Biology of the Pea Plant and Microbial Water Quality

Chapter 27: Environmental Microbiology

• The chapter focuses on environmental microbiology, encompassing microbial diversity, habitats, soil microbiology, biogeochemical cycles, aquatic microbiology, and sewage treatment.

Objectives

• Study microbial diversity and habitats
• Examine soil microbiology and biogeochemical cycles
• Investigate aquatic microbiology and sewage treatment

Microbial Diversity and Habitats

• Microbes inhabit diverse habitats due to their adaptable abilities.
• They utilize various carbon and energy sources.
• They can thrive under diverse physical conditions.
• Extremophiles are organisms living in extreme environments.
• Extremophiles exhibit tolerance to extreme pH, temperature, and salinity.
• Extremophiles produce extremozymes, enzymes enabling tolerance to these environmental extremes.
• Thermus aquaticus bacteria produce Taq polymerase, a heat-resistant enzyme used in PCR.

Symbiosis

• Symbiosis involves two different organisms living in close association, benefiting one or both.
• Ruminants (like sheep and cows) and rumen bacteria display symbiosis.
• Rumen bacteria ferment cellulose, and protozoa control bacteria populations.
• Mycorrhizae contribute to plant growth by expanding the root surface area.

Mycorrhizae

• Fungi form close associations with plant roots.
• Endomycorrhizae (vesicular-arbuscular) form spores that germinate into hyphae, penetrating plant roots.
• Nutrients travel from soil to arbuscules, releasing nutrients for the plants.
• Ectomycorrhizae do not form vesicles or arbuscules.
• Truffles, underground mushrooms, are ectomycorrhizal fungi frequently associated with tree roots.
• Truffles are highly valued as a food source.

Biogeochemical Cycles

• Soil may contain billions of bacterial cells and kilometers of fungal hyphae.
• Biogeochemical cycles (for carbon, nitrogen, and sulfur) involve the oxidation and reduction of elements in organic materials by microorganisms.
• The greatest microbial population in soil exists in top few centimeters, declining with depth.

The Carbon Cycle

• All organisms contain carbon in organic compounds like cellulose, starches, fats, and proteins.
• Trees derive cellulose from atmospheric carbon dioxide through photosynthesis.
• Chemoheterotrophs (animals and protozoa) consume autotrophs and other animals.

The Nitrogen Cycle

• All organisms synthesize proteins, nucleic acids, and other nitrogen-containing compounds.
• Molecular nitrogen (N2) constitutes 80% of Earth's atmosphere.
• Nitrogen fixation converts N2 into organic forms usable by plants.
• Microbial activities are pivotal for converting nitrogen into usable forms.
• Nitrification is a process that oxidizes ammonium to nitrate.
• Denitrification is a process by which nitrate is reduced to nitrogen gas (N2).

The Sulfur Cycle

• Microorganisms decompose proteins and amino acids containing sulfur.
• Microbial dissimilation converts amino acids to H2S.
• Further microbial processes convert H2S to SO₄²⁻
• Plants and microbes assimilate SO₄²⁻.

Decomposition by Microbes

• Microbes effectively degrade natural organic matter.
• Bioremediation utilizes microbes to detoxify or degrade pollutants, such as petroleum.
• Bioremediation efficiency is affected by temperature; metabolism slows with decreasing temperatures.

Aquatic Microbiology and Sewage Treatment

• Aquatic microbiology investigates microorganisms and their activities in natural waters (lakes, ponds, streams, rivers, estuaries, and oceans).
• High microbial numbers often signify high nutrient levels in water bodies.
• Wastewater from sewage and industry contain high bacterial counts.

Microbial Water Pollution

• Microbes filtered from water entering groundwater often lead to good water quality in springs and deep wells.
• Pathogens can transmit diseases through drinking water.
• Fecal contamination is a significant cause of severe water pollution.

Water Purity Tests

• Tests for water purity focus on detecting specific indicator organisms.
• Coliforms (E. coli, Klepsiella, Citrobacter, enterobacter, Serratia) and Enterococcus are examples of indicator organisms indicating fecal contamination.
• MPN (most probable number) method estimates coliform numbers.
• Membrane filtration is a direct method for determining coliforms.

Water Treatment

• Many cities obtain water from polluted rivers needing treatment before consumption.
• Water treatment aims at removing disease-causing microbes and creating potable water suitable for consumption.
• Treatment steps often include coagulation, filtration, and disinfection.

Wastewater Treatment

• Sewage contains household, rainwater, and industrial waste.
• Sewage treatment often includes primary (removal of solids), secondary (biological oxidation of dissolved organic matter), tertiary (removal of BOD, nitrogen, and phosphorus), and disinfection stages.
• Septic tanks are used in areas without sewer systems, employing anaerobic decomposition.
• Oxidation ponds are a water treatment method used by industries and small communities.

Bioaugmentation and Composting

• Bioaugmentation adds specific microbes to degrade pollutants.
• Composting converts plant remains into humus.
• Thermophilic bacteria raise compost temperatures during composting.

This quiz explores essential aspects of the pea plant, including its nutrient absorption mechanisms and the role of rhizobia. Additionally, it delves into aquatic microbiology, focusing on microbial populations in water bodies and their implications for water quality and pollution control.