CHAPTER 6 MICROBIAL GROWTH- GENERAL MICROBIOLOGY CHAPTER 6 MICROBIAL GROWTH- INCREASE IN _________ OF MICROBIAL _______

MICROBIAL GROWTH REQUIREMENTS PHYSICAL temperature _______ __________ CHEMICAL Carbon (C) Oxygen (O) Nitrogen (N) Sulfur (S) Phosphorus Organic growth factors Trace elements

PHYSICAL REQUIREMENTS for GROWTH : TEMPERATURE _________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

CLASSIFICATION OF MICROBES: TEMPERATURE RANGE of GROWTH 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

ACID BASE CHEMISTRY pH scale - logarithmic scale used to measure ____ – 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

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 ___ 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 _____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 Nitrogen In amino acids, proteins Sulfur In amino acids, thiamine, biotin Some bacteria use SO42 or H2S Phosphorus In DNA, RNA, ATP, and membranes PO43 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 Carbon Structural organic molecules, energy source Chemoheterotrophs use _______________ sources Ex. Humans, fungi, protozoa, most bacteria, helminths Autotrophs -use ______ as carbon source Ex. Plants

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 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 _____ + 02 dismutase Peroxide anions (02-2) 2H2O2 ________ 2H2O + O2 H2O2 + 2H+ peroxidase 2H2O

_________ CULTURE METHODS 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 3. ANAEROBIC JAR 4. ANAEROBIC CHAMBER

_______________ Def.: Bacteria that require high ______ concentration

____________ Microbial communities Form _____ or hydrogels Bacteria attracted by _________ via quorum sensing Share nutrients Sheltered from harmful factors 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 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 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

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 Lactose nonfermenter on MacConkey 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 Lactose nonfermenter on MacConkey Agar Lactose Fermenter on Mac Conkey Agar Figure 6.9a

BOTH SELECTIVE and DIFFERENTIAL MEDIA 1.__________ Agar SELECTIVE for Gram (-) bacteria DIFFERENTIAL 2. ___________________ (EMB )Agar SELECTIVE for Gram (-) bacteria DIFFERENTIAL

___________ MEDIA nutritionally fortified media which encourages the growth of a wide range of microorganisms Blood Agar Plate also differential

ISOLATED COLONIES on AGAR PLATE ____________ 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)

PRESERVING BACTERIAL CULTURES Deep-freezing: -50°to -95°C Lyophilization (_______________): Frozen (-54° to -72°C) and dehydrated in a vacuum

____________ in PROKARYOTES ________________ ________________ Budding Conidiospores (actinomycetes) Fragmentation of filaments

Bacterial _______________ Curve GENERATION TIME: Time required for a cell to____________ Figure 6.13

FOUR PHASES of TYPICAL BACTERIAL_GROWTH Figure 6.15

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 ____________ COUNT The 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 ________ :Indirectly Measures number of cells present, ____________ Figure 620

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 _________________