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Microbio > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

Domain bacteria

A

Contains single-celled organisms
Prokaryotic
Ubiquitous in the environment and the body
An estimated 10^9 species

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2
Q

Aurotrophs

A

Photosynthetic bacteria
-Can produce energy from light and CO2
Chemosynthetic Bacteria
-Can produce energy from inorganic chemicals such as hydrogen sulfide, methane, etc

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3
Q

Heterotroph groups

A

(4 main groups)
Gram positive cocci
Gram positive bacilli
Gram negative cocci
Gram negative bacilli
(3 less common groups)
Spirochaetes
Rickettsia
Mycoplasma

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4
Q

Describing bacteria include

A

Always include the following characteristics when giving a basic description of a bacteria cell:
Morphology
Size - of the individual bacterium (cell)
Arrangement
If Gram stain is available, include if the bacterium is Gram positive or Gram negative

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5
Q

Cocci

A

(singular coccus)
Spheres
Always give the diameter

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6
Q

bacilli

A

(sing. bacillus)
Rods
Can be filamentous (long and thin; almost string-like)

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7
Q

Coccobacilli

A

(sing. coccobacillus)
Short, plump rods; almost ovals in appearance

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8
Q

Vibrios

A

(eg. Cholera)
Common-shaped, curved rod
Singular

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9
Q

Spirilla

A

Rigid helix
Flagella for motility
Singular, less commonly found in short chains

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10
Q

Spirochetes

A

Corkscrew (telephone cord)
Move using flagella to “wind” or by spring-type creeping
Singular

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11
Q

Pleimorphism

A

Pleio = many
Morphology = shape
Pleiomorphism = having more than one shape or form
Refers to variability in shape
Many bacteria have SOME variation in shape
Different lengths of rods
Sporulated versus non-sporulated forms
May depend on health of bacteria during various stages of growth; or if grown under different conditions

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12
Q

Size of bacteria, how to measure it

A

Always measure individual cells
Always in microns (μ)
Most bacteria are 0.5 to 3 microns in width
Cocci – Give the diameter
Rods – Give width x length of an individual cell
Filamentous, spirilla, spirochetes – Give length while curved/folded
Slight pleiomorphism – Describe the most commonly represented size

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13
Q

cocci

A

Singular

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14
Q

Diplococci

A

pairs

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15
Q

Streptococci

A

chains

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16
Q

Staphylococci

A

chains

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17
Q

Tetrads

A

4 cocci in a square

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18
Q

Sarcinae

A

8 cocci in a cube

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19
Q

Bacillus

A

Singular
Say single when putting it on papers

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20
Q

Dipobacilli

A

pairs

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21
Q

Streptobacilli

A

Chains; 3 or more arranged end to end

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22
Q

Palisades

A

Picket-fence; arranged side by side

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23
Q

Bacteria colony

A

Term used to describe a discrete mound of bacteria cells visible with the naked eye
All the cells in the mound are derived from a single bacteria cell
Can exist in vitro or in vivo

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24
Q

In vitro bacteria colony

A

Different bacteria produce colonies with distinct shapes and colours when grown in vitro under specific growth conditions
These macroscopic (visible to the naked eye) characteristics are used to help identify the genus

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25
Q

Colony forming unit

A

A SINGLE colony is created from a SINGLE bacterium that replicates many times until there are enough cells to see with the naked eye
A COLONY FORMING UNIT (CFU) refers to the single bacterium that started the colony
Because, all cells within the colony are identical, each colony represents ONE colony forming unit
THE DOTS YOU CAN SEE IN A PETRI DISH

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26
Q

Cytoplasmic membrane is

A

AKA cell membrane, plasma membrane
Main component is a phospholipid bilayer
Also contains many different types of proteins, carbohydrates and cholesterol
Surrounds the contents of every living cell
Thin, flexible
The cytoplasmic membrane is a selectively permeable barrier

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26
Q

The bacterial cell has

A

Unicellular
Prokaryotic
Lack internal membranes
Small

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27
Q

Channels and transporters of a cytoplasmic membrane

A

Move substances (nutrients, toxins, waste products) into and out of cells
Some antibiotics are designed to only target bacteria cells by using these transporters to move into the cell

