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161 Cards in this Set

  • Front
  • Back

What is a microbe?

A living organism that requires a microscope to be seen

Some microbes consist of a ___________ cell.

single

Name some microbial cell sizes

Supersize




Microbial communities




Viruses

Microbes include members of the three domains of life:

Bacteria


Archaea


Eukarya

Bacteria and Archaea include what?

Prokaryotes

Eukarya include what as what?

Algae and plants


Fungi and animals


Protists




Eukaryotes

Define resolution

the smallest distance by which two objects can be separated and still be distinguished

What is thee resolution of the human retina?

150 micrometers (1/7 mm)

Define magnification:

An increase in the apparent size of an image to resolve smaller separations between objects

Light microscopy uses?

uses light to resolve images of individual cells

What are the 4 visualizations through LIGHT MICROSCOPY?

- Bright-field


- Dark-field


- Fluorescence


- Phase contrast

Bright-field:




Light or electron?

images viewed as dark objects against light-filled field




LIGHT

Dark-field:




Light or electron?

images viewed as halos of bright light against darkness




LIGHT

Fluorescence:




Light or electron?

incident light is absorbed by the specimen and reemitted at a longer wavelength




LIGHT

Phase contrast:




Light or electron?

Reveals differences in refractive index as patterns of light and dark




LIGHT

Electron microscopy uses:

uses electrons to resolve images. Electrons behave light light waves.

What are the two patterns from electron microscopy?

Scanning (SEM)


Transmission (TEM)

Scanning (SEM):




Light or Electron?

electrons SCAN the outer surface. Reveals external features


Reveals external features in 3D




ELECTRON

Transmission (TEM):




Light or Electron?

electrons PASS through the specimen. Reveals internal structures.


Reveals internal structures in 2D




ELECTRON

How to increase resolution under Bright-Field Microscopy?

Use shorter wavelength light (higher energy)


Use immersion oil

The detection and resolution of cells under a microscope are enhanced by:

Fixation


Staining

Fixation:

Cells are made to adhere to a slide in a fixed position

Staining:

Cells are given a distinct color

Name the four differential stains for bright microscopy:

Gram stain


Acid-fast stain


Spore stain


Negative stain

Gram positive V Gram negative

Gram positive retains the crystal violet stain because of their thicker cell wall


Gram negative bacteria do not

Acid-fast stain

Carbolfuchsin used to stain Mycobacterium species

Spore stain

Malachite green used to decect spores of Bacillus and Clostridium

Negative stain

Colors the background, which makes capsules more visible

Which kind of microscopy detects scattered light normally missed with bright field? What does t require to detect the scattered light?

Dark field microscopy




A modified condenser

Which kind of microscopy can see flagella?

Dark field

What can Phase-contrast be used to view?

Live cells and cellular organelles

Light patterns:




Dark field =


Phase Contrast =

Scattering


Refraction

How does Phase Contrast work?

1. The specimen retards light by 1/4 of wavelength


2. The phase plate (coated with refractive material) retards light again by 1/4 wavelenth


3. Light is now retarded by 1/2 wavelength


4. Light from the specimen and the transmitted light are completely out of phase (PHASE-CONTRAST)


5. When both lights reach the eye the image appears dark against bright background

How does fluorescence Microscopy work?

The specimen is first stained with a fluorophore.


The fluorophore absorbs light at a certain wavelengh, The light is them emitted at a higher wavelength,


The eye sees that a fluorescent color corresponding to the emission wavelength.


More than one fluorophore can be used on the same sample to "label" different structures, e.g. membrane and nucleus

What is a fluorophore?

A fluorescent molecule

In electron microscopy, electrons behave like light waves but they have:

- Very high frequency


- allows very great resolution, a few nanometers

How does electron microscopy get the sample to absorb electrons?

