GENERAL MICROBIOLOGY
CHAPTER 6
MICROBIAL GROWTH-
INCREASE IN
________
OF
MICROBIAL
CELLS
MICROBIAL GROWTH
REQUIREMENTS
• PHYSICAL
– ___________
– pH
– osmotic pressure
• CHEMICAL
–
–
–
–
Carbon (C)
Oxygen (O)
____________
Sulfur (S)
• Phosphorus
• _________________
factors
• Trace elements
PHYSICAL REQUIREMENTS for GROWTH :
TEMPERATURE
• MINIMUM GROWTH
TEMPERATURE
– _______ temperature at
which a species will
grow
• OPTIMUM GROWTH
TEMPERATURE
– Temperature at which
species will grow ____
• MAXIMUM GROWTH
TEMPERATURE
– _______ temperature at
which growth is possible
CLASSIFICATION OF MICROBES:
TEMPERATURE RANGE of GROWTH
• __________PHILES
- ________ loving microbes
• Optimum growth temperature: 15oC
• Capable of growing at 0oC, but __________
• Found in ocean depths, polar regions
– Psychrotrophs-less temperature sensitive, some food
spoilage
• ______PHILES - moderate temperature loving microbes
– Optimum growth temperature: 25-40oC
– Most common microbes
– Food spoilage and disease
• ________PHILES heat loving microbes
• Optimum growth temperature: 50-60oC
• Minimum growth temperature: 45oC
• Found in hot springs, compost piles
ACID BASE CHEMISTRY
– ____ – a substance that
dissociates into
hydrogen ions _____ and
negative ions in aqueous
solution
Ex. Hydrochloric acid,
citric acid
– BASE – a substance that
dissociates into
hydroxide ions ____ and
positive ions in aqueous
solution
Ex. Sodium hydroxide
pH scale - logarithmic scale used to measure
H+ concentration
PHYSICAL REQUIREMENTS for GROWTH cntd.:
pH
– Most bacteria grow between pH __________
– Molds and yeast grow between pH ________
– Acidophiles grow in acidic environments
____ – compounds that keep pH from
changing drastically; ex. peptones,
amino acids, phosphate salts-very
important in the preparation of
microbial media!!
PHYSICAL REQUIREMENTS for GROWTH cntd.
Osmotic Pressure
the force used by a solvent in moving from an area with a
lower solute concentration to an area of higher solute
concentration
– ______ environments - concentration of solute (ex.
salt or sugar) is higher _____ cell, causes plasmolysis
• Results in loss of water from a cell
– __________ bacterial growth
– Used to preserve food, ex.Salted fish
______philes - require higher salt
concentrations in their environment
and therefore high osmotic pressure
•
CHEMICAL REQUIREMENTS for GROWTH
•
Carbon
•
– Structural organic
molecules, energy
source
•
Chemo__________
use _________ carbon
sources
•
Ex. Humans, fungi,
protozoa, most
bacteria, helminths •
Autotrophs -use CO2
as carbon source
Ex. Plants
Nitrogen
– In amino acids, proteins
Sulfur
– In __________, thiamine, biotin
– Some bacteria use SO42 or H2S
Phosphorus
– In DNA, RNA, ATP, and membranes
– PO43 is a source of
phosphorus
__________ Elements
– Inorganic elements required in small
amounts: Fe, Cu, Mb, Zn
Organic Growth Factors
– Organic compounds obtained from
the environment
– Vitamins, amino acids, purines,
pyrimidines
CHEMICAL REQUIREMENTS for GROWTH
cntd. - OXYGEN
Facultative
Obligate
anaerobes- anaerobes ____tolerant
MicroObligate
growth ____ -no growth anaerobesaerophiles
_______-O2
can
tolerate
_______
when O2
need
is required when O not
O2 but can’t
present________ O2
2
for growth
use
it
for
present, O2 _________
concentrations
growth
O2
preferred
_______ FORMS of OXYGEN
Produced in small amounts during normal metabolic
processes-harmful to cells
Some Forms of Toxic Oxygen
– Superoxide free radicals (O2-1) – very unstable, steal electrons
from cellular molecules
– Peroxide anion (O2-2) – contained in hydrogen peroxide
– Hydroxyl radicals (OH-) – most reactive
MECHANISMS of ELIMINATION
Superoxide free radicals (02-1)
02- + 02- + 2H+
superoxide
dismutase
H202 + 02
Peroxide anions (02-2)
2H2O2 __________ 2H2O + O2
H2O2 + 2H+ peroxidase 2H2O
________ CULTURE METHODS
1. _________ media
contains chemicals (sodium thioglycolate) that combine with O
2
Media is heated to drive off O
2
2. OxyPlates
________ (oxyrase) that reduces oxygen to water is added to growth
media, transforms petri plate into an anaerobic chamber
3. ______________
4. ANAEROBIC CHAMBER
_________PHILES
Def.: Bacteria
that require
_________
concentration
____________
• Microbial communities
• Form slime or hydrogels
– Bacteria attracted by
chemicals via quorum
sensing
• Share ____________
• Sheltered from harmful
factors
• Involved in @70% of
infections
– ________, heart
________, contact
lenses, dental caries
Figure 6.5
CULTURE MEDIA
important terms
• Culture Medium: _________ (or any material) prepared for the
growth of microbes in a laboratory
• Sterile: No _________ microbes
• Inoculate: Introduction of microbes into medium
• Culture: Microbes growing in/on culture medium
• ____ culture - contains only ________ or strain of bacteria
• Agar: Complex ___________ (from marine algae)
– Used as solidifying agent for culture media in Petri plates,
slants, and deeps
– Generally not metabolized by microbes
– Liquefies at 100°C
– Solidifies ~40°C
CULTURE MEDIA
Chemically Defined Media: Exact
chemical composition is known
-Fastidious microorganisms- they
require many growth factors provided
in chemically defined media.
