Environmental Microbiology and Water Microbiology
What is Environmental Microbiology
Study of microorganisms and their activities in the environment for understanding their role in maintaining the biosphere.
Classic focus: cycling of elements/nutrients; influence on global climate.
Modern expansion: with new technologies, includes novel concepts, discovery of new steps in nutrient cycling, and broader roles for microbes in environmental processes.
Modern Environmental Microbiology: Scope and Discoveries
Discovery and identification of new microbes, microbial activities, and microbial products that protect the environment.
Examples of applied microbial products replacing chemicals:
Pests/pesticides with microbial products that have long residence times in the environment.
Microbially enhanced oil recovery.
Microbially enhanced mineral recovery.
Bioremediation targeting hydrocarbons, organics, and metals.
Discoveries expanding understanding of element cycling, e.g.,
Anaerobic oxidation of ammonia (anammox).
Anaerobic oxidation of methane (AOM).
A key insight: Archaea are more abundant in the world’s oceans than previously thought; questions about their ecological roles in marine environments.
Environment: Internal vs External
Environment can be internal (inside the body) or external (outside the body).
In this course, focus is on the external environment.
External Environment: Biotic and Abiotic Components
External environment consists of two main components:
Biotic – living components (plants, animals, microorganisms)
Abiotic – non-living components (gases/air, liquids/water, minerals/soil)
We will examine biotic and abiotic aspects across different environmental components.
Water in Environmental Microbiology
Water is central to life and microbial ecology; microorganisms in water respond to water quality and can impact health.
Rationale for studying water microbiology:
Microorganisms living in water change with water quality and can adversely affect health.
Microbes in water can be transported from one habitat to another.
Types of Water
Based on origin/nature: Ground water and Surface water (two major types).
Ground water:
Originates from deep wells and subterranean springs.
Virtually free of bacteria due to soil filtration, deep sand, and rock filtering.
Surface water:
Includes streams, rivers, shallow wells.
May become contaminated from rain/run-off, industrial discharges, etc.
Water Use Categories (Based on Use)
Four main types:
Potable water – for drinking and food preparation.
Recreational water – for sports and leisure (swimming, beaches, pools).
Labour/Agricultural water – used in irrigation, cleaning, processing, and other industrial activities.
Wastewater – contaminated or polluted water.
Potable Water: Characteristics and Treatment
Potable water is for drinking/food prep.
Public health authorities discourage high concentrations of bacteria in drinking water, even if fecal contamination is not evident.
Filtration and disinfection aim to produce near-sterile water and typically water devoid of coliforms.
Recreational Water
Activities include wading, swimming, boating, water skiing, white-water rafting.
Venues: pools, ponds, beaches, lakes, rivers.
Swimming pool water is usually filtered and disinfected, but user density is high; natural venues have less control over contamination.
Beaches may receive storm runoff; contamination control is more challenging in natural venues.
Labour/Agricultural Water
Workers contact water in fields during irrigation and in food processing (washing/transport of products and wastes).
Potential for direct ingestion of contaminated water and infection through skin or cuts.
In areas with limited water, recycling is common; without appropriate treatment, recycling increases infection risk.
Water Pollution/Contamination: Basic Concept
Water becomes contaminated when it contains biological, chemical, or physical characteristics that cause undesirable effects (e.g., color or turbidity).
Pathogenic microorganisms in water can cause diseases.
Water Pollution: Physical Pollution
Turbidity: cloudiness due to suspended particulates (sand/soil/algal blooms).
Suspended solids and floating materials (e.g., plastics).
Thermal pollution: release of hot water (e.g., from power plants).
Chroma: colored materials (e.g., textile dyes).
Remediation notes:
Turbidity/solids are removible by sedimentation and filtration.
Thermal pollution can have serious long-term ecological impacts.
Color from dyes can be considered chemical pollution as well.
Water Pollution: Chemical Pollution
Introduced organic and inorganic wastes into water.
Fertilizers, organic matter (fuel for biological growth).
Dyes, pesticides, other industrial chemicals.
Household/hotel waste (food waste, detergents).
Water Pollution: Biological Pollution
Arises from microorganisms entering the water.
Normally, a water body can handle some biological material due to resource limits; problems arise when water becomes stagnant or overloaded with waste.
Pollution of Recreational Waters
Contaminants mobilized by storm runoff enter streams, storm drains, beaches, and adjacent waters.
Animal waste can continually contaminate recreational waters.
Where human waste disposal is on land (cesspools/septic systems), storms can cause direct contamination of recreational waters.
Microorganisms in Swimming Pools
Sources of contamination include:
Faecal contamination from bathers (diarrheic stool, especially in children).
Warm-blooded animals (rodents, birds) can contaminate water.
Non-faecal human shedding (vomit, mucus, skin, saliva) can introduce disease-causing microorganisms.
Maintenance failures can lead to public health problems.
Microbial Components of Water: Unpolluted vs Polluted
Unpolluted vs polluted microbial components include various groups (examples listed in slides):
Actinomycetes, Coliform/faecal coliform bacteria, Yeasts, Desulfovibrio, Bacillus spores, Faecal streptococci, Clostridium spores, Protozoan cysts, Eukaryotic organisms like Euglena, Paramecium, Cyanobacteria, Autotrophic bacteria, Enteric viruses, etc.
Note: Do not attempt to memorize the entire visual list; use it to understand typical microbial signatures in different water quality contexts.
