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Flashcards in Exam I Deck (101):
1

You diagnose a young, college patient with a bacterial infection. They ask how do you compare a bacterial cell to a eukaryotic cell, on a broad scale. What do you say?

Both have:
Cell Envelope Structures
1.Cell membranes
Cell Walls
Ribosomes (80s Eukary, 70s Prokary)
Prokarys have Surface Polymers

2

All Bacterial Cells contain...

Cell Membrane
Bacterial Chromosomes or Nucleoid
Ribosomes
Cytoplasm

3

Characteristics of the cell wall

Determine the shape of the bacterium

Provides strong structural support to keep the cell from bursting
or collapsing due to osmotic pressure

Contains Peptidoglycan

4

True or False: Peptidoglycan in found in Eurkaryotic and Prokaryotic Cells

False.
It is found in Prokaryotic Cells.
– Unique macromolecule composed of glycan chains cross linked with
short peptide fragments
– Provides a strong but flexible support framework

5

If one wants to view the cell wall structure of bacteria, what method can they use?

Gram Staining
– Developed in 1884 by Hans Christian Gram
– Delineates two major groups of bacteria
• Gram-positive
• Gram-negative
– Differences lie in the structure of the cell wall

6

Gram Negative stain

– Outer membrane
– Thin cell wall
– Inner cytoplasmic membrane

7

Gram Positive stain

– Thick cell wall composed of
peptidoglycan
– Inner cytoplasmic membrane

8

Gram-Positive Cell Wall

• Thick, homogenous sheath of peptidoglycan, 20 – 80 nm thick.
• Teichoic and lipoteichoic acid

9

Teichoic and lipoteichoic acid function as...

• Cell wall maintenance
• Enlargement during cell division
• Acidic charge on cell surface

10

Gram- Negative Cell Wall

• Single, thin sheet of peptidoglycan, 1 – 3 nm thick.
• Somewhat rigid structure
• Thinness gives gram-negative bacteria greater flexibility and sensitivity to lysis

11

Acid Fast Cells

Acid fast stain
Waxy layer of glycolipids and fatty acids
Hydrophobic
Difficult to Gram stain – lightly gram-positive

Example
• Carbolfuchsin
Mycobacterium spp. and Nocardia spp.

12

Bacteria can lack cell walls?

True

Examples include:
-Mycoplasma
-Ureaplasma
Membrane contains sterols
-L-forms
Bacteria that have lost cell walls

13

The Gram-Negative Outer Membrane

Contains specialized polysaccharides and proteins

• Lipopolysaccharide
Polysaccharide chains function as antigens and receptors • Endotoxin: stimulates fever and shock reactions
Lipoproteins: anchor the outer membrane to peptidoglycan

• Porin proteins:
– Completely span the outer membrane
– Only allow relatively small molecules to penetrate
– Size can be altered to block the entrance of harmful chemicals
– Act as a defense against certain antibiotics

14

The external structure of bacteria includes?

• Flagella and axial filaments: provide motility

• Fimbriae and pili: provide attachment points or channels

15

Flagella can only be located at one section of bacteria?

False.

• Polar: flagella attached at one or both ends of the cell.

– Monotrichous: single flagellum
– Lophotrichous: small bunches or tufts
– Amphitrichous: flagella at both poles of the cell

• Peritrichous: flagella are dispersed randomly over the surface of the cell.

16

What is the function of flagella?

• Chemotaxis: movement in response to chemical signals

– Positive chemotaxis: movement of a cell in the direction of a favorable chemical stimulus
– Negative chemotaxis: movement of a cell away from a
repellant or potentially harmful compound

17

True or False: Flagella are located in the periplasm

True.

Axial filament:
• Two or more long coiled threads found in
spirochetes
• Internal flagellum enclosed between the cell
wall and cell membrane
• Impart a twisting or flexing motion to the cell

18

Appendages for Mating and Attachment

– Pilus (plural: pili)
– Fimbria (plural: fimbriae)
• Both provide adhesion but not locomotion
– Flagella can also be used for attachment in some species

Attachment can enhance pathogenicity in some bacteria

19

Pili

Also known as a sex pilus
– Long,rigid tubular structure made of pilin protein
– Only found in gram-negative bacteria
– Used in conjugation, the partial transfer of DNA from
one cell to another
– Production of pili is controlled genetically

20

Frimbriae

Small,bristle-likefiberssproutingoffthe
surface of certain species of bacteria

– Composition varies, but most contain protein
– Have the inherent tendency to stick to each
other and to surfaces
– May be responsible for the formation of biofilms
– E. coli and the gonococcus use fimbriae to
adhere to epithelial cells

21

Glycocalyx

• Slime layer:
– Forms loosely around the cell
– Protects the cell from loss of water and
nutrients

• Capsule:
– More tightly bound to a cell than a slime layer – Denser and thicker than a slime layer

22

What are the internal structures of a bacterial cell?

