Pathogens in Aquatic Environments

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Pathogens in Aquatic Environments
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Environments
AIR
SOIL
WATER
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Plankton

• Phytoplankton primary producers
• (CO2 solar energy --gt carbohydrates)

Dissolved organic matter
Particulate organic matter
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Aquatic Environments

• Eutrophic
• nutrient rich
• typically shallow, warm
• Oligotrophic
• low productivity, nutrient-poor

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Marine Environments
Annual fluctuation of temperature (triangle), pH
(circle) and salinity (square) in seawater
(Adriatic Sea, Maugeri et al., 2004)
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the Ocean

• Photic zone
• light can penetrate
• 200m down in clear water
• 1m in turbid coastal zones
• Aphotic zone
• No light
• Neuston
• air-water interface
• Pelagic zone
• water column, planktonic habitat
• Upper part is epilagic zone photic zone
• Benthopelagic zone
• sea-sediment interface

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Aquatic Environments

• Benthic interface between water column and
  mineral sub-surface
• Lentic standing water
• Lotic runnic water

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Benthic habitat

• Benthos a transition zone between
• water column and mineral subsurface
• Rich in organic matter and life forms
• benthic life forms include enteric viruses, which
  were detected for up to 17 mo after dumping

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Microbial mats
Freshwater puddle
Dragon Springs in Montanta www.montana.edu/
observatory/misc/gallery.html
Lake Boney, Antarctica
http//aslo.org/photopost/
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Pathogens in Aquatic Environments

• Sources
• run-off
• shedding from animals
• humans (directly)
• many are normal aquatic microloflora,
  opportunistic pathoges
• Factors influencing survival
• Die-off
• varying oxygen concentration, pH, UV
• predation by amoeba, phages, predatory bacteria

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Just how many of them are there?
Distribution of bacterial pathogens in seawater
(straits of Messina)
Magueri et al., 2004
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Viruses in Aquatic Environments

• Survive in shellfish
• Are carried by currents
• Viruses can move 2 mph (in one study up to 141
  mph(?)
• Environmental conditions affect survival
• Reoviruses (and other viruses) are only found
  during cooler months. Why?
• HAV, enteroviruses, Norwalk-type viruses are
  detected in oyster beds after rains, and coincide
  with human outbreaks
• Survive better in cooler temps (22C vs 33C),
  based on studies in the Keys

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Survival of pathogens in aquatic environments

• Viable, non-culturable state
• culturable counts decrease, bacteria are visible
  microscope, nucleic acids are detectable
• respond to influx of DOM
• Synthesis of new macromolecules to the break
  down
• dwarf cells, round cells

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Survival of pathogens in aquatic environments

• Viable, non-culturable state
• culturable counts decrease, bacteria are visible
  microscope, nucleic acids are detectable
• respond to influx of DOM
• Synthesis of new macromolecules to the break
  down
• round cells

cells of w.t. and mutant E.coli exposed to
nutrient limitation
From Santos et al., 2002
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Plankton free ride for the pathogens

• Using DNA probes and staining, Binsztein et al
  (2004) detected V. cholerae on phyto- and
  zooplankton, and in water.
• Many V. cholerae cells were VBNC

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Plankton-associated human pathogensMagueri et
al., 2004
Free living pathogens in seawater
Only culturable bacteria detected
Associated with small (lt64 microns) plankton
Associated with large (gt 64 microns) plankton
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Zooplanktonbacteria eat it and develop appetite
for humans

• Chitin - one of the most abundant C sources in
  the ocean
• V. cholerae can grow on chitin as a sole C-source
• V. cholerae has chitin-binding proteins on its
  surface
• Human epithelial proteins are decorated with
  chitin monomers

From Kirn et al., 2005
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Aquatic Environments sushi sampler special for
Salmonella

• 4 are of human faecal origin, 20 are native
  bacteria and viruses
• 80 of mussels tested positive for at least one
  of the following
• Salmonella, Clostridium, E.coli-O157,
  Plesiomonas, Vibrio spp.
• California study. Miller et al., 2006
• Compared to other foods, seafood is still
  relatively safe!