Water and Wastewater Microbiology: Why Important?
Focus on disease-causing organisms in water and wastewater.
Transmission routes are often faecal-oral.
Disease cycle connections to public health.
Faecal-Oral Transmission Pathway (Illustrative Model)
Faeces → flies/hands → water/food → mouth → infection (faeco-oral route).
Water-Borne Diseases: General Threats
Water-borne diseases pose serious societal threats by potentially infecting large numbers quickly.
They can be incapacitating and have higher death rates if untreated; risk is higher for children, elderly, and immunocompromised individuals.
The ‘Big Five’ Diseases of Tropics and Temperate Regions
Disease: Cholera; Organism: Vibrio cholerae; Symptoms: Severe diarrhoea, dehydration
Disease: Salmonellosis; Organism: Salmonella spp.; Symptoms: Watery diarrhoea, abdominal cramping, nausea, vomiting, fever, chills
Disease: Typhoid fever; Organism: Salmonella typhi; Symptoms: Fatigue, headache, abdominal pain, elevated temperature; Approximately death rate
Disease: Gastroenteritis/Campylobacteriosis; Organism: Campylobacter jejuni; Symptoms: Watery diarrhoea with cramps, nausea, vomiting, fever, chills
Disease: Dysentery/Shigellosis; Organism: Shigella spp.; Symptoms: Bloody diarrhoea, abdominal cramps, rectal pain; Some species can cause toxin-mediated kidney injury (hemolytic uremic syndrome expected in some cases)
Note: Symptoms are provided for study; memorization details may vary by course; focus on organism-disease associations and general clinical features.
Measuring Water Pollution: Microbiological Testing
Core question: How can we measure microbial water quality?
Indicator-based testing is used to infer the presence of pathogens rather than testing every pathogen directly.
Indicators of Microbial Pollution: Rationale
Testing for all pathogens is costly, time-consuming, and complex (multiple media, varying incubation times).
Faecal pollution indicates risk from a broad range of enteric pathogens; detecting faecal pollution is essential for public health protection.
Pathogen Testing: Time and Cost Considerations
Pathogen testing involves trade-offs between speed, cost, and accuracy; indicators provide a practical alternative for routine monitoring.
Indicators and Detection: Key Bacteria
Total Coliforms: Includes species of Escherichia, Enterobacter, Klebsiella, Citrobacter.
They represent a broad group used for general water quality assessment.
Faecal Coliforms: Thermotolerant coliforms; includes E. coli and other organisms such as Klebsiella pneumoniae.
Their presence indicates faecal material from warm-blooded animals; source differentiation (human vs animal) is not possible from coliform presence alone.
Escherichia coli (E. coli) as an Indicator:
Advantages: present in wastewater and polluted waters when pathogens are present; commonly outnumber pathogens; share similar survival characteristics with pathogens in water treatment contexts; generally not able to multiply in natural waters; often non-pathogenic strains used as markers; detectable in low numbers at low cost.
Limitations: some pathogenic strains exist; presence does not guarantee pathogen presence, and absence does not guarantee safety.
Other indicators: Streptococcus, Aerobes, Enterococcus, Listeria spp., Enterobacteriaceae, and various total mesophiles and facultative anaerobes; these groups help characterize microbial communities and potential fecal contamination.
Detection Methods for Coliforms and Indicator Bacteria
Presence-Absence Test: Simple yes/no result for coliform presence; often uses McConkey Broth or similar.
Most-Probable Number (MPN): Statistical method estimating concentration based on dilution series; details are typically covered in practical sessions.
Membrane Filtration (MF): Filtration of a known volume through a membrane, followed by culture on a differential medium to count colonies (e.g., E. coli colonies on selective/differential media).
Presence-Absence Test (Illustrative)
Procedure: Inoculate medium (e.g., McConkey Broth) with sample; observe for coliform growth (positive/negative).
MPN Test (Overview)
An established statistical approach with presumptive, confirmed, and completed testing stages; used to estimate the concentration of coliforms/indicator organisms in a water sample.
Details are typically covered in practical laboratory sessions.
Membrane Filtration (MF) Method (Overview)
Process: Filter a known volume of water through a membrane; place membrane on differential/selective medium; incubate and count E. coli colonies.
Visual: Growth on membrane filter on differential medium (as demonstrated in slides).
Failures and Limitations of Indicator-Based Testing
Absence of coliforms does not guarantee absence of human pathogens (viruses and protozoa can be resistant to common disinfection and filtration methods).
Cryptosporidiosis (Cryptosporidium parvum) is a notable example of a protozoan that can be resistant to common water treatment and not readily detected by coliform indicators.
Why Water-Borne Disease Incidence Might Be Low in Sri Lanka (SL)
Factors contributing to low incidence include:
Treatment of drinking water
Water quality standards
Community wastewater treatment systems
Mandatory vaccinations (e.g., polio)
Next Topic: Potable Water Treatment Process
Transitioning to potable water treatment processes and their role in ensuring safe drinking water.
REMEMBER:
Key equations/numbers to memorize for exams include:
of Total Coliforms are Faecal Coliforms.
Fermentation of lactose by E. coli at is used in certain faecal coliform tests.
Protective role of disinfection/filtration leading to near-sterile potable water (qualitative, not a single numeric value).
E. coli lactose fermentation: typical detection parameters include growth within at for certain standard tests.