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FPP Micro > Bacteria > Flashcards

Bacteria Flashcards

1
Q

Properties of a bacteria cell

A

Prokaryotic
◦ Organelles not membrane bound
◦ DNA is one circular molecule

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2
Q

Knowledge of the cell structure and function of a bacteria is important in _____ & _____

A

Diagnosis
Pathogenicity

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3
Q

The bacteria cell wall is made of

A

Peptidoglycan

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4
Q

Peptidoglycan cell wall is made up of Repeating _______ with ____ _____ in a side chain extending from each disaccharide

• This results in a ____ _____ ____ _____

A

Disaccharides

Amino acids

Stable cross linked structure

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5
Q

5 cell wall functions is to

A

• maintains cell shape
• acts as a barrier, protects cell contents from external environment
• maintains cell osmotic pressure in a hypotonic environment
• contributes to sensitivity to certain antimicrobial agents (penicillin) and the immune system (antibodies, phagocytes)
• determines reactivity to Gram stain

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6
Q

Characteristics of gram positive cell wall

A

peptidoglycan (60-90% of the cell wall)

Techoic acid – polysaccharide, antigenic (Important for serologic identification of some bacteria)

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7
Q

If peptidoglycan is digested away from the cell, gram positive cells lose their cell walls and become_____.

These must be maintained in _____ ______in order to survive.

A

protoplasts

Isotonic solutions

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8
Q

Characteristics of gram negative cell wall

A

􏰀 Very thin peptidoglycan
􏰀 No techoic acid
􏰀 A unique outer cell membrane
• Periplasmic space
• An external layer of lipopolysaccharide (LPS)

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9
Q

The 3 unique cell membrane of the gram negative bacteria features

A

◦ excludes all hydrophobic molecules (This protects the bacteria from the action of bile salts and toxins of the gut)

◦ contain narrow, restrictive protein channels called porins which permits passage of low molecular weight hydrophilic molecules.

◦ Large antibiotic molecules penetrate the outer membrane slowly (antibiotic resistance)

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10
Q

The peiplasmic place exists where and contains what

A

between the cytoplasmic membrane and the outer membrane which contains digestive enzymes and other transport proteins

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11
Q

The external layer of lipopolysaccharide (LPS) consists of

A

• polysaccharide O antigens used in typing gram negatives
• lipid A or endotoxin. Endotoxin can trigger fever and septic shock in gram negative infections
• LPS also protects the cell from phagocytosis, penicillins and the antibacterial enzyme lysozyme

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12
Q

Flagella are long filaments extending from the cell surface, which enable them to move in their environment.
They are built of ______ and are strongly ____.
The ___ antigens are important targets of protective antibody response

A

Proteins
Antigenic
H

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13
Q

The flagella may be
_____ (single cell, restricted to the pole)

_____ (a tuft at one pole)

______ (one or more flagella at both ends of the cell

______ (distributed over the cell surface).

A

Polar

Lophotrichous

Amphitrichous

Peritrichous

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14
Q

Flagella can help in identifying certain types of bacteria e.g, _______ species show a rapid ‘______’ type of growth on solid media.

A

Proteus

Swarming

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15
Q

The bacteria capsule is

A

A gelatinous polysaccharide and/or polypeptide outer covering

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16
Q

The capsule may be firmly attached or loosely attached as a slime layer
Within the slime layer many cells can come together to form a ______, which may protect them from _____ & _____

A

Biofilm

Antibiotics and toxins

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17
Q

5 important Characteristics of the capsule

A

• Virulence factor, protecting bacteria from phagocytosis by immune cells e.g Streptococcus pneumoniae .
• Permit bacteria to adhere to cell surfaces and structures such as medical implants, catheters and so on. [Adherence is an important first step in colonization and sometimes leads to disease].
• Capsules can be a source of nutrients and energy to microbes. [Streptococcus mutans, which colonizes teeth, ferments the sugar in the capsule and the acid byproducts contribute to tooth decay.]
• Prevents cell from drying out (desiccation)

• Polysaccharides from certain capsules is antigenic and can elicit production of protective antibodies
[Included in vaccines
Such a vaccine is used against Hemophilus influenzae , Streptococcus pneumoniae and Neisseria meningitidis.]

18
Q

In the nucleus of bacteria

the cytoplasm contains ___,which is typically a single circle concentrated in a nucleoid region and not membrane bound
􏰀 Genetic information is carried in a long ____
_____ ____. This is the chromosome, which comprise genes.
􏰀 Genetic information may also be extrachromosomal, present as ____

A

DNA

Double stranded DNA

Plasmids

19
Q

Plasmids are?

