Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

microbiology > Structure and Classification of Bacterial > Flashcards

Structure and Classification of Bacterial Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

state three similarities of prokaryotic and eukaryotic cells

A

chemically similar, cell membrane, encode genetic information in DNA molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

characteristics of prokaryotic cells

A
  1. smaller cells (0.5-2 um)
  2. unicellular
  3. no nucleus/membrane bound organelles
  4. DNA usually circular
  5. ribosomes smaller
  6. binary fission
  7. asexual
  8. eg: bacteria, archae
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

characteristics of eukaryotic cells

A
  1. larger cells (> 10 µm)
  2. often multicellular
  3. always have nucleus and other membrane-bound organelles
  4. DNA is linear and associated with proteins to form chromatin
  5. ribosomes are larger (80S)
  6. divide by mitosis or meiosis
  7. asexual or sexual
  8. eg: plants, animals, fungi and protists
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Three basic shapes of bacteria

A
  • Spherical (coccus; plural: cocci)
  • Rod-like (bacillus; plural: bacilli)
  • Spiral:
  • Wavy-shaped (spirillum)
  • Corkscrew-shaped (spirochete)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

irregular shapes

A
  • Appendaged bacteria: extensions of their cells as long tubes or stalks * Filamentous bacteria: long, thin cells or chains of cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Bacteria of the same kind can sometimes vary in size and shape

A
  • Pleomorphic: bacteria that vary widely in form even within a single culture
  • Monomorphic: single shape
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Prokaryotic cell consist

A
  • cell membrane that is usually surrounded by a cell wall
  • cytoplasm w ribosomes, a nuclear region and granules /vesicles
  • external structures – capsules, flagella and pili
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

characteristics of cell membrane

A

*dynamic and constantly changing
*consist of phospholipids and proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Tail part of the phospholipid

A
  • two long fatty acid
  • non polar hydrocarbon
  • very hydrophobic
  • do not interact w water
  • facing inwards
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

head part of the phospholipid

A
  • charged phosphate group
  • very hydrophilic
  • interacts with water
  • facing outwards
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

characteristics of prokaryotic cell wall

A
  • Semi-rigid
  • very porous
  • does not play a major role in regulating the entry of materials into the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

function of prokaryotic cell wall

A

1.Maintains shape of the cell
2. Prevents cell from bursting when fluids flow into the cell by osmosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Gram staining

A
  • Gram-positive (purple coloured)
  • Gram-negative (pink coloured)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why gram-staining has diff reaction?

A

due to differences in cell wall structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

steps in gram staining

A
  1. application of crystal violet
  2. application of iodine
  3. alcohol wash
  4. application of safranin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Peptidoglycan characteristics

A
  • rigid layer
  • responsible for strength of cell walls
  • both in gram +ve n gram -ve has very similar chemical composition
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Polymer of peptidoglycan

A
  • large macromolecular polymer network
  • N-acetylglucosamine (NAG) alternate with molecules of N-acetylmuramic acid (NAM)
  • linked by β-1,4 glycosidic bonds and cross-linked by tetrapeptides (chains of four amino acids)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Teichoic-acid in gram-positive cell wall

A
  1. consists of glycerol, phosphates and the sugar-alcohol ribitol – occurs as polymers connected by phosphate esters and can be up to 30 units long
  2. have other sugars and D-alanine attached
  3. extend beyond the rest of the cell wall
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

The Gram-negative Cell Wall

A

peptidoglycan layer is thin but there is an additional cell wall layer called the outer membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Outer membrane of the gram-negative cell wall

A
  • Effectively a second lipid bilayer made of lipopolysaccharide (LPS) as well as proteins
  • LPS gives the bacterial outer surface a net negative charge
  • Has protein channel called porins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Function of porins

A
  • form channels thru outer membrane
  • specific and non-specific channels for the transport of low molecular-weight molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Elements of LPS in GN

A

Polysaccharides and Lipid A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Polysaccharides in Gram-negative bacteria

A
  • found in repeating side chains extending outwards from the organism
  • used to identify different Gram-negative bacteria serologically (O antigen)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

LPS in Gram-negative bacteria

A
  • the one that responsible for toxic properties
  • toxic to many animals (endotoxin)
  • causes fever and dilates blood vessels leading to drastic drop in blood pressure
  • induce tissue necrosis and circulatory collapse
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Why Gram-positive cells remain purple despite the safranin counterstain?

