthetic capabilities

light

where phototrophs get their energy

carbon dioxide (CO2)

where autotrophs get their carbon

organic molecules/food

where heterotrophs get their carbon

chemicals (organic or inorganic)

where chemotrophs get their energy

chemoheterotrophs

An organism that must consume organic molecules for both energy and carbon.

example of photoautotrophs

cyanobacteria (blue/green algae), algae & plants

example of chemoheterotrophs

you, MOST bacteria, protozoa & fungi

competitive or antagonistic

type of relationships in a community:

producing antibiotics or other anti-microbials (colicins)

type VI secretion system - tit for tat

cooperative or synergistic

type of relationships in a community:

secreting a growth factor needed by another member

aerobes using up oxygen so anerobes can grow

macronutrients

elements: C,H,O,N,P,S carbon, hydrogen, oxygen, nitrogen, phosphorus and sulphur

potassium

micronutrients

elements: elements: Mg, Zn, Ni

magnesium, zinc & nickel

plasmolysis

Collapse of a walled cell's cytoplasm due to a lack of water or hypertonic environment

fastidious

an organism with complex nutritional needs - finicky

hyperbaric oxygen therapy

use of oxygen in a special chamber with increased air pressure to promote healing and fight infection -

used in wound infection treatment

enriched

type of media necessary for fastidious microorganisms

-provides growth factors

organic nutrients

required for growth and contain carbon and hydrogen atoms

-usually the products of living things

organic nutrient examples

carbohydrates, fats, proteins

inorganic nutrient examples

minerals, water, salts & carbon dioxide

inorganic nutrients

required for growth but do not contain carbon & hydrogen

-usually products of the envirnoment

saprobe

organisms that obtain food from detritus (decaying organic matter)

parasite

derive nutrients from cells or tissues of living host

fungi & bacteria

examples of saprobes

viruses, bacteria, fungi, protozoans & helminths

examples of parasites

ectoparasite

lives on the surface of the host

-ex. fungal skin infection

endoparasite

lives in the organs & tissues

-tapeworm

intracellular parasite

lives within cells

-ex. Listeria

obligate intracellular parasite

-unable to grow outside of a living host

-ex. virus

quorum sensing

ability to detect & respond to cell population density thru signaling molecules

quorum sensing

communication method for turning on genes related to biofilm production or virulence when a critical mass is reached

Pseudomonas aeruginosa

hard to kill bacterium

causes HAIs in opportunistic hosts

Staphylococcus aureus

halotolerant & lives on skin

hard to kill bacterium

#1 cause wound infections

as a biofilm

How most bacteria grow