Microbiology - Outcome 1 Flashcards

1
Q

what are bacteria?

A

prokaryotes

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2
Q

what are prokaryotes?

A

unicellular (single celled) organisms that lack a defined nucleus or other organelles

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3
Q

what are the 2 categories of bacteria?

A

eubacteria and ancient bacteria

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4
Q

what are eubacteria?

A

true bacteria

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5
Q

what are ancient bacteria?

A

they inhabit extreme environments and carry out unusual metabolic reactions

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6
Q

what is the morphology of a bacterial cell?

A

its shape and size

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7
Q

what are the three main groups that bacteria morphology can be divided in to?

A
  • cocci
  • bacilli
  • vibrio and spirillum
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8
Q

what is the shape of a bacterium if it has a cocci shape?

A

spherical or oval

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9
Q

if a bacteria name has the prefix diplo- what would its arrangement look like?

A

it would be in pairs

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10
Q

if a bacteria has the prefix strepto- what would its arrangement look like?

A

it would be in an arrangement of chains

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11
Q

if a bacteria has the prefix staphylo- what would its arrangement be?

A

it would be in an arrangement of clusters

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12
Q

what is the shape of a bacterium if it is rod shaped?

A

bacilli

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13
Q

what is the shape of a bacterium if it is curved or has comma-shaped rods?

A

vibrio

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14
Q

what is the shape of a bacterium if it has thick rigid spirals (in wave shapes)?

A

spirillum

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15
Q

what are the common structural components that all bacteria have?

A
  • a genome (DNA)
  • ribosomes
  • cell membrane
  • cell wall
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16
Q

what is a bacterial cell wall composed of?

A

peptidoglycan

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17
Q

what are the two groups bacteria are divided into based on their reaction to the Gram Stain?

A

gram positive and gram negative

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18
Q

describe a gram positive cell wall

A
  • are thick (20-80 nm)
  • contain several layers of peptidoglycan
  • contain teichoic acids
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19
Q

describe a gram negative cell wall

A
  • are thinner (1-3 cm)
  • contain less peptidoglycan
  • have an outer membrane which surrounds peptidoglycan layer of gram negative cell walls
  • outer membrane contains a unique component called lipopolysaccharide (LPS)
  • LPS is known as an endotoxin - plays a role in infection
  • lipid A is the toxic component of endotoxin
  • the space between the outer membrane and the cell membrane is called the periplasmic space
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20
Q

describe what happens to a gram positive cell wall when it undergoes the gram stain

A

retain purple colour of grams crystal violet dye and so appear purple when viewed under microscope

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21
Q

describe what happens to a gram negative cell wall when it undergoes the gram stain

A

they do not contain crystal violet dye and instead stain the pink colour of the counterstain safranin

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22
Q

what is peptidoglycan and what is its structure?

A
  • a large polymer
  • it has a backbone of alternating sugar molecules known as NAG and NAM
  • it has some short lengths of protein used as cross linkers
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23
Q

what does the cross-linking of proteins in peptidoglycan result in?

A
  • very large peptidoglycan sac whose units are interconnected
  • the sacs are very strong yet also elastic
  • also porous - allows molecules to pass through sturcture
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24
Q

what can peptidoglycan be attacked by?

A

antibiotics and enzymes

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25
Q

how does penicillin attack peptidoglycan?

A

inhibits formation of protein cross linkers, so cell walls are weaker and easily damaged

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26
Q

how does the enzyme lysozyme attack peptidoglycan?

A

cuts sugar backbone of peptidoglycan molecule, so it damages cell wall and lyses bacterial cells (ie kills them)

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27
Q

what cell wall type is more susceptible to damage from enzymes and antibiotics and why?

A

a gram positive cell wall is more susceptible to damage because it contains more peptidoglycan than a gram negative cell wall does

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28
Q

the structure of peptidoglycan in a gram positive wall is similar to that of a gram negative cell wall except what?

A

there is a greater variety of peptide arrangements and cross-linking

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29
Q

what is the function of the cell wall?

