Microbial ecology

Essential nutrients

those that must be supplied by the environment

• that includes macronutrients and micronutrients

Macronutrients needed for microbial growth

• needed in large concentrations

  1. Carbon

  2. Nitrogen

  3. Phosphorus

  4. Hydrogen

  5. Oxygen

  6. Sulfer

• we need a series of ions at high concentration, they function as coenzymes and used to generate an equilibrium within the cell

  1. Mg2+

  2. Fe2+

  3. K+

  4. Ca2+

Micronutrients needed for microbial growth

Micronutrients needed at smaller concentrations but they are still essential

1. Cobalt

2. Cu+

3. Mn2+

4. Mo2+

5. Ni2+

6. Zn2+

• components of cofactors or enzymes

Where does the energy come from to build cells?

chemical reactions including anabolic and catabolic reactions

Anabolism

build molecules

• endergonic: requires energy

Catabolism

Breakdown of molecules

• exergonic ; releases energy

Primary Producers

Primary producers make biomass by converting inorganic matter or light energy into organic compounds (e.g., plants, algae, photosynthetic bacteria).

Grazers

• Grazers (e.g., herbivores) consume primary producers (e.g., grass, plants).

• They rely on the organic energy produced by primary producers to fuel their own metabolism.

Consumers

• Consumers are organisms that obtain their energy from primary producers or other consumers.

• They eat organic matter created by primary producers and are part of higher trophic levels in the food web.

Decomposers

• When consumers die, their nutrients are trapped within their bodies.

• Decomposers (mainly microbes) break down dead organisms to release nutrients back into the ecosystem.

• This process is vital for recycling minerals and nutrients in the food web.

Classification based on metabolism

Phototrophs

Organisms that obtain energy from light.

1. Autotrophs

2. Heterotrophs

PhotoAutotroph

• Organisms that produce their own compounds using light energy and inorganic substances like carbon dioxide.

  Examples

  1. Cyanobacteria

  2. Vascular plants

     

PhotoHeterotrophs

Organisms that use light energy to produce ATP, but require organic compounds (rather than carbon dioxide) for their carbon source.

• examples:

  1. Heliobacteria

  2. Most green non-sulfer bacteria

Chemotrophs

Organisms that obtain energy from chemical reactions, typically by oxidizing compounds.

ChemoAutotroph aka chemolithotrophs

Organisms that obtain energy from chemical reactions and use inorganic compounds (such as carbon dioxide) as their carbon source.

• EXAMPLES)

  1. Sulfer-oxidizinf bacteria

  2. hydrogen bacteria

Chemoheterotrophs aka Chemoorganotrophs

Organisms that obtain both energy and carbon from organic compounds.

• includes, mammals, funghi, most bacteria

• organotrophic

Organotrophic

using organic compounds as source of electrons and carbon

Role of Microbes in Carbon Cycling

Microbes play a key role in carbon fixation, decomposition, and respiration, facilitating the movement of carbon through the ecosystem.

• Autotrophic microbes (e.g., cyanobacteria, green algae, photosynthetic bacteria) capture carbon dioxide (CO₂) from the atmosphere during photosynthesis and convert it into organic carbon (e.g., glucose).

Role of microbes in nitrogen cycling

because most of the nitrogen in the atmosphere is unusable for most organisms, microbes can fix it and turn it into a usable form

• nitrogen fixers: called diazotrophs have nitrogenase enzyme which converts inorganic N2 to Ammonium Ion

Example of nitrogen fixer

Rhizobium bacteria