PROKARYOTES 20.2

Introduction to Prokaryotes

• First discovered by Anton van Leeuwenhoek in 1683 (invention of light microscope)

• Are prokaryotes– No nucleus– Exist everywhere– Grow in colonies so

great you can see them with the unaided eye

Classification• Kingdom: Monera???• Domain: Bacteria-Kingdom Eubacteria• Domain: Archaea-Kingdom

Archaebacteria

Characteristics of ALL Bacteria

• Single Celled• Microscopic (1-10 micrometers)• Prokaryotic• Cell Wall• Ribosomes• Nucleoid Region (chromosome)

Archaea – Extremophiles?• Look like bacteria under microscope… but LACK

PEPTIDOGLYCAN in their cell walls, have different lipids in their membranes, and DNA sequences of key genes are more similar to eukaryotes than bacteria

• Referred to as ancient bacteria• Halophiles – “Salt Lovers” thrive in very salty places

– Great Salt Lake, Dead Sea

• Methanogens – live in anaerobic environments, give off methane, a major greenhouse gas– intestines and mud at bottom of lakes

• Thermoacidophiles – “Heat Lovers” thrive in very hot, acidic environments– Hot acidic pools – Yellowstone National Park* Some are found in moderate environments

Eubacteria – True Bacteria

Pilus – used for attachmentFlagellum – whip-like structure used for movementCapsule – outermost structure in some bacteria, protectCell Wall – protects cell from injury and determines shapeCell Membrane – controls what enters and leavesChromosome – genetic info Plasmid – extra circular ring of genetic material found in some bacteria

Classified by SHAPE

Shape Name Example Diagram

Rod Bacillus –(s) Bacilli - (p)

Bacillus anthracis (cause of anthrax)

Sphere Coccus – (s) Cocci -(p)

Streptococcus (cause of scarlet fever and strept throat)

Spiral Spirillum (s) Spirilla (p)

Vibrio comma (cause of cholera)

Shape Continued

• Prefixes used:– Micro – single– Diplo – pairs– Strepto – in chains– Staphylo – in clusters

• Examples:– Streptococcus

• “Chains of spheres”

Cell Wall (is also used to classify)

• Because of differences in cell wall composition…– Absorb stain differently– Allow for identification of

bacteria• Gram Stain

– Uses 2 dyes • Crystal violet (purple)• Safranine (red)

– Gram +: one thick layer of carbohydrate & protein (peptidoglycan) = retains purple dye

– Gram -: more complex (have 2nd outer layer of lipid & carbs) = retain red

Bacterial Movement (is also used to classify)

• One or more flagella

OR

• Lash, snake, or spiral forward

OR

• Glide along a slime layer they secrete

OR

• Nonmotile

How Bacteria Obtain Energy

• Autotrophs: make own energy– Phototroph – use sun’s energy– Chemotroph – obtain energy from inorganic

molecules (H2S, S, Fe – found in harsh environments)

• Heterotrophs: break down organic compounds for energy (aka chemotrophic heterotrophs)– Refers to most bacteria– i.e. Salmonella– Phototrophic Heterotrophs – use sun for energy in

addition to processing organic compounds

Bacterial Respiration

Bacterial Growth & Reproduction

• Binary Fission – asexual, grow & replicate DNA, split in half- identical– FAST!!!– Some can reproduce in under 20 minutes– If no limiting factors – in just 48 hours they would mass

4000x the mass of the Earth

• Endospore – thick internal wall protecting DNA in harsh conditions; remains dormant until favorable conditions arise

• If reproduce asexually how do they evolve?• Mutations• Conjugation – sexual, small portions of genes

(usually in the form of a plasmid) passed over a protein bridge; new combo of genes introduced

• Binary Fission • Conjugation

Importance of Bacteria

• Production of food– Cheese, yogurt, buttermilk, sour cream, pickles,

sauerkraut, vinegar (to name a few…)

• Industry– Digest petroleum – help clean up oil spills– Remove waste products & poison from water– Mine materials from the ground– Synthesize drugs and chemicals through techniques of

genetic engineering

• Symbiosis– At least one organism benefits– Ex.. E. coli in our intestines helps us digest food, it gets

nutrients and a place to live

Bacteria in the Environment• Nutrient Flow

– Soil is teeming with bacteria– Recycle & decompose dead material (DECOMPOSERS)– Saprophytes – use molecules from once living

organisms as their source of energy• Sewage Decomposition

– Break down complex compounds in the sewage into simpler compounds

– Produces purified water• Nitrogen Fixation

– Converts unusable atmospheric nitrogen into usable form

• Producers– Cyanobacteria are major producers in the ecosystem

20.3 Diseases Caused by Bacteria and Viruses

Pathogen – disease causing agents (can be prokaryotes or viruses)

