Environmental Microbiology
•
Study of the relationship of
microorganisms with one another and with their environment
•
Microorganisms are affected by biotic and abiotic factors
–
Biotic factors – living or dead organism surrounding the microorganism
–
Abiotic factors – nonliving components (chemicals – minerals, temperature, pH,
light)
The Organization of Ecosystem
•
Planet Earth
–
Lithosphere
–
Hydrosphere
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Atmosphere
–
Biosphere
•
Ecosystem
–
A natural unit consisting of all living organism in an area functioning together
with all of the non-living factors of the environment
•
Community
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Clustered association of different organisms living at the same place
•
Population
–
Group of individual organisms of the same kind
A food chain or energy pyramid
Organized in three categories:
•
Producers
•
Consumers
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Decomposers
The Role of Microorganisms in Ecosystem
•
Primary producers
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Photosynthetic organisms: Algae, photosynthetic bacteria
•
Consumers
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Protozoa that feed on algae and bacteria
•
Decomposers
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Heterotrophic bacteria and fungi that degrade dead plant and animal material
•
Parasites
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Living and feeding on a host (viruses, bacteria, fungi, protozoa)
Interactions Between Organisms
•
Mutualism
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Biological interaction between individuals where both organisms derive a benefit
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Example: Lichens
•
Commensalism
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Relationship between two organisms where one benefits and the other is not
affected
–
Example: Bacteria living on the surface of algae
•
Co-metabolism
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The waste product of one microbe is a nutrient for the other
•
Parasitism
–
A relationship in which the parasite benefits from a close association with the
host, which is harmed
•
Synergism
–
A relationship in which two or more organisms working together to produce a
result not obtainable by any of the agents independently
•
(Degradation of the pesticide (Diazinon) possible only in the presence of two
bacterial species Arthtrobacter and Streptomyces)
Biogeochemical Cycles
•
Exchange of compounds (elements) between biota and soil and oceans
•
Chemical transformation of biogenic elements (N, C, P, S) by microorganisms
The Carbon Cycle
•
An essential element in biomolecules
•
50% of biomass accounts for carbon
•
During photosynthesis (cyanobacteria, algae, bacteria, plants) CO2 is reduced
into organic carbon compounds (cellulose, starch, fats, proteins)
Organic carbon compounds produced by photosynthetic organisms are:
•
consumed by animals
•
degraded and released in the form of CO2
Carbon is stored in:
•
Rocks/soil - limestone (CaCO3)
•
Oceans - in the form of (HCO3)2-
•
Fossil fuels (coal, petroleum)
•
Atmospheric CO2
•
Biomass
The Nitrogen Cycle
Nitrogen is needed for synthesis of proteins, nucleic acids and other molecules
Proteins (dead bodies of plants or animals) are decomposed
proteolysis
Amino acids
ammonification
Ammonia
(HN3) + H2O ------- NH4
(ammonium)+ OH
Nitrification
1. NH4 -----
NO2 (nitrite) Nitrosomonas
2. NO2 -----
NO3 (nitrate) Nitrobacter
Denitrification
NO3 -----
NO2
------ N2O
------ N2
nitrate
---- nitrite ----
nitrous oxide ---- nitrogen gas
Nitrogen fixation
•
70% of air is N2.
Some microbes can use N2 as a source of nitrogen
N2 -------
NH3
Free-living N2-fixing bacteria
•
Heterotrophic bacteria found in the rhizosphere (the region in vicinity of
roots)
•
Photoauthotrophic - cyanobacteria
–
Cyanobacteria have specialized cells heterocysts - sites of nitrogen fixation
Symbiotic N2-fixing bacteria
•
Rhizobium – symbiotic bacterium that forms root nodules in leguminous plants
(beans, peas, soybean, and peanuts)
•
Cyanobacteria – Lichens, fern (Azolla), cycades
Soil Microbiology
•
Soil is the site of biogeochemical cycles
•
Contains great array of different microorganisms (bacteria, algae, fungi,
protozoa, viruses)
•
These organisms interact with plants in the rhizosphere
–
Plants excrete organic compounds – used by microbes
–
Microbes produce hormones and growth factors
•
Soil is the site of biogeochemical cycles
Mycorrhizae
•
Mutualistic partnership between a plant and fungi
•
The plant feeds the fungus with organic compound synthesized during
photosynthesis
•
The fungus captures water from the soil and transfers it to the plant
Aquatic Microbiology
•
Aquatic Microbial Ecology
–
Interaction of microorganisms and their environment
•
Water Monitoring
–
Prevention of diseases
•
Role of Microorganisms in Water Purification Process
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Preparation of drinking water
–
Sewage treatment
Role of microorganisms in water quality
Transmission of infectious diseases
–
Causative agents of various diseases are transmitted through water (Salmonella,
Shigella, Vibrio, hepatitis A)
–
2 million deaths/year caused by cholera (Vibrio cholerae)
Problems associated with non-pathogenic aquatic microbes
•
Red tide – massive development of marine alga Karenia brevis (formerly
known as Gymnodinium breve) common in Gulf of Mexico
•
Produces neurotoxin brevitoxin – concentrated in shellfish
•
Causes paralytic shellfish poisoning
Water Bloom
•
Input of excess of nutrients - leads to Eutrophication -massive development of
algae – water bloom
•
Decaying biomass depletes oxygen from the environment – fish kill
•
Some cyanobacteria produce cyanotoxins
Water quality assays
•
Water quality of drinking and recreational waters are routinely checked by
coliform enumeration
•
Coliforms (E. coli; Enterobacter, Citrobacter) are Gram negative bacteria
residents of bird and mammal intestines
•
E. coli is the indicator organism. Its presence indicates fecal contamination
•
Coliform enumeration is performed by membrane filtration technique
Membrane filtration technique
•
Water sample is filtered through the membrane filter - bacterial cells are
retained on the filter
•
Filter is placed on the surface of solid nutrient medium - colonies appear on
the filter
•
Differential medium is used – E. coli colonies can be distinguished from other
bacteria
Role of microbes in water purification
•
Microbes degrade organic pollutants
–
Natural process that occurs in streams, rivers, oceans - self purification
•
Sewage treatment applies the same principles
–
Growing of selected microbes in control conditions
Water treatment
–
Municipal water purification - removal of microbes
–
Sewage wastewater treatment - use of
microbes
Chapter 25
Applied and Industrial Micorbiology
Municipal water purification consists of the following phases:
·
Coagulation – removal colloidal materials – clay
·
Sedimentation – removal of the formed floc
·
Filtration – removal of the small particles
·
Disinfection, chlorine, ozone, UV light
Sewage treatment
•
Primary sewage treatment
–
Screening out of the large floating material
•
Secondary treatment
–
Aeration tanks containing high concentration of waste degrading microorganisms -
activated sludge
–
Degradation of dissolved organic matter
–
Activated sludge removed
•
Purified water disinfected and release