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18.2: Bacteria. prokaryote, chemosynthesis, binary fission, conjugation, obligate aerobe, obligate anaerobe, endospore, toxin, nitrogen fixation. Diversity of Prokaryotes. Prokaryotes: unicellular organism that do not have a nucleus or membrane-bond organelles

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18 2 bacteria

18.2: Bacteria

prokaryote, chemosynthesis, binary fission, conjugation, obligate aerobe, obligate anaerobe, endospore, toxin, nitrogen fixation

diversity of prokaryotes
Diversity of Prokaryotes
  • Prokaryotes: unicellular organism that do not have a nucleus or membrane-bond organelles
  • There are two kingdoms of prokaryotes because of the many biochemical differences between the two.
    • Archaebacteria
    • Eubacteria
  • There are three types of archaebacteria that live mainly in extreme habitats where there is usually no free oxygen available.
Methane Producing Archaebacteria: live in oxygen-free environments and produce methane gas and are found in marshes, lake sediment, and live in the digestive tracts of some mammals such as cows. They also are found at sewage disposal plants, where they breakdown sewage. Archaebacteria
Salt-Loving Archaebacteria: live only in waters with high concentrations of salt, such as in Utah’s Great Salt Lake and the Middle East’s Dead SeaArchaebacteria
Heat-and Acid-Loving Archaebacteria: live in hot, acidic waters of sulfur springs. They are also anaerobic and can thrive in cracks deep in the ocean floor. Archaebacteria
eubacteria the heterotrophs
Eubacteria: The Heterotrophs
  • Live almost everywhere and use organic molecules as their food source.
  • Some are parasites, obtaining their nutrients from other living organisms
  • Some are saprophytes: organisms that feed on dead organisms or organic waste
    • This is important in recycling nutrients through the environment
eubacteria the photosynthetic autotrophs
Eubacteria: The Photosynthetic Autotrophs
  • Live in places with sunlight so they can use the light to make organic molecules that are their food.
eubacteria the photosynthetic autotrophs1
Example: Cyanobacteria

Contain the pigment chlorophyll that traps solar energy, which they can then use in photosynthesis.

Most are blue green in color and some can be red or yellow.

They are commonly found in ponds, streams and moist areas of land.

Eubacteria: The Photosynthetic Autotrophs
eubacteria the chemosynthetic autotrophs
Eubacteria: The Chemosynthetic Autotrophs
  • These also make organic molecules for food.
  • Instead of using sunlight, they break down and release energy of inorganic compounds containing sulfur and nitrogen in a process called chemosynthesis
  • These bacteria are important for plants because they convert atmospheric nitrogen into the nitrogen-containing compounds that plants need.
bacteria structure
Bacteria Structure
  • Capsule: Some bacteria have a sticky gelatinous capsule around the cell wall. A bacterium with a capsule is more likely to cause disease than a bacterium without.
  • Cell Wall: surrounds the plasma membrane and gives the cell it’s shape and prevents osmosis from bursting the cell.
  • Chromosomes: A single DNA molecule, arranged as a circular chromosomes and not enclosed in a nucleus, contains most of the bacterium’s genes
bacteria sturcture
Bacteria Sturcture
  • Flagellum: long, whip-like protrusion that enables them to move (not all bacterium contain flagella)
  • Plasmid: A few genes are located in a small circular chromosome piece called a plasmid. A bacterium can have one or more plasmid.
  • Pilus: some bacteria have pili- extensions of their plasma membrane. A hair-like pilus helps a bacterium stick to a surface. It is also like a bridge through or on which two bacteria can exchange genetic information.
bacteria sturture
Bacteria Sturture
  • Plasma membrane: surrounds the cell and regulates what enters and leaves the cell.
  • Ribosomes: site of protein synthesis



Cell Wall


Plasma membrane



journal drawing
Journal Drawing
  • Draw a Typical Bacterial Cell in your Journal (Figure 18.10 pg. 487)
  • Label and Define the Structures
identifying bacteria
Identifying Bacteria
  • Scientists have developed ways of distinguishing bacteria.
  • One way is how they react to gram stains, which distinguish between two types of bacteria.
identifying bacteria1
Identifying Bacteria
  • Gram stains reveal structural differences in cells cell walls. These differences are important in understanding what type of antibiotic will work effectively against the bacteria.
    • Gram positive: appears purple when stained
    • Gram negative: appears pink when stained
identifying bacteria2
Identifying Bacteria
  • Bacteria also have different shapes.
      • Coccus: spheres
      • Bacillus: rods
      • Spirillum: spirals
identifying bacteria3
Identifying Bacteria
  • Bacteria can have different arrangements
      • Diplo: paired cells
      • Staphylo: arrangement of cells resembling grapes
      • Strepto: chains of cells
journal drawing1
Journal Drawing
  • Draw an example of each shape and arrangement of bacteria in your journal
  • Refer to figure 18.12 pg. 489
  • Binary fission is a form of asexual reproduction used by bacteria.
    • First, genetic information (chromosomes) are copied.
    • The cell grows larger and the chromosomes move to opposite ends of the cell
reproduction binary fission
Reproduction: Binary Fission
  • Then a partition forms between the two chromosomes and separates the cell into two cells.
reproduction binary fission1
Reproduction: Binary Fission
  • Because each new cell has either the original or the copy of the original chromosome, the resulting cells are genetically identical.
  • Under ideal conditions some bacteria can reproduce every 20 minutes, producing enormous numbers quickly, but due to lack of nutrients and predators they do not always reproduce so quickly.
reproduction binary fission2
Reproduction: Binary Fission


reproduction conjugation
Reproduction: Conjugation
  • Conjugation is a form of sexual reproduction used by some bacteria
    • In conjugation, one bacterium transfers all or part of its chromosome to another cell through a bridge-like structure called a pilus that connects the two cells.
reproduction conjugation1
This results in bacteria cells with a new genetic composition

Then binary fission can occur, producing more cells with the same genetic makeup.

