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MICR222 > Water Microbiology And Public Health > Flashcards

Water Microbiology And Public Health Flashcards

1
Q

Different freshwater habitats

A

Groundwater (aquifiers) and surface water (rivers, lakes and reservoirs)

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2
Q

Nutrient definition of freshwaters

A

Oligotrophic (low in nutrients)
Compare to mesotrophic (medium nutrients) and eutrophic (high in nutrients)

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3
Q

Microbes that live in freshwater

A

Allochthonous (not usually found in the habitat eg microbes from surrounding soil- gram +ve as need protection)
Autochthanous (usually found there)
Motile, aerobic gram negative rods
Mostly at surface level

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4
Q

Why are microbes in freshwater gram negative (tend to be)

A

Water body supports the microbe so doesnt need thick cell wall
A thick wall could be detrimental and hinder the microbe’s movement through the environment

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5
Q

Formation and features of an aquifier

A

Water from rain goes through soil= takes out impurities and many nutrients (filter)
Water lands on an impermeable surface eg rock
The environment around the water acts as a selection pressure on the microbes that can live in the aquifier
When contaminated, difficult to treat and takes a lot of time to get back to being drinkable
~1/3 NZ have nitrate (due to human activity)
~20% NZ have faecal matter (due to human activity)

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6
Q

Features of rivers for microbe inhabitance

A

Usually shallow and constantly moving/ flowing= oxygenated
Oligotrophic but this can vary- if good nutrients then microbes there will be like soil microbes from surrounding soil (as soil has high nutrients), clean rivers with essentially no nutrients will have low microbial numbers
Microbes attach to surfaces such as rocks in rivers (making slippery) so they get nutrients from the water flowing over the top of them

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7
Q

7 variables for grading rivers

A

Turbidity
Dissolved oxygen
Total phosphorus
Total nitrogen
Nitrate/ nitrite ratio
Dissolved phosphorus
E.coli levels

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8
Q

Where does river pollution come from

A

Natural- native bush debris and leaves
Agricultural- use of the nearby land, use pesticides and fertilizers= high N
Industrial- need consent to dump into a river
Urban- storm waters= microbes, rubbish and oil

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9
Q

Three things a lake needs to become stratified

A

Be in a temperate zone (arctic to tropic of cancer and tropic of capricorn to antarctica)
Occur in summer- sun warms top layer which is less dense and light winds dont disrupt this
Greater than 10m depth

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10
Q

What happens in a stratified lake

A

Top= epilimnion which is warm from the sun and contains oxygenic photosynthetic bacteria
Zone of transition= metalimnion which contains anoxygenic photosynthetic bacteris from the angle the sun hits, gets this deep for photosynthesis- zone of rapid change for O2 and temp
Bottom= hypolimnion which is cold and has microbes which perform anaerobic fermentation, sulphate reduction and methanogenesis= methane released and exits top out bubbles and H2S also released which stays at the bottom

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11
Q

Oxygen in lakes

A

Oxygen has low solubility in water (0.07%). Amount of oxygen decreased with increasing depth

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12
Q

Leibig’s law of the minimum

A

Total biomass of an organism will be determined by the nutrient present in the lowest concentration relative to the organism’s requirements (in oligotrophic waters)

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13
Q

Shelfords law of tolerance

A

There are limits to environmental factors below and above which a microorganism cannot survive and grow, regardless of the nutrient supply eg temp, pH and O2 levels

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14
Q

What does eutrophication lead to

A

Increased organic material (N and P)
Increased oxidation by decomposers
Decreased oxygen
Leads to anoxic conditions and the production of toxic products by anaerobes proliferating such as amines, hydrogen sulfate

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15
Q

Why is a river able to go back to normal oxygen levels when they have been depleted by eutrophication

A

Because it is flowing and becomes more oxygenated as it moves

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16
Q

Why do shallower lakes have more issue with eutrophication

A

They are not deep enough to absorb the increasing organic material- dont have the capacity
Deep waters are able to absorb so are therefore usually more pristine

