Microbio Exam 1

What are the three domains of cellular life?

Bacteria Archaea and Eukarya

What information did Carl Woese use to group organisms into the three domains?

Ribosomal RNA sequence information

What characteristics can be used to classify microorganisms?

Cell structure biochemical and physiological characteristics and nucleic acid or rRNA sequences

What are typical characteristics of Domain Bacteria?

Usually single-celled organisms and most have cell walls containing peptidoglycan. They include both disease-causing and non-disease-causing organisms

What are typical characteristics of Domain Archaea?

They have unique rRNA sequences membrane lipids and cell walls. Some have unusual metabolic characteristics and many live in extreme environments

What microbial groups discussed in lecture belong to Domain Eukarya?

Protists and fungi

What are protozoa?

Eukaryotic protists with animal-like metabolism

What are algae?

Photosynthetic eukaryotic protists

What forms can fungi take?

Unicellular forms such as yeast or multicellular forms such as molds and mushrooms

Why are viruses considered acellular agents?

They are noncellular and depend on a cellular host to reproduce

What is the order of bacterial taxonomy through family?

Domain → Phylum → Class → Order → Family

How is a bacterial genus and species name formatted?

Both genus and species are italicized. Genus begins with a capital letter and species is lowercase

What classifications can occur below the species level?

Subspecies designations including serovars serotypes and strains

What is the purpose of Koch's postulates?

To establish a causal relationship between a microorganism and a disease

What is Koch's Postulate 1?

The microorganism is present in the diseased host and absent from healthy hosts

What is Koch's Postulate 2?

The microorganism is isolated and grown in pure culture with no other microbes present

What is Koch's Postulate 3?

The pure microorganism is introduced into a healthy host and the host becomes sick

What is Koch's Postulate 4?

The same microorganism is re-isolated from the newly diseased host

What do Molecular Koch's postulates investigate?

Virulence factors or genes associated with a disease-causing microorganism

What is Molecular Koch's Postulate 1?

The phenotype under study should be associated with pathogenic strains of a species

What is Molecular Koch's Postulate 2?

Specific inactivation of the suspected virulence gene should cause a measurable loss of virulence or pathogenicity

What is Molecular Koch's Postulate 3?

Reversion or replacement of the mutated gene should restore pathogenicity

What is the difference between Koch's and Molecular Koch's postulates?

Traditional Koch's postulates determine whether a particular microorganism causes a disease while Molecular Koch's postulates determine whether particular genes or virulence factors contribute to pathogenicity

What is resolution?

The ability to distinguish objects from one another rather than seeing them as a single larger object

What is magnification?

Increasing the apparent size of an object

What is the difference between resolution and magnification?

Magnification makes an object appear larger while resolution determines whether nearby objects can be distinguished as separate

How does wavelength affect resolution?

Shorter wavelengths produce greater resolution

Why does electron microscopy have greater resolution than light microscopy?

Electron beams have much shorter wavelengths than visible light

What does bright-field microscopy produce?

A dark image against a lighter background

Can bright-field microscopy examine stained and unstained specimens?

Yes

Why are staining methods useful for viewing microbes?

Many microbes are unpigmented and lack sufficient contrast with their surroundings

What is a simple stain used for?

Increasing contrast so cells can be visualized

What is a differential stain used for?

Distinguishing different groups of microorganisms or cellular features based on structural differences

What is the Gram stain?

A differential stain used in bright-field microscopy that separates bacteria into Gram-positive and Gram-negative groups based on differences in cell wall structure

What does fluorescence microscopy allow scientists to identify?

Specific cellular structures or components tagged with fluorescent dyes or probes

How does fluorescence microscopy work?

Fluorochromes absorb light and emit visible fluorescent light

What can fluorochrome-labeled probes or antibodies identify?

Unknown pathogens or specific proteins and cellular constituents

What does confocal microscopy produce?

Sharp composite three-dimensional images of fluorescently labeled specimens

What is confocal microscopy especially useful for studying?

Biofilms

How does confocal microscopy improve the image?

An aperture eliminates stray light outside the plane of focus

What does TEM stand for?

Transmission Electron Microscopy

What does TEM allow you to examine?

Detailed internal structures of a specimen

How does TEM form an image?

Electrons pass through a thin specimen and denser regions scatter more electrons and appear darker

Why must TEM specimens be very thin?

Electron beams are easily absorbed and scattered by solid matter

What does SEM stand for?

Scanning Electron Microscopy

What does SEM allow you to examine?

Detailed surface features of a specimen

What kind of image does SEM produce?

A realistic three-dimensional image of surface features

What is the key difference between TEM and SEM?

TEM shows internal structures while SEM shows three-dimensional surface features

What is cryo-electron microscopy used for?

Visualizing biomolecules such as proteins and generating high-resolution structures

How does cryo-electron microscopy generate a 3D image?

