62 terms

Chapter 6 microbial growth

an organism that thrives in a relatively acid environment
Microorganism requiring alkaline pH environments.
An organism with a growth temperature optimum of 15 degrees Celsius or lower and a maximum growth temperature below 20 degrees Celsius.
A ____ is a mesophile that is able to grow at cold temperatures.
..., bacteria that prefer moderate temperature and develope best at temperatures between 25C and 40C
..., an organism that has adapted to living in very high temperatures (heat), such as bacteria or algae
A microorganism that has a growth temperature of 80 degrees Celsius or greater.
Organic growth factor
..., Essential organic compounds which the organism is unable to synthesize and must be obtained from their environment. e.g., humans and their vitamins
..., an organism especially a bacterium that requires air or free oxygen for life
..., an organism (especially a bacterium) that does not require air or free oxygen to live
Facultative anaerobe
..., organism that can survive with or without oxygen
..., Microbes that grow better at high CO2 concentrations
..., an organism that does not grow at normal atmospheric concentrations of oxygen but requires a small amount in metabolism.
Superoxide dismutase
..., an enzyme that catalyzes the conversion of superoxide into hydrogen peroxide and oxygen
..., enzyme found in most plant and animal cells that functions as an oxidative catalyst
Selective growth media
..., Contains chemicals and/or dyes to prevent certain bacteria from growing. Can also be used to select for antibiotic resistant organisms.
Differential growth media
..., Contains various substrates and pH indicators to indicate presence/absence of certain chemical reactions; organisms not prevented from growing. Commonly used to identify organisms that break down a particular substrate.
Enrichement growth media
Complex media
..., culture media that is made up of nutrients. When liquid it is called a nutrient broth. When contains agar called nutrient agar
Defined media
..., Culture media whose exact chemical composition is known.
microorganism that grows best at neutral pH range (5.5-8.0)
Microbial growth
increase in number of cells, not cell size
Bacteria pH
pH must be between 6.5-7.5, unless the bacteria makes food--then it likes the pH lower than 6.0
Fungi pH
5 - 6 acidic
Obtain almost all nutrients in solutions from surrounding water so they grow best in an environment largely made of water.
Obligated halophiles
Require high levels of salt, members of the Domain Achaea
Facultative halophiles
Tolerate a high salt concentration, also called osmotolerant. (Ex.Staphylococcus grows in 7.5% NaCI)
Water: chemical requirement
All metabolic active cells require adequate amounts of moisture.
Carbon: chemical requirements
Structural backbone of all organic cell components
Nitrogen: chemical requirements
Needed for synthesis of protein and nucleic acids
Sulfur:chemical requirements
Needed to synthesize protein and some vitamins
Phosphorus: chemical requirements
Needed to make nucleic acids,phospholipids and ATP
Trace elements: chemical requirements
Mineral elements required by microbes in very small amounts. Usually function as cofactors.
Organic growth factor: chemical requirements
Essential organic compounds that an organism is unable to synthesize. Some bacterial require many,some require few, some none at all.
Steals electrons from other molecules creating free radicals.
Enzyme superoxide dismutase
Degrades (SOD) to hydrogen peroxide and oxygen
Hydrogen peroxide
Oxides cellular components
Enzyme catalase
Degrades this to water and oxygen, peroxides also degrades this to water also.
Any nutrient material prepared for the growth of microbes in the lab
Medium requirements
Must meet physical and chemical needs of the microorganism
Medium requirement
Must be sterile before being incoculated
Medium requirement
Pure culture versus mixed culture
Cultural solid media
Contains about 1.5% agar; most bacteria absorb nutrients from medium; colonies grow faster at edges
Culture liquid media
Grow of microbes make broth turgid; some species will not grow in certain areas of the broth due to oxygen requirements
Selective media
Contains special additives to encourage growth of desired microbes while inhibiting the growth of others.
Differential media
Contains agents that make it easier to distinguish colonies of the desired microbe.
Enrichment media
Allows for growth of organism present at low numbers, usually precedes growth on selective media
General media: complex
Contains variety of ingredients including meat juices,digestive proteins, beef and yeast extract; exact composition and amounts of each are unknown and variable; used to grow a variety of microbes
General media: Defined
Mixture of pure chemicals, exact chemical compositions is known; used to study the study the nutritional requirements of bacteria
Binary fission
Type of asexual reproduction in which an organism replicates its DNA and divides in half, producing two identical daughter cells
Bacterial growth curve: Lag Phase
No increase in cell numbers but cells are very metabolically active, is a period of adaptation
Bacterial growth curve: Log/exponential phase
Dramatic increase in cell number,cell divide at constant rate so generation time is measured here,bacteria are most susceptible to chemicals,ends when nutrients are depleted and wastes accumulates
Bacterial growth curve: Stationary phase
Rate or reproduction equals rate of death
Bacterial growth curve: Death/Decline phase
Death rate exceeds the rate of reproduction, cells may undergo involution,can avoid death by transferring cells to fresh culture medium
Stock cultures
Pure cultures stored,serve as a source for working cultures,never used in lab studies
Preservation of bacterial cultures
Frequent culture transfer:keeps cells active, refrigerated for short-term storage, deep freezing at -70C in glycerol, cells are frozen, dehydrated,sealed under vacuum
Cells are frozen,dehydrated,sealed under vacuum
an organism that can grow in, or favors environments that have very high salt concentrations
Generation time
time required for cell to grow and divide, population doubles
15-20 degrees celsus
25-40 degrees celsus
80 or higher degrees celsus