1. Describe the members of the microbial world.
- Microorganisms are organisms and acellular entities that are too small to be clearly
seen by the
... [Show More] unaided eye. Some microorganisms are smaller than one micrometer,
and others are macroscopic. Microorganisms are relatively simple in their
construction and lack highly differentiated cells and distinct tissues.
2. Why are microorganismsimportant?
- Microorganisms are important for many reasons. They are the most populous and
diverse group of organisms. They can be found everywhere on the planet where life
is possible. They can play a major role in recycling essential elements. They can be a
source of nutrients. Some carry out photosynthesis to generate one-third of the
atmospheric oxygen. Some can also fix the atmospheric N2 to NH3. They can benefit
society by their production of food, beverages, antibiotics, and vitamins. Some
however cause disease in plants and animals. An interesting fact about
microorganisms is that the human gastrointestinal track contains an estimated 1014
bacteria, belonging to about 1,000 species.
3. Describe the divisions and types of microbes. Describe the types of microbial cells.
- Organisms and biological entities studied by microbiologists can be cellular or
acellular. Cellular entities include fungi, protists, bacteria, and archeae. Acellular
entities need a host to reproduce. Acellular entities include viruses, viroids, satellites,
and prions. Viruses are composed of protein and nucleic acids. Viroids are composed
of RNA. Satellites are composed of nucleic acid enclosed in a protein shell. Prions are
composed of protein.
- The types of microbial cells are prokaryotic cells and eukaryotic cells. Prokaryotic
cells lack a true membrane-delimited nucleus (there are exceptions to this).
Eukaryotic cells have a membrane-enclosed nucleus, are more complex
morphologically, and are usually larger than prokaryotic cells.
4. What is the three domain system of microorganisms? Compare and contrast the three
domains of microorganisms.
- The three domain system, based on a comparison of ribosomal RNA genes divides
microorganisms into three types. The three domains are Bacteria, Archaea, and
Eukarya.
- In the domain Bacteria, the organisms are usually single-celled. The majority have a
cell wall with peptidoglycan. Most lack a membrane-bound nucleus. They are
ubiquitous, and some live in extreme environments. [Show Less]