Unit 8: Environmental Microbiology

The Ecosystem

• A community of living things in a non-living environment
• A specific location with biogeochemical cycles and energy transformations
• Ecosystems have boundaries that overlap with other ecosystems
• Ecosystems are divided into living (biotic) and non-living (abiotic) components
  • Abiotic components: sunlight, temperature, precipitation, soil, air, and chemicals.
  • Biotic components: living producers and consumers

Niche

• The role that an organism plays in the ecosystem
• Microorganisms occupy specific niches
• We are interested in how these organisms interact with the abiotic components
• Their value to us as organisms
• How they contribute to our existence
• Microbes can be producers, consumers, or detritivores

Biogeochemical Cycling

• The movement of elements and compounds through living (biotic) organisms and the non-living (abiotic) environment
• Important cycles
  • Carbon Cycle
  • Nitrogen Cycle
  • Oxygen Cycle
  • Phosphorus Cycle
  • Sulfur Cycle
  • Water Cycle
• Microorganisms play a critical role in ALL of these cycles
  • For example, phytoplankton in the ocean produce the bulk of Earth’s oxygen!!

Bacteria in Soil

• Soil is full of life and is the primary interaction between living (biotic) and non-living (abiotic) that makes soil a living system.
• Microbes and other biotic entities extract abiotic factors from the soil
• Soil acts as a filter to clean groundwater
  • Soil particles act like a filter to remove contaminants

Five Major Groups of Organisms in Soil

• Bacteria – most numerous (~95%)
  • Nitrogen fixing, sulfur fixing, carbon fixing
  • Aerobic bacteria (74%)
  • Anaerobic bacteria (14%)
  • Actinomycetes – denitrifiers – (13%)
• Protozoans – feed on bacteria
• Fungi – decomposers (3%)
  • Feed on dead material
• Other (0.2%)
  • Algae - Found on the soil surface
  • Worms - nematodes, earthworms

Microbes in Air

• Microbes don't generally grow in air
• They are contained on dust and water droplets
• Air in buildings contains microorganisms
  • Higher dust and moisture contents
  • Lots of people sweating and breathing
  • Poor circulation
• Mold is the most common microorganism found in air

Wastewater Treatment

• Large scale treatment can be accomplished through Cl injection
• Small scale treatment can be through the addition of bleach
• Coliform bacteria: Rod-shaped, Gram-negative, Non-spore forming, Motile or non-motile bacteria which can ferment lactose with the production of acid and gas when incubated at 35–37°C.
• Sewage treatment plants require more complex methods
  • Contains 99% contaminated water
  • 1% solids
    • Household wastes (faeces, detergents, grease, hair)
    • Industrial wastes (acids, oil, chemicals, organic matter)
• Two levels of treatment of sewage: primary and secondary

Primary Treatment of Raw Sewage

• Screens and course filters
• Remove solids and large debris
• Place in sedimentation tanks

Secondary Treatment of Raw Sewage (Effluent from 1 Treatment)

• Trickle filters – spray over rocks/sand covered in bacteria
• Activated Sludge – agitate and aerate sludge
• Aerobic breakdown of organic matter
• Check BOD and release to rivers/streams/Oceans

Tertiary Treatment (If Required)

• Effluent from 2 treatment processed for removal of PO4 & NO3
• Involve:
  • Physical and chemical treatment
  • Sand and charcoal filtration
  • Denitrifying bacteria to remove nitrogenous compounds
  • Chlorination to kill bacteria
  • UV light to kill Cl resistant organisms

Bioremediation

• An alternative to Sewage Plants
  • Bacteria introduced to raw contaminants
  • Organisms treat effluent and contents

Symbiosis

• When two organisms develop a relationship it is symbiotic.
• The larger organism is the host, the smaller, the symbiont

Types of Symbiotic Relationships

• Commensal – beneficial to the MO but does not harm the host
  • Bacteria on the skin
  • Bacteria in the respiratory and gastrointestinal tract
• Mutualistic – bacteria and host benefit from the relationship
  • Assist the immune system
  • Assist in nutrient metabolism, vitamin production, and waste processing.
• Parasitic - the bacteria benefit while the host is harmed
  • Blood flukes (shistosomiasis) a.k.a. bilharizia
  • Tape worms
• Competition – One species outcompetes another