_________ Media: Exact chemical
composition _______; Extracts and
digests of yeast, meats (organs), or
plants Ex. Nutrient broth, nutrient
agar
CULTURE MEDIUM for
__________ MICROORGANISMS
SELECTIVE MEDIA
• ________ unwanted microbes and
encourage desired microbes.
Ex. Eosin Methylene Blue Agar(EMB) and MacConkey
agar-allows Gram___ bacteria to grow but not
Gram (+) bacteria.
EMB Agar
EMB Agar
Figure 6.9b, c
DIFFERENTIAL MEDIA
• Used to ________ colonies of different microbes
based on specific properties such as: lactose
fermenting bacteria from lactose non-fermenting
bacteria; Ex.: MacConkey and EMB agar
Lactose Fermenter
on___________ Agar
Lactose nonfermenter on
MacConkey Agar
Figure 6.9a
BOTH SELECTIVE and DIFFERENTIAL MEDIA
1.MacConkey Agar
DIFFERENTIAL
SELECTIVE
for Gram (-) bacteria
2. Eosin Methylene Blue (EMB )Agar
DIFFERENTIAL
SELECTIVE for Gram (-) bacteria
ENRICHED MEDIA
nutritionally fortified media which ___________ the
growth of a wide range of microorganisms
__________ Plate
also differential
STREAK PLATE METHOD
PROCEDURE for STREAKING
for ISOLATION
ISOLATED COLONIES on
AGAR PLATE
______- a population of cells arising from a __________ or spore or from a group of
attached cells
A colony is often called a colony-forming unit (CFU)
PRESERVING BACTERIAL
CULTURES
• Deep-freezing: -50°to -95°C
• Lyophilization (____________):
Frozen (-54° to -72°C) and dehydrated in a
vacuum
REPRODUCTION in PROKARYOTES
• ___________
• Budding
• Conidiospores
(actinomycetes)
• Fragmentation of
filaments
BINARY FISSION
Bacterial Exponential Growth Curve
____________
TIME:
Time required for
a cell to
______________
Figure 6.13
FOUR PHASES of TYPICAL
___________GROWTH
Figure 6.15
METHODS to DETECT and MEASURE
BACTERIAL GROWTH (Numbers)
• DIRECT
– ___________*
– Filtration
– Most Probable
Number (MPN)
– Direct
Microscopic
Count*
• __________
– ____________
Measurements*
– _____________
Determination
– Metabolic Activity
Measurements*
DIRECT __________ METHOD
• Inoculate Petri
plates from serial
__________ of
sample
• Used to count
_______ bacterial
cells only
______ MICROSCOPIC COUNT
The number of microbes in a specific volume of bacterial suspension are counted using a
special slide
Ex.: PETROFF HAUSSER
Does not distinguish between living and dead cells
Estimating Bacterial Numbers by Indirect
Methods
________:_______ Measures number of cells present, dead or alive
Figure 620
Estimating Bacterial Numbers by
Indirect Methods
• ____________ activity
– Amount of certain metabolic products is in
direct proportion to number of bacteria
present
– Examples:
» O2 Consumption
» Acid Production
• Dry weight
– Weight of packed cell mass is proportional
to the number of cells in culture
– Used for filamentous fungi