A

Dehydration by alcohol causes the pores in the walls to close, preventing insoluble crystal violet-iodine complex from escaping

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Mechanism of why Gram-negative cells is pink

A
  • Alcohol readily penetrates the lipid-rich outer membrane and the thin peptidoglycan layer does not prevent solvent passage
  • Crystal violet-iodine complex formed is easily removed
  • Addition of safranin counterstain → Gram-negative cells stained pink
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Summary of Gram-positive

A

Gram reaction - Stained purple
Peptidoglycan layer - Many layers (thick)
Teichoic acids - Present
Outer membrane - Absent
LPS - None

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Summary of Gram-negative

A

Gram reaction - Stained pink
Peptidoglycan layer - One or very few layers (thin)
Teichoic acids - Absent
Outer membrane - Present
LPS - High

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Components of the cell wall for bacteria genus Mycobacterium (Acid-Fast cell wall)

A
  • large amount of waxes (complex, branched hydrocarbons known as mycolic acids)
  • peptidoglycan
  • external asymmetric bilayer:
    • Inner leaflet contains mycolic acids linked to arabinoglycan
    • Outer leaflet contains other lipids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How Mycobacterium cell wall enables these bacteria to be resistant to many harsh chemicals, including detergents and strong acids?

A

Hydrophobic nature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is the method needed to stain Mycobacterium cell?

A

acid-fast or Ziehl-Neelsen stain to observe under the microscope (appear red/pink)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Characteristics of the bacteria genus Mycoplasma?

A
  • no cell wall
  • cell membrane strengthened by sterols (typical in eukaryotic cell)
  • Vary widely in shape (extreme polymorphism)
  • lack a target for cell wall-inhibiting antibiotics
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Why are Mycoplasmas, such as Mycoplasma pneumoniae, resistant to β-lactam antibiotics like penicillins and cephalosporins?

A

Lack of a cell wall. These antibiotics work by targeting and inhibiting the synthesis of peptidoglycan, a key component of bacterial cell walls. Since Mycoplasmas do not have a cell wall or peptidoglycan, there is no target for the antibiotics to act upon, making these bacteria naturally resistant to them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What enables motility in bacteria?

A
  • Flagella (thin, long appendages)
  • A bacterium can have one flagellum or many flagella with several different arrangements
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the bacterial flagellum made of ?

A

Thousands of protein subunits called flagellin, which aggregate to form a helical structure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Why is flagellum significant in immune responses?

A

Flagellins are highly antigenic and are recognized as H antigens, playing a role in serological diagnosis and triggering immune responses against infections.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What is serological diagnosis?

A

Method used to identify diseases by detecting specific antibodies or antigens in a patient’s blood or other bodily fluids.

38
Q

What are pili in Gram-negative bacteria?

A

Rigid surface appendages found on many Gram-negative bacteria. They are shorter and finer than flagella and are rarely involved in motility. Pili are composed of protein subunits called pilins.

39
Q

Two classes of pili

A
  1. Attachment pili
  2. Sex pili
40
Q

How do attachment pili contribute to the pathogenicity of bacteria?

A

Help bacteria attach to surfaces of host cells, enhancing their ability to colonize and cause disease.

41
Q

Example of bacteria w attachment pili

A
  • Neisseria gonorrhoeae
  • adhere to epithelial cells in the urogenital region, making them highly infectious
42
Q

What are sex/conjugation pili?

A

Structures used by bacteria for DNA transfer during conjugation.

43
Q

How do sex pili contribute to genetic variation?

A

They enable the exchange of genetic material, like antibiotic resistance genes.

44
Q

What is glycocalyx?

A

Glycocalyx is a polysaccharide-containing substance surrounding the bacterial cell.

45
Q

Where is glycocalyx made?

A

It is made inside the cell and excreted to the cell surface.

46
Q

What does glycocalyx generally contain?

A

Composition varies among different microorganisms. Generally contains:
- glycoproteins
-various polysaccharides.

47
Q

What is a capsule in bacteria?

A

A thick, rigid layer of glycocalyx organized in a tight matrix outside the cell wall.

48
Q

What is the function of a bacterial capsule?

A

It protects bacteria from host defenses, such as phagocytosis by macrophages.

49
Q

Name some pathogenic bacteria with capsules.

A
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Neisseria meningitidis
  • E. coli
  • Klebsiella pneumoniae
50
Q

What is the cytoplasm and its composition in prokaryotic cells?

A
  • Semifluid substance inside the cell membrane.
  • Contain abt 80% water.
  • Compounds found are proteins, carbohydrates, lipids, inorganic ions, and low molecular weight compounds.
51
Q

What are the major structures in the prokaryotic cytoplasm?

A

DNA, ribosomes, and inclusions.

52
Q

What are endospores?

A
  • Endospores are differentiated, highly resistant cells formed by some bacteria.
  • Resistant to heat, radiation, and harsh chemicals.
  • They are formed internally to the bacterial cell membrane.
53
Q

How long can endospores remain dormant?

A

Extremely long periods, endospores of Antarctic bacteria remain dormant for at least 10,000 years at a temperature of 14oC in ice 430 m deep

54
Q

What makes endospores durable?

A

They are dehydrated cells with thick walls and additional layers.

55
Q

What are the most well-known endospore-forming bacteria?

A

-Bacillus
- Clostridium

56
Q

What is taxonomy?

A

Taxonomy is the science of classifying living organisms.

57
Q

What is a taxon?

A

Taxon is an orderly arrangement or grouping of organisms.

58
Q

What is common among organisms in the same taxon?

