environmental_microbiology_micro5

Environmental Microbiology Overview

Course Title

• Environmental Microbiology MICRO5

Learning Goals

• Understand the role of microbes in fixing nitrogen in the environment.

• Explain eutrophication and how it can occur.

• Describe examples of microbes with symbiotic relationships.

• Explain the basics of water treatment and sewage treatment.

Identifying Microbes in Extreme Environments

• Sequencing is an effective method to identify bacteria present in difficult-to-culture environments.

• Process to identify: Collect sample ➔ extract DNA ➔ sequence 16S rRNA gene.

Nitrogen Fixation by Microbes

Importance of Nitrogen

• Atmosphere is approximately 80% N2 gas.

• Plants and animals cannot use atmospheric nitrogen and require nitrogen compounds (e.g., amino acids).

Nitrogen Cycle

• Involves cycling nitrogen through different forms in the environment.

• Nitrogen-fixing bacteria convert N2 into ammonia (NH3) using the enzyme nitrogenase.

• Reaction: N2 ➔ NH3 (process known as nitrogen fixation).

Cyanobacteria

• Perform nitrogen fixation in specialized cells called heterocysts.

• Heterocysts provide an anaerobic environment for nitrogen-fixing activity.

Eutrophication

Definition

• Eutrophication: The process of enrichment of aquatic systems with organic nutrients (nitrogen and phosphorus) leading to oxygen depletion.

Process

• Nitrogen and phosphorus are typically in low supply, limiting algae/cyanobacteria growth.

• Increased nutrient input from agricultural and industrial runoff can stimulate algal blooms.

• After blooms die, decomposition by bacteria depletes oxygen, resulting in fish kills.

Examples of Symbiotic Relationships with Microbes

General Definition of Symbiosis

• Symbiosis refers to the relationship between two organisms where at least one benefits from the association.

E. Coli in Humans

• E. Coli synthesizes vitamins B and K, providing health benefits to humans while benefiting from the nutrient-rich environment of the intestines.

Rhizobium in Legumes

• Rhizobium bacteria infect legumes' root nodules, forming symbiotic relationships.

• Plant offers anaerobic conditions and growth nutrients, while bacteria fix nitrogen for plant use.

Methanogens

• Found in the guts of ruminants like cows.

• Break down cellulose releasing methane (CH4), a significant greenhouse gas.

Mycorrhizae

• Networks of fungi that associate with plant roots, enhancing nutrient and water absorption.

• Fungi receive carbohydrates from the plant, forming a mutualistic relationship.

Ophiocordyceps unilateralis: A Pathogenic Fungus

1. Fungal spores infect ants, infiltrating their central nervous system (CNS).

2. Secreted metabolites alter ant behavior, prompting them to climb and die at optimal heights for fungal growth.

3. The fungus then consumes the ant and spreads its spores from the dead host.

Water Treatment Basics

Flocculation

• Flocculant: a chemical that forms aggregates (floc) to remove contaminants (e.g., aluminum potassium sulfate).

• Effective at removing viruses and bacteria.

Filtration

• Utilizes layers of fine sand or crushed coal to filter water.

• Removes protozoan cysts and oocysts effectively.

Disinfection

• Techniques such as UV light treatment further disinfect water and eliminate pathogens.

Sewage Treatment

• Similar to water treatment; involves filtration and oxidation of organic matter by microbes.

• Disinfectants ensure removal of pathogens before water is released.

Bay Area Sewage Treatment

• Tertiary treatment processes allow sewage to be filtered to a level suitable for drinking.

Opportunistic Pathogens

• Define: Opportunistic pathogens that usually do not cause infections but can when conditions favor them.

• Examples: E. coli can cause urinary tract infections if located improperly.

• Various factors such as immune suppression or environmental changes can increase the risk of infections.