A
  • gives bacterial cell shape and provides protection from osmotic lysis
  • pathogenic bacteria have components which contribute to their ability to cause disease ie. pathogenicity
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30
Q

what is the function of teichoic acids?

A
  • gives gram positive cells a negative charge and contributes to they ability to cause the production of antibodies (antigenicity)
  • also aids in attachment of bacterial cells to tissues
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31
Q

what is the function of LPS (endotoxin?)

A
  • confers toxicity
    -determines virulence ie ability to infect body
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32
Q

what us the function of an outer membrane?

A
  • presents outer surface with strong negative charge which helps bacterial cell evade phagocytosis
  • needs to allow passage of nutrients through porins (special protein channels)
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33
Q

what do bacterial cell membranes consist of?

A

mainly of lipids with saturated fatty acids and do not normally contain sterols such as cholesterol

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34
Q

what does the bacterial cell membrane do due to the cell not containing any organelles?

A
  • the cell membrane takes on all the functions for which a double membrane is required in eukaryote cells
  • eg site of respiration and in photosynthetic bacteria it is the site of photosynthesis
  • site of biosynthesis of lipids and cell wall component eg peptidoglycan
  • thought to be involved in coordination of DNA replication during cell division
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35
Q

what does selectively permeable barrier mean?

A
  • regulates the passage of substances into and out of the cell
  • allows free passage of water and small uncharged molecules
    -larger molecules and charged molecules require transport systems
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36
Q

what receptors do bacterial cell membranes contain and what does this allow?

A

they contain receptors which allow the bacterial cell to respond to chemicals in the environment in chemotaxis

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37
Q

what are mesosomes and where are they observed and what is their role?

A
  • in-foldings of the bacterial cell membrane
  • observed in both gram positive and gram negative bacteria
  • they are artefacts
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38
Q

what is the bacterial chromosome?

A

one large circular molecule of DNA which lies free in the cytoplasm in an area called the nucleoid

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39
Q

what are plasmids?

A

smaller, circular extra chromosomal pieces of DNA

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40
Q

what is the genome?

A

the total DNA content of the prokaryotic cell

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41
Q

what are inclusion bodies?

A
  • distinct granules of organic or inorganic material contained in the cytoplasm
  • usually reserve materials
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42
Q

what can some inclusion bodies be?

A

membrane bound vesicles in the cytoplasm containing photosynthetic pigments or enzymes

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43
Q

what are examples of cytoplasmic inclusion bodies and their functions?

A

glycogen granules
- reserve carbon and energy source

gas vesicles
- buoyancy in water

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44
Q

what group of bacteria notably form endospores?

A

gram positive bacteria

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45
Q

what are endospores?

A

highly resistant structures which enable bacteria to survive periods when the environment is hostile to growth eg exhaustion of an essential nutrient

they are NOT reproductive structures

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46
Q

what are flagella and what Is it composed of?

A

filamentous structures composed of the protein flagellin which are attached to the cell surface

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47
Q

what is the function of flagella?

A

to allow a swimming cell movement or motility

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48
Q

how do bacterial flagella move?

A

they rotate like a propeller

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49
Q

what are the 3 structures that a flagellum is composed of?

A
  • the filament
  • the hook
  • the basal body
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50
Q

what is the function of the filament in a flagellum?

A
  • largest part of flagellum
  • extends from the cell surface to the tip of the flagellum
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51
Q

what is the function of the hook in a flagellum?

A

short curved segment linking the basal body to the filament

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52
Q

what is the function of the basal body in a flagellum?

A

anchors the flagellum and is composed of a system of rings

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53
Q

what are the two patterns of flagella distribution in bacteria and how is it determined?

A
  • flagella distributed over the whole surface
  • flagella arising from one or both poles of the cell

the pattern distribution is genetically determined and can be used to distinguish between bacteria

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54
Q

what are pili and what are they composed of?

A
  • short, fine, hair like structures on the surface of bacterial cells
  • shorter and more rigid than flagella
  • composed of proteins called pilins
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55
Q

what are the two types of pili found?

A
  • common pili
  • f pilus
56
Q

what is the function of common pili?

A
  • involved in attachment - in nature usually surfaces as an animals teeth of ships hull
  • determinants of bacterial virulence because they allow pathogenic bacteria to attach to the hosts cell and resist phagocytosis
57
Q

what is the function of f plus?

A
  • only produced in bacterial cells which contain a special plasmid called the f plasmid
  • the f plasmic brings about genetic exchange (mating in bacteria) through a process called conjugation
58
Q

what is a capsule?

A
  • a polysaccharide
  • a well organised layer outside the cell wall which is not easily washed off
59
Q

what are the functions of capsules?

A
  • aid in attachment of bacterial cells to surfaces
  • aids in pathogenicity, protect bacterial cells from engulfment by protozoa and by phagocytosis
  • protect bacterial cells against desiccation (dried)
60
Q

how do bacteria reproduce?

A
  • by an asexual process called binary fission
  • results in the formation of two genetically identical cells from one original cell
  • requires duplication of chromosome
  • cell then elongates
  • plasma membrane pinches inward at centre of cell
    -when nuclear material been evenly distributed, cell wall thickens and grows inward to separate dividing cell.
61
Q

what is the generation time?

A

the interval of time between one division and the next

62
Q

what does binary fission as used by bacteria result in?

A

exponential growth and a growth curve forms

63
Q

what are the phases of bacterial growth?

A
  • lag phase
  • log phase/exponential phase
  • stationary phase
  • death phase
64
Q

describe the lag phase

A
  • little growth occurs because cells re adapting to new environment
  • shock of transfer may kill some organisms, but biochemical activity is intense as they store nutrients, synthesise enzymes and prepare for binary fission
65
Q

describe the lag phase in cold temperatures

A

lag phase is longer due to proteins (enzymes) work more slowly

66
Q

describe the log phase

A
  • stage of active growth
  • rate of growth accelerates until a constant rate of growth is reached and population is in ‘logarithmic’ or ‘exponential’ growth
  • at some point growth will start to decline due to nutrients etc become depleted/ there is an increase of toxic materials
67
Q

describe the log phase in cold temperatures?

A
  • log phase is longer due to proteins (enzymes) work more slowly
  • on growth curve, the log phase is shallower as rate of binary fission is slower
68
Q

describe stationary phase

A
  • growth rate here is zero (cell growth is balanced by cell death)
  • most cells are resting
  • microbial population at its maximum
69
Q

describe death phase?

A
  • number of cells dying is greater than the number of new cells being formed
  • resources have decreased so much the population cannot be retained
70
Q

what are psychrophiles?

A
  • cold-loving bacteria
  • cause food spoilage in fridge
71
Q

what are mesophiles?

A
  • live around room temperature and human body temperature
72
Q

what are thermophiles?

A
  • heat-loving
  • contaminants of dairy produce, can withstand pasteurisation
73
Q

how have psychrophiles adapted?

A
  • accumulate a high concentration of solutes in their cytoplasm to prevent freezing
  • requite proteins that can work more efficiently at low temperatures
74
Q

how have thermophiles adapted?

A
  • have thermostable proteins (do not denature when temperature rises)
  • able to maintain structure of their membrane ie can’t be allowed to become too fluid
  • need to prevent H-bonds holding DNA helix together from destabilising
75
Q

how have acidophiles adapted?

A
  • accumulate H+ ions as H+ ions diffuse into cell from acidic environment
  • H+ ions are actively pumped out to maintain an approx. neutral internal pH
76
Q

how have alkalophiles adapted?

A
  • H+ ions tend to diffuse out of cell (moving down conc. gradient)
  • have to be actively pumped into the cell to maintain an approx. neutral internal pH
77
Q

what would happen if the adaptions to different pHs failed?

A

pH would affect charges on amino acids used to build proteins, can’t form chemical bonds needed to maintain
protein structure and the proteins would denature

78
Q

what are macronutrients and what are they used for?

A
  • major essential nutrients that are required in significant quantities
  • P H S N O C
  • used to synthesise carbohydrates, lipids, proteins and nucleic acids
  • they repair cells and produce new cells
79
Q

what are micronutrients?

A

other trace elements needed in very small amounts
- Mn Co Zn Ni Mb
can usually be obtained in sufficient amounts as contaminants of water

80
Q

what are autotrophs?

A
  • photosynthetic bacteria that typically use CO2 as sole source of cellular carbon
  • CO2 is reduced to form organic cell constituents and energy is required to do this
81
Q

what are heterotrophs?

A

bacteria that obtain carbon largely from organic nutrients ( eg sugars) which enter an energy-yielding metabolic pathway, usually resulting in production of CO2

82
Q

what is glucoses dual role ?

A
  • source of energy
  • source of carbon for the assembly of other molecules
83
Q

what are the 4 groups that micro-organisms can be categorised into depending on oxygen requirements?

A
  • obligate aerobes
  • facultative anaerobes
  • obligate anaerobes
  • microaerophiles
84
Q

describe obligate aerobes

A
  • require oxygen for respiration as oxygen is used as terminal electron chain in ETS
  • without CO2 aerobic respiration can’t occur
85
Q

describe facultative anaerobes

A
  • aerobic bacteria that can respire in absence of oxygen by using alternative terminal electron acceptors such as nitrate or sulphur
86
Q

describe obligate anaerobes

A
  • need an oxygen-free environment
  • find oxygen toxic because they lack enzymes needed to overcome the toxicity problem of ‘free radicals’
87
Q

describe microaerophiles

A
  • grow at optimally low oxygen concentrations
  • use oxygen as the terminal electron acceptor in respiration but find high concentrations of oxygen toxic
88
Q

what are antibacterials?

A

chemicals that are used to inhibit growth of bacteria

89
Q

what does bacteriostatic mean and what are some examples ?

A

prevents the growth of a bacterium
- antibiotics (tetracycline)limit their growth by interfering with cellular processes such as protein synthesis, DNA replication, or other aspects of bacterial cellular metabolism
- chemicals include preservatives such as nitrites/nitrates and also lactic acid, used to prevent microbes in food from reproducing and causing food spoilage.

90
Q

what does bacteriocidal mean and what are some examples?

A

kills bacteria
- chlorine-based disinfectants kill off original population of bacteria
- antibiotics (penicillin) inhibit cell wall synthesis

91
Q

what must the environment provide for a bacterium to survive?

A
  • essential nutrients
  • optimal physical conditions
  • absent of any bacterial agents
92
Q

which parts of the body are populated by various microbial species and which parts ARE NOT?

A
  • surface tissues eg skin and mucous membranes are populated
  • internal tissues (organs, blood, muscle etc..) are free of micro-organisms
93
Q

what is normal flora?

A

a population of micro-organisms that infect the body without necessarily causing disease.

94
Q

what is microbial antagonism and how does it work?

A
  • involves competition between micro-organisms
  • they benefit the host by preventing the overgrowth of harmful organisms
  • normal flora use all available space and nutrients, which stop more dangerous pathogenic microbes from becoming established
95
Q

what happens if the balance of normal flora becomes unbalanced and what is an example of this and what causes it?

A
  • disease can occur
  • in human vagina - normal flora of bacteria (Lactobacilli)
  • Lactobacilli maintains a pH of 3.5-4.5 and inhibits growth of yeast Candida albicans (cannot grow in acidic conditions)
  • antibiotics kill off ‘friendly’ bacteria causing pH to become neutral, causes increase in C. albicans and causes thrush
96
Q

what is symbiosis?

A

the relationship between the body and its normal flora

97
Q

what is mutualism?

A

the symbiosis is beneficial to both the body and the micro-organisms (+/+)

98
Q

what is an example of mutualism?

A

lactobacillus living in human vagina
- derives nutrients from environment
- produces acid to prevent overgrowth of other organisms

99
Q

what is commensalism?

A

the symbiosis is only beneficial to the micro-organisms and the body gains no effect (+/0)

100
Q

what is an example of commensalism?