Diseases caused by bacteria:• Only a few actually cause disease• Louis Pastuer was the first person to show that

bacteria cause disease, developed “germ theory of disease”

• Examples: diphtheria, tuberculosis, typhoid fever, tetanus, Hansen disease, syphilis, cholera, bubonic plague

• 2 ways to cause disease– Damaging host tissue– Release toxins (poisons) into the host

Bacterial Diseases

Controlling Bacteria

– Antibiotics – compounds that attack and kill bacteria

– Sterilization – use chemicals (disinfectants) or heat to kill bacteria

– Food Processing/Preservation – refrigeration, canning, salt, water, vinegar to prolong life of foods and protect it from bacteria

– Physical Removal – wash to dislodge– Antiseptics and Disinfectants

Diseases Caused By Viruses

• Examples (viruses) – smallpox, polio, measles, AIDS, mumps, influenza, yellow fever, rabies, the common cold

• Prevention is the BEST DEFENSE– Vaccine – substance that contains a weakened

form of the disease-causing virus, stimulates a heightened immune response from the host

• Interferon – proteins that interfere with the infection of body cells by viruses– Genetically engineered interferon can be

produced by bacteria• Antiviral Drugs – AZT, acyclovir• Hygiene

Viral DiseasesDisease Effect Transmission

Common Cold Sneezing, sore throat, fever, headache, muscle aches

Contact with contaminated objects, droplets inhalation

Influenza Body aches, fever, sore throat, headache, dry cough, fatigue, nasal congestion

Flu viruses spread in respiratory droplets cause by coughing and sneezing

AIDS Helper T cells are destroyed Contact with contaminated bodily fluids

Chicken pox SKIN RASH OF BLISTERLIKE LESIONS VIRUS PARTICELS ARE SPREAD IN RESPIRATORY DROPLETS CAUSED BY COUGING OR SNEEZING – HIGHLY CONTAGEOUS

Hepatitis B Jaundice, fatigue, abdominal pain, nausea, vomiting, joint pain

Contact with contaminated bodily fluids

West Nile Fever, headache, body ache Bite from an infected mosquito

Human Papilloma virus (HPV)

Genital and anal warts, some cancers (anal, cervical, penile)

Sexual contact

Emerging Viruses

• Viruses that make an apparent sudden appearance possible due to environmental disturbances or spreads from host species

• We have little or no resistance to them and lack methods to control them– Ex SARS

Superbugs

• Bacteria that are resistant to whole groups of antibiotics and that transfer drug resistance genes from one bacterium to another through conjugation– MRSA- Methicillin resistant Staphylococcus

aureus

Prions

• Prions – pathogens that are proteins, are transmissible — from host to host of a single species and, sometimes, even from one species to another (such as a laboratory animal)

• Destroy brain tissue giving it a spongy appearance

Prion Diseases•

• Kuru Kuru - was once found among the Fore tribe in Papua New Guinea whose rituals included eating the brain tissue of their recently deceased members of the tribe. Since this practice was halted, the disease has disappeared. Before then, the disease was studied by transmitting it to chimpanzees using injections of autopsied brain tissue from human victims.

• Scrapie Scrapie - This disease of sheep (and goats) seems to be transmitted from animal to animal in feed contaminated with nerve tissue. It can also be transmitted by injection of brain tissue.

• Bovine Spongiform EncephalopathyBovine Spongiform Encephalopathy (BSE) or "Mad Cow Disease" – In 1986, without warning, cows began acting strangely, losing control of their movements, staggering and stumbling, and eventually dying. Farmers watched helplessly as the disease they called “mad cow” spread through their cattle. – The disease affected more than 30,000 cattle in 1991. Studies of the brains

of cattle killed by mad cow disease showed that large areas of the animals’ brains had been destroyed. Under the microscope, the holes in the tissue make the brain resemble a sponge (BSE).

• Its origin appears to have been cattle feed that: • contained brain tissue from sheep infected with scrapie • had been treated in a new way that no longer destroyed the

infectiousness of the scrapie prions.– The use of such food was banned in 1988 and after peaking in 1992, the

epidemic declined quickly.• Creutzfeldt-Jakob DiseaseCreutzfeldt-Jakob Disease (vCJD) is the "mad cow" disease that people

contract when they are exposed to food contaminated with bovine spongiform encephalopathy (BSE).

Mad Cow Disease

• Mad Cow Disease