Microbiology W1-1

Microbial Diversity and Techniques

• Enrichment culture was developed by Martinus Beijerinck, its key aspect being the ability to selectively cultivate specific microbes from a natural sample by manipulating nutrient and incubation conditions
• Sergei Winogradsky introduced the concept of Chemolithotrophy, explaining that specific bacteria are linked to specific biogeochemical transformations
• Chemolithotrophy involves harnessing energy from the oxidation of inorganic compounds, with Chemolithotrophs utilizing carbon from CO₂.
• Winogradsky also demonstrated the process of nitrogen fixation and nitrification, emphasizing their crucial roles in nutrient cycling.

Antibiotics and their Origins

• Sir Alexander Fleming discovered Penicillin G from the mold Penicillium notatum, marking the beginning of modern antibiotics.
• Penicillin G works by hindering the formation of peptidoglycan cross-links in bacterial cell walls.

History of Life and the Last Universal Common Ancestor

• Earth is approximately 4.6 billion years old, with the first cells appearing between 3.8 and 4.3 billion years ago.
• Early Earth had an anoxic atmosphere, devoid of oxygen, until around 2.6 billion years ago, leading to predominance of anaerobic metabolisms.
• LUCA, the last universal common ancestor, is a significant concept in understanding the evolutionary history of life.

Microbial Ecology and Ecosystem Impact

• Microorganisms, both bacteria and archaea, play a crucial role in shaping Earth’s ecosystems and influencing other organisms.
• The Earth harbors an estimated 2 x 10³⁰ microbial cells, significantly outnumbering human cells in the human body.
• Microbial activities and transformations have a profound impact on habitats and other organisms.

Extremophiles and their Habitats

• Extremophiles thrive in extreme environments that are generally unsuitable for other life forms, including hot springs, glaciers, and highly saline, acidic, or alkaline conditions.

Impact of Microorganisms on Society

• Microorganisms are both beneficial and harmful to humans, playing a significant role in disease, food production, agriculture, and environmental cleanup.
• Nitrogen-fixing bacteria are critical for plant growth, while cellulose-degrading microbes support digestion in animals.
• Microorganisms contribute significantly to bioenergy generation and environmental remediation.

Microorganisms and disease

• Microorganisms can cause disease
• Disease causing microorganisms are called pathogens
• Common pathogens include bacteria, fungi, parasites, and viruses

Beneficial Microorganisms

• Most microorganisms are beneficial
• Gut microbiome is an example of a beneficial community
• Human gut microbiome:
  • Digests complex carbohydrates
  • Synthesizes vitamins and other nutrients

Commensal Microorganisms

• Commensal microorganisms live harmlessly in or on hosts
• Commensal microorganisms are essential for human survival
• Commensal populations of microbes play a critical role in:
  • Metabolism of food products
  • Providing essential growth factors
  • Protecting against infection from virulent microorganisms
  • Stimulating the immune response

Microorganisms and Food

• Microorganisms can have both positive and negative impacts on food
• Negative impacts:
  • Food spoilage
  • Foodborne disease
  • Influence harvest, storage, and safety
• Positive Impacts:
  • Improving food safety
  • Food preservation
  • Dairy products (e.g. cheese, yogurt, buttermilk)
  • Other food products (e.g. sauerkraut, kimchi, pickles, chocolate, coffee, leavened breads, beer)

Microorganisms and Industry

• Microorganisms can be used for industrial processes
• Biofilms: communities of microorganisms, on submerged surfaces
  • Example surfaces: pipes, storage tanks, implanted medical devices
• Industrial microbiology:
  • Uses naturally-occurring microbes to produce low-cost products
  • Products include antibiotics, enzymes, and chemicals
• Biotechnology and synthetic biology:
  • Genetically engineered microbes produce high-value products in small amounts
  • This is an exciting area for future research
• Biofuel production
  • Examples of biofuels: methane and ethanol
• Wastewater treatment
• Bioremediation- using microorganisms to clean up pollutants

Structure of Microbial Cells

• The cell is the basic unit of life
• The cell is a compartment that interacts with the environment
• All cells share these common features:
  • Cytoplasmic (cell) membrane: separates the inside and outside of the cell
  • Cytoplasm: an aqueous mixture of macromolecules, small organics, ions, and ribosomes
  • Ribosomes: synthesize proteins
  • Cell wall: present in some microbes; provides structural strength

Prokaryotic and Eukaryotic Cells

• Prokaryotes:
  • Include Bacteria and Archaea
  • No membrane-enclosed organelles
  • No nucleus
  • Single circular chromosome, forming the nucleoid region
  • Might also have plasmids
  • Small, compact (0.5–10 million base pairs)
• Eukaryotes:
  • Include plants, animals, algae, protozoa, and fungi
  • Contain organelles
  • DNA enclosed in a membrane-bound nucleus
  • Linear and much larger/more DNA (up to billions of base pairs)

Activities of Microbial Cells

• Cells live in communities
• Metabolism: chemical transformation of nutrients
• Enzymes: protein catalysts
• Transcription: DNA information converted to RNA
• Translation: RNA used by ribosomes to synthesize proteins
• Motility: Many cells move independently through self-propulsion
• Differentiation: Some microbes modify structures to form specialized cells
• Intercellular communication: Some microbes communicate with other microbes
• Evolution: Genetic changes are passed to offspring

Microbial Life

• Microbial life includes viruses, bacteria, parasites, fungi, and archaea.
• Viruses are extremely small, often less than 200 nanometers, and require a host cell for replication.
• Bacteria are simple unicellular organisms that reproduce asexually.
• Parasites are complex eukaryotic microbes that can be unicellular or multicellular.
• Fungi are eukaryotic organisms that can be unicellular (yeast) or filamentous (mold).
• Archaea are single-celled prokaryotes with a lack of morphological diversity.

Bacterial Structures

• Surface Structures include pili, fimbriae, and glycocalyx.
  • Pili are involved in the transfer of genetic material.
  • Fimbriae assist in the adhesion to surfaces.
  • Glycocalyx is a polysaccharide and protein film that surrounds bacterial cells.
• Cell Walls are categorized as Gram-positive or Gram-negative.
  • Gram-positive cell walls have a thick peptidoglycan layer.
  • Gram-negative cell walls contain an outer membrane with lipopolysaccharide (LPS).
• Inner Structures
  • Cytoplasmic membrane encloses the bacterial cell.
  • Nucleoid contains the bacterial DNA.
  • Inclusion bodies store various compounds.

Bacterial Features

• Bacterial Spores are dormant, multishelled structures that allow bacteria to survive harsh conditions.
• Biofilm is a highly hydrated polysaccharide matrix that provides bacteria with protection against the environment and antibiotics.

Bacterial Pathogenesis

• Bacterial Disease Production is caused by damage produced by the bacteria and the response of the innate and immune systems.

Sterilization, Disinfection, and Antisepsis

• Antisepsis uses chemical agents to inhibit or eliminate microbes on living tissue.
• Disinfection uses physical procedures or chemical agents to destroy most microbial forms, but may not eliminate spores.
• Sterilization uses physical procedures or chemical agents to destroy all microbial forms, including spores.