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Microbiology MBBS > Morphology And Physiology Of Bacteria > Flashcards

Morphology And Physiology Of Bacteria Flashcards

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1
Q

The bacteria which are not really strained and require special strain for demonstration

A
  1. Spirochaetes (Treponema and Leptospira) thin spirally coiled bacilli
  2. Mycoplasma
  3. Rickettsiae and Chlamydiae (obligate intercellular bacteria)
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2
Q

Gram positive cocci:
Paired lanceolate shaped

Paired or in short chain, spectacle shaped

Tetrad
…

A

Pneumococcus-lanceolate shaped

Enterococcus-spectacle shaped

Micrococcus- tetrad
…

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3
Q

Gram negative cocci

A

Paired lens shaped: meningococcus

Paired kidney shaped: gonococcus

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4
Q

Bacteria which contain two chromosomes

A

Vibrio
Leptospira interrogans
Brucella

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5
Q

Bacteria which do not contain muramic acid in their cell wall

A

Chlamydia

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6
Q

Biofilm

A 
If there is a colony of bacteria sometimes their slime-glycocalyx (polysaccharide) combined to form biofilm
Roles for bacteria:
1. Anti-phagocytic
2. Adhesion
3. Mechanical barrier for antibiotics
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7
Q

Bacteria which produce slime

A 
Streptococcus mutans 
Staphylococcus epidermidis (of nostril)
Pseudomonas aeruginosa
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8
Q

Smooth to rough variation

A

When repeated subcultures off bacteria are done , it will lose its capsule (loss of its most important virulence factor)

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9
Q

Quellung reaction

A

When specific antibodies react with the bacterial capsule, the capsule swells

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10
Q

Demonstration of capsule

A

By negative staining using India ink or nigrosine

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11
Q

Capsulated bacteria mnemonic

A

Yes some very smart bacteria have killer and mean capsules

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12
Q

Capsulated bacteria (based on mnemonic)

A 
Yersinea pestis 
Streptococcus pneumoniae
Vibrio parahemolytic
Vibrio cholera
Some groups of beta haemolytic streptococcus 
Bacteroides fragilis
Bordetella pertussis
Haemophilus influenzas
Klebsiella pneumoniae
Bacillus anthracis
Meningococcus 
Clostridium perfringes
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13
Q

Specialty of the capsules of Bacteroides fragilis

A

Zwitter ionic capsule

The most common bacteria of the GIT of human

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13
Q

Specialty of the capsule of Bordetella pertussis

A

Non antigenic capsule

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14
Q

Specialty of the capsule of Bacillus anthracis

A

Polypeptide capsule

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15
Q

Peptidoglycan layer of cell wall

A

Each layer is a murein chain, composed of alternating units of N-Acetyl muramic acid and N-Acetyl glucosamine (cross linked to each other)
Tetrapeptide:L-alanine~D-glutamine ~L-lysine ~D-alanine
L-lysine of one tetrapeptide chain is covalent you linked to the terminal D-alanine of adjacent chain via apentaglycine bridge

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16
Q 
Gram positive bacilli arranged in
Chain
Cuneiform
Palisade
Branched and filamentous
A

Chain :Bacillus anthracis
Cuneiform: Corynebacterium diphtheriae
Palisade: Diphtheroids
Branched and filamentous: Actinomycetes and Nocardia

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17
Q 
Gram negative bacteria
Pleomorphic
Thumb print 
Curved 
Chain
Spirally coiled, flexible
Rigid spiral
A 
Pleomorphic: Haemophilus, Proteus
Thumb print: Bordetella pertussis 
Curved: Campylobacter and Helicobactor
Chain: Streptobacillus
Spirally coiled, flexible: Spirochaetes 
Rigid spiral: Spirillum
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19
Q

Difference between peptidoglycan part of gram positive and gram negative bacteria

A
  1. 80 nm thick in gram positive while 10-25 nm thick in gram negative
  2. Gram positive contains 50-100 layers of cross-linked murein monomers but gram negative contains only 2 non cross linked layers
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20
Q

Differences between gram positive and gram negative cell wall (except that of peptidoglycan part)

A
  1. Only gram negative contains aromatic and sulphur containing amino acids
  2. Only gram positive contains teichoic acids
  3. Only gram negative contains: outer membrane, periplasmic space, endotoxin/ lipopolysaccharide
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21
Q