COATED WITH HEAVY METAL TO MAKE THEM ABSORB ELECTRONS

Sample preparation for Electron Microscopy:

The specimens are:


1. Embedded in a polymer for thin sections - microtome is used to cut slices


2. The specimen is then treated with a heavy-metal salt such as uranyl acetate


*Note: For SEM, specimen is coated with heavy metal and it is not sliced

Most prokaryotes share fundamental traits:

- Thick, complex outer envelope


- Compact genom


- Tightly coordinated cell functions

Cytoplasm

Consists of gel-like network

Cell membrane

Encloses the cytoplasm

Cell wall

Covers the cell membrane

Nucleoid

Non-membrane bound area of the cytoplasm that contains the chromosome in the form of looped coils

Flagellum

External helical filament whose rotary motor propels the cell

What is the structure that defines the existence of a cell?

Cell membrane

What are cell membranes made up of?

Phospholipids and proteins

Describe the structure of a phospholipid

Water loving head ad lipid loving tail


- They are arranged in a bilayer

Membrane proteins serve numerous functions:

- Structural support

- Detection of environmental signals


- Secretion of virulence factors and communication signals


- Ion transport and energy storage



Microbial cells can range from:

a few nanometers to a fraction of a millimeter in size

Microscopes increase _____________ by increasing ______________.

RESOLUTION


MAGNIFICATION

What can cross the cell membrane?

Small uncharged particles such as O2 and CO2, easily permeate the membrane by passive transport


Water tends to diffuse across by osmosis

What cannot cross the membrane?

charged particles like sugars and vitamins


Ions

For the molecules that cannot get across the membrane freely, how do they get across?

Transporter proteins help them cross to the cytoplasm

Name the two kinds transport.

Passive and Active

Passive transport:

Along concentration gradient, e.g. from high concentration outside the cell to the low concentration in the cytoplasm

Active transport:

against concentration gradient; requires expenditure

What cell organ is the outside layer of the cell?

The cell wall

What does the cell wall do?

Confers shape and rigidity to the cell, and helps it withstand turgor pressure

Most bacterial cell walls are made up of ______________.

peptidoglycan

Peptidoglycan is made up of ________ and _________.

peptides and glycan




glycan = sugar

Bright field: resolution increases by ____________ and ___________.

FIXATION and STAINING

In bright field microscopy, dark objects appear on a bright background. Resolution is enhanced by using________, e.g. Gram, Spore, Acid-fast, negative.On the other hand, in fluorescence microscopy, objects are labeled with__________that absorb light at a certain wavelength and emit it at a higher wavelength.

Stains and Fluorophores

Coupled transport where the 2 molecules move in the same direction is known as ____, while coupled transport where the 2 molecules move in opposite direction is known as ______

Symport and Antiport

Both ABC transporters and group translocation transporters require energy expenditure. This is manifested in the form of ATP hydrolysis for both kinds of transporters.


TRUE OR FALSE

False

If you have a mixture of 2 organisms A and B that you want to separate into pure cultures, you can either use a selective medium to grow one but not the other, or a differential medium that allows growth of both organisms, albeit with a different phenotype.


TRUE OR FALSE

True

List the four phases of the bacterial growth curve IN ORDER.

Lag


Log


Stationary phase


Death phase

Compared to Gram-positive bacteria, Gram-negative bacteria have an ______ composed mainly of _______

Outer membrane


Lipopolysaccharide(LPS)

The bacterial cell wall is made up of peptidoglycan, whose glycan backbone consists of repeating ______and______, while the bacterial cell membrane is made up of______and a bilayer of______

NAG


NAM


Phospholipids


Proteins

What is a cell envelope?

Everything outside the plasma membane

What do envelope layers do?

Provide structural support and protection

Difference between Gram + and Gram -


bacteria

+ has thick cell wall and - has thin cell wall




+ has amino acid cross links in peptidooglycan and - has an outer membrane composed of LPS

List the three main structural components of Lipopolysaccharide

Lipid A


Core polysaccharide


O-antigen or -polysaccharide

Which component of the LPS is the toxic portion?

Lipid A

Organisms surviving under conditions outside the "normal" ranges are known as _______. They are able to do so since their ______ are best suited for these conditions.

