Bacteria

Question 1

What shapes can bacteria be?

Answer 1

‣ Coccus (spheres) – strep: spheres in chains, staph: in clusters

‣ Bacillus (rods)

‣ Spirillum (spirals)

Question 2

What colour is the staining of gram positive bacteria by crystal violet?

Answer 2

Stain BLUE by gram staining – large amounts of PEPTIDOGLYCAN (polysaccharide) in cell walls. Have no outer membrane.

Question 3

What colour is gram negative bacteria when stained with cystal violet and why?

Answer 3

Stain PINK. Only thin layer of peptidoglycan in walls and have an outer membrane that prevents stain penetrating. Has outer membrane.

Question 4

Define aerobic bactera

Answer 4

Bacteria that can survive in an oxygenated environment

Question 5

Define facultative anaerobic organism

Answer 5

organism that can make ATP by aerobic respiration is O2 present but can switch to anaerobic

Question 6

Define obligate aerobes

Answer 6

NEED oxygen to grow

Question 7

Define antimicrobial

Answer 7

A substance which KILLS/INHIBITS bacterial growth. Synthetic molecules that interfere with microbial cell functions

Question 8

Define antibotics

Answer 8

Also KILLS/INHIBITS bacterial growth. Agents are derived from a microorganism (blurred distinction between antimicrobial)

Question 9

What is a disinfectant?

Answer 9

An antimicrobial applied to NON-LIVING MATERIAL to destroy microorganisms (Dettol spray)

Question 10

Define antiseptic

Answer 10

An antimicrobial applied to NON-LIVING MATERIAL to destroy microorganisms (Dettol spray)

Question 11

Define bactericidal

Answer 11

KILLS BACTERIA. (or viricidal/fungicidal)

Question 12

Define bacteriostatic

Answer 12

INHIBITS BACTERIA. Antimicrobials can be bacteriostatic and bactericidal at diff levels

Question 13

Define exogenous bacteria

Answer 13

Introduced to closed BIOLOGICAL SYSTEMS from external world via inhalation, consumption or cutaneous transmission. Exist in aquatic environments/atmosphere

aquatic (waterborne) Cholera ‣ Saprophytic (via soil) ‣ Zoonotic (food/drink)

Question 14

Define endogenous bacteria

Answer 14

Endogenous bacteria – Naturally reside in a closed system (internal)

‣ e.g. E.coli of GIT enters urinary tract or normal flora of skin entering wound

Question 15

Define virulence

Answer 15

Ability to cause disease (surface associated – flagella ,pili – or extracellular toxins)

Question 16

What is commensalism?

Answer 16

bacterium benefits host and is neither harmed nor helped

‣ e.g. Staphlococcus/Micrococcus on human skin

Question 17

What is symbiosis?

Answer 17

bacterium and host BOTH BENEFIT ‣ e.g. harmless oral bacteria preventing Candida albicans colonisation thus preventing a candida infection - thrush

Question 18

What is parasitism?

Answer 18

‣ bacterium benefits, HOST IS HARMED ‣ e.g. Neisseria gonorrhoeae causing gonorrhoea

Question 19

Describe streptococcus bacterium’s structure, class and role in disease

Answer 19

‣ Facultative anaerobic cocci. Produce energy via anaerobic glycolysis. Gram positive

‣ Occurs in chains or pairs

‣ Produce lactic acid. Like pH 5.5.

‣ S. mutans - the pioneer species associated with smooth surface caries and endocarditis. Appear after tooth eruption due to new hard surface habitats. Convert SUCROSE into glucose and fructose, or use other sugars to produce lactic acid.

‣ S. sanguis – can also colonise heart valves – bacterial endocarditis

‣ S. salivarius – soon colonise oral cavity of newborn

‣ Glycosyltransferases– an enzyme induced by streptococci. Convert sucrose into sticky polysaccharide fructose. Fructose and glucose are adhesives.

Question 20

What type of respiration does actinomyces engage in?

What disease is this bacterium associated with?

Answer 20

Faculatative anaerobe

Root caries

Question 21

What type of respiration does lactobacilli engage in?

What disease are they associated with?

Answer 21

Facultative anaerobic

Poduce lactic acid - dental caries

Question 22

Is staphyloccus gram negative or positive?

What type of respiration does this organism engage in?

Answer 22

Positive

Facultative anaerobe

Question 23

What gram negative bacteria are in the mouth and what diseases are they associated with?

Answer 23

• Porphyromonas

‣ P.gingivalis – subgingival. major periodontal pathogen ‣ SUBGINGIVAL BACTERIA ARE ANAEROBES, ASACCHAROLYTIC ARE PROTEOLYTIC – conditions suit them.

• Prevotella

‣ P.intermedia (prevotella intermedia) -> periodonatal disease/ abscess/gingivitis (acute necrotising)

• Actinobacillus

‣ A. ACTINOMYCETEMCOMITANS – AGGRESSIVE PERIODONTITIS ‣ Peptidases and proteinases promote sub-gingival assachrolytic species

• Veilonella

‣ Converts acidic products to less acidic (specifically lactate into weaker acids) ‣ Very common bacteria in mouth along with streptococci