Lecture #14 Bio3124 Medical Microbiology Microbial Pathogenicity.
GENERAL MICROBIOLOGY INCREASE IN _________ OF MICROBIAL _______ CHAPTER 6 MICROBIAL GROWTH-
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Transcript of GENERAL MICROBIOLOGY INCREASE IN _________ OF MICROBIAL _______ CHAPTER 6 MICROBIAL GROWTH-
GENERAL MICROBIOLOGY
INCREASE IN _________
OF MICROBIAL
_______
CHAPTER 6
MICROBIAL GROWTH-
MICROBIAL GROWTH REQUIREMENTS
• PHYSICAL– temperature– _______– __________
• CHEMICAL– Carbon (C) – Oxygen (O)– Nitrogen (N)– Sulfur (S)
• Phosphorus• Organic growth factors• Trace elements
PHYSICAL REQUIREMENTS for GROWTH :
• _________GROWTH TEMPERATURE– Lowest temperature at
which a species will grow
• __________GROWTH TEMPERATURE– Temperature at which
species will grow ____
• MAXIMUM GROWTH TEMPERATURE– _______ temperature at
which growth is possible
TEMPERATURE
CLASSIFICATION OF MICROBES:
• PSYCHROPHILES - cold loving microbes
• Optimum growth temperature: _________• Capable of growing at 0oC, but not at 250C• Found in ocean depths, polar regions
– Psychrotrophs-less temperature sensitive, some food spoilage
• ___________ - moderate temperature loving microbes
– Optimum growth temperature: __________– Most common microbes– Food spoilage and disease
• THERMOPHILES - _____loving microbes
• Optimum growth temperature: 50-60oC• Minimum growth temperature: 45oC• Found in hot springs, compost piles
TEMPERATURE RANGE of GROWTH
ACID BASE CHEMISTRY
– ____ – a substance that dissociates into hydrogen ions (H+) and negative ions in aqueous solution
Ex. Hydrochloric acid, citric acid
– ____ – a substance that dissociates into hydroxide ions (OH-) and positive ions in aqueous solution
Ex. Sodium hydroxide
pH scale - logarithmic scale used to measure
H+ concentration
– Most bacteria grow between pH __________– Molds and yeast grow between pH _________– Acidophiles grow in acidic environments
_______ – compounds that keep ___ from changing drastically; ex. peptones, amino acids, phosphate salts-very important in the preparation of microbial media!!
PHYSICAL REQUIREMENTS for GROWTH cntd.:pH
PHYSICAL REQUIREMENTS for GROWTH cntd.
Osmotic Pressure
the force used by a solvent in moving from an area with a lower _____concentration to an area of higher __________concentration– _____ environments - concentration of solute (ex. salt
or sugar) is higher outside cell, causes plasmolysis • Results in loss of water from a cell
– Inhibits ______________–Used to preserve food, ex.Salted fish
__________ - require higher salt
concentrations in their environment
and therefore high osmotic pressure
________ REQUIREMENTS for GROWTH
• Carbon– Structural organic
molecules, energy source
Chemoheterotrophs
use _______________ sources
Ex. Humans, fungi, protozoa, most bacteria, helminths
Autotrophs -use ______
as carbon source
Ex. Plants
• Nitrogen– In amino acids, proteins
• Sulfur– In amino acids, thiamine, biotin– Some bacteria use SO4
2 or H2S• Phosphorus
– In DNA, RNA, ATP, and membranes– PO4
3 is a source of phosphorus
• Trace 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
Obligate _______-O2
is required for
growth
Facultative anaerobes- growth ___ _____ when
O2 not present, O2
preferred
Obligate anaerobes-no growth when O2
present-_____ by
O2
Aerotolerant anaerobes-
can _______ O2 but can’t
use it for growth
Micro-
aerophiles need very low
O2
concentrations
_______ FORMS of OXYGENProduced 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 ELIMINATIONSuperoxide free radicals (02
-1)
02- + 02
- + 2H+ superoxide _____ + 02
dismutase
Peroxide anions (02-2)
2H2O2 ________ 2H2O + O2
H2O2 + 2H+ peroxidase 2H2O
_________ CULTURE METHODS
3. ANAEROBIC JAR 4. ANAEROBIC CHAMBER
1. Reducing media
contains chemicals (sodium thioglycolate) that combine with O2
Media is heated to drive off O2
2. OxyPlates
_________________ that reduces oxygen to water is added to growth
media, transforms petri plate into an anaerobic chamber
_______________Def.: Bacteria that require high ______ concentration
Figure 6.5
____________
• Microbial communities
• Form _____ or hydrogels– Bacteria attracted
by _________ via quorum sensing
• Share nutrients
• Sheltered from harmful factors
• 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 one species 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 MEDIAimportant terms
CULTURE MEDIA
Chemically Defined Media: Exact chemical composition is known
____________Media: Exact chemical composition not known; Extracts and digests of yeast, meats (organs), or plants Ex. Nutrient broth, nutrient agar
CULTURE MEDIUM for __________ MICROORGANISMS
• ___________ 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
SELECTIVE MEDIA
Figure 6.9b, c
EMB Agar
• 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
DIFFERENTIAL MEDIA
Figure 6.9a
Lactose nonfermenter on
MacConkey Agar
Lactose Fermenter on
Mac Conkey Agar
BOTH SELECTIVE and DIFFERENTIAL MEDIA1.__________ Agar
2. ___________________ (EMB )Agar
DIFFERENTIAL SELECTIVE for Gram (-) bacteria
DIFFERENTIALSELECTIVE for Gram (-) bacteria
___________ MEDIAnutritionally fortified media which encourages the
growth of a wide range of microorganisms
Blood Agar Plate also differential
____________ METHOD PROCEDURE for STREAKING
for ISOLATION ISOLATED COLONIES on AGAR
PLATE
Colony- a population of cells arising from a single cell or spore or from a group of attached cells
A colony is often called a colony-forming unit (CFU)
• Deep-freezing: -50°to -95°C
• Lyophilization (_______________): Frozen (-54° to -72°C) and dehydrated in a vacuum
PRESERVING BACTERIAL CULTURES
____________ in PROKARYOTES
• ________________
• Budding
• Conidiospores (actinomycetes)
• Fragmentation of filaments
________________
Figure 6.13
Bacterial _______________ Curve
GENERATION
TIME:
Time required for a cell
to____________
Figure 6.15
FOUR PHASES of TYPICAL BACTERIAL_GROWTH
METHODS to DETECT and MEASURE BACTERIAL __________ (__________)
• DIRECT– _______________*– Filtration– Most Probable
Number (MPN)
– Direct _____________ Count*
• INDIRECT– ______________
Measurements*– Dry Weight
Determination– Metabolic Activity
Measurements*
DIRECT ________ COUNT METHOD
• Inoculate Petri plates from ______________
______________
• Used to count _______ bacterial cells only
DIRECT ____________ COUNTThe number of microbes in a _____________ of bacterial suspension are counted using a special slide
Ex.: PETROFF HAUSSER
Does not distinguish between ______________________
________
Estimating Bacterial Numbers by Indirect Methods
Figure 620
:Indirectly Measures number of cells present, ____________
Estimating Bacterial Numbers by Indirect Methods
• Metabolic activity– Amount of certain metabolic products is in
direct proportion to number of bacteria present
– Examples:» _____________» ___________ Production
• Dry weight– Weight of packed cell mass is proportional
to the number of cells in culture– Used for _________________