Water Microbiology Part I

Question 1

Photic zone

Answer 1

In clear water light will penetrate max depth of 300 m.
- turbidity decreases this depth

Primary producers (oxygenic photoautotrophs) like algae and cyanobacteria living in this zone

Question 2

Marine environment salinity, depth and temp

Pelagic zone

Main primary producer in pelagic zone

Answer 2

3% salinity - requires halotolerant microbes

75% is deeper than 1000 m with extreme pressure
- temp 2-3°C constant - cryophiles

pelagic zone = open ocean, low primary productivity = oligotrophic
- some areas have upwelling of nutrients from ocean floor promoting productivity

Main primary producers: prochlorophytes like Prochlorococcus (similar to cyanobacteria phylogenetically)

Question 3

Adaptations for microbes in pelagic zone

Ex.

Answer 3

1) Reduced size (high SA to volume ratio)
2) High affinity transport systems

Ex. Trichodesmium - filamentous cyanobacteria which can float on the surface of the ocean
- contains phycobillins and can N fix

Question 4

Costal waters

Answer 4

Eutrophic environment due to run off from the land (agricultural run off of P and N)
- causes red tides of dinoflagellates which produce neurotoxins

Primary producers: algae and cyanobacteria
- supports higher level of zooplankton and aquatic animals

Question 5

Deep sea environment

Answer 5

300-1000m chemoheterotrophs degrade organic matter that falls from photic zones
- temp: 2-3°C (psychrophilic)

Below 1000m carbon is scarce - oligotrophic environs

Question 6

Hydrothermal vents

Answer 6

Provide heat, source of e-, and e- acceptors

Community in hydrothermal vents:
Ex.Tube worms which do symbiosis with sulfur oxidizing chemoautotrophs
- worms trap and transport nutrients to bacterial symbionts

Question 7

Fresh water environments

Answer 7

Highly variable in terms of nutrient availability and aeration

Oligotrophic lakes: N + P limiting nutrients, [O2] is high bc dissolution is faster than consumption

Eutrophic lakes: High primary production with algal blooms, rapid chemoheterotroph growth and rapid depletion of O2
- poor light penetration: anaerobic photosynthesis H2S –> sulfate
- health risks: pathogens, blooms –> toxins

Lakes are usually poorly oxygenated/mixed

Rivers are more mixed and oxygenated
- generally no fermentation unless there is dumping into river causing anaerobiosis

Question 8

Layers of eutrophic lakes

Answer 8

Bottom layer: anaerobic, high in organic dead matter
- supports denitrifiers, methanogens and sulfate reducers (from anaerobic photosynthesis)
- gives bad odor
- H2S + lack of O2 can kill fish and other aerobes

Stratification occurs during summer (and winter) due to thermocline (change):
- epilimnion - less dense, aerobic layer
- hypolimnion - colder, denser anaerobic layer underneath

Spring/fall mixing of water column

Question 9

BOD

Answer 9

Biochemical Oxygen Demand = measure of how much pollution is in a body of water (measure of oxygen consumption)

Higher BOD –> more anaerobic, chemoheterotroph consume organic material
- more fermentation, sulfate/nitrate reduction as a result of low [O2]

Dumping of sewage into water ways causes eutrophication

Question 10

Biofilms

Answer 10

Biofilm = microbial cells embedded in ECM (protein, polysaccharides, DNA)
1) Attachment 2) Colonization + CHO prod 3) Growth 4) Active dispersal (when nutrients ↓)

Creates resistance to stress compared to planktonic (free-living) cells

Found in water systems, wet surfaces, medical devices

Question 11

Waterborn bacteria and viruses to know

Answer 11

Salmonella typhi - typhoid fever in humans, healthy carriers –> systemic infection

Vibrio cholerae - cholera –> severe diarrhea due to enterotoxin

Shigella - bacterial dysentery (bloody diarrhea)

Salmonella - gastroenteritis

Campylobacter - gastroenteritis (most common in Canada)

Enteroviruses: poliovirus, norovirus (highly transmissible, very common), rotavirus (children)

Hepatitis A virus - vaccines available

Question 12

Waterborne pathogenic protozoa to know

Prevention challenges

Answer 12

Entamoeba histolytica - amoebic dysentery

Giardia lamblia - backpacker’s disease (associated with drinking water in wilderness), chronic diarrhea

Cryptosporidium parvum - chronic/acute diarrhea, problem in immunocompromised, present in 90% sewage samples and 28% drinking water

Note: Hard to make drugs for eukaryotes since we share structures
- Giardia lamblia and C. parvum make cysts that are resistant to disinfectants including chlorine
- C. parvum cysts too small to filter out