A

They share certain common characteristics but also exhibit diversity.

59
Q

What system is used for scientific naming of organisms?

A

The Binomial System of Nomenclature.

60
Q

How is a scientific name structured?

A

It includes the genus and species names, and sometimes a strain.

61
Q

Give an example of a scientific name with a strain.

A
  • Escherichia coli O157
  • Pseudomonas aeruginosa ATCC 49189
62
Q

What are trivial names in nomenclature?

A

Common or descriptive names for organisms, such as tubercle bacillus (Mycobacterium tuberculosis).

63
Q

What is the trivial name for Streptococcus pyogenes?

A

Group A streptococcus.

64
Q

How is a bacterial species defined?

A

A bacterial species is a collection of strains sharing many common features and differing significantly from other strains.

65
Q

What is a bacterial strain?

A

Group of descendants from a single isolation in pure culture.

66
Q

What is a type strain in bacteriology?

A

A type strain is a designated strain of a species, usually the first described and well-characterized.

67
Q

Where are type strains preserved?

A

They are preserved in type culture collections, such as the American Type Culture Collection (ATCC).

68
Q

What is ATCC?

A

ATCC is a nonprofit organization established in 1925 to collect, preserve, and distribute authenticated type cultures of microorganisms

69
Q

Classification of Bacteria

A
  1. Phenotypic Characteristics
  2. Genotypic Characteristics
70
Q

Classification of bacteria: Phenotypic Characteristics

A
  1. Size, shape, and internal/external structures (flagella, pili, and capsules)
  2. Gram-staining and other stains
  3. Characteristics in liquid and solid media, colony morphology, development of pigment
71
Q

Phenotypic characteristics for cocci species

A
  1. Gram-positive cocci in pairs – diplococci e.g., Streptococcus pneumoniae
  2. Gram-positive cocci in chains – streptococci – e.g., Streptococcus pyogenes
  3. Gram-positive cocci in clusters – staphylococci – e.g., Staphylococcus aureus
72
Q

Phenotypic characteristics for rods species

A
  1. Gram-negative rods -eg: Escherichia coli
  2. Gram-positive rods -eg: Clostridium tetani
73
Q

What are biochemical tests used for in bacteria?

A

To determine their nutritional requirements and metabolic properties

74
Q

Give examples of specific biochemical tests for bacterial classification.

A

Sugar fermentation, starch hydrolysis, citrate utilization, indole production, and nitrate reduction.

75
Q

Classification of bacteria according to growth temperature

A
  • Psychrophiles: 0 – 20oC
    *Mesophiles: 25 – 40oC
  • Moderate thermophiles: 50 – 60oC
  • Extreme thermophiles: 70 – 110oC
76
Q

Classification based on oxygen requirements?

A
  1. Aerobes
  2. Obligate aerobes
  3. Microaerophiles
  4. Facultative anaerobes/aerobes
  5. Anaerobes
  6. Obligates anaerobes
77
Q

What are aerobes?

A

Bacteria capable of growth at full oxygen tension (21% O₂).

78
Q

What are obligate aerobes?

A

Bacteria that strictly require O₂ for growth, e.g., Pseudomonas aeruginosa.

79
Q

What are microaerophiles?

A

Bacteria that require O₂ but at levels lower than atmospheric, e.g., Campylobacter jejuni.

80
Q

What are facultative anaerobes?

A

Bacteria that grow aerobically when O₂ is present but can switch to anaerobic metabolism, e.g., Streptococcus pyogenes.

81
Q

What are obligate anaerobes?

A

Bacteria that cannot grow in O₂ and may be killed by it, e.g., Clostridium tetani.

82
Q

What is molecular taxonomy?

A

It uses genotypic characteristics like DNA:DNA hybridization and DNA sequencing for bacterial classification.

83
Q

What genotypic techniques are used in bacterial taxonomy?

A

DNA:DNA hybridization and DNA sequencing.

84
Q

How is a new bacterial species proposed based on 16S rRNA?

A

If the 16S rRNA sequence differs by more than 3% from other organisms.

85
Q

Why are ribosomal RNAs used in bacterial classification?

A

Ribosomal RNAs are ancient, universally distributed, and found in all cells as part of the protein synthesis machinery.

86
Q

What makes ribosomal RNAs useful for studying evolutionary relationships?

A

They are functionally constant, with both highly conserved and variable regions.

87
Q

Why is 16S rRNA particularly suitable for prokaryotic classification?

A

It is of reasonable size, about 1,500 bp in length, and provides sufficient information for analysis.

88
Q

What is the eukaryotic equivalent of 16S rRNA?

A

18S rRNA.

89
Q

What is the current gold standard for characterizing bacterial isolates?

A

Whole genome sequencing.

90
Q

Why has whole genome sequencing become widely used?

A

Advances in DNA sequencing technology have made it more available and affordable.

91
Q

What does whole genome sequencing provide for bacterial classification?

A

Comprehensive genetic information for detailed characterization

microbiology (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions