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BIO 121 > Key stuff - Bacteria > Flashcards

Key stuff - Bacteria Flashcards

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Biology 101 flashcards
1
Q

Bacterial cell clusters: names with examples.

A

diplococci - Neisseria meningitides

streptococci - Streptococcus pneumonia

clump of cocci - Staphylococcus aureus.

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2
Q

Gram-positive cell wall

A

Almost 90% peptidoglycan - thick layer.

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3
Q

Gram-negative cell wall

A

Consists of a thin layer of peptidoglycan surrounded by an outer membrane. Outer membrane composed of lipids, proteins, and lipopolysaccharide (LPS).

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4
Q

Peptidoglycan only found in Bacteria and makes up their cell wall. What is it’s structure?

A

Made up of G-M bonds, with chains linked via peptide bridges.

G = N-Acetylglucosamine

M = N-Acetylmuramic acid

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5
Q

Fimbriae (singular = fimbria) - Bacteria

A

short, thin, hair-like, proteinaceous appendages (up to 1,000/cell)

recognition and attachment to surfaces

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6
Q

Pili (s., pilus; sometimes called sex pili) - Bacteria

A

similar to fimbriae except longer, thicker, and less numerous (1-10/cell), required for mating

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7
Q

polar flagellum

A

flagellum at end of cell

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8
Q

monotrichous

A

one flagellum

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9
Q

amphitrichous

A

one flagellum at each end of cell

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10
Q

lophotrichous

A

cluster of flagella at one or both ends

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11
Q

peritrichous

A

spread over entire surface of cell

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12
Q

Plasmids

A

Usually small, closed circular DNA molecules

Exist and replicate independently of
chromosome

Not required for growth and reproduction

May carry genes that confer selective advantage (e.g., drug resistance)

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13
Q

Cellular inclusions

A

Granules of organic or inorganic material that are reserved for future use.

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14
Q

Cellular inclusions - Specialist bacteria with magnetosomes

A

Contain iron in the form of magnetite

Use is to orient cells in magnetic fields

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15
Q

Cellular inclusions
 - Gas vesicles

A

Used for buoyancy in some aquatic bacteria.

Eg. Cyanobacteria that perform photosynthesis and need sunlight.

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16
Q

Endosprores

A

made by some gram-positive bacteria.

Can survive for hundreds or even thousands of years
- produced under unfavourable conditions; perhaps when cells run out of nutrients.

Highly resistant to heat, drying, radiation, & chemicals very low water content.

Contain calcium dipicolinate – binds free water and helps dehydrate cell

Special proteins protect DNA

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17
Q

How to bacteria acquire iron.

A

not readily available so have proteins which strip out iron from blood.

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18
Q

Chemically defined media

A

exact chemical composition is known.

if you want specific strains/species.

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19
Q

Complex media

A

exact chemical composition not known.

Whole range of species will grow.

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20
Q

How do we grow in lab?

A

Solid culture meda : Nutrient agar plates.

inoculating loops physically drag cells across agar and this separates them so individual cells can be counted, essentially serial diluting.

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21
Q

microbiology growth.

A

increase in cell numbers

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22
Q

Bacterial generation time

A

Time needed for a population to double = doubling time= generation time.

different strains have different doubling times.

E.coli - 20 mins at 37degrees.

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23
Q

Exponential growth

A

growth with a constant doubling time.

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24
Q

Batch culture

A

culture grown in ‘closed system’

no additional nutrients added and no bacterial waste products removed during the culture period.

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25
Q

Typical growth curve for a bacterial population.

A

Lag phase: Time interval between inoculation and maximal division rate:
Cells adjust to new environment.

Log (exponential phase): Bacteria grow exponentially:
-Constant doubling time
-Growth rate is maximal

Stationary phase: Bacteria can no longer reproduce but are still alive
(e.g., no nutrients left or growth inhibited by bacterial products)

Death (decline) phase: Bacteria die.

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26
Q

Culturable bacteria

A

can be grown on media (liquid/solid).

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27
Q

Viable but nonculturable bacteria.

