IUPUI Microbiology Davidson Exam 1

What is a prokaryotic cell?

A cell without a nucleus with no membrane bound organelles

What is an example of a prokaryotic cell?

bacteria

What is a eukaryotic cell?

Cell with a nucleus and membrane bound organelles

What is an example of a eukaryotic cell?

plant and animal cells, as well as parasites

What do viruses consist of?

Nucleic acid packaged within a protein coat. No cell membrane

What are fimbriae?

hairlike appendages that allow for attachment

What is the purpose of flagella?

helps bacteria move around, provides motility

What is the purpose of pilli?

Sexual reproduction: conjugation

Transfer DNA from one cell to another

Bacteria become resistant to drugs

What makes up the cell envelope?

Composed of the glycocalyx, cell wall, cell membrane

What is the cell membrane's purpose?

Flexible thin skin that encloses the cell's interior, controls in and out of substances

Increases the internal surface area for membrane function

Most enzymes needed for biochemical reactions are located on the membrane

What is the importance of the glycocalyx?

Coating of macromolecules: protects the cell, helps cell adhere to its environment

Describe the glycocalyx's slime layer:

loose, soluble polysaccharide; not bound to the cell; aids bacteria in colonizing surfaces (attaches to surface)

Describe the glycocalyx's coating capsule layer:

Bound to the cell

Thick gummy consistency

What is the importance of the glycocalyx's coating capsule layer?

Gives colonies a sticky, mucoid characteristic

Makes bacteria more virulent: protect bacteria from phagocytosis by the cells of the host

Prevents drying out of bacteria

Aids in attachment to surfaces for colonization

What is made up of subunits found nowhere else in nature?

the cell wall

What cell structure causes symptoms of disease in many creatures and is the site of action of some of the most effective antibiotics?

The cell wall

What is the cell wall's most important job?

To provide shape to the cell and to prevent it from bursting

Bacterial cytoplasm is concentrated solution of what?

Salts and molecules

What is the cell wall chemical structure made up of?

Composed of peptidoglycan

Only found in bacteria

Similar to chitin found on lobster, insects, and cutin of plants

What is the typical structure of the cell membrane?

phospholipids with proteins

Some areas of the cell membrane fold inwards forming what?

Mesosomes

Describe protoplasm:

Site of biochemical and synthetic activity

Contains: 70-80% water, sugars, amino acids, salts, enzymes, chromatin body, ribosomes, mesosomes, granules

Describe the chromatin body:

Bacterial chromosome

DNA aggregates in dense area called the nucleoid

Describe a plasmid:

Circular piece of DNA: extrachromosomal strand

Protective function: provides resistance to drugs

Advantage to man: use this in genetic engineering techniques

What do ribosomes do?

Used in protein synthesis

What is the job of inclusion granules?

Concentrate nutrients inside the cell, storage & are not permanent

What is chemotaxis?

Chemical attraction of phagocytes to bacteria

What are chemical attractants?

microbial products, components of damaged tissue, and products of complement systems.

What is adherence in phagocytosis?

attachment of a phagocyte to the surface of the microorganism

Describe the phagocytoic process of ingestion:

Plasma membrane of phagocyte extends out projections called pseudopods that surround the microbe

Forms a sac called phagosome

Describe digestion in phagocytosis:

Phagosome comes into contact and fuses with lysosomes that contain digestive enzymes and bactericidal substances

Forms a larger vacuole called the phagolysosome

Ingested bacteria are killed

Phagolysosome moves to cell membrane

List the phases of phagocytosis in order:

Chemotaxis, Adherence, Ingestion, Digestion, Excretion/Exocytosis

Describe a gram positive cell wall:

Thick layer of peptidoglycan associated with teichoic acids

Describe the staining associated with a gram positive cell wall:

Retain crystal violet stain

Mordant joins with crystal violet forming large molecules

Can't escape at the decolorization step (gets trapped in the peptidoglycan layer)

Describe a gram negative cell wall:

Thin layer of peptidoglycan

Outer membrane and periplasmic space

Describe the staining associated with a gram negative cell wall:

Crystal violet-mordant molecule can escape when decolorized

Safranin, a counterstain, is then used to color the cell wall

Crystal violet is a..

primary stain

Gram's iodine is a..

mordant

Acetone alcohol is a..

decolorizer

Safranin is a..

counterstain

Describe the gram staining procedure:

Apply primary stain (stains all bacteria)

Apply mordant, binds with the stain inside the cell wall making a larger molecule

Decolorize with acetone/alcohol: this causes the stain to escape some bacterial cell walls rendering them unstained/colorless

Add a counterstain: this adds color to the cells that were decolorized

What are you supposed to do between each application in the gram staining procedure?

Rinse between each application

A gram positive cell wall is ____ permeable whereas a gram negative cell wall is ____ permeable

more, less

A gram positive wall has ____ layer(s) whereas a gram negative wall has ____ layer(s)

one, two

True or False: a gram positive cell wall has an outer-membrane

False

Why is penicillin toxic to bacteria?

it inhibits the synthesis of the peptidoglycan layer

Is penicillin more effective against gram positive or gram negative bacteria? Why?

Gram positive (except for staphylococci), because the outer membrane of gram negative prevents the penicillin from reaching the peptidoglycan layer

Define transmissible:

An infectious disease agent that is transmitted from either a reservoir or a portal of exit to another host's portal of entry.

What are the three modes of disease transmission?

contact, vehicle, vector

Describe the different modes of contact transmission:

Direct - person-to-person (kissing, touching, sexual, etc.)