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28
Q

Signal receptors of cytoplasmic membrane

A

Proteins that bind to “signals” from the outside environment
Tell the bacteria cell to:
start or stop replicating
move away from harm
produce enzymes to metabolize nutrients
produce enzymes required to inactivate specific antibiotics

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29
Q

Metabolic proteins

A

Bacteria do not have mitochondria
Energy producing machinery is located along folds/invagination in the cytoplasmic membrane (called mesosomes)

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30
Q

Attachment proteins on cytoplasmic membrane

A

Bacteria use these proteins to attach to specific cells in the host animal
Certain bacteria can only attach to certain cells
Essential for infection

31
Q

Surface antigens on cytoplasmic membrane

A

Any protein or portion of a protein on the surface of a bacteria cell that can be recognized by the ANIMAL’s immune system
Antigens are the molecular “ID tags” that are found on all cells
Different bacteria have different surface antigens
Often used as a method of identifying different strains of the same species

32
Q

Functions of the cytoplasmic membrane

A

Enclose the cytoplasm
Barrier function
Regulates movement of molecules in and out of the cell
Interacts with the environment – via signal receptors
Site for energy production
Attachment – part of the infection process

33
Q

Cytoplasm is and cytoskeleton

A

Fluid or gel that fills the cell
60-70% water
Cytoskeleton
Molecular scaffold
Metabolically active
Biochemical reactions

34
Q

Ribosomes

A

Complex structures consisting of protein and ribosomal RNA
Site of protein synthesis
Where the RNA is “read” and used to assemble proteins in the process known as translation

35
Q

Chromosomal DNA

A

A single strand of circular DNA contains all essential genes
Fewer genes than in eukaryotic cells
Strand of DNA is organized by DNA binding proteins and supercoiled into a tight bundle
The bundled chromosomal DNA is located in the nucleoid
The immune system can recognize bacterial DNA

36
Q

Plasmids are

A

“Extra”, small, circular pieces of DNA containing 1 or 2 genes
NOT part of the chromosomal DNA
Located outside the nucleoid
Genes located on plasmids are not essential to life, but are beneficial to survival by providing an evolutionary advantage

37
Q

Antibiotics and plasmids

A

Proteins that provide antibiotic resistance such as the beta- lactamase enzyme (resistance to penicillins)
Genes for specific toxins or attachment proteins
Genes that enable the bacteria to produce capsules

38
Q

Plasmid replication and size

A

Can have none, one or more than one different plasmid
Plasmids replicate independently of the chromosomal DNA
Once a bacteria acquires a plasmid, it will duplicate itself inside the cell until there are 100’s to 100,000’s of copies per cell
Very resistant to degradation
may remain stable in the environment after the bacteria cell has died

39
Q

Plasmids are transfered how

A

During replication – any time the bacteria cell divides, plasmids also duplicate and an equal number of plasmids are transferred to the “daughter” cell
Transformation – process where the cell membrane opens up and allows the bacteria cell to take up a plasmid from the environment
Bacterial conjugation – process where there is direct contact between 2 bacteria cells through the creation of a temporary cytoplasmic membrane bridge that allows transfer of plasmids

40
Q

Cell wall is

A

All bacteria (except Mycoplasma) have a cell wall
Rigid - surrounds the cytoplasmic membrane
Names are based on staining properties
The type of cell wall is used to help identify the genera

41
Q

Cell wall can be

A

Gram - or Gram + or acid fast

42
Q

Function of the cell wall

A

Maintains shape of bacteria
Protects cell from lysis due to osmotic pressure
Helps protect from toxic materials
Including antibiotics
Small molecules (< 2nm) can diffuse between peptidoglycan chains; large molecules are excluded
Helps with attachment
Prevents phagocytosis by white blood cells in the immune system

43
Q

Ways to break down the cell wall

A

Lysozymes - enzyme found in tears and saliva
Beta-lactams - class of antibiotics (including penicillins and cephalosporins) prevents proper synthesis of the cell wall

