11 - Water Microbiology Flashcards
Aquatic primary producers
Photoautotrophs, phytoplankton
- Algae
- Cyanobacteria
What do the biological activities of an aquatic ecosystem depend on?
The activities of primary producers for :
- food for other otganisms
What eats primary producers
Chemoautotrophs:
- bacteria
- protozoa
- zooplankton
- fish
- other aquatic animals
Activities of phytoplankton depend on :
- Temperature
- Light received
- Nutrient availability : nitrogen, phosphorus
Photic zone
zone of water that receives sunlight:
deepest 300m in clear water
Accessory pigments
help microorganism harvest light at great water depths
Halotolerants
organism that can survive high salinity environments ( 3%)
Pelagic zone
Open ocean: little nutrients : N, P little primary production - Oligotrophic - 75% of the ocean
Primary production in pelagic zone
Primary production is low : Lack of inorganic nutrients ( nitrogen, phosphorus, iron)
-> Oligotrophic
Winds and currents can cause nutrient upwelling promoting burst of productivity
Primary PRODUCERS in open ocean
Mostly prochlorophytes
Procholococcus
a prochlorophyte:
- tiny phototrophs
- phylogenetically related to cyanobacteria
- bulk of primary production in open ocean
Microorganic adaptation in pelagic zones:
- reduced size -> high surface area/volume ratio
- high affinity transport systems
Trichodesmium
- filamentous cyanobacteria
- contains phycobilins
- nitrogen fixer
Coastal waters
High primary production: influx of nutrients from rivers and polluted water sources (nitrogen, phosphorus)
Eutrophic
Red tides
Algal bloom : dinoflagellates, neurotoxins
Limited by nitrogen
Costal waters primary producers
Algae
Cyanobacteria
Supports higher concentration of zooplankton and aquatic animals
Deep sea 300-1000m
Chemoheterotrophs degrade organic material that falls from photic zones
- 2-3C
- Psychrophiles (cold water)
Deep sea bellow 1000m
Organic carbon is very scarce
- No light
- Oligotrophic
- very few microorganisms : psychrophilic& barophilic or barotolerant (high pressure)
Hydrothermal vents
Source of : - Heat - Nutrients - Eletron donors &acceptors creates communoty of microorganisms and animals
Tube worms
Symbiosis with sulfur oxidizing chemoautotrophs
Tube worms trap and transport nutrients to bacteria
Freshwater Environment
Highly variable
Microbial activity depending on nutrient availability
fresh water microorganism activity depends on :
Nutrient, oxigen and light availability
Limited by : nitrogen and phosphorus
Lakes (general)
Poor mixing/aeration
can be eutrophic or oligotrophic
Rivers
Good mixing/aeration
-> ensures (within limits) degradation of organic matter
- no fermentation
- no H2S production
Excess organic matter -> anaerobiosis (no fish or other aerobic organisms)
Oligotrophic Lakes
Nitrogen and phosphorus are limiting
Oxygen supply is high -> lake remains aerobic even at higher depths
organic mater is degraded completely.
clear water -> deep light penetration
Primary production is low, availability of organic matter is low
Eutrophic Lake
Primary production is high -> availability of organic matter is high
Rapid growth of chemoheterotrophs -> rapid depletion of oxygen -> anaerobic zones created
Poor light penetration
Health risks of eutrophic lakes
Pathogens
Cyanobacterial/algae blooms (secrete toxins)
Eutrophic lakes : Bottom sediments
Anaerobic and contain organic matter :
Supports the growth of denitrifiers methanogens and sulfate reducers
Anaerobic photosynthesis: uses H2S as electron donor and produces sulfate-> used by sulfate reducers
Eutrophic Lakes: H2S and organic acids
Excessive H2S production from anaerobic photosynthesis and organic acids from fermentation :
- gives water bad odour
- with lack of oxygen -> kills fish and other aerobic organisms
Summer stratification
Separation of the lake into zones determined by temperature
- may develop anaerobic zones -> lake becomes thermally stratified
Water mixing, in the spring and fall only, bring nutrients from the bottom to the top
Epilimnion
lake stratification : top layer
- warmer
- less dense
- aerobic
Thermocline
lake stratification : middle layer
Zone of rapid temperature change
Hypolimnion
Lake stratification : bottom layer
- more dense
- colder
- anaerobic
Pollution of fresh waters
- deliberate discharge of effluents into a waterway
- mostly sewage
Sewage pollution of water
- sewage is rich in organic materials and contains many microorganism
- high chance of containing pathogens
- BOD is high
Biochemical Oxygen Demand
[BOD]
- used as a measure of the extent of organic matter pollution
High BOD
Water tends to be anaerobic
Microbial metabolisms : fermentation, sulfate reduction, nitrate reduction …
Biofilms
microbial cells (mixed species) embedded inside an extracellular matrix. Extracellular matrix: proteins, polysaccharides, DNA Cells inside biofilms are more resistant to stresses
Water-borne pathogens
Most from intestinal tracks -> contamination comes from fecal matter
Sources of infection :
- contaminated drinking water
- recreational water
Salmonella typhi
Water-borne pathogen Causes: - Typhoid fever in humans - systemic infection Healthy carriers
Vibrio cholerae
Water-borne pathogen
Causes:
- Cholera
- severe diarrhea (enterotoxin: affecting the digestive tract)
Shigella spp.