Plasmids replicate _____ of the chromosome
carry genes that are not essential for cell survival but may give some advantage to an organism e.g?

A

Small, extrachromosomal DNA circles.

Independently

they can carry genes for antibiotic resistance and toxin production.

20
Q

Pili Also project from the cell wall but are more rigid than the ____
􏰀 Also called _____
􏰀 They function in attachment to host
cells (act as ______)
􏰀 They prevent ______

A

Flagella
Fimbriae
Adhesins
Phagocytosis

21
Q

Pili are Present in many Gram negative bacteria
◦e. g ______ ______uses its fimbriae to attach to the lining of the genital tract and initiate an ___

Sex pili act to join bacterial cells for transfer of DNA from one cell to another known as ____

A

Negative

Neisseria gonorrhoea
STD

Bacterial conjugation

22
Q

Fimbriae also act as ______ for viruses that infect bacteria called ________

• Fimbriae and cell walls of Streptococcus ____ are coated with ___ ______.

• M protein acts as an important virulence factor by _____ & _____

A

Receptors
Bacteriophages

Pyogenes
M protein

adhering to host cells and resisting phagocytosis

23
Q

Ribosomes are
• Composed of ____ & ____
• the site of ______ in cells
• typically comprised of two subunits?
• Antibiotics inhibit protein synthesis at the subunits
• 50s subunit – – e g ?
• 30s subunit — e g ?

A

Protein & RNA
Protein synthesis
50s & 30s
Erythromycin
Tetracycline

24
Q

Clinical importance

A

􏰀 Gram positive thickly meshed peptidoglycan layer does not block diffusion of low molecular weight compounds so, some substances (antibiotics, dyes, detergents), can pass through
􏰀 Antibiotics and chemicals that are able to attack the peptidoglycan cell wall () are unable to pass through the Gram negative cell wall
􏰀 Crystal violet is trapped in the thick peptidoglycan layer, so the dark blue colour is retained

􏰀 The outer cell membrane of the Gram negative cell wall is partially destroyed by alcohol, so crystal violet is washed out and a counterstain can be taken
􏰀 Virulence of bacteria depends on certain cell structures

25
Q

What makes up flagella

A

Flagellin

26
Q

Sex Pili is also known as

A

F pili

27
Q

Sub units of pili

A

Pilins

28
Q

Which part of the bacteria has the most antigenic variation

A

The capsule

29
Q

Drugs affecting 50s

A

Chloramphenicol
Macrolides
Clindamycin

30
Q

Drugs affecting 30s subunit

A

Tetracyclines
Aminoglycosides

31
Q

Based on oxygen dependence, bacteria is classified into

A

Obligate aerobes
Facultative aerobes
Microaerophilic eg H. pylori
Obligate anaerobes eg Clostridium, Bacillus

32
Q

Hemolytic pattern

A

Explains how bacteria reacts in blood agar

33
Q

Beta hemolysis
And example

A

Complete hemolysis. The bacterium can lyse of red cells
Clear areas of bacterium in culture

GBS
GAS
Group B & A streptococcus

34
Q

Alpha hemolysis

A

Partially hemolysis of red cell

Green area around the bacteria in culture

Streptococcus viridans

35
Q

Gamma hemolysis

A

Doesn’t lyse the rbc

Eg peptostreptococcus

36
Q

Capsulated Bacteria(and one Fungus)

YES Some Nasty Killers Have Pretty Big Capsules.

A

Y - Yersinia pestis
E - Escherichia coli (Extraintestinal strains)
S - Salmonella typhi
Some - Streptococcus pneumoniae and pyogenes
Nasty - Neisseria meningitidis
Killers - Klebsiella pneumoniae
Have - Haemophilus influenzae
Pretty - Pseudomonas aeruginosa
Big - Bacillus anthracis and Bordetella pertussis
Capsules - Cryptococcus neoformans
Others: Francisella, Brucella, Pasteurella

37
Q

Teichoic acud is present in the cell wall of

A

Gram +ve bacteria

38
Q

Outer cell membrane is present in

A

Gram -ve bacteria

39
Q

H antigens are components of

A

Flagella

40
Q

O antigen are components of

A

Lipopolysaccharide

41
Q

Erythromycin inhibits protein synthesis at

Tetracycline at?

A

50s subunit

30s subunit

FPP Micro (5 decks)

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