44
Q

Cell wall structure and components

A

Primary component is peptidoglycan
2 different polysaccharides linked together alternately to make long chains
Peptide cross-links
Short polypeptide chains

45
Q

Gram differentiation

A

Gram stain is a specific method of staining bacteria
Separates most bacteria genera into 2 major groups based on differences in cell wall structure
Gram positive- purple
Gram negative- pink
Whether bacteria are Gram positive or Gram negative is important with respect to certain growth requirements, pathology and treatment during an infection

46
Q

Gram positive cell wall

A

Thick cell wall - makes up 40-90% of total cell mass
20-80 layers of peptidoglycan
Layers joined by peptide cross-links
Enzyme called transpeptidase is required to make these cross-links
Teichoic acid
Long molecules that help embed the cell wall to the cytoplasmic membrane
May have additional teichoic acids on surface of cell wall that help bacteria attach to other bacteria and/or animal cells

46
Q

Gram Positive Cell Wall and Beta-Lactam Antibiotics

A

Gram positive bacteria are susceptible to the beta-lactam class of antibiotics
Penicillins, cephalosporins
Beta-lactam antibiotics bind to and block function of the transpeptidase → prevents formation of the peptide cross-links between peptidoglycan strands
Without cross-links, cell wall cannot withstand osmotic pressure and cell lyses

46
Q

Gram negative cell wall and their layers

A

Thin ~ 10% of total cell mass
Multiple layers:
Peptidoglycan layer
Closest to the cytoplasmic membrane
1 to 2 layers only
Outer membrane
Complex - composed of two lipid layers
Inner layer is a single sheet of phospholipids
Outer layer is single sheet of lipopolysaccharide (LPS)
Periplasmic space
Space between the cytoplasmic plasma membrane and outer membrane

47
Q

Lypoplysaccharide is and the 3 parts

A

Molecule that makes up the very outmost layer of a Gram-negative cell wall
Part of the outer membrane layer
Important to the bacteria for establishing infection; important to host while fighting off an infection
3 parts:
O-antigen
Core polysaccharide
Lipid A(aka endotoxin)

48
Q

O-antigen is

A

Repeats of polysaccharide units
“Smooth” – bacteria with long O chains
“Rough” - bacteria with very short or lacking O chains
Hydrophilic
Certain species or strains are distinguished by the specific sugar molecule in their O chain

49
Q

O-antigen is important for bacteria to

A

Establish infection
WBCs are unable to grab “smooth” bacteria; WBCs can easily phagocytose rough cells
O-antigens take part in attaching to epithelial cells
Some bacteria can alter the sugars that make up the O-antigen; variation over time allows the bacteria to evade the immune system

50
Q

Immune system uses the O-antigen

A

when trying to fight off infection
Sometimes, immune system can recognize sugars in the O chain and targets these cells for destruction
Presence of O chain will trigger non-specific inflammation

51
Q

Lipid A

A

Aka endotoxin
“Tail” made up of lipid chains
Same in all Gram negative bacteria
Hydrophobic
Function to hold the LPS molecule in place
Normally hidden from the environment - if Gram negative bacteria dies, small amount is released into environment
One of strongest activators of inflammation

52
Q

Endotoxic shock

A

Condition in the body where overwhelming inflammation causes blood vessels to dilate → drops blood pressure → systemic shock
Caused by sudden release of large amounts of lipid A during a Gram negative infection
Lipid A enters circulation and turns on systemic inflammation
Can be fatal if not treated right away

53
Q

Bacteria that do not gram stain

A

Some bacteria are neither Gram + nor Gram -
Do not have the cell wall structures described above
Acid-fast bacteria
Cell wall structure is very similar to Gram-positive, but contain large numbers of mycolic acid (waxy molecules) in the cell wall
E.g. Mycobacterium
Mycoplasma
Do not have a cell wall
Plasma membrane more resistant to osmotic pressure
Very pleomorphic

