MODULE 3 - Water Microbiology and Public Health Flashcards
water environments are generally oligotrophic. What does this mean?
very low in nutrients
what does mesotrophic mean?
medium amount of nutrients
what does eutrophic mean?
high amount of nutrients
why are most microbes found in surface levels of water?
in water environments the number of nutrients conc. decreases with depth so most found at surface
what are allochthonous microbes?
microbes not usually found in that habitat i.e. microbes in freshwater washed in from soil around it
what are autochthonous microbes?
microbes where water is their natural habitat. These microbes usually motile, aerobic and gram-neg rods
why are most water microbes gram-neg?
because the water body supports the bacteria so they don’t need thick cell wall which could also inhibit them from moving through the environment
how are aquifers formed?
if water is able to form on an impermeable substance e.g. starts as rain, travels down through soil layer and settles on bed rock
soil layer acts as filter and takes out a lot of impurities and nutrients
different aquifer environments form depending on what the rock is made up of so environment forms a selection pressure on the microbes that inhabit it naturally
once aquifers are contaminated…
they are very hard to purify again
what kind of freshwater environment are rivers?
classified as oligotrophic but vary
if good nutrient supply, microbes similar to those in soil enviro will inhabit it
highly oxygenated
river microbes adhere to surfaces so they aren’t washed away
what are seven variables regional councils look at when grading waters?
turbidity
dissolved oxygen
total phosphorous
total nitrogen
nitrate/nitrite ratio
dissolved phosphorous
E. coli levels
what are the four main sources of river pollution?
natural
agricultural
industrial
urban
when are lakes in temperate zones stratified and why?
during summer cause top layer warmed up making it less dense
summer winds usually light so top layer not disrupted
in autumn surface layer cools i.e. more dense i.e. mixes with lower layers i.e. no stratification
what are the three factors required for lake stratification?
temperate zone
summer
lake deeper than 10m
what are the different layers of a stratified lake?
warm surface layer called epilimnion
cold bottom layer called hypolimnion
between these layers is a zone of transmission called the metalimnion
different microbes inhabit each layer
what kind of energy production occurs in the epilimnion (top layer)?
here u get primary production by oxygenic photosynthesis
oxygen limited solubility in water so very quickly as u move down through water u get area with no oxygen available for microbes to carry out oxygenic photsynth
what kind of energy production occurs just below the metalimnion/thermocline?
anoxygenic photosynthesis which is an anaerobic process and only occurs in summer as only then does angle of sunlight allow sun to reach this layer
so there is sunlight but no oxygen
what kind of production occurs in the mud sediment below the stratified layers of the lake?
bacteria similar to soil environments live here
anaerobic fermentation, sulfate reduction (releases H2S) and methanogenesis (produces methane)
these all prod gas and methane isn’t soluble in water so disappears as bubbles well H2S doesnt
in the metalimnion, what two parameters decrease rapidly?
oxygen concentration and temperature
so it is a zone of transition of rapid change for two of our parameters
what is the third parameter in a stratified lake and where is it concentrated the highest?
hydrogen sulfide
generated in sediment so high conc. in lower areas of lake and we lose a lot of it and it never reaches the metalimnion hence why metalimnion only a zone of transmission for two of our parameters
what is leibig’s law of the minimum?
the population of organisms in an ecosystem is determined not by total quantity of nutrients present but by the nutrients present in lowest amount relative to the organisms requirement
i.e. a microbe will grow until a nutritional requirement becomes limiting
what is shelfords law of tolerance?
regardless of nutrient supply there are limits to environmental factors below and above which a microbe cannot survive /grow
e.g. if u put microbe in enviro with lots of nutrients but it is outside optimal temp./pH/oxygen conc. it still cannot grow
what two laws govern how/if a microbe can grow in an ecosystem?
leibig’s law of the minimum
shelfords law of tolerance
what is eutrophication?
when lots of nutrients present. high organic material (high in N and P) means we get increased oxidation by decomposing microbes which uses up oxygen = anoxic conditions and proliferation and production of toxic products by anaerobes
can be temporary or permanent
what is the general process (incl successions) of eutrophication?