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17
Q

Microbe adaptations to the aquatic environment

A

Small cells (ultramicrobacteria) ~0.3 micrometers- maximises surface area: vol to deal with oligotrophic conditions
Sheathed bacteria for protection and attachment to solid objects
Pigment production for protection from UV light
Motility to move towards O2 or nutrients or away from UV light with flagellum or gas vacuoles (gas cavities which give bouyancy)
Magnetotactic bacteria- magnetosomes
Utilisation of nutrients in low concentrations= increased uptake/ high affinity enzymes or changing physical appearance eg stalk to act as anchor and increase surface area

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18
Q

Features of magnetosomes

A

Membranous vesicles containing chains of iron oxide magnetite particles which respond to geomagnetic fields in the Earth
Bacteria in N hemisphere swim northward and downward
Bacteria in S hemisphere swim southward and downward
Function is to move microbes towards sediments, towards areas of optimal oxygen concentration

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19
Q

Stratification in oceans

A

Can occur but is impacted by depth and currents

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20
Q

Depth and surrounding NZ oceans and fishing

A

Two shallow regions (~200m) are the chatham rise and the Campbell clatou. Most of our fishing is done in these regions because more shallow waters will have more microbes and therefore, more fish

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21
Q

Oxygen concentration in the ocean

A

Oxygen concentration is low (0.007%) which is impacted by temperature and atmospheric pressure

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22
Q

Salt concentration in the ocean

A

Salt concentration is 3.2-3.8%, mostly NaCl, sometimes MgCl and CaCl

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23
Q

Hydrostatic pressure in the ocean

A

Hydrostatic pressure, 1000m= 100ap (increases going down)
Increases 1atm every 10m deep

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24
Q

Sunlight penetration in the ocean

A

Sunlight penetration, sufficient for photosynthesis depends on season (angle of sun), latitude (angle of sun) and turbidity (up to 50m in turbid waters). Can get up to 1000m deep