Water-borne pathogen
Causes:
- shigellosis
- bacterial dysentery (bloody diarrhea, inflamation of the intestinal mucosa)
Salmonella spp.
Water-borne pathogen other than typhi
Causes:
- salmonellosis
- gastroenteritis
gastroenteritis
- inflammation of the stomach and intestines causing diarrhea and vomiting
Campylobacteria spp.
Water-borne pathogen
Causes:
- gastroenteritis (most common cause in canada)
Enterovirus
Water-borne virus
- poliovirus
- norovirus
- rotavirus (children)
Hepatitis A
water-borne virus
Entamoeba histolytica
Water-borne pathogenic protozoa
- amoebic dysentery (intestinal infection)
Gardia lamblia
Water-borne pathogenic protozoa
Causes:
- giardiasis (backpacker’s disease/beaver fever)
- chronic diarrhea
Often associated with drinking water in the wilderness often carried by local animal life
Cryptosporidium parvum
Water-borne pathogenic protozoa Causes: - chronic and acute diarrhea Self limiting in healthy individuals-> major problems in immunocompromised individuals. No reliable treatment
Transmission of C. parvum and G. lamblia
Both form cysts which are resistant to most disinfectants: including chlorine
C. parvum cysts are not effectively removed by water filtration: present in 28% of drinking water samples
Water quality control
Impossible to test for all organism-> test for common fecal microorganisms
Most water-borne pathogens are associated with fecal material
Water quality indicators:
Coliforms
Fecal coliforms
Presences of these (E.coli especially) indicated fecal contamination
Absence does not ensure purity (cysts)
Coliforms
- facultative aerobic
- gram negative
- non spore forming
- rod shaped
- can ferment lactose -> with gas formation
Includes a variety of bacteria not with fecal origins
Fecal coliforms
coliforms derived from the intestines of warm blooded animals
- thermotolerant (44.5C)
Most Probable Number
MPN
Presumptive test for coliforms:
- sample is added to lactose broth -> gas production indicates positive test
Membrane filtration
Tests for coliforms and fecal coliforms
- test large volume of water
- faster and easier than MPN
Water treatment aims:
- removes pathogens
- improves clarity of water
- removes compounds that cause bad smell & taste
Extent of treatment depends on water origins
Steps in water treatment
1- Sedimentation 2- Coagulation 3- Filtration 4- Disinfection 5- Storage & distribution
Sedimentation
Water is left to stand in a reservoir/sedimentation basin
- allows large particles(sands) to settle
Coagulation/ Flocculation
Chemical coagulation treatment
- a flocculating chemical (coagulant) is added
- water is transferred to a flocculation basin and allowed to settle
- as the flocs form, they trap fine particles (clay, bacteria, protists&some organic chemicals)
Removes +- 80% of bacteria, colour and particulates
Filtration
- water is filtered throuhg sand -> removes remaining particles and G. lamblia cysts
After this 98-99.5% of bacteria have been removed
Filter is backflushed regularly-> prevents clogging
Disinsection
Using chlorine (chlorination) or ozone Ozone: is more effective than chlorine but much shorter half-life Water is now safe for human consumption
Chlorination
- chlorine is very active in water -> forms a strong oxidizing agent
- kills remaining microorganisms (some are resistant)
- neutralizes chemicals causing bad taste & odor
Residual chlorine
amount of chlorine that remains in the water that has left the treatment plant .
needed to protect the distribution system
Wastewater treatment: aims and steps
(sewage treatment) Aims: - reduce BOD - destroy pathogens Steps : - Primary treatment - Secondary treatment - Tertiary treatment
Primary treatment
Sedimentation tanks: 40-70% of suspended solids settle. Flocculating chemicals can be added.
Produces: primary sludge
Reduction :
BOD: 25-40%
Bacteria:25-75%
–> discharged to waterways or secondary treatment
Secondary treatment
uses microorganisms to reduce BOD and bacterial concentrations further
- Trickling filter
- Activated sludge
Trickling filter
Liquid from primary treatment is sprayed over either a bed of rocks or plastic honeycomb.->microorganism form a biofilm coating rocks/honeycomb -> oxidizes organic matter
Reduction:
BOD:80-95%
Bacteria:90-95%
Activated sludge
air is blown through liquid from primary treatment.
Slime-forming bacteria grow and clump -> form flocs (activated sludge) -> oxidizes organic matter
Next material passes through a settling tank, sludge is removed for disposal or secondary treatment
Reduction:
BOD:85-95%
Bacteria:90-98%
Secondary treatment : Sludge
Primary and secondary sludge contains:
- Cellulose
- other organic compounds
is subject to microbial digestion under anaerobic conditions -> produces:
- CH4 which can be used as an energy source for the treatment plant
- remaining material is incinerated or buried
Reduction:
BOD: 90%
Tertiary treatment
Further reduces BOD, bacteria, nitrogen and phosphorus concentrations May involve any combination of: - biological treatment (ponds: algae) - Flocculation - Filtration - Chlorination/Ozonation Produces : Final liquid affluent
Final liquid affluent
waste water that has gone through primary, secondary, and tertiary treatment
Maybe suitable for human consumption if coliform and fecal coliform levels are bellow limits
Septic tank
Minimal waste water treatment
Settling of the material and minimal sludge digestion-> effluent flows to a leaching field: soil acts as a filter organisms decompose organic matter
possibility of groundwater and nearby water way contamination
Tank require regular emptying