Samples are rapidly frozen and multiple TEM images are taken at different angles and combined

What is a coccus?

A spherical bacterial shape

What is a bacillus?

A rod-shaped bacterium

What is a vibrio?

A comma-shaped bacterium

What is a spirochete?

A flexible spiral-shaped bacterium

What are hyphae?

Long filaments that can form a network called a mycelium

What does pleomorphic mean?

Variable in shape

What is a bacterial cell envelope?

The plasma membrane and all layers surrounding it

What structures may be included in a bacterial cell envelope?

Plasma membrane cell wall outer membrane capsule slime layer or other external layers

What are major functions of the bacterial plasma membrane?

Selective permeability nutrient and waste transport environmental sensing and metabolic processes such as respiration and photosynthesis

How are phospholipids arranged in the bacterial plasma membrane?

Hydrophilic polar heads interact with water while hydrophobic nonpolar fatty acid tails face inward toward each other

What are hopanoids?

Hydrophobic bacterial membrane molecules similar to cholesterol that influence membrane fluidity and shape and help form functional membrane microdomains

What are peripheral membrane proteins?

Proteins loosely associated with the membrane that are relatively easy to remove

What are integral membrane proteins?

Amphipathic proteins embedded within the membrane that are not easily removed and often function in transport

What is peptidoglycan?

A mesh-like polymer of repeating subunits that forms the bacterial cell wall

What two sugars alternate in peptidoglycan?

N-acetylglucosamine or NAG and N-acetylmuramic acid or NAM

Where do amino acid chains extend from in peptidoglycan?

NAM

What gives peptidoglycan its strength?

Cross-linking between peptide chains

What is the basic Gram-positive cell envelope structure?

One plasma membrane covered by a thick peptidoglycan layer

What special molecules are commonly found in Gram-positive cell walls?

Teichoic acids

What are functions of teichoic acids?

They help maintain the cell envelope protect against environmental substances and may help bacteria bind to host cells

What is the basic Gram-negative cell envelope structure?

An inner plasma membrane a thin peptidoglycan layer and an outer membrane

What molecule is characteristic of the Gram-negative outer membrane?

Lipopolysaccharide or LPS

Are teichoic acids present in Gram-negative bacteria?

No

What are the three parts of LPS?

Lipid A core polysaccharide and O side chain or O antigen

What are important functions of LPS?

It contributes negative charge stabilizes the outer membrane creates a permeability barrier protects against host defenses and can act as an endotoxin when released

What do porins do?

Form channels in the Gram-negative outer membrane that allow small molecules to enter the periplasm

What is a monoderm?

A cell envelope with one membrane

What is a diderm?

A cell envelope with two membranes

What is the easiest structural comparison between Gram-positive and Gram-negative bacteria?

Gram-positive has one membrane thick peptidoglycan and teichoic acids while Gram-negative has two membranes thin peptidoglycan and LPS

What are macronutrients?

Nutrients required in relatively large amounts

What are examples of macronutrients?

Carbon oxygen hydrogen nitrogen sulfur and phosphorus

What are micronutrients or trace elements?

Nutrients required in small amounts that commonly assist enzyme catalysis and maintain protein structure

What are examples of micronutrients?

Manganese zinc cobalt molybdenum nickel and copper

What are growth factors?

Essential cellular components that a cell cannot synthesize and therefore must obtain from the environment

What are examples of growth factors?

Amino acids purines pyrimidines and vitamins

What is the difference between macronutrients and micronutrients?

Macronutrients are required in large amounts while micronutrients are required in small amounts

What is the difference between a micronutrient and a growth factor?

A micronutrient is required in a small amount while a growth factor is an essential component the cell cannot synthesize and must obtain from its environment

What is passive diffusion?

Movement across a membrane down a concentration gradient without energy input

Which molecules does lecture identify as readily crossing by passive diffusion?

H2O O2 and CO2

What is facilitated diffusion?

Movement across the plasma membrane down a concentration gradient with the help of transport proteins

What is primary active transport?

Transport that directly uses energy from ATP hydrolysis to move substances against their concentration gradient without modifying them

What is secondary active transport?

Transport that uses the potential energy of an ion gradient to cotransport substances without modifying them

What is symport?

Transport of two substances in the same direction

What is antiport?

Transport of two substances in opposite directions

What is group translocation?

Energy-dependent transport that chemically modifies a molecule as it enters the cell

What is the classic example of group translocation?

The phosphoenolpyruvate sugar phosphotransferase system or PTS which imports sugars while phosphorylating them

What is a bacterial capsule?

A well-organized external polysaccharide layer that is covalently bonded and difficult to wash away

What is an important function of a capsule?

Protection from the host immune response during infection

What is an S-layer?

An external layer with a geometric pattern made of protein

What is an important function of an S-layer?

Protection from ion and pH fluctuations in the environment