Lecture 10 [Exam 3] Flashcards
Microbes need the following to grow:
*Carbon source *Energy source
True or False: Microbes have a remarkable plasticity of microbial genomes
True
What are compounds that microbes must need from the environment (they cannot make them)?
Essential nutrients
What are 2 types of essential nutrients?
Macronutrients
Micronutrients
What are some macronutrients (needed in large amounts)?
Carbon (C), Nitrogen (N), Oxygen (O), Phosphorus (P), Sulfur (S), Hydrogen (H)
Magnesium (Mg2+), Iron (Fe2+), Potassium (K+), Calcium (Ca+)
What are some micronutrients (needed in small amounts)?
Cobalt (Co2+), Copper (Cu), Manganese (Mn2+), Molybdenum (Mo2+), Nickel (Ni2+), and Zinc (Zn2+)
Which macronutrients are found in macromolecules (i.e. carbohydrates, lipids, nucleic acids, and proteins)?
Carbon (C), Nitrogen (N), Oxygen (O), Phosphorus (P), Sulfur (S), Hydrogen (H)
Which macronutrients are found in enzyme cofactors and regulatory molecules?
Magnesium (Mg2+), Iron (Fe2+), Potassium (K+), Calcium (Ca+) (VITAMINS)
What are micronutrients typically used for?
Components of enzyme cofactors
What element are all of Earth’s life forms based on?
Carbon
______________ use CO2 as a carbon source and assemble into organic molecules (mainly sugars).
Autotrophs
_____________ consume the organic compounds made by autotrophs to gain carbon (some are converted to CO2 as waste)
Heterotrophs
The carbon cycle requires both ____________ and _____________.
Autotrophs and Heterotrophs
All organisms require an ________________.
energy source
_____________ obtain energy from chemical reactions triggered by LIGHT.
Phototrophs
______________ obtain energy from OXIDATION-REDUCTION REACTIONS.
Chemotrophs
What are the two classes of chemotrophs?
*lithotrophs *organotrophs
What class of chemotrophs se inorganic molecules as a source of electrons?
Lithotrophs
What type of molecules do lithotrophs use as a source of electrons?
H2, H2S, NH4+, NO2–, and Fe2+
What class of chemotrophs use organic molecules (sugar) as electron donors?
Organotrophs
What form of energy is contained in the high-energy phosphate bonds in adenosine triphosphate (ATP)?
Chemical energy
What form of energy is stored in the form of an electrical potential generated between compartments separated by a membrane and is known as the membrane potential (more negative inside than outside)?
Electrochemical energy
____________ is a type of electrochemical energy that is generated when chemical (or light) energy is used to pump protons
outside of the cell.
Membrane potential
The H+ gradient plus the charge difference
form an electrochemical potential called
the _______________.
Proton Motive Force (PMF)
What processes does the proton motive force (PMF) drive?
transportation of nutrients,
flagellar rotation, and synthesis of ATP via F1FO ATP synthase
What element comprises 79% of Earth’s atmosphere, but is unavailable for use by most organisms?
Nitrogen
What type of bond between two nitrogen atoms (N2) is highly stable and takes considerable energy to break?
Triple
____________ possess nitrogenase, which converts
N2 to ammonium ions (NH4+).
Nitrogen fixers
What is is used to make amino acids and other nitrogen-
containing compounds needed for growth?
Ammonium NH4+
What are 2-types of nitrogen fixing bacteria?
Non-symbiotic and symbiotic
____________ are free-living in soil or water and fix majority of nitrogen (i.e. cyanobacteria/blue-green algae)
Non-symbiotic
____________ form symbiotic associations with plants.
Symbiotic
What are some examples of symbiotic bacteria (specifically symbionts with leguminous plants like soybeans, chickpeas, and clover)?
Rhizobium, Sinorhizobium, and Bradyrhizobium
Once fixed into organic compounds, how does nitrogen
get back into the atmosphere?
Nitrification and Denitrification (via the nitrogen cycle)
_______________ oxidize ammonia to nitrate (NO3–)
Nitrifiers
What are some examples of bacteria that oxidize ammonia to nitrate?
Nitrosomonas, Alcaligenes, Nitrobacter
____________ convert nitrate to N2.
Denitrifiers
What type of bacteria performs denitrification?
Paracoccus
What are the three steps in the nitrogen cycle?
1)Nitrogenase fixes atmospheric nitrogen to ammonia
2) Nitrifiers oxidize NH4+ to generate energy
3) Denitrifiers use oxidized forms (i.e. nitrate) as alternative electron (-) acceptors
How do we capture bacteria and study them?
They must be grown separately in pure culture for detailed studies
After almost 140 years of trying, what percentage of bacteria have we have succeeded in culturing?
less than 1%
Bacteria are grown in 2 main types of culture media:
Liquid (broth) or Solid
What are liquid (broth) or solid culture useful for?
studying the growth characteristics of a pure culture
_______________ is a culture containing only a single strain or species of microorganisms.
Pure culture
Why are solid cultures (usually plated with agar) useful?
separate mixed cultures from clinical specimens or natural environments
_____________________ contain only those nutrients that are essential for growth of a given microbe.
Minimal defined medium
______________ is a complex media to which specific blood components are added (some microbes are fastidious)
Enriched medium
___________________ favor the growth of one organism over another.
Selective medium
Asolidmediumcontainingbilesaltsandcrystalvioletis a selective media that favors the growth of _______________.
