Introduction to Microorganisms

1

Lesson Objectives:

– Define microbiology.– List the organisms included in the field of microbiology .– Discuss the role microorganisms play in the

environment, the food industry and the medical field. – List the distinguishing characteristics of bacteria, fungi,

algae, protozoa and viruses. – Describe how bacteria are named.– List the microorganisms that are classified as

prokaryotes and eukaryotes.

Microbiology

The study of living organisms too small to be seen with the naked eye.

Question: (with a partner) What event, discovery, or invention marked the start of Microbiology?

Answer:________________________________

Members• Bacteria

• Fungi (yeasts and molds)

• Protozoa

• Algae

• Viruses

Prokaryote Cell

Cellular Organization

• Prokaryotes-Pre nucleus– Bacteria– Simple cells– Small– No membrane- bound nucleus. DNA is organized

into one large circular strand (genome) and smaller circles (plasmids)

– No membrane-bound internal structures (ribosomes present)

– Cell division quick-Binary Fission

Eucaryote

Eukaryotes

• True (good) nucleus• Membrane bound organelles• Includes fungi, algae, and protozoa, plants and

animals• More structurally complex • Cell Division is by mitosis and meiosis

Microbes and the Planet

• First life on the earth• Prokaryotes (bacteria) appeared about 3.5

billion years ago• Eukaryotes ( all other microbes) arose 2 billion

years ago• Ubiquitous– Adaptable to any niche that exists

Microbes and the Planet

• Essential for life– Photosynthesis• Microbes are responsible for over 70 % of Earth’s

photosynthesis– First photosynthesis—did not produce oxygen!

When oxygen was formed, an environment suitable for man and animals resulted.

Earth’s environment is a result of microbial productssoilwateratmosphere

Scope of Microbiology

• Environmental• Most microbes are

beneficial– Genetic engineering– Bioremediation– Food production– Symbionts—provide

necessary processes to other organisms.

Microorganisms and the Environment

• Decomposition-recyclers of nutrients

• Can breakdown complex organic compounds to simple compounds

• Return CO2 N2, and H20 to atmosphere and soil

Scope

• Food Microbiology

Examples of food made possible by microbes:

Microbes and Man

Normal flora Pathogens

Found in which parts of body?

Approximately what percentage of microbes are pathogens?

Figure 1.5

Medical Antibiotics

fungus

Why is there a clear zone here?

Classification and Nomenclature

Names were originally based on visible characteristics of microbes:

• Microscopic appearance (Staphylococcus—”bunch of grapes,” Bacillus—”rod”)

• Discoverer of the organism or the disease (Salmonella: Daniel Salmon, Listeria: Joseph Lister)

• ??????????? (Pseudomonas: “false monad”)

Taxonomy: Organizing, Classifying and Naming Living Things

• Formal system originated by Carl von Linné (1701-1778) • Concerned with: – classification – orderly arrangement of organisms into

groups– nomenclature – assigning names– identification – discovering and recording traits of

organisms for placement into taxonomic schemes

Woese System of Classification

Carl Woese compared a macromolecule found in all cells (rRNA) and used the sequence of bases in this molecule as a basis of comparison in thousands of organisms.

Why use ribosomal RNA

1. Every organism on the planet has rRNA, and it always has the same function.

2. The sequence of nucleotides (adenine, guanine, cytosine, uracil) in certain parts of rRNA undergo very little change throughout evolution. Therefore…

3. All members of a given species have the same rRNA sequence (in certain areas).

Woese’s conclusion

• Three major “domains” of living cells:BacteriaArchaeaEukarya

• The first two are prokaryotes, the third is all eukaryotes

• Bacteria and Archaea are as different from each other as each is from Eukarya

Nomenclature

• Binomial • Latinized • Genus-noun• Species-adjective• Genus (always capitalized) species (never

capitalized)– Staphylococcus aureus– S. aureus– S. epidermidis