Extremophiles


proteins and macromolecules

What is endotoxin?

a component that can stimulate host immune response

LPS of G- bacteria acts as ___________.

Endotoxin

Eukaryotes have a __________________ nucleus.

membrane-bound

Prokaryotes have a ____________ region that extends throughout the cytoplasm.

nucleoid

What does the nucleoid contain?

DNA strands

Pili or fimbriae:

straight filaments of protein monomers called pilin

What is the function of pili or fimbriae?

Attachment or adherence to surfaces

Sex pili:

involved in conjugation (transfer of DNA from a donor cell to a recipient cell)

Name three external structures of a cell.

Pili or fimbriae


Sex pili


Flagella

Peritrichous:

Cells have flagella randomly distributed around the cell

Lophotrichous:

cells have flagella at the end(s)

Monotrichous:

cells have a single flagellum

Each flagellum is a spiral filament of protein monomers called ___________.

Flagellum

Where does the energy come from for rotation of the flagella?

ATP Hydrolysis

Macronutrients:

major elements in cell macromolecules (carbs, proteins, lipids)


They are ions necessary for protein function

Micronutrients:

Trace elements necessary for enzyme function

Selective permeability is achieved in 3 ways:

1. Membrane-spanning protein channels or pores -> those are like facilitated diffusion transporters


2. Substrate-specific carrier proteins, or permeases that span the membrane -> those are common in active coupled transport


3. Dedicated substrate-binding proteins that are present in the periplasmic space -> those are part of ABC transporters

What is periplasmic space?

space between inner and outer membranes

What does passive transport do?

Helps solutes move across a membrane from a region of high concentration to one of lower concentration

Does passive transport require energy?

It does not and it cannot move a molecule against its gradient

It is the ____________ family that transports water and small polar molecules such as glycerol.

aquaporin

What are coupled transport systems?


Passive or active?

They are those in which energy released by moving a driving ion down its gradient is used to move a solute up its gradient.


ACTIVE

What happens in symport?

two molecules travel in the same direction



What happens in antiport?

the actively transported molecule moves in the direction opposite to the driving ion

What kind of transport is symport?

Active coupled transport

What kind of transport is antiport?

Active coupled transport

What does ABC stand for in ABC transporters?

ATP-binding cassette superfamily

Active ABC transporters have two main types:

- Uptake ABC transporter are critical for transporting nutrients


- Efflux ABC transporters are generally used as multidrug efflux pumps

What is group translocation?

the process that uses energy to chemically alter the substrate during its transport


"Active Translocation"

What is an example of group translocation and is present in all bacteria?

phosphotransferase system (PTS)

How does PTS work?

First a phosphate group is attached to specific sugars (e.g. glucose -> glucose-P)


Because the transported molecule is chemically different than the molecule outside the cell, it is not considered moving against its concentration gradient. But this transport could still be considered active since it requires energy expenditure in the first step where the substrate is chemically modified.

Culture medium is of two main types:

Liquid or broth


Solid (usually gelled with agar)

What are the two main techniques in isolating colonies?

Dilution streaking


Spread plate

What are the types of culture media?

Complex


Synthetic (also called defined medium)


Selective


Differential

Complex media:

Nutrient-rich but poorly defined (e.g. components like yeast extract in a medium provides nutrients but its composition is not defined)

Synthetic media:

(also called defined medium) are precisely defined


Selective media:

Favor the growth of one organism over another (one will grow and the other will not)

Differetial media:

exploit differences between two species that grow equally well in the medium but display a different phenotype

Most bacteria divide by ______________, where one parent cell splits into 2 equal daughter cells.

binary fission

What is generation time?

the time is takes for a population to double

What are the 4 phases of the bacterial growth curve?

1. Lag phase


2. Log phase


3. Stationary phase


4. Death phase

Lag phase:

Bacteria are preparing their cell machinery for growth

Log phase:

Growth approximates an exponential curve (straight line, on a logarithmic scale)

Stationary phase

Cells stop growing and shut down their growth machinery while turning on stress responses to help retain viability

Death phase

Cells die with a "half-life" similar to that of radioactive decay, a negative exponential curve.