Gram negative (-)
__________________ exploit differences between two species that grow equally well (usually by exposing biochemical differences).
Differential media
Several media used in clinical microbiology can be both _____________________.
selective and differential
What is an example of a selective and differential medium used in clinical microbiology?
MacConkey medium
List characteristics of the MacConkey medium.
*Only Gram-negative bacteria grow (selective)
*Only a species capable of fermenting lactose produces pink colonies (differential)
___________________ produce acid from lactose and absorb neutral red (stays red at acidic pH)
Lactose fermenting bacteria
__________________makealkalineproducts, neutral red is colorless at alkaline pH so it doesnot alter appearance of the medium
Lactose non-fermenting bacteria
Most bacteria divide by ______________.
Binary fission
What happens during binary fission?
One parent cell splits into two equal daughter cells.
True or False: Some microbes divide ASYMMETRICALLY in binary fission.
True
_____________ divides by budding and releases a smaller cell from a stalked parent.
Hyphomicrobium
Exponential growth never lasts indefinitely in which type of culture?
Batch culture
List all of the characteristics of a batch culture.
*A liquid medium within a closed system
*No fresh medium is added during incubation
*Nutrientconsumptionandtoxicby-products accumulation occur
*Greatly affect bacterial physiology and growth.
*Illustrates the remarkable ability of bacteria to adapt to their environment.
Plottingculturegrowth versusincubationtime, makesitpossibletodo what?
Seetheeffectof changingconditions ongenerationtime as well as revealthestagesof growth.
In what culture do all cells in a population achieve a steady state which allows detailed study of bacterial physiology?
Continuous culture
What is a continuous culture system that ensures logarithmic growth by constantly adding and removing equal amounts of culture medium?
Chemostat
True or False: The human gastrointestinal tract is a crude chemostat.
True
What happens to bacteria when they are faced with environmental stress?
They undergo complex molecular reprogramming that includes changes in cell structure
What are examples of some bacteria that undergo complex changes in response to environmental stress?
*Endospores of certain Gram-positive bacteria
*Heterocysts of cyanobacteria
*Fruiting bodies of Myxococcus xanthus
*Aerial hyphae and arthrospores of Streptomyces
What species can produce dormant spores that are heat and desiccation resistant?
Clostridium and Bacillus
Starvation initiates an elaborate 8-hour genetic program (sporulation) that involves:
An asymmetrical cell division process and production of a forespore (ultimately an endospore)
__________ is divided into discrete stages based on morphological appearance.
Endospore formation
The process of ___________________ wakes the dormant cell, dissolves the spore coat, and releases a viable vegetative cell once proper nutrient requirements are met.
Germination
Spore resistance to heat and chemical insults:
- The thick covering
-The synthesis of Dipicolinic acid
stabilizes and protects spore DNA
-The uptake of calcium into the coat of the spore
Desiccation:
-have only 10–30% of a vegetative cell’s water content
-Packed with small acid-soluble proteins (SASPs)
-Bind and protect DNA from damage by ultraviolet light and
various toxic chemicals
True or False: Only gram positive bacteria form endospores in the genuine sense.
True
Cyanobacteria are:
-Filamentous and multicellular
-Carry out photosynthesis
-Fix nitrogen anaerobically into
specialized cells called heterocysts.
What is nitrogenase?
-the enzyme required to fix nitrogen
-very sensitive to oxygen (by product
of photosynthesis)
Heterocysts:
-A tightly regulated genetic program converts every tenth photosynthetic, vegetative cell to a heterocyst
-Form a specialized envelope as a barrier to atmospheric 02
-Degrade the photosynthesis machinery that produces O2
-Supplies nitrogen compounds to the adjacent vegetative cells, which, in turn, send carbon sugars to the heterocyst
What is Myxococcus xanthus?
-Gram-negative, soil-dwelling bacteria
-uses gliding motility (involving a type of pilus)
-travel on surfaces as individuals or move together as a mob
__________ triggers the aggregation of approx. 100,000 cells.
Starvation
Over the course of 72 hours of starvation myxcoccus xanthous rises into a ______________.
fruiting body
Specialized, surface-attached,
collaborative communities
formed by bacteria in nature are called _________________.
Biofilms
The mixture of facultative and
anaerobic bacteria (Streptoc
occi) form ________________.
dental plaque
True or False: Bacterial biofilms form when nutrients are plentiful
True
True or False: Once nutrients become scarce, individuals detach from the
community to forage for new sources of nutrients.
True
The formation can be signaled by different environmental parameters such as:
pH, iron concentration, temperature, oxygen availability, and the
presence of certain amino acids
Chemical signals allow bacteria to communicate within the biofilm is also called ____________.
Quorum sensing
The Gram-negative bacterium Pseudomonas aeruginosa can form a single-species biofilm on _______________, _____________, and _______________.
-the lungs of cystic fibrosis patients
-medical implants
-ventilators used to assist respiration
