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, 1m.

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-, SO3

-

Reduced 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+ + HCO3- CH4 + 3H2O

Energy -136kJ (but as low concentrations = -30kJ)

Low pE (anaerobic) environments Inhibited in Marine sediments Other substrates include Acetate, Methanol, Formate etc.

Complex polymers

Monomers

Acetate

H2 + CO2Acetate

AcetateH2 + CO2

PropionateButyrateAlcohols

METHANE

Hydrolysis

Fermentation

Acetogenesis Syntrophs Fermentation

MethanogensAcetoclastic

MethanogensH2-Utilising, Acetoclastic

Sugars, amino acids

Protein, Cellulose

METHANOGENESIS

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 5m 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 C10H17O6N- or Organic C + N } i.e. low ratio N:C and some need therefore tolerate vitamins 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. OxygenNormally 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 wherecold 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 Associationsthick, slimy growths on river bed pulp mill, dairy or strong sewage

Leptomitis lacteus 4% Geotrichum 7% FUNGIFusarium aqueductum 3% Other fungi 10%

Sphaerotilus natans 89% BACTERIA*Zoogloea 94%

Stigeoclonium 10% Diatoms 18% ALGAEUlothrix 4%

Sewage Fungus - therefore a misnomer Mainly bacteria

Fungi in Activated Sludge

Rare, unless high proportion of trade wastes(e.g. Canneries, Dairies, Distilleries)

High C:N ratioLow pHLow DOOverloadingUnder aeration

Give rise to BULKING SLUDGE.*Geotrichum Pullularia pullulans Sporotrichum

Also filamentous bacteria give rise to same probleme.g. Nocardia, Sphaerotilus natans, Thiothrix, Microthrix + many others

Fungi in Trickling Filters

Leptomitis lacteus often present in feed channels.Fusarium aqueductum Colonise surface of filter Geotrichum candidum Able to withstand impact of

sewage.

Sepedonium spp. Subbaromyces speldens Common in sub-surfaceAscoidea rubescens zone.

Phoma, Saprolegnia, Leptomitis lacteus occasionally present.

In winter, species with low optimum temperaturee.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.