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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
Layers of cell wall in a gram negative bacteria
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
26
Parts of endotoxin or lipopolysaccharide
``` 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 ```
27
Effects of endotoxin or lipopolysaccharide
1. Activates alternate complement 2. Activated tissue factor 3. Induces cytokines release from immune cells
28
Toll like receptor-4 (TLR-4)
On the surfaces of macrophages and dendritic cells | Binds to the lipid-A part of the released LPS of lysed gram negative bacteria
29
Cytokine release by lipopolysaccharide LPS of gram negative bacteria
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
Pharmacological effects of endotoxins
1. Fever 2. Hypotension 3. Increased vascular permeability 4. Intravascular coagulation ➡️ DIC ➡️ shock
31
Gram positive bacteria with LPS in cell wall
Listeria
32
Exotoxins which is released only in lysis (like endotoxins)
Botulinum toxin
33
Limulus amebocyte lysate (LAL) assay
Detects endotoxins of gram negative bacteria via coagulation | Very sensitive
34
Special functions of cell membrane of bacteria
1. Contains permeases for transport | 2. Cytochromes, respiratory chain enzymes and synthetic enzymes of cell wall
35
Parts of a flagellum
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
Examples of monotrichous flagella
Vibrio | Pseudomonas aeruginosa
37
Lophotrichous flagella examples
Helicobactor pylori | Campylobacter
38
Amphitrichous flagella are present in
Campylobacter | Spirillum
39
Peritrichous flagella
Bacillus and Clostridium (spore forming genera) Enterobacteriaceae Vibrio parahemolyticus: on solid medium Listeria: only at room temperature (not body temperature)
40
Endoflagella
Flagella present in periplasmic space | Present in spirochaetes
41
Flagella demonstration
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
Corkscrew motility
Treponema pallidum
43
Darting or shooting star motility is exhibited by
Vibrio and campylobacter
44
Stately motility is exhibited by
Clostridium and Salmonella
45
End to end or tumbling motility is exhibited by
Listeria
46
Special motility exhibited by non flagellate bacteria
Gliding- Mycoplasma | Twitching- Eikinella corrodens
47
Differential motility
Non motile at 37•C but motile at 25-28•C Listeria Yersinia enterocolitica Yersinia pseudotuberculosis
48
Common pili/ fimbriae
Mediate adhesion | Only in the surface in gram negative bacteria
49
Sex pili
For conjugation Takes part in horizontal transfer of plasmids (having tra genes/ sex pilus genes) Gram positive and gram negative containing F plasmid
50
Examples of spore producing bacteria
``` 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
Layers of bacterial spore
1. Core 2. Spore wall 3. Spore cortex 4. Spore coat 5. Exosporium-lipoprotein in nature
52
Core of a bacterial spore
Contains the genome Glycolytic enzymes Stored energy (3-phospho glycerate) Calcium dipicolinate (heat resistance)
53
Spore wall of bacteria
Contains typical peptidoglycan | Future wall of the vegetative bacterium
54
Spore cortex of bacteria
Atypical peptidoglycan | Thickest layer
55
Spore coat of bacteria
Keratin like protein | Resistance to chemical disinfection
56
Conjugative plasmids
``` Plasmids which can take part in vertical or horizontal transfer Examples: F/sex plasmid R plasmid Col plasmid ```
57
Bacteriocin
``` 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
Metabolic plasmids
Encode enzymes for metabolising special substrates. Example urea
59
Virulence plasmids
``` They encode special virulence factors Example: Capsule of B. anthracis (polypeptide) Labile toxin of ETEC (enterotoxigenic E. coli) Anthrax toxin ```
60
How does phenol kill bacteria
Phenols work by disrupting cell membrane which causes lysis and release of cell contents
61
What is phenol coefficient
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
Normal human microbiota classification
``` 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
Human viral microbiota
Collection of viruses in and on human body | Example: skin virome
64
In bottle feed infants the human microbiota is
Bifidobacterium- major Comes from core milk or solid food Enterics, bacteroids
65
Human microbiota of jejunum , ileum, colon
Enterococci | Lactobacillus
66
Human microbiota of nostril
Staphylococcus epidermidis | Staphylococcus aureus
67
Human microbiota of nasopharynx
Streptococcus
68
Human microbiota of oral cavity
Virodans streptococci Those involved in dental plaque (opportunistic tooth infections) Streptococcus sanguis Streptococcus mutans
69
The sterile sites of the human body with respect to human microbiota are
Bladder, cervical, uterus, middle ear, sinuses, brain
70
Most common flora of the GIT is
Bacteroides fragilis | Among aerobes it is E. coli
71
Advantages of human microbiota
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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