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25
How much of the ocean is more than 1000m deep
3/4
26
Temperature in the ocean
Waters <200m temp varies based on global location and depth Freezing point of ocean water is -2 to -3 deg Ocean ranges 5 to -1.5 deg
27
pH of the ocean
8.3 to 8.5= alkaline
28
Nutrients in the ocean
Oligotrophic, containing trace elements- some sulphur but most is from photosynthetic organisms
29
Features of the ocean meaning that microbes decrease with depth
Hydrostatic pressure increases with depth Sunlight penetration decreases with depth Temperature decreases with depth Nutrients decreases with depth
30
Three adaptations in microbes making them suited to the ocean environment
Halotolerant or halophilic Piezotolerant or piezophilic Mutualistic relationships for low nutrients
31
Halotolerant or halophilic for ocean microbes to deal with salt concentrations
Halotolerant= need 2.5-4% salt in the environment, they can change their active transport and how they concentrate ions in a cell depending on the salt concentration (found in estuaries) Halophilic= require Na for high maintenance of intracellular potassium concentrations (found in pure ocean environments)
32
What is a saltwater wedge
Changes with freshwater constantly coming in and out at estauries Saltwater is more dense so is found below freshwater at these wedges= microbes here are halotolerant and need to change and adapt to the changing salt concentrations
33
Piezotolerant or piezophilic microbes for dealing with ocean pressure
<3000m deep (300atm)= piezotolerant microbes >3000m deep (300atm)= piezophilic microbes Pressure affects the cellular physiology- enzymes fold differently for protection and there are also some outer membrane adaptations
34
Three examples of mutalism for microbes int he ocean dealing with low nutrients
Tubeworms Luminescent bacteria Shipworms
35
How does the tubeworm mutualistic relationship work
Tubeworms live by hydrothermal vents- absorb hydrogen sulfide from them Also absorb oxygen and CO2 from the seawater Goes to the trophosome where bacteria (primary producers, chemolithotrophic) are where they perform sulfide oxidation, making ATP used in the calvin cycle to make organic carbon for the tubeworm and the microbe Bacteria gets salfe environment, protection and gases for nutrients Tubeworm gets nourishment from the bacteria
36
How does hydrogen sulfide block respiration
It blocks respiration by blocking O2 binding sites on haemoglobin and poisoning cytochrome c
37
How does the tubeworm cope with hydrogen sulfide
Has modified free haemoglobin with high carrying capacity for O2 (can also bind hydrogen sulfide) Modified cytochrome c which is not inhibited by hydrogen sulfide
38
Mutualistic relationship between luminescent bacteria and fish
Photobacterium= chemolithotroph Light is generated instead of ATP Enzyme luciferase converts RCHO (will be oxidised) + FMNH2 + O2 -> FMN (excited form which releases energy as light) + RCCOH carboxylic acid + light Fish gets to scare away enemies and attract prey Bacteria gets safety and protection This is induced- reaction makes autoinducer which when made in high amounts allows the reaction to occur
39
Shipworm mutualistic relationship
Shipworms are mollusks Only have wood for nutrition Have Teredinibacter turnerae bacteria in the gland of Deshayes Obligatory marine bacteria- cant survive in freshwater Bacteria degrade cellulose and fix nitrogen from the N dissolved in seawater to allow the shipworm to live in wood Bacteria get safety and protection
40
What are algae blooms and how do they work
Eutrophic conditions Temporary and rapid growing Lead to toxins produced from the microbes which is harmful to humans and dogs Shellfish can accumulate the toxin Produces saxitoxin which block sodium ion channel= paralytic outcomes- closure of shellfish beds and economic losses Bloom forming cyanobacteria has increased since European settlement
41
Things which affect water borne pathogens
Temperature- 10deg decrease= 50% increase in survival Type of water
42
What is a water borne pathogen
A pathogen able to be transmitted by water
43
Waterborne disease infection cycle
Infected person Pathogens in faeces Contaminated water source (Control point) Consumption of non-potable water (risk point) Susceptible person
44
Infectious dose of waterborne pathogens
Depends on the pathogen ~1x10^8 cells If highly virulent= lower
45
Features of campylobacter
Zoonotic infection from chickens Gram-negative, microaerophile, spiral rods, motile with flagella, optimum temperature for growth is 42degC C.jejuni most common in NZ Low infectious dose Symptoms 2-5 days after ingestion (depends on amount ingested) Lasts 7-10 days, diarrhoea (bloody), fever, ab pain Can lead to Guillain-Barre syndrome by molecular mimicry (autoimmunity)
46
What makes campylobater a good pathogen
Low infectious dose (~500 cells) Cell shape and motility- helical shape and flagella allow entering cells easy through propulsion and corkscrew rotation Adherence from adhesion proteins Invasion mechanisms- penetrates intestinal mucosal layer Toxin production- cytolethal distending toxin= membrane associated and affects target cell processes
47
Treatment of campylobacter
Erythromycin however, resistance is increasing due to the use of it in animals
48
Two examples of water borne protozoa
Giardia intestinalis= flagellate subgroup Cryptosporidium parvum= sporozoan subgroup
49
What are protozoa
Photosynthetic unicellular organisms with eukaryotic cell structure Eukaryotic microbes No cell wall
50
Giardia lifecycle