Reproduction: Conjugation
adaptations in bacteria
Obligate aerobes: bacteria that require oxygen from respiration

Mycobacterium tuberculosis, the organism that causes the lug disease tuberculosis.

Adaptations in Bacteria
adaptations in bacteria1
Adaptations in Bacteria
  • Obligate anaerobes: killed in the presences of oxygen
    • Treponema pallidum, causes syphilis, a sexually transmitted disease and the bacterium that causes botulism, a type of food poisoning.
  • Some bacteria can live in the presence of oxygen or without oxygen.
adaptations in bacteria2
Endospores: a tiny structure that contains a bacterium’s DNA and a small amount to its cytoplasm, encased by a tough outer covering that resists drying out, extreme temperatures, and harsh chemicals.Adaptations in Bacteria
bacteria adaptations endospores
Bacteria Adaptations: Endospores
  • If a bacterium is killed the endospore will rest until the conditions are favorable and germinate into the bacterium and grow and reproduce.
  • Some have germinated after thousands of years in a resting state.
  • Although useful to the bacteria, they can cause problems for people because they are difficult to terminate.
  • This is why foods and surgical instruments must be sterilized properly
bacteria adaptations endospores1
The bacterium Clostridum botulinum easily gets into foods being canned and the endospores can germinated because they are obligate anaerobes.

This can eventually produce a powerful and deadly poison, called a toxin, as they grow.

If food is eaten with this toxin it can cause botulism.

Bacteria Adaptations: Endospores
importance of bacteria
Importance of Bacteria
  • Nitrogen Fixing
    • Most of the nitrogen in the world consists of nitrogen gas (N2), and it makes up 80 percent of the atmosphere.
    • Few organisms can use this nitrogen directly from the air.
    • Nitrogen fixation: a process in which several species of bacteria have enzymes that convert N2 into ammonia (NH3)
    • Other bacteria convert ammonia into nitrite (NO2-), which plants can use.
    • Some nitrogen fixing bacteria live symbiotically within the roots of trees and legumes (peas, peanuts, and soybeans).
importance of bacteria1
Importance of Bacteria
  • Recycling of Nutrients
    • Decomposing bacteria break down the organic materials in dead organisms and wastes, returning nutrients, both organic and inorganic material, to the environment.
importance of bacteria2
Food and Medicine

Many foods you eat- Swiss cheese, , pickles, yogurt- would not exist without bacteria.

During respiration, different bacteria produce diverse products, many of which have distinctive flavors and aromas. So they are used in many foods for these flavors (vinegar, cheeses, sauerkraut)

Importance of Bacteria
importance of bacteria food and meds
Importance of Bacteria: Food and Meds
  • Bacteria also live in your intestines and produce vitamins and enzymes that help digest food
  • Some bacteria produce important antibiotics that destroy other types of bacteria.
bacteria cause diseases
Bacteria Cause Diseases
  • Bacteria can cause diseases in plants and animals, causing crops and livestock losses that impact humans indirectly.
  • Disease causing bacteria usually enter human’s bodies through openings, such as you mouth or an open wound.
  • The growth of the bacteria can interfere with normal function of body tissues, or it can release a toxin that directly attacks the host.
bacteria cause diseases1
Bacteria Cause Diseases
  • In the past bacterial illness had a greater affect on the human population.
  • In 1900 the life expectancy in the US was only 47, because the most dangerous disease at that time was cause by bacteria (tuberculosis and pneumonia).
  • The human life expectancy has increased to about 75 years, due to better public health systems, improved water and swage treatment, better nutrition and better medical care (including antibiotics)
diseases caused by bacteria
Diseases Caused By Bacteria
  • Strep throat: inhale or ingest through mouth; caused by Streptococcus.
  • Tuberculosis: inhale
  • Tetanus: puncture wound
  • Lyme disease: bite of infected tick
  • Dental cavities: bacteria in mouth
  • Diphtheria: inhale or close contact
diseases caused by bacteria1
Diseases Caused By Bacteria
  • Treatment can include cleaning, antibiotics or vaccinations.
bacteria you need to know
Bacteria You Need to Know…
  • Cyanobacteria
  • Mycobacterium tuberculosis
  • Treponema pallidum
  • Streptococcus
  • Clostridum botulinum
  • Know diseases bacteria cause as well.
  • Archaebacteria: 3 types, where they are found
  • Eubacteria: Heterotrophs, Photosynthetic, Chemosynthetic
  • Structure: Be able to label and describe the functions
  • Identification: gram stain, shape, arrangement
  • Adaptations: anerobic, aerobic, endospores…
  • Importance: Nitrogen Fixing, Food and Medicine, Recycling Nutrients
  • Bacteria that cause disease: How, examples, prevention