Cross linking of the tetrapeptides of the NAM molecules is mediated by

A

Carboxypeptidases and transpeptidases (penicillin binding proteins PBP)
All beta lactam antibiotics bind to these transpeptidases and inactivate them

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22
Q

Teichoic acid of gram positive bacteria

A

Polymers of glycerol or ribitol joined by phosphate group
Two types:
1. Cell wall teichoic acid
2. Lipoteichoic acid/ cell membrane teichoic acid
Have role in adhesion and integrity of cell wall

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23
Q

Cell wall teichoic acids

A

Polymers of ribitol phosphate

covalently linked to NAM molecules of peptidoglycan

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24
Q

Cell membrane teichoic acid

A

Polymers of glycerol phosphate
Also called lipoteichoic acid
attached to lipid groups of the membrane

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25
Q

Layers of cell wall in a gram negative bacteria

A

Cell membrane
2 layers of main or peptidoglycan in the periplasmic space
Outer phospholipid bilayer with lipopolysaccharide

The outer phospholipid layer contains:

  1. Two types of proteins, porins (or channels) and integral or structural proteins (located only on the outer surface)
  2. Lipopolysaccharide forming the outer surface
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26
Q

Parts of endotoxin or lipopolysaccharide

A 
1. Lipid A:
Embedded in outer membrane
Actual endotoxins activity
2. Core polysaccharide:
Short chain of 6-10 carbohydrates
Unique carbohydrates-KDO (ketodeoxyoctanoic acid) and heptose
3. O / somatic antigen:
Polysaccharide
Outermost 
Most variable
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27
Q

Effects of endotoxin or lipopolysaccharide

A
  1. Activates alternate complement
  2. Activated tissue factor
  3. Induces cytokines release from immune cells
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28
Q

Toll like receptor-4 (TLR-4)

A

On the surfaces of macrophages and dendritic cells

Binds to the lipid-A part of the released LPS of lysed gram negative bacteria

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29
Q

Cytokine release by lipopolysaccharide LPS of gram negative bacteria

A

When it binds to TLR-4, it activated Nuclear transcription factor-kappa B (NK-kB)
Release of cytokine like interleukins 1, 6 and TNF-alpha

30
Q

Pharmacological effects of endotoxins

A
  1. Fever
  2. Hypotension
  3. Increased vascular permeability
  4. Intravascular coagulation ➡️ DIC ➡️ shock
31
Q

Gram positive bacteria with LPS in cell wall

A

Listeria

32
Q

Exotoxins which is released only in lysis (like endotoxins)

A

Botulinum toxin

33
Q

Limulus amebocyte lysate (LAL) assay

A

Detects endotoxins of gram negative bacteria via coagulation

Very sensitive

34
Q

Special functions of cell membrane of bacteria

A
  1. Contains permeases for transport

2. Cytochromes, respiratory chain enzymes and synthetic enzymes of cell wall

35
Q

Parts of a flagellum

A
  1. Filament
  2. Hook
  3. Basal body rings:
    Rotated by proton dependent pump
    In gram -ve; 4 MSPL rings
    In gram +ve; 2 MS rings
36
Q

Examples of monotrichous flagella

A

Vibrio

Pseudomonas aeruginosa

37
Q

Lophotrichous flagella examples

A

Helicobactor pylori

Campylobacter

38
Q

Amphitrichous flagella are present in

A

Campylobacter

Spirillum

39
Q

Peritrichous flagella

A

Bacillus and Clostridium (spore forming genera)
Enterobacteriaceae
Vibrio parahemolyticus: on solid medium
Listeria: only at room temperature (not body temperature)

40
Q

Endoflagella

A

Flagella present in periplasmic space

Present in spirochaetes

41
Q

Flagella demonstration

A
  1. Direct method (EM, impregnation strain)
  2. Indirect
    A) Hanging drop preparation
    B) Soft agar medium (0.2-0.5 %): motility test agar, Craigie’s tube, U-tube
42
Q

