Transcript Spectrophotometry, Colour and Turbidity

Aquatic Bacteria & Fungi
 Objective
 To know the main cellular features, physiology and function of
bacteria & fungi in water and wastewater environments
 To know the species interactions in anaerobic digestion
 to understand how substrate conditions and nutritional requirements
determine the competitive success of these microbes in pollutant
degradation processes.
 References
 Gray N.F. Biology of Wastewater Treatment
 Lester J.N. & Birkett J.W.
Microbiology and Chemistry for
Environmental Scientists & Engineers
 Madigan M.T., Martinko J.M., Parker J.
Brock - Biology of
Microorganisms
 Stanier R.Y.
General Microbiology
 Kiely G
Environmental Engineering
 Lecture Outline
 Bacteria - Cell Structure Physiology & Function
 Fungi- Cell Structure Physiology & Function
Bacteria
What are they?
 Prokaryotic organisms
 Bacteria (eubacteria), Archaea (archaebacteria)
Importance in Environmental Engineering
 Biodegradation
 Nutrient Cycling
 Pathogens in Contaminated Waters
Bacterial Cell Structure
Size
 smallest living organisms, 1m.
Shape
 typically cocci or rods (bacilli), spiral, stalked,
filamentous.
 multicellular swarms (gliding myxobacteria, myxococcus)
DNA
 circular, supercoiled, no nuclear membrane.
 Extranuclear DNA or Plasmids.
Reproduction
 Asexual = Binary fission, Conjugation via Pili.
Cell Structure
Cell Wall
 Two types, Gram Positive, Gram Negative
 Both have Peptidoglycan
 Gram Negatives also have Lipopolysaccharide (LPS)
Archaea
 similar to G+ve, have pseudopeptidoglycan
Cell Structure
Flagellum




May be present - Motile
Polar or peritricious
Driven by Proton motive Force (PMF)
Chemotaxis - tumble frequency increases.
Cytoplasm
 complex subcellular organelles usually absent.
 vesicular and lamellar structures (mesosomes) form by
invagination of cytoplasmic membrane (e.g. N-fixing,
Nitrifying, and Phototrophic bacteria).
 cytoplasmic membrane essential (maintains PMF).
 Ribosomes - Protein synthesis
 Enzymes - metabolism
 Granules (Inclusions)
 Gas Vesicles (buoyancy, e.g. cyanobacteria)
Characteristics
Oxygen Requirements




Aerobic
Microaerophilic
Facultative (aerobe)
Anaerobic (strict)
Growth Requirements - Organic substrates
 Heterotrophic (Chemoorganotrophs)
– Pseudomonas, Bacillus, Zoogloea, etc.
 Key role in Nutrient Cycling
 Biodegradation of Organic Detritus
 Soluble low molecular weight substrates e.g. acetate,
methanol, sugars.
 Polymers degraded by extracellular hydrolytic Enzymes.
Metabolism
Growth Requirements - Inorganic substrates
 Autotrophic (Chemolithotrophic, Phototrophic)
– Nitrosomonas, Nitrobacter, Methanococcus, Chlorobium, etc.




Reduced forms of sulphur H2S, S0, S2O32-, SO3Reduced forms of nitrogen NH3
Hydrogen H2
Iron Fe2+
Growth Requirements - Light




Photosynthetic (phototrophic)
light and CO2
oxygenic
blue-green (cyanobacteria)
anoxygenic
green-sulphur (Chlorobium sp.)
Bacteria in Aquatic Environments
 Natural Waters
 Energy source (depends on metabolism and dissolved species)
 Cellular Nutrient Requirements




C, H, O, N, P, S.
vitamins, growth factors, trace elements.
Dissolved Gases (O2, CO2, H2S)
Nitrogen is usually limiting in oligotrophic waters.
 Origin of Nutrients




Algal secretions, death.
Zooplankton feeding, death.
Soil run-off
discharge of treated (& untreated) effluents.
Bacteria in Aquatic Environments
 Planktonic
 suspended free cells
 vertical movement
– O2
– stratified nutrients (in anoxic zone)
 Particulate
 associated with POM
 Biofilms
 surfaces of stones and plants (epiphytic)
 can be slow growing, psychrophilic environments.
Methanogenesis
Methanogenic Bacteria (Archaea)
 Chemolithotrophic (autotrophs)
 H2 and CO2
 e.g. Methanobacterium, Methanococcus,
Methanospirillum
 4H2 + H+ + HCO3CH4 + 3H2O
 Energy -136kJ
(but as low concentrations = -30kJ)
 Low pE (anaerobic) environments
 Inhibited in Marine sediments
 Other substrates include Acetate, Methanol, Formate etc.
METHANOGENESIS
Complex polymers
Protein, Cellulose
Hydrolysis
Monomers
Sugars,
amino acids
Fermentation
H2 + CO2
Acetogenesis
Acetate
Propionate
Butyrate
Alcohols
Acetate
Syntrophs
Fermentation
H2 + CO2
Methanogens
Acetoclastic
METHANE
Acetate
Methanogens
H2-Utilising, Acetoclastic
Methanogenesis
Methanogenesis involves Co-operation
 Inter-species Hydrogen transfer
 Several Steps from a complex substrate (Cellulose)
1. Hydrolysis (depolymerisation) to cellobiose (G-G)
2. Fermentation of Glucose to Fatty acids, H2 and CO2
3. Fatty acids oxidised to H2 and CO2 (SYNTROPHS)
4. Methanogens produce CH4
 Syntrophs require H2 to be consumed
 Typically H2 < 10-4 M
Fungal Cells
Size
 Typically 5m diameter filament, variable length
Structure
 Filamentous – hyphae bundled as Mycelia (moulds)
Usually branched
 Rods (Yeasts )
 Chitin and cellulose cell walls
DNA
 chromosomes, nuclear membrane.
Reproduction
 Asexual = tip cell, sexual = spores called conidia.
Physiology of Fungi
 No chlorophyll, produce extra-cellular enzymes.
 Heterotrophic nutrition. Parasitic or Saprophytic
 Very slow rate of growth cf. bacteria. Tolerate low DO, low
pH, High C:Nratios. Dairy & Trade wastes
Environmental Requirements
1. Nutrients - Only organic C
- or Organic C + N }
and some need
vitamins
C10H17O6N
i.e. low ratio N:C
therefore tolerate
N deficiency.
2. Moisture relatively low concentration H2O (75-80%)
(Usually 95-98% in bacteria etc.)
Therefore can grow on moist and aquatic
environments.
Physiology of Fungi
3. pH
Normally prefer low pH (produce acid themselves)
4. Oxygen
Normally prefer O2 (i.e. aerobic) although some species can
tolerate anaerobic conditions temporarily.
Aerobic respiration:
C6H12O6
6CO2 + 6H2O
Anaerobic respiration fermentation:
C6H12O6
2C2H5OH + 2 CO2 (Yeasts)
5. Temperature
Grow in range 2 - 25oC, optimum = 15oC
i.e. psychrophilic - cold-loving
Importance of Fungi in Freshwater
1. Fungi play similar role to bacteria.
Very important in breakdown of complex organics to
simpler substances for algae (i.e. NH3 mineralization)
White rot fungi (Phenaerochete) degrade lignin and produce
enzymes that degrade complex pollutant molecules
Associated with polluted waters because of high nutrient
requirements.
2. Indicators of pollution
Fusarium, Leptomitis and Geotrichum associated with a
mesosaprobic zone in Saprobian system.
Importance of Fungi in Freshwater
3. Actinomycetes and Fungi
Give Taste and Odour problems in treated water.
a)
Grow on reservoir walls, and release complex organic
compounds when dead. (TASTE AND ODOUR).
Also grow on dead algae.
Very common after algal blooms. Saprophytic
b)
Grow in cold water systems in buildings, especially where
cold and hot water pipes are adjacent.
4. Sewage Fungus
growths in rivers receiving certain industrial wastes
(e.g. wood pulping and dairy wastes).
5. Marine Waters
Sewage Fungus
WRC Survey of 90 Sewage Fungus Associations
thick, slimy growths on river bed pulp mill, dairy or strong sewage
Leptomitis lacteus
Geotrichum
Fusarium aqueductum
Other fungi
4%
7%
3%
10%
Sphaerotilus natans
Zoogloea
89%
94%
Stigeoclonium
Diatoms
Ulothrix
10%
18%
Sewage Fungus -
FUNGI
BACTERIA*
ALGAE
4%
therefore a misnomer
Mainly bacteria
Fungi in Activated Sludge
Rare, unless high proportion of trade wastes
(e.g. Canneries, Dairies, Distilleries)
High C:N ratio
Low pH
Low DO
Overloading
Under aeration
Give rise to BULKING SLUDGE.
*Geotrichum
Pullularia pullulans
Sporotrichum
Also filamentous bacteria give rise to same problem
e.g.
Nocardia, Sphaerotilus natans, Thiothrix, Microthrix + many others
Fungi in Trickling Filters
Leptomitis lacteus
Fusarium aqueductum
Geotrichum candidum
Sepedonium spp.
Subbaromyces speldens
Ascoidea rubescens
often present in feed channels.
Colonise surface of filter
Able to withstand impact of
sewage.
Common in sub-surface
zone.
Phoma, Saprolegnia, Leptomitis lacteus occasionally
present.
In winter, species with low optimum temperature
e.g. Sepedonium dominate.
Fungi in Trickling Filters
Industrial Wastes e.g. from Canneries, Dairies, Distilleries
etc. encourage growth of fungi
(High C:N ratio)
Problems caused by Fungi:
Heavy growth causes PONDING, especially in winter.
Operational procedures:
Film accumulation controlled by
 Recirculation,
 Alternating double filtration
 low frequency dosing.
Colonisation of Trickling Filters
Fungi, high energy of maintenance (40-50 mg/l BOD)
Bacteria have much lower saturation constants than fungi
(Ks = 0-20 mg/l BOD for sewage bacteria)
Therefore bacteria continue to grow at low substrate
concentrations
i.e. Bacteria have a competitive advantage over fungi
at low substrate concentrations.
Vice versa at high substrate concs.