54
Q

Periplasmic spaces and contains what proteins

A

Space between cytoplasmic membrane and start of peptidoglycan layers in Gram positive cell
Space between cytoplasmic membrane and OUTER MEMBRANE in Gram negative cell
peptidoglycan layer is in the periplasmic space
Contains many proteins
Proteins to digest macronutrients
Proteins to break down toxic compounds (including antibiotics) before they can cross the plasma membrane
Synthesis and storage of pathogenic factors (i.e., collagenase, some toxins)

55
Q

Flagella

A

Threadlike appendages that allow motility
Only found on some bacteria
All spirochetes and spirilla, half bacilli, rarely on cocci
Proteins that make up flagella may be recognized and targeted by the immune system or used to identify the bacteria (i.e., act as antigens)
The number and placement of flagella is used to identify bacteria
Can have one or more flagella
Location on cell and number of flagella determines the type of movement
Example. If polar flagellum (one end of cell), will act like a propeller and push bacteria in one direction.
Bacteria with many flagella that act together tend to move faster
Cannot see flagella under a light microscope; but can see if fast motility is present or not
Only some bacteria are motile

56
Q

Benefits of motility

A

Can move towards environments that are more supportive of growth (increased nutrients), also ideal temp, moisture, presence or absence of oxygen
Can move away from harmful substances (antibiotics, disinfectants, metabolic waste)

57
Q

Flagellar movement

A

Fastest
Flagella acts like propeller to swim through liquids

58
Q

Spirochete motility

A

Corkscrew motion due to periplasmic flagella; is specific to spirochete bacteria

59
Q

Twitching

A

Mediated by fimbriae; crawling on surface or through liquids

60
Q

Gliding

A

Pushed by slime

61
Q

Chemotaxis

A

Bacteria have sensors (aka receptors) on their cell surface that identify what is in the environment
Activation of a receptor results in the bacteria turning on or off genes involved in motility
Process of identifying and then moving toward or away from a chemical is called chemotaxis

62
Q

Positive chemotaxis

A

Moves towards attractants

63
Q

Negative chemotaxis

A

Move away form repellants

64
Q

fimbriae

A

Short, thin, hair-like, protein structures that extend outwards from the cell wall
May be up to thousands per cell
Primary function is attachment to surfaces

65
Q

Pili is and functions

A

Few per cell; very large protein threads that extend from cell wall
2 functions:
Attachment to other cells and surfaces
Forms the initial connection between 2 bacteria during the conjugation process.

66
Q

Capsules

A

Sugar units are well organized
Attached to cell and not easily removed - rigid
Primary functions are (1) resistance/protection (including from drying out, exposure to chemicals, phagocytosis) and (2) attachment

67
Q

Slime layer

A

Not uniform; sugar units form loose coating around the cell wall and is easily removed
Primary functions (1) resistance/protection, (2) attachment; (3) formation of biofilms, (4) motility

68
Q

Advantages of having a capsule/slime layer

A

Resistant to phagocytosis – macrophages cannot grab onto bacteria
Protects from drying out in the environment – capsules/slime contains water
Protects from some detergents
Protects from bacteriophage (viruses that infect bacteria)
Protects from antibiotics
Improves attachment
Slime may aid motility

69
Q

Capsules and slime layers

A

Some bacteria produce polysaccharides that are secreted AROUND the cell wall

70
Q

Biofilms

A

Communities of bacteria (and yeast) embedded in a matrix that attaches to a surface
A biofilm can be made up of single or hundreds of different species of bacteria
Matrix sticks microbes to one another and onto a surface - either living or inanimate; usually moist

71
Q

Steps of biofilm formation and where they are found

A

Cell attachment to surface (by receptors, flagella, fimbriae)
Cells produce exopolysaccharides
Biofilm matures – number of bacteria increase; size of matrix increases
Cells from biofilm disperse and can reattach elsewhere
Common to: standing water, roughened surfaces, surgical implants, catheters, heart valves, teeth
Biofilms are self-sustaining; very hard to treat with antibiotics or disinfectants

72
Q
A

Microbio (11 decks)

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