A

in a state of low metabolic activity and do not divide but are alive and have the ability to become cultural once resuscitated.

Or they can’t grow on conventional media (e.g Legionella pneumophila)

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28
Q

Total count:

A

Non-specific dye that stains all bacteria - (culturable, viable and VBNC and in many cases dead cells)

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29
Q

Viable count:

A

uses fluorescent activity dyes

counts all cells (cultural, viable and VBNC) with activity (e.g. enzymatic, active membranes etc).

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30
Q

Culturable count:

A

counts cells that can form colonies on solid media or increase turbidity in liquid media.

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31
Q

Direct: Microscopic Count

A

easy and fast

uses special microscope counting slide

does not differentiate between live and dead bacteria.

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32
Q

DAPI

A

general stain

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33
Q

Acridine orange

A

general stain, binds to cell walls.

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34
Q

Measuring bacterial growth using agar plates

A

Counting colony so is a culturable count, assuming each culturable cell will grow and divide to yield one colony.

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35
Q

Measuring bacterial growth via serial dilution.

A

To obtain appropriate colony numbers so individual cells or colonies can be counted.

36
Q

Vibrio Cholerae

A

infects intestine and causes cholera.

In Africa villages reduced cholera by using their safe as a filter to pour water. into a collection vessel. Physical barrier as the bacteria are associated to zooplankton by attaching to chitin.

Can boil water to kill off the bacteria.

37
Q

Indirect measurement of bacterial growth.

A

Spectophotometer for turbidity of bacterial growth - cells scatter light passing through the suspension.

38
Q

Bacteriostatic antimicrobial agent.

A

Total and viable/culturable cell count stays the same but bacteria are stopped in tracks. Growth can continue once agent wears off.

39
Q

Bacteriocidal antimicrobial agent.

A

Total cell count remains same but viable/culturable count decreases. Killed but still intact.

40
Q

Bacteriolytic antimicrobial agents.

A

Both cell counts decrease. Cells killed and falls apart.

41
Q

Heterotrophs

A

require organic molecules made by other organisms.

42
Q

Autotrophs

A

CO2 is a principal carbon source.

43
Q

Phototrophs

A

use light as energy source.

44
Q

Chemotrophs

A

oxidise organic or inorganic compounds.

45
Q

Obligate aerobes

A

Needs O2 for growth.

46
Q

Obligate anaerobes

A

Cannot grow in presence of O2

47
Q

Facultative anaerobes

A

Can grow with and without O2.

48
Q

Aerotolerant anaerobes

A

Do not need O2, but tolerate it

49
Q

Microaero-phillic

A

Need O2, but tolerate it only at a low concentration.

50
Q

Psychrophiles

A

grow best below 15degrees

don’t grow above 20degrees

can grow below 0degrees

51
Q

Mesophiles

A

grow best between 20-40degrees

many bacteria in our body are mesophiles.

52
Q

Thermophiles

A

grow best between 45-80degrees

live in hot springs, compost heaps etc.

53
Q

Hyperthermophiles

A

grow best above 80degrees

live in hot springs.

54
Q

Acidophiles

A

grow best in acidic habitats

55
Q

Alkaliphiles

A

grow best in alkaline habitats

56
Q

Halophiles

A

grow in habitats with high salt concentration.

57
Q

How many bacteria live in and on our body?

A

10^14

10^12 in gut helping with immune system.

58
Q

Host

A

organism which supports growth of viruses, bacteria and parasites.

59
Q

Pathogen

A

organism that causes disease, by impairing or interfering with the normal physiological activities of the host.

60
Q

Pathogenicity

A

the ability to cause disease

61
Q

Virulence

A

the degree or intensity of pathogenicity (determined by toxicity and invasiveness).

62
Q

Infection

A

bacteria persist in host without necessarily causing tissue damage.

63
Q

disease

A

overt damage to the host, parts of body cannot fulfil their normal functions.

64
Q

Dr. William Farr

A

prominent supporter of the miasma theory. Convinced that cholera was transmitted by air.

