19.1%20Bacteria

Bacteria

Bacteria • Most microorganisms are prokaryotes – single celled organisms that lack a nucleus.

– Prokaryotes can be divided into two very different kingdoms: –Eubacteria.

–Archaebacteria.

• Bacteria represent the most ancient groups on Earth. They have adapted to almost every environment, and they have evolved more ways to obtain nutrients than all eukaryotic organisms combined.

Chapter 19.1

Eubacteria

All bacteria:

Ribosome

• Are unicellular.

• Lack a cell nuclei.

• Lack membrane bound organelles.

Peptidoglycan

Cell Cell wall membrane

• Larger (in number) kingdom.

• Live almost everywhere – Land, fresh water, ocean, in the human body.

Flagellum

DNA

Pili

• Surrounded by a cell wall for protection and determination of shape.

• May also contain a 2nd cell membrane outside of the wall.

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Archaebacteria • Look very similar to eubacteria, but are very different chemically.

– Lack the peptidoglycan of eubacteria.

– Have different membrane lipids than eubacteria.

• DNA sequence of archaebacteria is more like those of eukaryotes.

– Based on DNA evidence, scientists have suggested that archaebacteria may be the ancestors of eukaryotes.

• Tend to live in extremely harsh environments – such as oxygen free environments or extremely salty environments.

Bacterial Cell Walls • Bacteria have an inner cell membrane made of lipids and an outer cell wall made of polysaccharides. (See Diagram A) • Some bacteria have a 3rd layer – a cell membrane outside of the cell wall made up of polysaccharides that are bound to lipids.

(See Diagram B) 3rd Outer Membrane

Cell Wall

Bacteria Shape • Bacteria come in three shapes: – Spherical-shaped or cocci (Strep) – Rod-shaped or bacilli (E-Coli) – Spiral-shaped or spirilla (Leptrospira)

Gram-Staining •

• •

•

The chemical difference between the two types of walls is important for diagnosing and treating diseases.

The difference in the walls is revealed by a staining procedure.

Gram-positive bacteria are violet (the primary stain which dyes the peptidoglycan) and are single walled.

Gram-negative bacteria appear pink (stained by the red counter stain) because they lack peptidoglycan and are double layered. Gram negative bacteria are unaffected by antibiotics.

The drugs have difficulty penetrating the outer cell wall.

Membrane

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Movement • • • •

Some bacteria do not move.

Others are propelled by flagella.

Some lash, snake, or spiral forward.

Others glide along the slime they produce.

Releasing Energy • Like all organisms, bacteria are in need of a constant supply of energy • Energy is released by the process of cellular respiration, fermentation, or both.

Metabolic Diversity • Heterotrophs - organisms that cannot make their own food.

– Most bacteria fall in this category.

– Many feed on dead plants, fallen leaves, dead animals, petroleum, pesticides, nylon and other industrial products.

• Autotrophs - organisms that make their own food.

– Some bacteria can use light energy to produce food – photoautotrophs.

– Others bacteria use chemicals such as ammonia, or sulfur, to produce energy – chemoautotrophs.

Growth and Reproduction • When conditions are favorable (correct temperature, ample food and space), some bacteria can divide as often as every 20 minutes.

– Binary Fission – when a bacterium doubles in size, replicates its DNA and divides in half.

– Genetic information is not exchanged or recombined.

– Form of asexual reproduction.

– Conjugation – when some genetic material is transferred to another bacteria cell.

– does not result in more bacteria.

– does provide for genetic variation.

– Spore Formation – when conditions become unfavorable, many bacteria form spores and remain dormant until conditions become more favorable.

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Importance of Bacteria • Bacteria are vital to maintaining the living world. Bacteria can take on the role of producer or decomposer.

• Decomposers - return nutrients to the soil.

– Without decomposers nutrients like phosphorous and nitrogen would be locked up in the dead bodies of organisms.

• Nitrogen Fixing Bacteria enrich plants.

– Nitrogen is a component of protein.

– Bacteria transform atmospheric nitrogen into an absorbable form, ammonia.

• Human Uses of Bacteria – Used in manufacturing of food.

• Yogurt, olives, pickles, sauerkraut …

– Biotechnology - Used to make drugs such as insulin.

Common Diseases Caused by Bacteria Disease

Pathogen

Prevention

Tooth decay

Streptococcus mutans

Regular dental hygiene

Lyme disease

Borrelia burgdorferi

Protection from tick bites

Tetanus

Clostridium tetani

Current tetanus vaccination

Tuberculosis

Mycobacterium tuberculosis

Vaccination

Salmonella food poisoning

Salmonella enteritidis

Proper food-handling practices

Pneumonia

Streptococcus pneumoniae

Maintaining good health

Cholera

Vibrio cholerae

Clean water supplies

Bacteria Spreads • By Air - airborne water droplets – sneezing, coughing, spitting - Most airborne diseases affect the respiratory tract – Ex. TB, scarlet fever, whooping cough

• By Sexual Contact – Ex. syphilis

• By Insects – Examples • Lice- typhus • Ticks- Lyme disease • Fleas- carry bacteria that causes the Plague or “Black Death”

• By Touch – Ex. Leprosy, Staph infections

• By Contaminated Food/Water – Ex. Cholera, Salmonella and E-coli

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Bacteria & Disease • Pathogen - a disease causing agent.

• Bacteria are harmful because they damage their host's tissues by: • a direct attack on the host's cells.

• releasing poisonous toxins.

• Heat and cold help protect food from bacterial contamination.

• Pasteurization is a common industrial practice that involves heating the product to a temperature that kills most bacteria.

Controlling Bacterial Diseases • Sanitation.

• Clean water.

• Sewage treatment plants.

• Managed waste removal.

• Personal Hygiene.

• Wash your hands frequently!

• Vaccines.

• Diphtheria, tetanus, whooping cough.

• Antibiotics.

• Antibacterial drugs such as penicillin.

Problems with Antibiotic Resistance • Bacteria reproduce quickly.

– They mutate.

• Antibiotics kill most of the harmful bacteria.

• The few that survive will reproduce and are resistant to the antibiotic.

• People cause Antibiotic Resistance – Overuse of antibacterial products.

– Overuse of antibiotics, not finishing the full course of treatment.

– Use of antibiotics in our food supply - cattle, poultry etc.

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