A

aerobic bacteria Staphylococcus epidermis
- lives on conjunctiva of eye
- no benefit to humans as well as no harm

101
Q

describe the bacterial populations on the skin

A
  • Staphylococcus and Propionibacterium acnes ( P. acnes)
  • skin is not favourable environment due to lack of moisture, salt from sweat and acidic pH of skin
  • moister areas of skin tend to have largest microbial populations
102
Q

describe the bacterial populations on the oral cavity

A
  • Streptococci (capsule) species of bacteria found here
  • availability of moisture, nutrients, suitable pH and temperature ideal for colonisation.
  • microbes found in mouth will be aerobes and facultative aerobes within hours of birth
  • once teeth emerge, anaerobes become established due to nature of gingival groove
  • as teeth grow - various streptococci species attach to enamel using their capsules and adherence factors.
  • this contributes to formation of plaque, tooth decay and gum disease
103
Q

describe the bacterial populations of the large intestine (colon)

A
  • colon has largest microbial population in the body
  • majority of microbes recorded here are anaerobic
  • main component is gram negative, such as E. coli
104
Q

plants can form close symbiotic associations with microbes to what?

A

fix nitrogen

105
Q

what is an example of plants forming symbiotic association with microbes?

A
  • Rhizobium can establish a symbiotic relationship with legumes (peas, clover etc..)
  • fix atmospheric nitrogen for use by the plant
  • bacterium encodes large plasmid that is not used when it grows as a free-living organism in soil
  • vital for infection of susceptible host plant
  • bacterium infects root hairs and causes ‘nodules’ to form
  • nodules reduce nitrogen gas to ammonia and other nitrogen-containing compounds
106
Q

what is the equation for nitrogen fixation?

A

N2(g) –> NH3 / NH4+

107
Q

what are bacteria and fungi principal decomposers of and what are they responsible for?

A
  • decomposers of plant liter and animal carcasses
  • responsible for nutrient recycling within soil - contribute to soil fertility
108
Q

how do autotrophs (including photosynthetic cyanobacteria) fix and corporate CO2 into organic matter?

A

by using energy from sunlight

109
Q

what happens to organic compounds (CO2) of autotrophs when they are eaten by larger microbes and then they in turn are eaten by other animals?

A

the organic compounds are digested and resynthesised

110
Q

what form of nitrogen do higher plants utilise?

A

NO3- (nitrates) and NH4+ (ammonium)

111
Q

how do microorganisms obtain sources of nitrogen?

A

vary their nitrogen source
- NO2- (nitrite)
- NO3-
- NH4+
- N2
- organic nitrogen

112
Q

what determines the microbial population in a natural body of water?

A

by the physical and chemical conditions which are present

113
Q

what conditions impair the microbial life in water?

A
  • temperature
  • salt levels
  • light levels
  • oxygen concentrations
114
Q

what is the biggest population of bacteria found in water?

A

psychrophiles - some include photosynthetic cyanobacteria like anabaena species

115
Q

what are some examples of pathogenic microbes that can be found in water?

A
  • vibrio cholerae
  • salmonella thyphi
116
Q

how do UK domestic water supplies prevent water contamination?

A

by physically separating water supplies from the sewage supplies and the water is filtered and chlorinated to removed any pathogens

117
Q

what is a transient population?

A

where bacteria will be added and removed from the original location

118
Q

what bacterial species is directly beneficial to humans and what are the benefits of it?

A

E. coli in the human gut
- gains nutrients moisture and warmth
- produces vitamin K needed for blood clotting
(mutualism)

119
Q

what are some bacterial species that is beneficial to humans outside of the body and how do they work?

A
  • Streptococcus lactis and lactobacillus are used in cheese manufacture
  • lactobacillus bulgaricus is used in yoghurt manufacture
  • bacteria convert the sugar (lactose) in milk into lactic acid, causes milk proteins to denature and milk to curdle and thicken
120
Q

what are examples of bacteria being genetically engineered to produce valuable chemicals?