In people and reservoir in animals Into stomach- protection from acid by cell wall Bile and alkaline conditions of SI duodenum= excysting 2 trophoziotes Attach to epitheliam cells via sucking disc- flatten villi= malabsorption and watery diarrhoea Divide asexually through binary fission Encyst in colon due to cholesterol starvation
51
Cryptosporidium lifecycle
In people and animal reservoirs Enters stomach, leaves oocysts in SI into two types of sporozoites (4) Type 1 enter epithelial cells of SI mucosal and develop and divide asexually with binary fission= 8 merozoites Merozoites undergo sexual reproduction and oocysts form and are released back into the environment
52
Difference between cysts and oocysts
Cysts are from asexual reproduction (binary fission) Oocysts are from sexual reproduction and have a thicker wall
53
Similarities between giardia and cryptosporidium
Animal reservoirs- GI tract Widespread in environment Causes frothy, watery diarrhoea and abdominal cramps Infection usually self-limiting in healthy adults Polymorphic= take on different forms in its lifecycle (trophozoites, cysts, sporozoites, merozoites, oocysts) in GI tract Cysts resistant to chlorine at levels found in drinking water Cysts should be removed by modern water treatment plants Low infectious dose (giardia= 10 cysts, crypto= 100 oocysts) Antibiotic treatment available (metronidazole/ nitazoxanide)
54
Differences between giardia and cryptosporidium
Motility- giardia= flagella, crypto= non-motile Attachment to mucosal cells- G= surface with sucking disc, C= enters cells Replication- G= asexual, C= asexual and sexual Cysts and oocysts Numbers of trophoziotes (2) and sporozoites (4) after excystation Susceptible individuals (immunocompromised, especially in C) Resistance of cysts in chlorine- C= 20% more resistant than G
55
Norovirus as a water-borne pathogen
Ss+ RNA Non-enveloped Caliciviridae 30nm About 10 viral particles= infectious dose Closed communities eg hospital wards, prisons, cruise ships No vaccine Highly contagious and low mortality Affects infants due to rapid dehydration Bloodgroup O more affected
56
Rotavirus as a water-borne pathogen
DsRNA Non-enveloped Reoviridae 75nm About 100 viral particles infectious dose Infants and children susceptible due to rapid dehydration Vaccine available Enterotoxin Highly contagious, low mortality
57
How did the romans treat their water
Build big aqueducts which carried water on top 50km away= 17m drop Covered to keep it cool and keep stuff out and keep UV light off= no algae growth Distributed into reticulations At low flow only passes over middle= communal drinking fountains Medium= communal drinking and public conveniences eg baths High= communal drinking, public conveniences and to every home
58
Different sources of potable water
Surface waters- rivers, lakes reservoirs Ground water- aquifiers, spring water (harvested via bores) Desalination of sea water= costly
59
What is catchment area
Area of land around a surface water source
60
Sources of contamination of source water- natural pollution (geochemical processes and soil)
Salts and minerals (soils) Animal or plant waste (increase organic material- too much can decrease O2) Dissolved gases (CO2= incr carbonate, SO2= incr sulfate) Run-off from peat bogs, silt (acidic= turbid, coloured and change in pH) Natural radioactivity, heavy metals (eg arsenic in soils naturally in India)
61
Sources of contamination of source water- human pollution
Thermal (eg using to generate electricity and increasing heat as put back in) Pathogenic microorganisms Organic matter from industries (meat waste, dairy waste= decrease available O2) Toxic compounds (pesticides, herbicides, accumulating heavy metals) Eutrophication (anaerobic conditions) Detergents (high P= conc of O2 soluble in water is low) Radioactivity
62
Water treatment systems- protection of source water
Water catcher in absence of natural and human pollution Ideally no agriculture, no landfills, no humans and no industry (In dunedin there is tussock there which acts as a natural filter)
63
Water treatment systems- sedimentation or screening
pH of raw water ~6.4-6.7 Remove as much solid material as possible Sedimentation= reservoirs/ basins where sediments go to bottom, water is taken from the middle) Screening= 3mm mesh screens
64
Water treatment systems- aeration
Removes dissolved gases Makes it smell better
65
Water treatment systems- chemical flocculation
Add polyaluminium chloride Causes aggregates of finely suspended solids into flocs pH of water decreases to 5-5.5 After flocculation, pH adjusted with lime to about 6.5 Then use dissolved air flotation- air under pressure at the bottom of the tank, where bubbles rise and pick up the floculated material and bring to surface where it is scraped off
66
Water treatment systems- filtration through sand
Water through troughs-> anthracite coal-> sand-> gravel Heat indicators indicate the pressure in the filter Travels down through the layers Traps microbes and other organisms Membrane filtration added to upgrade and be barrier to cryptosporidium cysts Needs to be back washed to clean, how often depends on the source water Backwash water needs to be put in waste
67
Water treatment systems- chlorination
Final residual concentration= 0.2mg/L right through distribution system Kills microbes and protects water as it travels through pipes with biofilms Good as is available as gas, liquid or powder, cheap, soluble in water, leaves hypochlorus acid which is strong oxidising agent which stops microbe activity Cryptosporidium are resistant
68