65
Q

Robert Koch (1843-1910)

A

Koch’s lab established germ theory of disease.

Formulated criteria for proving that a specific microorganism causes diseases: “Koch’s Postulates”

Developed simple methods for obtaining bacteria in pure culture

66
Q

Filippo Pacini

A

a Italian physicist, first discovered cholera.

67
Q

Koch’s postulates.

A

Key concepts:

a specific infectious disease is caused by a specific microbe.

determine aetiology (cause) of disease, first step in treatment and prevention.

Microbiologists used these steps to identify causes of emerging diseases.

68
Q

Opportunistic pathogens

A

only cause serious disease when host defences are impaired.

69
Q

Primary pathogens (Obligate)

A

Capable of causing disease in absence of immune defects.

Need to cause disease to survive.

70
Q

colonisation

A

establishment of a stable population of bacteria in the host.

pathogen must be able to compete successfully for nutrients and surface attachment sites.

71
Q

Association

A

involves non-specific forces. (e.g charge and hydrophobicity)

72
Q

Adhesion

A

Involves specific bacterial adhesions and host receptors.

73
Q

biofilm

A

clump of bacteria, can be mixed or monoculture.

74
Q

Adhesins

A

Fimbriaae and pili
Capsules and slime layers
Flagella (in some species)
(lipo)trichroic acids (Gram-positives)

75
Q

Host receptors

A

Blood group antigens
Extracellular matrix proteins e.g fibronectin, collagen.

76
Q

Barriers to colonisation or infection.

A

Eyes: Lysozyme dissolves cell walls

Skin: physical barrier produces antimicrobials normal flora inhibits pathogens,

Normal flora competes with pathogen.

Mucus in lungs and trachea prevent colonisation.

Stomach pH inhibits or kills bacteria

Flushing of urinary tract prevents colonisation.

77
Q

Lytic compounds that attack host tissue:

A

collagenase, phospholipase, haemolysins

78
Q

Bacterial avoidance of phagocytosis:

A

bacteria produce structures preventing effective contact: capsules, special surface proteins.

survival inside phagocytic cells: often by very pathogenic bacteria: they can escape one of the most effective defences.

some can burst macrophages e.g legionella.

79
Q

Avoidance of antibodies

A

Capsules (sometimes not immunogenic because they resemble host structures)

Antigenic variation: bacteria can switch between different types of a surface structure

e.g streptococcus pneumoniae can make over 50 capsule variants.

Sometimes degration of antibodies.

Capsules can prevent compliment activation.

Lipopolysaccharides (gram-negatives) sometimes hinder pore formation.

80
Q

Nutrient acquisition Iron uptake.

A

Tissues:free iron levels are below that required to support bacterial growth.

Bacteria express high affinity iron uptake systems.

  1. Siderophores : bind iron with high affinity
  2. Direct binding of iron transport proteins. e.g transferrin.
81
Q

Bacterial toxins

A

Exotoxins - act on specific targets (e.g protein synthesis)

Endotoxin (LPS): bound to cell
action is indirect: activates many host systems that cause damage.

82
Q

Exotoxins

A

Made by Gram + and -ve

Protein

secreted by living bacteria

usually heat labile

highly immunogenic (very easily cause a immune response.)

potentially lethal

83
Q

Endotoxin

A

Made by Gram-ve

LPS (liopolysaccharide)

Part of cell membrane,

released on cell lysis.

usually heat stable

weakly immunogenic

lethal at higher concentrations.

84
Q

Tetanus toxin (exotoxin)

A

a neurotoxin, interferes with synapse function

85
Q

Diphtheria toxin (exotoxin)

A

inhibits mammalian protein synthesis.
-Diphtheria has a mortality of up to 20% in very young/old.

86
Q

Endotoxin structure

A

0-specific polysaccharide connected to core polysaccharide connected to lipid A.

-Lipid A part has endotoxin activity.

-Activates many host systems that cause damage, leading to fever; shock; blood coagulation; inflammation.

-Core polysaccharide is variable.

87
Q
A

BIO 121 (7 decks)

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