large input of nutrients e.g. sewage
O2 drops
bacterial numbers spike
ammonium spikes and then oxidised to nitrate (two-step process)
nitrogen products spikes
as everything returns back to normal except algae and cyanobacteria begin to proliferate
why are lakes more difficult to reverse eutrophication than rivers?
they aren’t moving bodies of water
lakes shallower than 10m vulnerable cause less capacity to absorb organic materials (why deep lakes are generally more pristine)
what can we do to help reverse eutrophication of lakes in the first place?
install buffer zones around farms and surface water
reduce livestock density
reduce fertiliser applications
plant more native trees in wetland areas
what are six adaptations that microbes have made to aquatic environments?
smalls cells (ultramicrobacteria); helps increase s to v ratio to deal with oligotrophic conditions
sheathed bacteria; provides protective function and helps them attach to objects
pigment production; protects from UV
motility (two methods); flagella or gas vacuoles: helps bacteria move to nutrients or away from hazards
magnetotactic bacteria; magnetosomes are membrane vesicles containing chains of iron oxide particles so bug can respond to geomagnetic fields of earth
utilisation of nutrients in low conc; increased uptake/high affinity enzymes, stalk (anchors bacteria to solids and increases SA)
what are gas vacuoles?
one of two methods of motility in aquatic microbes - gas vacuole made up of many gas vesicles arranged in randomly orientated bundles
what is the biological purpose of magnetosomes?
bacteria in N hemisphere swim northward and downward
bacteria in S hemisphere swim southward and downward
allows microbes to move towards sediments and towards areas of optimal oxygen conc.
how are magnetosomes arranged and what could they be used for in medicine?
orientated in parallel lines
generally 35-125nm
could be used as contrast in MRI scans or as biological probes
what are the seven factors which effect microbes in a marine environment?
O2 conc. (generally low in marine enviro)
salt content (ocean salty so marine microbes mild halophiles)
hydrostatic pressure (increases as you go deeper)
sunlight penetration (depends on season, latitude and turbidity)
temp. (decreases w depth)
pH
nutrients (marine is oligotrophic)
what are the three environmental extremes marine microbes are faced with?
high salt
high pressure
low nutrients
what are halotolerant microbes?
microbes that can withstand significant changes in salinity
what are halophilic microbes?
microbes that have an absolute need for high salt concentrations (often require sodium top maintain intracellular K+ conc.)
what is a saltwater wedge?
where both fresh and salt water (salt underneath cause more dense)
generally occur in estuaries and change w tide
due to change microbes living here highly adaptable i.e. mostly halotolerant
what are piezotolerant microbes?
tolerating pressure
what are piezophilic microbes?
dependent on pressure
most microbes deeper than 3000 metres are
pressure affects cellular physiology, deep sea microbes enzymes fold in different ways and sometimes outer membrane different to help cope
what type of gradient can be found around hydrothermal vents?
temperature gradient
they are also dark, pressurised and not much carbon
how do tubeworms survive in/around hydrothermal vents when there’s no organic material and they have no digestive system?
they have trophosome which is loaded with sulfur granules and bacteria
O2 and CO2 from seawater and H2S from vent absorbed in gill plume and then passed down to worm capillaries which then gets it to the bacteria living in trophosome
bacteria in trophosome are chemolithotrophic meaning they use reduce inorganic compounds as source of energy and electrons
what are the two reactions occurring inside tube worm?
sulfide oxidation (sulfide to sulfate); key part of this reaction is energy (ATP and NADH) produced which is used for second reaction
fixing carbon dioxide into organic carbon which is the food source for the worm and microbes inside
this means the chemolithotrophic bacteria are primary producers in thermal vent enviro
why is H2S a problem usually and how does the tube worm deal with it?
H2S blocks respiration by blocking O2 binding sites on haemoglobin (hb) and by poisoning cytochrome c
tube worm has modified free hb with high carrying capacity for O2, hb can also bind H2S, modified cytochrome c which H2S doesn’t inhibit
what are the advantages for the tube worm and the advantages for the bacteria in their mutualistic relationship?
tubeworm receives nourishment from reduced carbon
bacteria gets raw materials (O2, CO2 and H2S) and a safe environment