Cytoplasm
Chromosomes
Plasmid
Inclusion Bodies
Ribosomes
Cytoskeleton
Endospore

23

Cytoplasm description

70-80% water
Mixture of sugars, salts, amino acids

Also contain chromatin, granules, fibers, and ribosomes that act as the cytoskeleton

24

Bacterial Chromosome

Single circular DNA strand
Aggregated in dense area- nucleiod
DNA tightly coiled around basic protein to fit into the cell compartment

25

Plasmid

Non essential pieces of DNA
Double stranded circles of DNA
Duplicated and passed onto offspring
Protective traits
Important in genetic engineering

26

Ribosomes

Made of RNA and protein
dispersed throughout the cytoplasm
70S-bacterial
80S- eukaryotic

27

Inclusion Bodies

storage sites for nutrients during periods of abundance
single layered membrane
vary in size, number, and content

28

Cytoskeleton

Long polymers of proteins similar to eukaryotic actin
Helical ribbons around cell under the membrane
Contribute to cell shape

29

Endospores

Withstand hostile conditions and facilitate survival

Two phases
Vegetative: metabolically active
Endospore : inert, resting condition

30

The stimulus for endospores

Deletion of nutrients especially carbon and nitrogen sources

31

Sporangium

sporulating cell
transformation takes 6-8 hours in most species

32

Bacteria recognized with endospores

Bacillus and Clostridium

33

Major nutritional needs

• Carbon source for cellular constituents
• Nitrogen source for proteins
• ATP energy source for cell functions

34

Types of Growth Media

• Minimal medium
• Nutrient medium
• Enriched medium
• Selective medium
• Differential medium
• Transport medium

35

General purpose media

• Grow broad spectrum of microbes that do not have special growth
requirements
• Nutrient agar and broth
• Brain-heart infusion agar
• Trypticase soy agar (TSA)

36

Enriched media

•Contain complex organic substances, such as blood, serum,hemoglobin, or special growth factors
• Blood agar
• Thayer-Martin agar
• Chocolate agar

37

Differential media

Grow several types of microorganisms

Differences show up as variations in colony size or color, in media
color change

38

Nutrient Agar

Commonly used general growth medium

39

Tryptic Soy Agar

General purpose medium, base medium for other agar plates (i.e., blood agar
plates)

40

Phenylethyl alcohol agar

Selective for gram-positive bacteria
Inhibits growth of gram-negative bacteria

41

Blood Agar Plates

• General purpose agar: Grows gram-positive and gram negative bacteria
• Useful for determining an organisms ability to produce hemolysins

42

Chocolate agar

Blood Agar Plate
Used for growing difficult respiratory bacteria

43

Thayer Martin agar

Chocolate agar for isolation of Neisseria gonorrhea and N. meningitides

44

MacConkey agar

• Purpose: Gram-negative rods
• Inhibits gram-positive bacteria

Selective - gram negative rods
Differential - Clear: lactose non fermenter
Pink: lactose fermenter

45

Xylose lysine deoxycholate

• Culture of stool samples
• Inhibits gram-positive bacteria—facilitates growth of gram-negative bacteria

46

Mannitol salt agar

Differentiates organisms that ferment mannitol

47

Obligate aerobes

• Grow only in the presence of oxygen
• Aerobic cellular respiration

48

Obligate anaerobe

• Grow only in the absence of oxygen
• Inhibited or killed by the presence of oxygen

49

Aerotolerant anaerobes

• Can grow in the presence of oxygen but cannot use oxygen for energy
requirements
• Fermentationonly(obligatefermenters)

50

Facultative anaerobes

Grow either in the absence or presence of oxygen

• Aerobicrespirationwithoxygen—fermentationintheabsenceof
oxygen

51

Microaerophiles

• Require a low concentration of oxygen
• Approximately 2% to 10% less than atmospheric oxygen

52

Capneic

Require more carbon dioxide than present in regular atmosphere

53

pH

pH of natural environments ranges from approximately 0.5 in acidic soils and approximately10.5 in alkaline lakes