A
  • E. coli and lactobacillus have been engineered to produce large quantities of phenylalanine which is used in diet drinks
  • microbes have been genetically engineered to produce human insulin and human growth hormone (hGH)
  • insulin - E. coli given copy of human insulin gene, makes human insulin hormone - process carried out in yeast (fungi)
  • hGH- previous source was cadavers, now fungi is used
121
Q

how does tetanus affect the body?

A
  • C. tetani spores excreted in faeces to soil
  • when spores enter wound they revert back to vegetative bacilli that produce several toxins - tetanospasmin
  • this toxin acts at synapses inhibiting the removal of acetylcholine (Act) by interfering with cholinesterase, enzyme which normally breaks down Ach
  • with Ach left over in the synapse, synaptic impulses arise causing muscles to contract
  • toxin provides sustained and uncontrolled muscle contractions of muscles and spasms throughout body
122
Q

what is tetanus caused by?

A

Clostridium tetani - gram positive, anaerobic spore-former found in intestines of many animals

123
Q

what is anthrax caused by?

A

bacillus anthracis - gram negative, spore-forming rod
- spores germinate rapidly on contact with human tissues and the bacterial cells produce toxins which account for most of the damage done by this bacterium

124
Q

what are the three ways humans acquire anthrax?

A
  • working with animal hides, leads to inhalation of spores and pulmonary anthrax
  • consumption of contaminated meat, intestinal anthrax
  • contact with spores from soil, anthrax of skin ie cutaneous anthrax
125
Q

how does pulmonary anthrax affect the body?

A

involves haemorrhaging and severe blood infection and is usually fatal

126
Q

how does intestinal anthrax affect the body?

A
  • involves acute inflammation of intestinal tract
  • initial signs of nausea, loss of appetite, vomiting, fever followed by abdominal pain vomiting blood and diarrhoea
127
Q

how does cutaneous anthrax affect the body?

A
  • begins as a raised itchy bump that resembles insect bite, develops into painless ulcer
  • lymph glands in adjacent area may also swell
128
Q

what causes typhoid fever?

A

salmonella typhi - gram negative rod which is highly resistant to environmental conditions outside body
- acid resistant - can survive low pH of stomach

129
Q

how does typhoid fever affect the body?

A
  • invades tissues of small intestine causing deep ulcers and bloody stools
  • enters bloodstream an patient displays symptoms of increasing fever, lethargy and delirium
  • appearance of rose spots on abdomen indicates that blood is haemorrhaging in skin
  • bowel perforation and gall bladder infection may also occur
130
Q

how can typhoid fever be treated but what may happen to some individuals who do recover?

A

use of antibiotics - chloramphenicol
however some patients who recover continue to harbour and shed organisms for years and such individuals are termed carriers

131
Q

what is cholera caused by?

A

vibrio cholerae - gram negative bacterium

132
Q

how does cholera affect the body?

A
  • the bacteria enters intestinal tract in contaminated water or food
  • susceptible to stomach acid, if ingested in sufficient numbers, enough will remain and colonise intestine
  • secrete enterotoxin that stimulates a massive loss of fluid
133
Q

what are symptoms of cholera?

A
  • colourless watery stools
  • wrinkling of skin
  • sunken eyes
  • muscular cramps
  • thickening of blood
  • urine production ceases
  • shock and coma
134
Q

how can cholera be treated?

A
  • antibiotics - tetracycline - only kills bacteria
  • replenishing of body fluids must be replaced by IV injection of salt solutions, consumption of glucose and salts or consumption of an oral rehydration solution (ORS)
135
Q

what are opportunistic pathogens?

A

bacteria that do not usually cause disease in their normal habitat in a healthy person but which become pathogenic when they enter other habitats through broken skin, mucuous membrane

136
Q

what is meant by an indirect detrimental effect of bacteria on humans and what is an example of this?

A
  • indirect effects would be plant and animal diseases caused by bacteria that are not only a concern in terms of their possible impact on food safety but also on their economic impact if animals and crops have to be destroyed
  • and example of this is Agrobacterium tumefaciens - causes crown gall tumours in plants.
  • no direct effect to humans as not transmissible to humans yet commercial tree growers couldn’t sell trees with infection due to unattractive appearance