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 _________________