Basics of bacteriology

Question 1

Capsule (found in some species)?

Answer 1

Assist with adhesion
Prevents phagocytosis
Reservoir for polysaccharides
Helps the cell not to dry out

Question 2

Cell-wall?

Answer 2

Provides structural support

Protects against physical and chemical effects

Question 3

Cell-membrane (plasma-membrane)?

Answer 3

Separates inside from outside (selective barrier)

Regulates transport in and out of the cell

Question 4

DNA?

Answer 4

Present in a region called nucleoid

Usually a single circular chromosome

Question 5

Plasmids?

Answer 5

Extrachromosomal DNA (usually contains 5-100 genes)
Often encodes advantageous properties (antibiotic-resistance)
Are moved by pili via conjugation

Question 6

Pili (f-pili and p-pili)?

Answer 6

Some pili (fertility-pili) are used to transfer plasmids
Others are used by the bacterium to attach (p-pili)
Shorter than fimbriae

Question 7

Fimbriae?

Answer 7

Attachment

Question 8

Flagella?

Answer 8

Movement

Question 9

Cell-wall?

Answer 9

Provides structural support

Protects against physical and chemical effects

Question 10

Gram-staining?

Answer 10

Primary system of classification
The bacteria are exposed to different dyes
Gram-positive: blue-purple
Gram-negative: pink-red

Question 11

Gram positive?

Answer 11

Thick cell-wall
• 35-40 layers of peptidoglycan

Quite large quantities of teichoic acid (TA)
• Unique sort of polysaccahride
• Maintains structure of the cell-wall
o Attract cations such as Mg2+ och Na+
Lipoteichoic acid (LTA)
• Teichoic acid with a ”lipid-tail” that is
anchored within the cell-membrane

Question 12

Gram negative?

Answer 12

Thin cell-wall
• 1-2 layers of peptidoglycan
Has two membranes
• Inner cytoplasmic membrane
• Bacterial outer-membrane
Structures ”unique” for Gram-negatives
• Porins
• Lipopolysaccharides (LPS)

Question 13

Porins?

Answer 13

Crosses the bacterial outer-membrane
Acts as a pore
• Molecules can diffuse through
• Concentration-gradient is required
Other protein-systems then transport the molecules further

The genes encoding the porin-proteins can mutate
• The permeability changes

Question 14

LPS?

Answer 14

Present in most Gram-negative bacteria
Has a very complex lipid-structure
• Uncommon sugar and fetty-acids

Function
• Increases the negative charge of the cell-membrane
• Stabilizing the membrane-structure
Lipid A (endotoxin)
• Has fatty-acids associated that ”anchor” LPS to the cell-membrane
• Strongly immunogenic

Question 15

Structure cell-wall?

Answer 15

Mainly consists of peptidoglycan

• Polysaccharide that consists of two sugar-derivatives
o N-acetylmuramic acid (NAM)
o N-acetylglucosamine (NAG)

NAMs are ”linked” by short polypeptides

Question 16

Lysozyme?

Answer 16

An enzyme found in e.g. tears, saliva och intestines
• Prevents bacterial infections
• Break glycosidic bonds between
NAG and NAM (hydrolysis)

Gram-negatives often less sensitive than -positives
• Protected by the bacterial outer-membrane

Question 17

Coccus?

Answer 17

(Lat. cocci ≈ ”berry”)

• E.g. Staphylococcus spp. and Streptococcus spp.

Question 18

Bacillus?

Answer 18

(Lat. bacilli ≈ small rod)

• E.g. Bacillus spp.

Question 19

Vibrion?

Answer 19

(spiral, slightly bent)

• E.g. Vibrio cholerae

Question 20

Spirillum?

Answer 20

(spiral, twisted - one or several turns)

• E.g. Campylobacter jejuni

Question 21

Spirochaete?

Answer 21

(spiral, very thin, long and twisted)
• E.g. Borrelia spp.

And pleomorphic (change shape)

Question 22

Diplococcus?

Answer 22

(two and two)

• E.g. Streptococcus pneumoniae

Question 23

Tetrad?

Answer 23

(four and four)

• E.g. Micrococcus luteus

Question 24

Sarcinae?

Answer 24

(eight and eight)

• E.g. Sarcina spp

Question 25

Streptococcus?

Answer 25

(chains) | • E.g. Streptococcus pyogenes

Question 26

Staphylococcus?

Answer 26

(bunches) | • E.g. Staphylococcus aureus

Question 27

Single bacillus?

Answer 27

(one and one) | • E.g. Bacillus cereus

Question 28

Diplobacilli?

Answer 28

(two and two) | • E.g. Moraxella bovis

Question 29

Streptobacilli?

Answer 29

(chains) | • E.g. Streptobacillus moniliformis

Question 30

Palisades?

Answer 30

(picked-fence) | • E.g. Corynebacterium diphtheriae

Question 31

Capsule?

Answer 31

The capsule is glycoproteins firmly attached to cell-wall • Assist with adhesion to surfaces • Prevents phagocytosis from different immune-cells Examples of encapsulated bacteria • Streptococcus pneumoniae • Haemophilus influenzae typ B

Question 32

Slime-layer?

Answer 32

Slime is glycoproteins loosely attached to cell-wall • Assist with adhesion to surfaces • The slime-layer prevents the bacteria from drying out Examples of slime-producing bacteria • Streptococcus spp. o The slime-layer of S. mutans helps the bacteria to adhere the tooth-enamel • Staphylococcus spp. o The slime-layer of S. epidermidis helps the bacteria to survive on the salty hypertonic skin

Question 33

Biofilm?

Answer 33

A natural way for different bacteria to grow Consists of • Bacterial-cells • Polysaccharides • Proteins and nucleic acid ``` Formation • Bacteria adhere to a surface (colonization) • Growth • Production of exopolymers such as EPS • Formation of a biofilm • Other organisms attend • Spread ```

Question 34

Surfaces?

Answer 34

``` Important microbiological habitats • Physical forces • Nutrient-access • Protection • Toxic molecules ```

Question 35

Endospores?

Answer 35

Some Gram-positive bacilli can form endospores ``` Very robust structure • Radiation • Dehydration • Temperature • Starvation • Chemical disinfectants ```

Question 36

Spore-formation?

Answer 36

1. The chromosome is replicated • Aligns alongside the cell 2. The cytoplasmic membrane invaginates • A ”pre-spore” is formed 3. The cytoplasmic membrane grows and engulfs the ”pre-spore” • The DNA of the vegetative cell is dissolved 4. A cortex of calcium and dipicolinic acid is formed between the membranes • Most of the water is removed from the cell 5. A spore-coat is formed around the endospore • Consists for instance of keratin that makes the endospore extremely rough 6. Finally an outer spore-coat is formed • Increases its resistance to heat and different chemicals 7. The endospore is released • The vegetative cells goes through lysis