In nature, many bacteria form specialized, surface-attached communities called _________.

biofilms

How does biofilm formation start?

By attachment of cells to a surface followed by formation of microcolonies that ultimately grow into mature biofilms.

___________ and ____________ species can produce dormant spores that are heat-resistant.

Clostridium


Bacillus

With bacterial endospores, When conditions become unfavorable for growth, e.g. during starvation, what happens?

spore-forming bacteria initiate endospore formation

With bacterial endospores, when conditions become favorable again, what happens?

Endospores germinate into vegetative cells

What do endospores contain?

the genetic material of the cell

Group translocation modifies the substrate during _________ and requires energy expenditure.

transport

Any ecological niche outside this window is called "extreme" and organisms inhabiting them are called _______________.

extremophiles

What are "normal" or non-extreme growth conditions for microorganisms are:

Sea-level


temp 20 to 40 degrees C


neutral pH


0.9% salt


ample nutrients

Being able to survive and thrive in an environment (extreme or non-extreme) depends on the tolerance of that organism's _________________________________________ to the physical conditions within that environment.

proteins and other macromolecular structures

Each organism has an "__________" temp, as well as a min and max temp that define its growth limits.

optimum

The growth temp of psychrophiles

0 to 20 degrees C

The growth temp of mesophiles

15 to 45 degrees C

The growth temp of thermophiles

40 to 80 degrees C

The growth temp of hyperthermophiles

65 to 121 degrees C

What are barophiles or piezophiles?

Organisms adapted to grow at very high pressures. Up to 1,000 atm

Barotolerant organisms grow well over the range of _____________, but their growth falls off thereafter.

1 - 50 MPa

Why are many barophiles also psychrophiles?

the avg temp at the ocean floor is 2oC

Halophiles require what?

high salt concentrations

pH of growth range for Neutralophiles

pH 5 - 8

pH of growth range for Acidophiles

pH 0 - 5

pH of growth range for Alkliphiles

pH 9 - 11


This high pH is typically found in soda lakes and so organisms are also halophilic

____________ can only grow in oxygen.

Strict aerobes

______________________ grow only at lower O2 levels.

Microaerophiles

_______________ die in the least bit of oxygen.

Strict anaerobes

_________________________ can live with or without oxygen.

Facultative anaerobes

In natural environments, nutrient concentrations are typically ______.

low

Define Eutrophication

the sudden intro of large quantities of a formerly limiting nutrient


It can lead to a "bloom" of microbes, which can threaten the existence of competing species

What are some terms used to describe antimicrobial control measures?

Sterilization


Disinfection


Antisepsis


Sanitation

Define sterilization

killing of all living organisms

Define disinfection

killing or removal of pathogens from inanimate objects Might not kill non-pathogenic microorganisms and so is not considered sterilization

Define antisepsis

Killing or removal of pathogens from the surface of living tissues, e.g. skin

Define sanitation

reducing the microbial population to safe levels

Physical Agents to kill microbes:

1. High temp


2. Pasteurization


3. Filtration


4. Irradiation

Most heat is more effective than dry heat. _______________ kills most cells.

Boiling water

What does killing spores and thermophiles usually require?

A combination of high pressure and temp

What does irradiation involve?

Ultaviolet


gamma rays, electron beams and xrays

Chemical agents to kill microbes:

Commercial disinfectants and antiseptics


- ethanol


- iodine


- chlorine

What are antibiotics?

Chemical compounds synthesized by one microbe that kill or inhibit the growth of other microbial species

What does LTLT stand for?

(low temp/long time) - 63 degrees C for 30 minutes

What does HTST stand for?

(High-temp/short time) - 72 degrees C for 15 seconds

Both process of LTLT and HTST kill what?

Coxiella burnetii, the casuative agent of Q fever