Wainwright (Spring) Flashcards
Without MOs there’d be no life on Earth, why?
- maintain atmospheric mix (prod and consume N, O etc. by feedback)
- maintain soil fertility
- remove wastes, inc sewage
- break down leaf litter and wastes (mainly fungi)
- cycle elements, essential for plant growth
- -> bacteria cycle N, P and S
- -> fungi cycle C
- marine algae main CO2 adsorbers, phytoplankton decrease man made CO2 in oceans
What do all organisms req for growth?
- source of energy
- C for building biomass
What is heterotrophy and the 2 types?
- energy obtained by breaking down preformed C via resp
- aerobic (more efficient), C –> CO2 + H20 + heat
- anaerobic, C –> CH4 ( C also goes to form biomass)
What is autotrophy and the 2 types?
- gain energy by performing chem reactions
- C obtained by fixing CO2
- chemoautotrophy (bacteria), NH4+ –> NO2- –> NO3-
- photoautoptrophy (ps), in higher plants and algae
Purpose of nitrogen cycle
- N req by all living organisms to make protein
In what form do plants take up N?
- nitrate or NH4
Steps of nitrogen cycle
- ammonification/ N-minerilisation
- nitrification
- denitrification
- N fixation
Ammonification/ N-minerilisation
- 1st step
- converts organic N to NH4+
- done by most aerobic and anaerobic bacteria, so occurs under most env conditions, eg. waterlogged soils
Nitrification
- eg. of chemoautotrophy
- bacteria Nitrosomonas ox NH4+ to NO2- and gains energy, while fixing atmospheric CO2
- Nitrobacter ox NO2- to NO3- and gain energy while fixing CO2
Denitrification
- under anaerobic conditions (soil waterlogging), NO3- red to N2(g) (= dinitrogen)
- large no. heterotrophic bacteria do this
- NO3- lost to farm land (negative process)
- sewage operatives use to convert urea to safe waste gas
N fixation
- symbiotic process between certain plants and Rhizobium
- common in legumes or asymbiotic plants
- bacteria (eg. azotobacter) live as “free living” N-fixers and not in direct symbiotic assoc w/plants
Where does symbiotic N-fixation occur?
- root nodules
“Infection” process
- Rhizobium attracted to plant root
- infection occurs through crack in root
- Rhizobium multiplies greatly and prod bacteroid
- plant lays down nodule around bacteroid
- plant donates C (sugars) to Rhizobium, which donates N by fixing atmospheric N2
- this is mutualistic symbiosis
How is Rhizobium attracted to plant?
- each plant prod own specific attractant for specific Rhizobium
Why is sewage treatment needed?
- increasing pop, mainly Victorian London
Main aim of sewage treatment
- removes organic faeces and urine
- removes pathogens from drinking water
- remove solid C wastes
- remove N waste, urea leads to NO2- prod, toxic to newborns and NO3- prod, can cause stomach cancers
How did sewage systems evolve during industrial revolution?
- civil engineers, eg. Bazalgette, did lots to intro sewage systems in London etc.
- simple improvements made big difference, eg. egg shaped sewers to allow rapid flow at bottom
Where is sewage a major problem?
- urban centres w/ large pops
- industrial areas which prod heavy metals and pollutants
- intense agriculture, eg. large scale beef prod on feedlots
How can human and animal waste spread disease?
- bacteria cause cholera, food poisoning etc.
- viruses cause polio
Types of sewage system
- septic tank
- filter bed/contact bed
- activated sludge process
Septic tank
- simplest system
- aerobes at top of tank and anaerobes at bottom
- water passed into soil into distribution field
- MOs in soil finish purification
- distribution field must be away from water supply
FIlter bed/contact bed
- bed made of coke/limestone, covered w/ biofilm
- works in same way as septic tank
Activated sludge process
- most efficient
- aerobes at top of tank and anaerobes at bottom
- solid waste moved to anaerobic digester
- CH4 given off made into energy or sold
- some of material taken back to beginning to stop dilution of organisms
Testing drinking water for waste
- BOD (biochem O demand)
- full (no air bubbles), use O2 probe to measure amount, leave in dark for 3 days and measure again (so no ps), if MOs then O2 levels decrease as use O2
Testing drinking water for pathogens
- membrane coliform count (want it to be low)
- measure non pathogenic E. Coli (indicator organism)
- usually incubated at 37ºC, or 44ºC for faecal coliforms
What is MRSA?
- methicillin resistant staphylococcus aureus
Methicillin
- broad spectrum antibiotic
- resistant bacteria usually resistant to other penicillins
Last resort antibiotic
- vancomycin
- resistance to this also developing
MRSA big killer
- kills more is US and Europe than AIDS
- causes 1/2 soft tissue and skin infections in intensive care
Indolent infections
- slow to heal, esp in those w/ type II diabetes
Why are alternatives to antibiotics req?
- take time and money to develop
- little profit, so less incentive and req govt input
Biotherapy
- using live organisms on body
- distinct from use of chemicals prod by MOs
Maggot therapy
- treat long standing indolent antibiotic resistance wounds
- use green blowfly, not blue
- modern version dev by Baer = Debridement therapy
- maggots eat rotting flesh, won’t eat bone and prod own antibiotics that aid healing
Honey therapy
- used on external indolent wounds, eg. mastectomy
- many bacterial pathogens sensitive to antibac properties of manuka honey
- works by:
–> osmotic effect (low water activity as most water
molecules assoc w/ constituent monosaccharides)
–> H2O2 (released by slow ox of glucose, acts as
antiseptic
–> pH (too acidic for most bacteria to grow
–> non-peroxide antibiotic activity
Mycotherapy
- use of living mycelium of antibiotic prod fungus on wound
- prod penicillin, patulin and complex chemicals
- ‘homemade penicillin’
Danger of fungal infections
- major killer in AIDS patients, as immunocompromised
In what form can fungal infections survive?
- saprophytes
Where do fungal infections affect?
- affects skin and mucus membranes, as like damp
- eg. throat, vagina, anus
Dermatophytases
- skin infections by filamentous fungi
- eg. ringworm
- breakdown skins keratin by prod keratinases
- can be caught from soil or animals, =keratinophilic
Predisposition
- genetically susceptible to infections
Mucosal yeast
- eg. thrush
- looks like large bacteria
- reprod by budding
- often latrogenic infections (= passed on by doctors)
- dimorphic
Systemic mycoses
- eg. Farmers lung, airborne spores grow inside lung, mimics TB
- can infect organs, eg. lungs, heart, liver
- can be fatal
Mycetoma
- eg. Madura foot, grows in lymph system and blocks it, liquid build up
- common cause of limb loss in dev countries
Fungi infections in AIDS
- P. carinii thought to be protozoa, found to have life cycle on lungs
- thrush main killer, final infection
- now antifungal antibiotics, but no antifungal immunisation vaccines
Antifungal antibiotics
- griseofulvin, dermatophyte skin infections
- nystatin, thrush infections by peccary/douche
- amphotericin B, systemic fungal infections
- fluconazole, thrush infections, taken orally