54

Neutrophils

5-8

55

Acidophils

below 5.5

56

Alkaliphiles

above 8.5

57

Environmental Factors influencing Bacterial Growth

pH
temp
gaseous composition of the atmosphere

58

Generation time

Time required for one cell to become two

59

Growth curve

• Lag
• Log
• Stationary • Death

60

Determination of cell numbers

• Directcounts
• Plate counts
• Density

61

Bacterial size

• 0.4μmto2μm
• Averagesize1μm
• Thiomargarita namibiensis: 100 – 750 μm • Mycoplasma: 0.15 – 0.30 μm
• Nanobacteria: 0.05 – 0.2 μm

62

Microscopic shapes

• Cocci
• Bacilli
• Spiral
• Pleomorphism

63

Common Stains

• Gram stain
• Acid-faststains
• Acridineorange
• Methyleneblue
• Lactophenol cotton blue
• Calcofluorwhite
• Indiaink
• Endospore stain

64

Gram Stain

• Heat fix (Methanol can be used)

• Crystal violet (1 min)
Primary stain

• Iodine(1min)
Fixes iodine

• Alcohol-acetone(quick on and rinse)
Decolorizer

• Safranin(30sec)
• Counter-stain

65

Acid Fast Stain

• Ziehl-Neelson method (heat) • Kinyoun (detergent)

• Carbolfuchsin
• Primary stain (red)
• Acidified-alcohol • Decolorizer
• Methyleneblue • Counterstain

66

Acridine Orange

• Stains nucleic acid orange under UV light
• Bacteria
• Living or dead
• Useful in samples with low bacterial numbers

67

Methylene Blue

Metachromaticgranulesin
Corynebacterium diphtheriae

68

Lactophenol cotton blue

Stains fungal cell walls blue

69

India ink

• Negative stain to visualize capsules

70

Incubation Conditions

• Most cultures grow between 35 and 37°C

• Oxygen conditions depend on organisms
• Aerobic
• Anaerobic
• Capnophilic
• Microaerophilic

• Time require
• Most held for 48–72 hours
• Some held 5–7 days

71

Importance of colonial morphology

Provide a presumptive diagnosis in times of critical need
• Enhance quality of patient care through rapid results and cost
effectiveness
• Play a significant role in quality control

72

Observe colony morphology

18-24 hours postculture
• Plating media
• Determine growth and colony morphology

73

Interpretations of Cultures

Initial distinctions between gram-positive and gram-negative isolates (selective)

Differentiation using plated media (differential)

Comparative analysis of the culture media is very important in initial interpretation

74

Hemolysis

• Observation in the media immediately
surrounding or underneath the colony
• Most important in presumptive ID of strep
• Use transillumination
• Light source behind the plate helps visualize hemolysis

α hemolysis - partial clearing of blood that results in a green discoloration of the
medium
• Ex. S. pneumoniae, certain viridans strep

• β hemolysis - complete clearing of blood cells around the colonies •Ex.S.pyogenes,S.agalactiae,Listeriamonocytogenes

75

Colony Size

Large,medium,small,orpinpoint

76

Form or Margin

Edge of Colonies

Smooth, filamentous, rough, or rhizoid
Swarming - hazy blanket of growth on surface

Bacillus anthracis- filamentous
diphtheroid- rough edges
Proteus- swarming

77

Elevation

Raised,convex,flat,umbilicate,orumbonate

78

Density

Transparent,translucent,opaque

79

Odor

Distinctive odors that help ID organisms

80

Color

White, gray, yellow, buff

81

Pigmentation

Inherent characteristics of specific organisms

82

Consistency

• Determine by touching a colony with a loop
• Brittle (splinters), creamy, dry, waxy, or sticky
• Sticky - entire colony comes off the plate

83

Streamers

• Vine-like growth in media, puff-ball like
• Streptococci

• Scum-like growth
• Yeast

84

Turbidity

• Overall cloudiness of liquid
• Gas bubbles present
• Enterics

85

Gram Positive Cocci

• Includeaerobicandanaerobicbacteria
• Range from harmless to very virulent forms •Micrococcus,Staphylococcus,Streptococcus

86

Endospore Forming Gram Positive Rods

Include Bacillus and Clostridium
• Important in medicine and food industry
• Spores are resistant to heat and disinfectants • Wide spread in the soil