Indirect - one host to another by fomites (inanimate objects) - needles, toothbrushes, drinking glasses, etc.

Droplet - droplets of mucus that exit mouth/nares during exhaling, coughing, and sneezing. (cold and flu)

Describe vehicle transmission:

the spread of pathogens via air, drinking water, and food. Also blood and body fluids handled outside the body.

Describe vector transmission:

animals that transmit diseases from one host to another.

Describe biological vectors:

biting arthropods, (e.g.) mosquitoes, ticks, lice, fleas, mites.

Describe mechanical vectors:

passively carry pathogens to new hosts on their feet or other body parts. (e.g.) houseflies, cockroaches.

Define epidemic:

Appearance of infectious disease or condition which attacks many people at the same time in the same geographical location. (e.g.) flu, food poison

Define pandemic:

Epidemic that occurs simultaneously on more than one continent. (e.g.) AIDS, H1-N1,H5-N1 flu, COVID-19

Define endemic:

A disease peculiar to and recurring continuously in a particular locality or population. (e.g.) Histoplasmosis -Ohio Valley

Define contagious:

A communicable disease that is easily transmitted from a reservoir or person. (e.g.) common cold, Legionnaires Disease

What does incidence mean in epidemiology?

The number of NEW CASES of a disease in a given area or population during a given period of time.

What does prevalence mean in epidemiology?

The TOTAL number of cases, new and existing in a given area or population during a given period of time.

How many infectious diseases are there a year worldwide?

750 million

How many deaths due to infectious diseases are there a year in the US?

>200,000

What are the leading causes of illness and death?

Respiratory and Diarrheal diseases

Why has there been a rise in infectious diseases?

Due to travel

1 in 5 come from a country where malaria, cholera, plague, and yellow fever still are common

Lax in vaccinating children because the disease is no longer prevalent

Use of medication to prolong life

Weaker immune systems tend to get opportunistic infections

Development of drug resistance

Describe ways that microorganisms help us:

Breakdown food in the gut

Produce foods: yogurt, cheese, sauerkraut, wine, breads

Used to make: vitamins, insulin, drugs

Decompose waste

Recycle nutrients back into the earth

Used as a food source for other organisms

Make chemical products: acetone, glycerin, organic acids, enzymes, alcohols

Agriculture

Define broth:

A liquid medium that contains various nutrients and is used to culture bacteria and other microorganisms in culture.

Define agar:

A gelatinous material derived from algae, specifically used as a culture medium of bacteria and other cells for diagnostic or laboratory experiments purposes.

What temperature is agar stored at?

Room temperature as a gel, remains firm at temperatures as high as 65 degrees C

Agar melts at?

approximately 85°C

At what temperature does agar solidify?

32-40°C

Agar temperature changes are referred to as:

Hysteresis

Describe deep:

used for a culture where you need a deep inoculation into a solid medium (as gelatin or agar) that is used especially for the growth of anaerobic bacteria

Describe slants:

a culture made on the slanting surface of a solidified medium in a test tube that has been tilted to provide a greater area for growth

Describe plates:

a Petri dish that contains a solid growth medium, typically agar plus nutrients, used to culture small organisms such as microorganisms.

Describe incubation:

Act of maintaining controlled environmental conditions for the purpose of favoring growth or development of microbial cultures.

Describe colony:

a visible mass of microorganisms all originating from a single mother cell, therefore a colony constitutes a clone of bacteria all genetically alike.

Describe picking colonies:

Selecting a colony from a plate and transferring it to another media or a slide.

Describe an anabolic reaction:

The phase of metabolism in which simple substances are built into the complex materials of living tissues

Describe a catabolic reaction:

The metabolic breakdown of complex molecules into simpler ones, often resulting in a release of energy

When energy is released during catabolism, where does it go?

Stored in cells as ATP

What do enzymes do?

increases the rate of a reaction that would normally occur at a slow rate

What are enzymes made up of?

Proteins

True or False: Enzymes may be used again for another reaction

True

Enzymes fit into:

substrates

Why are enzymes important?

their ability to lower the activation energy of a chemical reaction

Define activation energy:

the amount of energy needed to trigger a chemical reaction

A substrate has a higher energy than the _______

products

Enzymes are named after:

the substrate or the kind of reaction they catalyze

Normally enzymes end with "-ase" but what two enzymes are still used by their "original" names and what kind of enzymes are they?

trypsin and pepsin (digestive enzymes)

Is fermentation aerobic or anaerobic?

anaerobic

Anaerobes and Aerobes both:

Make carbon dioxide, uses glycolysis

Where does aerobic respiration occur?

cytoplasm and mitochondria

where does anaerobic respiration occur?

ONLY the cytoplasm

Aerobic respiration takes place in _____ organisms whereas anaerobic respiration takes place in _____ organisms

higher (humans, animals) , lower (bacteria, yeast)

Describe bacterial growth:

Bacterial cells build up protoplasm and double in size

Once doubled in size and each of its parts, the cell divides into two daughter cells.

What is bacterial reproduction called?

binary fission

What happens when a bacterial cell doubles in size?

It is hardly noticeable

Bacterial growth is measured by:

an increase in the number of bacterial cells, it is then transferred to a streak plate

Describe the pour/spread plate method

Add specific diluted homogenized specimen to melted agar and pour into sterile Petri dish - Quantitative

Observe and count colonies after incubation

How do you calculate serial dilution?

Number of colonies on plate x reciprocal of dilution of sample = number of bacteria per mL