Bacteria: Structure, Growth and Taxonomy

Question 1

What are bacteria

Answer 1

Unicellular microorganisms; can be free living or host dependent

In Protista kingdom

Question 2

Monera vs Protists

Answer 2

Monera:
Prokaryotes, Unpaired chromosome, no nucleus
Archaebacteria; Eubacteria

Protists: Eukaryotes, Paired chromosome, nuclear structure
Protozoa; Algae

Question 3

What is bacterial cell wall made of

Answer 3

Peptidoglycan

Question 4

Where is flagellum of bacteria anchored

Answer 4

Cytoplasmic membrane

Question 5

Pili

Answer 5

Hair like protrusions on bacteria that allow for their adhesion and preventing them being flushed away

Also called fimbriae

Made of pilin protein

Question 6

Answer 6

Question 7

Where is energy produced in prokaryotes

Answer 7

In their inner membrane

Question 8

Phenotypic Charactersitics to distinguish bacteria

Answer 8

Morphology
Biotyping - biochemical tests e.g. sugar fermentation rates/abilities
Antibiogram Patters

Question 9

Genotypic Characteristics to distinguish bacteria

Answer 9

%G+C Ratios
DNA Hybridisation (see if specified probe binds to certain region)
Chromosomal DNA fragment analysis
Ribotyping (comparing ribosomal DNA genes of bacteria)
MALTI - TOF mass spectrometry (something laser something - time of flight); mass to charge ratio

Question 10

Gram Stain

Answer 10

Differentiates bacteria on basis of their cell wall structure
First line test in diagnosis of bacterial infections
Can show shape and size of bacteria; may be definitive for particular bacterium genus
Allows empircal antibiotic treatment

Question 11

What do gram positive and gram negative reactions indicate

Answer 11

Gram Positive - Thick Cell Wall

Gram Negative - Thin Cell Wall

Question 12

How does gram staining work

Answer 12

Fix sample to slide

Stain everything in crystal violet dye

Flood sample with gram’s iodine which fixes crystal violet into peptidoglycan

Add decolouriser (alcohol/acetone) which removes violet from thin cell wall of gram - but not gram +

Flood with secondary dye to colour gram negative but gram + would stay violet

Question 13

What is the gram reaction of E coli

Answer 13

Gram Negative Bacillus

Question 14

Answer 14

Question 15

Which type of gram bacteria is more susceptible to penicillin and lysozyme

Answer 15

Gram +ve more susceptible to penicillin; gram +ve is sensitive to lysozyme but -ve isnt at all

Question 16

Lipopolysaccharide (LPS)

Answer 16

Basically just a complicated molecule on the outer membrane of gram -ve bacteria; is an endotoxin so can be shed and prompt an immune response

Question 17

Functions of bacterial cell wall

Answer 17

Maintains rigidity and cell shape/structure (meshlike exoskeleton)
Maintains osmolarity
Survival (interacts with host membranes)
Cell Division (cross-wall separating 2 daughter cells)

Question 18

Where can the rare d isomeric form of amino acids be found in nature

Answer 18

In bacterial cell walls

Question 19

Describe bacterial cell wall structure

Answer 19

Alternating disaccharide backbone (N-acetylglucosamine [NAG] and N-acetylmuramic acid [NAM])
Linked to the NAM is a stem peptide made of 5 amino acids
Adjacent stem peptides are linked via a transpeptidase enzyme (penicillin binding protein)

Question 20

Describe role of penicillins & cephalosporins; and also vancomycin

Answer 20

penicillins & cephalosporins binds to PBP and prevents cross bridging in cell walls
Vancomycin breaks connevtion to last D-alanine on stem peptide and prevents cross bridges

Question 21

How is bacterial cell wall synthesised

Answer 21

Peptidoglycan precursor (containing 1 NAM, 1 NAP and 1 stem peptide) synthesised inside the cell and exported across cell membrane (prevented by bacitracin)
Site is created by enzymic action (PBP)
(A bit more)
Cell grows

Question 22

Describe TB cell wall

Answer 22

Modified peptidoglycan layer
Covalently attached to arabinogalactan polymer
Contain mycolic acid waxy coat which causes its virulence
Poor gram stain

Question 23

Mycoplasma

Answer 23

bacteria that have no cell wall with slightly different cell membrane containing steroids

Question 24

Describe features of bacterial cell membrane

Answer 24

Lipid bilayer so hydrophobic
No steroids except in mycoplasmas
Involved in ion transport and energy production
Involved in developing mesosome

Question 25

Spores

Answer 25

Features of bacteria that allow them to survive in adverse conditions like heat or starvation; when they leave such conditions idk they get better? Can be bulging or inside; in the middle or in the end

Question 26

Bacterial Capsules

Answer 26

Protect against phagocytosis that can be in both gram +ve and -ve Gelatinous material from polysaccharides/polypeptides

Question 27

Flagella Distribution in bacteria

Answer 27

Can be 1-20; if 1 then usually in poles but if 20 can be all around Made of flagellin protein (similar to myosin)

Question 28

Facultative Anaerobes

Answer 28

Bacteria that can grow in both the presence or absence of oxygen (can use other ions as terminal electron acceptor in etc)

Question 29

Factors affecting bacterial growth

Answer 29

``` Oxygen Temperature Water pH Light (prefer to be in the dark) Osmolarity ``` OTWpLO On The Way; please look out

Question 30

Polymyxin

Answer 30

Antibiotic that punches holes in bacterial outer membranes (gram -ve)

Question 31

Gentamicin/Tetracyclines

Answer 31

Antibiotics that bind to bacterial ribosome and prevent function

Question 32

Virulence factors of bacteria

Answer 32

Gram -ve: LPS shedding that causes inflammatory response and releases cytokines and activates complement cascade; body response and potentially septic shot as body shuts down Gram +ve Teichoic acid and lipteichoic acid; similar to LPS Surface proteins (afimbrial adhesins) e.g. protein F that binds to a protein and causes a condition called strep throat