Water treatment systems- fluoridation
0.75 parts per million (0.75mg/L) 40% less tooth decay in kids
69
Water treatment systems- ultraviolet light treatment
At 254nm= disrupts microbial DNA/RNA Many bulbs means water isnt far from the UV light at a given time Inactivation of cryptosporidium cysts pH of water increased with lime to 7.5 for distribution
70
How could problems in water treatment occur
Pollution of source water- overload sand filters Increased demand for treated water Out of date pipes and plant Biofilms in pipes Inefficient treatment programme Contamination after treatment
71
Maximal turbidity (NTU)- and example of a case
At time of outbreak in Milwaukee regulation was NTU <5, 95% of the time Since outbreak= <0.5, 95% of the time NZ regulations= <0.3, 95% of the time Dunedin aim for <0.1, 99% of the time
72
Why contamination occurred in Milwalkee
Pathogen present in untreated water source Sources= cattle farming, freezing works, human sewage Inadequate treatment- recycling backwash water Spring rains and snow melt compounded problems Mechanical failures
73
What needs to be ensured when collecting a sample of water
Has to be representative of the whole body of water from the middle of the middle Use sterile container and aseptic technique Already moving or make movement: put container facedown and when in middle turn to face upstream and collect Held in a cool and dark place and transported to lab, tests done within 6hr of sampling
74
When to test water
Periodically test rivers, lakes etc Drinking; test before, at key points during, at the end and then at the end of distribution
75
Two ways to measure amount of dissolved O2, reflecting concentration of organic compounds (both show TRENDS)
Biochemical oxygen demand (BOD) Chemical oxidation demand (COD)
76
How does BOD work
Measure demand for O2 by anaerobic bacteria during degradation of organic matter, and indicates the concentration of organic compounds in water Put sample at 20degC in dark (no photosynthesis= O2 stays the same or decreases), measure after 5 days Adv= historic data to directly compare to, only measures biodegradable portion Disadv= 5 days is a long time and it is not complete after the 5 days= underestimate
77
How does COD work
Potassium dichromate oxidises organic compounds to CO2 and H2O Amount used is proportional to the organic material in the sample Adv= quicker Disadv= cant determine between biodegradable and non-biodegradable= overestimation
78
Why cant we just look for pathogens from faecal pollution in water
Many genera- need separate tests for each (impractical) and includes microbes we dont know about yet Special culture conditions required for each one- expensive and likely to miss many Not all can be cultured eg Norovirus- viruses, protozoa with cysts (normally tested via observation from faeces) Too late- water is already in circulation by the time a test is done
79
Bacterial indicators of faecal pollution
If water contains the indicator organism it is probably contaminated and probably isnt safe to drink
80
Features of an ideal faecal indicator organism
Bacterial inhabitant of only large intestine of mammals Non-pathogen= member of normal microflora Easy to culture and identify from all types of water Present in large numbers in faecal material- in greater number than faecal pathogens Survives longer in water than pathogens but does not reproduce in water No indicator organism meets all five
81
Features of coliforms
Family enterobacteriaceae Aerobes and facultative anaerobes Gram negative Nonspore forming, rod shaped Ferment lactose with gas within 48hr at 35degC Eg Escherichia, Klebsiella, Enterobacter, Serratia, Citrobacter (all except first one can be isolated from soil so can tbe used as they can give false positive result in water)
82
Faecal coliform
E.coli Ferment lactose at 44.5degC (elevated temp to the others)
83
Disadvantages of using indicator bacteria
Could fail to detect disease-causing viruses Doesn’t detect risk from toxic algae E.coli may have rapid die-off rates in certain waters (can die off quicker than pathogen due ot decreased temp and nutrients compared to human gut) Viable but non-culturable indicator bacteria could lead to erroneous conclusions (false negative, as still alive but could have been injured to make non-culturable) Clustering of microbes= may not be evenly distributed or in every sample (false -ve) and formation of biofilms (false +ve) could cause incorrect test results
84
Why is E.coli a good indicator bacteria
Present in high numbers in mammal faeces Doesnt multiply outside of host Inexpensive, simple, sensitive and specific Survives long enough under a broad range of drinking water conditions
85
Old method for testing for indicator bacteria
Filter catches bacteria Then culture it and incubate to see if they grow
86
New method for testing for indicator bacteria
Enzyme substrate coliform test (Colilert) Coliforms produce B-galactosidase which turns ONPG yellow Faecal coliforms produce B-glucuronidase which turns MUG fluorescent blue
87
Acceptable levels of contamination for drinking water
<1 E.coli/ 100mL <1 oocyst/ 100L
88
Interpretation of treated water with different things
Coliforms= treatment process has some issues or can be post-treatment eg from soil Faecal coliforms= faecal contamination Non-pathogenic bacteria in water
89
Acceptable E.coli in recreational water
Old= 260 E.coli per 100mL New= 540 E.coli per 100mL Increased amount able so that politically can increase number of swimable rivers

MICR222 (8 decks)

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