Pathogens in Air and Aquatic Environments

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Pathogens in Air and Aquatic Environments
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Environments
AIR
SOIL
WATER
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Environments intercontinental dispersal of dust
Bacterial counts early in the event 0-17,500
cfu/cu.m Arriving dust contains mostly
spore-forming and pigmented organisms Fungal
spore counts early in the event 30-30K cfu/cu.m
From C.Kellogg and D.Griffin, 2006
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How much dust is moving around?
Sometimes a million ton of dust/cloud
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10 ton/cloud
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How much dust is moving around?
Sometimes a million ton of dust/cloud
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_at_ 50kg/person
10 ton/cloud
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Movements of Dust
Coral Aspergilliosis has been linked to African
Dust Opportunistic human pathogens (Bacillus,
Aspergillus) were IDed in dust. Not (yet?)
linked to an outbreak
From Kellogg and Griffin, 2006
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Airborne plant pathogens soybean rust

• Caused by a fungus. Spores are airborne

www.ca.uky.edu
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Airborne citrus diseases
Phaeoramularia (fungus) fruit and leaf spot
(PFLS) spores are airborne
Citrus canker. Caused by Xanthomonas (bacterium)
www.apsnet.org/online/
Originated in SE Asia, spread almost world wide.
In US since 1910s (arrived on seedlings). Waves
of outbreaks. Eradicated in 1994. Isolated again
in 1995. Thought to be spread by hurricanes.
Citrus greening. Caused by an unculturable
bacterium
Considered the deadliest of citrus diseases. In
FL, not yet in CA, AZ. Spread by an insect
(psyllid)
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Pathogens in space

• 234 microbial species were identified on Mir
  after 15 years in orbit
• 108 bacterial species, 126 fungal
• The greatest diversity of technophylic fungi
  (eat polymers, corrode metals)
• Evidence of multispecies biofilm on decorative
  surfaces

Novikova 2004
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Factors that affect survival of pathogens in the
air

• Atmosphere is inhospitable to microbes
• UV, dessication, free radicals

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UV-induced damage
Change in the structure of the double helix leads
to mutations
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• Most airborne pathogens have mechanisms to resist
  UV, dessication
• spore formation
• pigments

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Survival of Bacillus spores
Bacillus sporulates in response to nutrient
limitation, the process also involves QS and
fratricide (review earlier presentations) Spores
are dormant, but can return to active metabolism
under opt conditions Spores can tolerate some UV
damage. Spores that are damaged too much
will not come out of dormancy --gt sophisticated
mechanisms of DNA repair
Exposporium present in some Bacili, a
loosely-fitting proteinaceuos structure
Spore coat consists of gt50 proteins. Function of
each is unclear, but coat is important
for resistance to chemicals, predation
Core contains enzymes, DNA, ribosomes, tRNA and
small molecules Water content of the core 27-55
(vs 80 of vegetative cells)
Setlow, 2006
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Survival of Bacillus spores
5-15 of dry weight of Bacillus,
Clostridium spores is dipicolinic acid It
contributes to repairing DNA UV
damage Contributes to keeping the water content
low (proteins, DNA that are not well hydrated
appear to be more resistant to heat,
UV) Chelates cations. Cations affect resistance
to wet heat
Setlow, 2006
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Aquatic Environments

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

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Plankton

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

Dissolved organic matter
Particulate organic matter
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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!

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V. vulnificus
Wound infections Liver infections Rarely
gastroenteritis
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Biotic and abiotic pressures in aquatic
environments and air