Week One Lecture 3: Microbes Shape Our History

how much microbes are cultural in a laboatory

0.1% rest in earths biosphere

Sergei Winogradsky

was one of the first scientists to study microbes in their natural habitats.

• developed enrichment culture methods and selective growth media to grow some bacteria while excluding others.

  • Enrichment and selective cultures help us identify microbes causing infection in hospitals today!

Marshes/wetlands support bacteria known as

• lithotrophs, which feed on inorganic molecules.

  • Uncommon materials in previously derived media types

nitrogen fixation

• Bacteria and archaea fix nitrogen (N₂) by reducing it to ammonia (NH₃)

  • This is necessary for plants to be able to utilize nitrogen

mutualism

• Certain bacteria fix nitrogen as partners with a host organism

Endosymbionts

• are bacteria that fix nitrogen inside a plant cell in a mutualism relationship

• They are also the type of bacteria found in human and animal guts that aid in digestion 

• Create microbiomes!

 microbiome

• Communities of bacteria can live in certain regions of the human body and are considered part of the microbiome of those regions

  • Also called microbiota

  • Certain bacteria types are very prominent in specific microbiomes

• Microbiomes can form as early as birth (and maybe before!) and can shift during your lifetime

members of a microbiome can actually provide

• health benefits to the colonized host based on the area/type

  • Not all bacteria are bad!

    • Skin microbiota can provide protection from unwanted microbes

    • Gut microbiota aids in digestion

• Disruption to the microbiome can cause disease/health challenges for the host

Endosymbiosis Theory

• Scientist Lynn Margulis theorized that eukaryotic cells came to contain mitochondria and chloroplasts by merging with bacteria to form composite cells by intracellular endosymbiosis

intracellular endosymbiosis

• Process where one cell internalizes another that grows within it

• Ultimately generates a single organism whose formerly independent members are now incapable of independent existence

Lynn Margulis

•  proposed that early in the history of life respirating bacteria similar to E. coli were engulfed by pre-eukaryotic cells where they evolved into mitochondria

  • Mitochondria are vital to energy generation in eukaryotic cells!

  • The DNA found in mitochondria and chloroplasts have many similarities to modern bacteria!

    • Similarities of mitochondria and bacteria can cause issues with antibiotic use!

Carl Woese

• First proposed a “new” form of prokaryotic life called archaea, with characteristics distinct from other bacteria and from eukaryotic life.

  • Archaea living in extreme environments produce sturdy enzymes that ca be used for industrial and clinical procedures and identification techniques like PCR

Microbial Discoveries Have Transformed Medicine and Industry

• Research in the microbiology field have allowed for unprecedented advances in human medicine and industry

  • Very prominent in genetic engineering!

• The discovery of the structure of DNA by Rosalind Franklin has allowed for large molecular research advancements

• Microbiologists have helped determine the beginning and endpoints of genes and their functions!

• Bacteria is often used for genetic research due to their easily sequenced genomes, ability to be genetically edited, and their ability to replicate quickly!

  • Can also produce a large quantity of proteins and enzymes in a short span of time

• The tools used in microbial molecular biology can also help us edit human DNA to treat disease!

• For example

• The AIDS virus HIV has been engineered in a lab to make DNA carrier molecules that can insert genes into cells of the human bodies in a process called chimeric antigen receptor T-cell (CAR-T) therapy to help treat specific cancers

• Clustered regularly interspaced short palindromic repeats (CRISPR) is a DNA editing tool that was engineered from the protein-RNA complex that defends bacteria against infection by viruses called bacteriophages. It is proposed as a way to treat cancer

• Adeno-associated virus (AAV) is a small, non-enveloped virus that can infect  wide range of cells with specific genetic material without causing disease, making them a candidate for gene therapy