Corkscrew motility

A

Treponema pallidum

43
Q

Darting or shooting star motility is exhibited by

A

Vibrio and campylobacter

44
Q

Stately motility is exhibited by

A

Clostridium and Salmonella

45
Q

End to end or tumbling motility is exhibited by

A

Listeria

46
Q

Special motility exhibited by non flagellate bacteria

A

Gliding- Mycoplasma

Twitching- Eikinella corrodens

47
Q

Differential motility

A

Non motile at 37•C but motile at 25-28•C
Listeria
Yersinia enterocolitica
Yersinia pseudotuberculosis

48
Q

Common pili/ fimbriae

A

Mediate adhesion

Only in the surface in gram negative bacteria

49
Q

Sex pili

A

For conjugation
Takes part in horizontal transfer of plasmids (having tra genes/ sex pilus genes)
Gram positive and gram negative containing F plasmid

50
Q

Examples of spore producing bacteria

A 
Only 2 genera (among the pathogenic ones) form spores
1. Bacillus:
non bulging
only in soil and culture
2. Clostridium:
bulging
soil, culture and human body
(except C. perfringes which does not sporulate in the human body)
51
Q

Layers of bacterial spore

A
  1. Core
  2. Spore wall
  3. Spore cortex
  4. Spore coat
  5. Exosporium-lipoprotein in nature
52
Q

Core of a bacterial spore

A

Contains the genome
Glycolytic enzymes
Stored energy (3-phospho glycerate)
Calcium dipicolinate (heat resistance)

53
Q

Spore wall of bacteria

A

Contains typical peptidoglycan

Future wall of the vegetative bacterium

54
Q

Spore cortex of bacteria

A

Atypical peptidoglycan

Thickest layer

55
Q

Spore coat of bacteria

A

Keratin like protein

Resistance to chemical disinfection

56
Q

Conjugative plasmids

A 
Plasmids which can take part in vertical or horizontal transfer
Examples: 
F/sex plasmid 
R plasmid
Col plasmid
57
Q

Bacteriocin

A 
Encoded by Col plasmids 
Antibiotic like proteins which only kill related bacteria
Survival advantage
Examples: 
1. E. coli , Shigella-colicins 
2. P. aeruginosa - pyocin
3. Klebsiella - klebocins
4. C. diphtheriae - diphthericins
58
Q

Metabolic plasmids

A

Encode enzymes for metabolising special substrates. Example urea

59
Q

Virulence plasmids

A 
They encode special virulence factors
Example: 
Capsule of B. anthracis (polypeptide)
Labile toxin of ETEC (enterotoxigenic E. coli)
Anthrax toxin
60
Q

How does phenol kill bacteria

A

Phenols work by disrupting cell membrane which causes lysis and release of cell contents

61
Q

What is phenol coefficient

A

Efficacy of disinfectant as compared to phenol
The efficacy is measured via the dilution
Other methods of testing disinfectants:
1. Chick Martin test
2. Kelsey Sykes (capacity) test
3. Kelsey and Maurer (in use) test

62
Q

Normal human microbiota classification

A 
1. Resident flora:
Harmless
Life long
2. Transient flora:
Do not produce disease as long as resident is intact
Temporary

Total 10^14 (around 10 times more than human cells)

63
Q

Human viral microbiota

A

Collection of viruses in and on human body

Example: skin virome

64
Q

In bottle feed infants the human microbiota is

A

Bifidobacterium- major
Comes from core milk or solid food

Enterics, bacteroids

65
Q

Human microbiota of jejunum , ileum, colon

A

Enterococci

Lactobacillus

66
Q

Human microbiota of nostril

A

Staphylococcus epidermidis

Staphylococcus aureus

67
Q

Human microbiota of nasopharynx

A

Streptococcus

68
Q

Human microbiota of oral cavity

A

Virodans streptococci

Those involved in dental plaque (opportunistic tooth infections)
Streptococcus sanguis
Streptococcus mutans

69
Q

The sterile sites of the human body with respect to human microbiota are

A

Bladder, cervical, uterus, middle ear, sinuses, brain

70
Q

Most common flora of the GIT is

A

Bacteroides fragilis

Among aerobes it is E. coli

71
Q

Advantages of human microbiota

A
  1. Prevents colonisation of pathogen
  2. Vitamin synthesis
  3. Waste produced may antagonise other bacteria
  4. Immune stimulation
  5. Prevents allergic diseases (hygiene hypothesis)
  6. Complement activation

Microbiology MBBS (16 decks)

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