• Clostridium perfringens is widely distributed in the environment
• Decaying matter, marine sediment, intestinal tract of humans and other
animals
• Commoncauseoffoodpoisoning
• Bacilli are either obligate aerobes or facultative anaerobes
• Includefree-livingandpathogenicspecies

87

Regular Nonsporing Gram Positive Rods

• Obligate or facultative anaerobes
• Complexnutritionalrequirements
• IncludeCorynebacterium,Lactobacillus,andListeria • Lactobacillus—vaginal smear


• Lactobacilli convert lactose and other sugars to lactic acid
• Most are harmless
• Some species used in industry
• Yogurt, cheese, sauerkraut, pickles, etc.
• Listeria monocytogenes—causative agent of Listeriosis

88

Irregular Nonsporing Gram Positive Rods

• Unusualshape—pleomorphic
• Mostly facultative anaerobes, few obligate aerobes

• Medicallyimportantspecies:
• Actinomyces—opportunistic
• Corynebacterium diphtheria—diphtheria
• Propionibacterium acnes—acne
• Actinomyces israelii—periodontal disease, lung infections

89

Facultative Anaerobic Gram-Negative Rods

• Large group of bacteria with simple nutritional requirements
• Present in soil, water, intestinal tract of animals and humans
• Enterics: Escherichia, Salmonella, Shigella, Enterobacter, Proteus,
Providencia
• E.coli—“workhorse”inmolecularbiology

90

G-Neg Aerobic Robs

• Diversegroup—extensivelyinvestigated
• Widelydistributedinnature
• Many are human and animal pathogens
• Respiratory metabolism—not fermentation
•Pseudomonas,Burkholderia,Legionella,Neisseria,Bordetella,
Francisella

91

Aerobic/Microearophillic Helical Viroid G-Neg bacteria

• They are either slightly curved or have multiple helical turns
• Motile with help of flagella
• Live in fresh or coastal waters
• Some cause disease in humans or animals: Campylobacter, Helicobacter,
Vibrio, Aeromonas
• Helicobacterpylori—pepticulcers,gastritis,duodenitis

92

Anaerobic G-Neg Rods

• Can be straight, curved, helical, motile, or nonmotile
• Predominate organisms in GI tract
• Present in the GI tract of humans and animals • Bacteroidesfragilis

93

Anaerobic G-Neg Cocci

Often occur in pairs
• Foundinmouth,intestines,vagina
• Veillonella causes rare opportunistic infections
• Often associated with long-standing gingivitis in dental patients

94

Mycobacteria

• Aerobic,acid-fastrods
• Tend to form filaments
• Widespreadinwater,soil,andfood
sources
• Some are obligate intracellular parasites in
humans and animals
• Difficult to grow in culture
• Can colonize in host without symptoms

• Infections are difficult to treat
• Neither truly gram-negative or gram-positive
• Difficult to treat—naturally resistant to many antibiotics • Mycobacteriumtuberculosis

95

Nocardioforms

• Aerobic,gram-positive,catalase-positiverods—formbranching filaments
• Widespreadintheenvironment
• Opportunistic
• Infection generally rare
• Originate in lungs and spread to other organ systems
• Nocardiasp.

96

Streptomycetes

• Gram-positive
• Predominantlyinsoilanddecayingvegetation
• Most are spore forming
• Generally not pathogenic—infrequently cause disease
• Important source for antibiotics

97

Intracellular: Rickettsias and Chlamydias


• Very small gram-negative bacteria
• Majority require host for replication
• Generally rod-shaped but also may look coccoidal
• Often cause disease
• Rickettsiae need a vertebrate and an arthropod
host
• Chlamydiaedonotinfectinvertebrates
• Rickettsiaerickettsii—RockyMountainspotted
fever
• Chlamydiaetrachomatis—urogenitalinfections
• Picture of pap smear with the organism

98

Spirochetes


• Group of helical, motile bacteria
• Twisting motions of their axial fibrils
• Foundinvariousaqueousenvironments
and in association with human or animal
hosts

• Pathogens:
• Treponema pallidum—syphilis
• Borrelia burgdorferi—Lyme disease
• Leptospira interrogans—Leptospirosis

99

Mycoplasma and Ureaplasma

Smallest of the free-living bacteria
• Do not have cell walls
• Pleomorphic
• Resistant to penicillin, cephalosporins, vancomycin, and other
antibiotics that interfere with cell wall synthesis
• Special growth requirements
• Can cause disease in humans, animals, and plants

100

most common staphlococcus

s. aureus

101

first test for g +

catalase