Chapter 1 lecture 1 Flashcards
Definition of life.
Cells and organization.
Response to environmental changes.
Growth and development.
Biological evolution.
Energy use and metabolism.
Regulation and homeostasis.
Reproduction.
What is microbiology?
Microbiology is the study of microbes.
- The field examines how microbes interact with humans, with food, and how they can be used BY humans (among other aspects).
The Importance of Microorganisms
Most populous and diverse group of organisms.
Found everywhere on the planet.
Play a major role in recycling essential elements.
Source of nutrients and some carry out photosynthesis.
Benefit society by their production of food, beverages, antibiotics, and vitamins.
Some cause disease in people, plants, or animals.
Characteristics of the Members of the Microbial World
Organisms and acellular entities too small to be clearly seen by the unaided eye.
Generally <1 mm, some macroscopic.
These organisms are relatively simple in their construction and lack differentiated tissues.
Microbiology revolves around two themes:
- Understanding basic life processes
Microbes are excellent models for understanding cellular processes in unicellular and multicellular organisms - Applying that knowledge to the benefit of humans and planet Earth
Microbes play important roles in medicine, agriculture, and industry
Types of Microbial Cells
prokaryotic cells
eukaryotic cells
prokaryotic cells
lack a true membrane-delimited nucleus
This is not absolute
eukaryotic cells
have a membrane-enclosed nucleus
are more complex morphologically
Classification Schemes
Two Group
Five Kingdom-Monera, Protista, Fungi, Animalia, Plantae
Three domain system – developed due to advances in molecular techniques
Carl Woese et al (1990 paper) based on a comparison of ribosomal RNA, divides microorganisms into:
Bacteria (true bacteria),
Archaea
Eukarya (eukaryotes)
Evolution of the Three Domains of Life
Universal phylogenetic tree.
Based on comparisons of small subunit rRNA (SSU rRNA).
Aligned rRNA sequences from diverse organisms are compared and differences counted to derive a value of evolutionary distance.
Relatedness, but not time of divergence, determined this way.
The 3 Classification Schemes
Three domain system, based on a comparison of ribosomal RNA genes, divides microorganisms into:
Bacteria (true bacteria).
Archaea.
Eukarya (eukaryotes).
Domain Bacteria
Usually single-celled.
Majority have cell wall with peptidoglycan.
Most lack a membrane-bound nucleus.
Ubiquitous and some live in extreme environments.
Cyanobacteria produce significant amounts of oxygen.
Domain Archaea
Distinguished from Bacteria by unique rRNA gene sequences.
Lack peptidoglycan in cell walls.
Have unique membrane lipids.
Some have unusual metabolic characteristics.
Many live in extreme environments.
Domain Eukarya
- Protists—generally larger than Bacteria and Archaea.
Algae—photosynthetic.
Protozoa—may be motile, “hunters, grazers”.
Slime molds—two life cycle stages.
Water molds—devastating disease in plants. - Fungi.
Yeast—unicellular.
Molds and mushrooms—multicellular.
Acellular Infectious Agents
Viruses.
- Smallest of all microbes.
- Requires host cell to replicate.
- Cause range of diseases, some cancers.
Viroids.
- Infectious agents composed of RNA.
Satellites.
- Nucleic acid enclosed in protein shell.
- Must coinfect a host cell with a virus to complete life cycle.
Prions—Infectious proteins.
