Microorganisms

Biology 112

March 22, 2007

Importance of Microorganisms (Microbes)

• Microbes are everywhere – there are more of them on a person’s hand than there are people on the entire planet

• Would our planet survive without them?

• NO!!

• We couldn’t digest food, grow plants, decay garbage, and there would be a lot less oxygen to breathe.

Microbiology

• Microbiology is the study of microorganisms.

• This study has lead to practical applications in the development of certain antibiotics, and the manufacture of dairy products.

Microbes

• Microbes are tiny creatures that individually are too small to be seen with the unaided eye.

• They include: bacteria, archaea, fungi, and protists.

• We also include viruses (even though there is the living/nonliving debate to consider).

Bacteria – A single teaspoon of topsoil contains over 1 million bacterial cells!

• We have already examined viruses, so our next step will be to look at bacteria.

• Bacteria belong to the Moneran Kingdom• Earliest forms of life from billions of years ago• They have MANY different positive and negative

functions• Bacteria consist of only a single cell• They are very dynamic and diverse: some can live

in boiling temperatures while others in freezing.

More Characteristics of Bacterial Cells

1. They are prokaryotes (no membrane bound nucleus or organelles)

2. Bacterial cells have a single chromosome.

3. Most bacteria reproduce by binary fission.

4. Bacteria show great metabolic diversity.

5. Found as single cells or in groups of two or more (called a colony)

Bacteria Cell Structures

Identification

There are three basic shapes that bacteria display.

1. Cocci (singular: coccus) which are spherical.

Identification

There are three basic shapes of the bacteria display.

2. Bacilli (singular: bacillus) which are rod-shaped.

Identification

There are three basic shapes of the bacteria display.

3. Spirilla (singular: spirillum) which are spiral shaped.

Dividing Clusters

• The three basic shapes, upon division, will often form clusters, colonies or chains.

• Strep throat is caused by Streptococci, a group of cocci that form chains. Remember that each piece of the chain are still individuals.

Did you Know???

• The Human Mouth is home to more than 500 species of bacteria.

– Commensal -relationship in which one species is benefited while the other is unaffected

Strep Throat

Strep Throat

What bacteria eat?

• Some are photosynthetic (autotrophs) – make their own food from the sunlight – like plants.

• Most bacteria absorb food from the material they live on or in. (heterotrophs) Ex: the bacteria that live in your gut absorb nutrients from the digested food you have eaten.

• Those that take food from living organisms are called PARASITES

• Those that take food from non-living organisms are called SAPROPHYTES – most fungi

The Fundamental Groups

• Bacteria (the most common organisms on Earth) can fit all 1700 species into the following 3 groups: – Archaebacteria, Eubacteria, and Cyanobacteria– Archaebacteria often live in environments without oxygen.

They can tolerate extreme environments (obligate anaerobes)– Eubacteria are the largest group of monerans which include

organisms traditionally recognized as bacteria. These are the ones that can make you sick!

– Cyanobacteria (blue/green algae) will photosynthesize. They grow in water (pond scum) where they produce much of the oxygen we breathe.

Respiration

• Obligate aerobes require oxygen to survive and for respiration.

• Obligate anaerobes conduct respiration in the absence of oxygen – oxygen can actually even poison it – survive in mud, bottom of a pond, human intestine.

• Facultative anaerobes can survive with or without oxygen - yeast

Reproduction – Some bacteria can grow and divide in as little as 20 minutes~

• Monerans reproduce asexually by binary fission (splitting in two).

• It may look like mitosis but it is much simpler.

Binary Fission

Binary Fission

The DNA molecule attaches to the cell membrane and copies itself.

In between the points where the DNA molecules are attached, the cell membrane begins to grow.

As it grows, the membrane pulls the two DNA molecules apart

When the cell is about twice its original length, the cell membrane indents

The cytoplasm is divided into roughly equal parts

Each part has ONE DNA molecule. Cell walls then grow and completely divide the two cells.

Importance of Bacteria

• Human disease (strep, food poisoning, wound infections, etc.)

• Disease in animals and plants

• Food spoilage

• HOWEVER, only a small % of bacterial species are actually harmful

Importance of Bacteria

• Decomposers• Produce vitamins in the human intestine• Vinegar, yogurt and cheese are made using bacteria• Some bacteria produce antibiotics• Fuel can be produced (methane) from metabolized wastes

from some• Natural pesticides: infect caterpillars that destroy crops.• Help produce Vitamin K in our intestines (used for blood

clotting)• Some bacteria (the flavobacterium) eat the poison

pentoclorophenol, found in wood preservative. Once the toxin is removed the microbe dies.

Antibiotics

• Whether a bacteria has a thin or thick cell wall will determine what antibiotic will work against it.

• Gram +ve/ Gram -/ve• Thick cell walls will retain dye from a cell

staining method discovered by Christian Gram• Thin cell walls do not (-ve)• Knowing the difference can save lives, money,

time and ensures that you receive the right treatment.

Bacteria Pics

• E. Coli – shape??

TB - tuberculosis

•

StreptomycesGive soil it’s “earthy smell”

•

Intestinal Bacteria

Assignment on Bacteria

• Textbook: Answer questions 11-17 on page 429.

Question 11

• What features are shared by most microorganisms?

• Unicellular, microscopic, many cause disease, most are capable of independent existence

Question 12

• How are monerans similar to and different from viruses?

• Some similarities are: both are microscopic, difficult to classify, can cause disease, neither has a nucleus or membrane-bound organelles.

• Some differences are: monerans are prokaryotes while viruses exist as simple molecular structures, monerans carry out an independentg existance, while viruses can function only once inside a living cell; and, monerans contain both RNA and DNA, while viruses contain one or another.

Question 13

• What feature(s) mignt cause cyanobacteria to be classified as plants by some biologists?

• Cyanobacteria are autotrophs and carry out photosynthesis. Their photosynthetic pigments enable these organisms to make their own food and produce oxygen as a by-product of photosynthesis.

Question 14

• Draw and classify three types of bacteria according to shape.

• Rod shaped (bacilli); spherical (cocci); and spiral (spirilla)

Question 15

• Why is endospore formation important to bacteria?

• Endospore formation is important b/c this process enables certain bacteria, some bacilli, for ex. To survive unfavorable environmental conditions such as low temperatures, low nutrient levels, or low levels of moisture/water. The endospore may lie dormant for hours or years. When suitable conditions return the spore coat dissolves and the endospore develops into a normal bacterial cell.

Question 16

• Describe the binary fission process in monerans:

• Binary fission is a form of asexual reproduction in which one cell divides into two identical cells. It involves only one parent and is simpler than mitosis in eukaryotes.

Question 17

• What is conjugation in monerans? Why is it important?

• Form of sexual reproduction that involves transfer of genetic material. A cell-to-cell contact occurs between two conjugal or mating cells and genetic exchange takes place across a “cytoplasmic bridge”. Following the transfer, the two monerans separate, resulting in offspring that are genetically different from the parents. This process is an important means of introducing variability into the moneran population.