Bacteria: Section 19-1 Vibrio cholerae Cholera has been very rare in industrialized nations for the last 100 years; however, the disease is still common today in other parts of the world, including the Indian subcontinent and sub-Saharan Africa. Cholera is an acute intestinal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. It has a short incubation period, from less than one day to five days, and produces an enterotoxin that causes a copious, painless, watery diarrhoea that can quickly lead to severe dehydration and death if treatment is not promptly given. Vomiting also occurs in most patients. Can cholera be treated? Cholera can be simply and successfully treated by immediate replacement of the fluid and salts lost through diarrhea. Patients can be treated with oral rehydration solution, a prepackaged mixture of sugar and salts to be mixed with water and drunk in large amounts. This solution is used throughout the world to treat diarrhea. Severe cases also require intravenous fluid replacement. With prompt rehydration, fewer than 1% of cholera patients die. Antibiotics shorten the course and diminish the severity of the illness, but they are not as important as rehydration. Persons who develop severe diarrhea and vomiting in countries where cholera occurs should seek medical attention promptly.  Vibrio cholerae    

Introduction to Bacteria

General Characteristics Single-celled; no nucleus or complex organelles What do we call this type of organism? Earliest known life forms Smallest and simplest living organisms Size 10-100 micrometers in diameter and 1-5 micrometers long Few hundred genes

Needle Tip

Bacterial Structure All bacteria have an outer cell wall: Glycoprotein is comprised of a carbohydrate (sugar) and a protein. They act as signal receptors originating from outside the cell and cell-to-cell communication. Bacteria Plant Bacteria (not Archaebacteria) have a peptidoglycan cell wall Archaebacteria are extremely diverse and their cell walls differ so much that it is difficult to make any generalizations

Glycocalyx- Gelatinous outer layer Capsule- Firm Slime layer-loose Bacteria consist of only a single cell—but don't let their small size and seeming simplicity fool you. They are an amazingly complex and fascinating group of organisms. Bacteria have been found that can live at temperatures above the boiling point and in those that would freeze your blood. They "eat" everything from sugar and starch to sunlight, sulfur and iron. There is even a species of bacteria that can withstand blasts of radiation 1,000 times greater than those that would kill a human being.

Figure 19-2 The cell walls of eubacteria contain peptidoglycan Cell Membrane Ribosomes Peptidoglycan A bacterium such as E. coli has the basic structure typical of most prokaryotes: cell wall, cell membrane, and cytoplasm. Some prokaryotes have flagella that they use for movement. The pili are involved in cell-to-cell contact. The cell walls of eubacteria contain peptidoglycan. Flagellum DNA Pili

Classifying Prokaryotes Bacteria are placed into two major kingdoms: Kingdom Archaebacteria – Cell walls lack peptidoglycan, different membrane lipids than eubacteria, DNA sequences are more like eukaryotes. Live in harsh environments Kingdom Eubacteria –Cell walls contain peptidoglycan. Many archaebacteria live in harsh environments, including thick mud, animal digestive tracts, salt lakes, and hot springs. Crash Course Archaebacteria vs. Bacteria vs. Eukaryote

Identifying Prokaryotes – 4 ways Shapes: There are three basic shape types: Cocci: Spherical shaped cells single cocci diplococci (pairs) Streptococci (chains) Staphylococci (clusters)

Staphylococcus aureus – appears in pairs, short chains or bunched like grapes. Causes food poisoning, toxic shock syndrome, skin and wound infections, & scarlet fever. MRSA - methicillin-resistant Staphylococcus aureus Staphylococcus aureus - Gram-positive, MRSA, coccus prokaryote (dividing); causes food poisoning, toxic shock syndrome and skin and wound infections such as scalded skin syndrome, scarlet fever, erysipelas and impetigo. MRSA infections that are acquired by persons who have not been recently hospitalized or had a medical procedure are known as CA-MRSA (Community associated-MRSA) infections. CA-MRSA infections in the community are usually manifested as skin infections, such as pimples and boils, and occur in otherwise healthy people. Magnification*: x13,335 Type: SEM In process of dividing On surface of small intestine

Bacillus (i) = Rod shaped cells Single bacilli Diplobacilli Streptobacilli

Bacilli Shape Alicyclobacillus spp. Causes food spoilage, especially in fruit juices. The spores can survive pasteurization treatments and heat can activate the spores to begin growth and cause contamination. Magnification*: x2,400 Caption: Alicyclobacillus spp. - an acidophilic, thermophilic, spore forming bacteiurm. Causes food spoilage, especially in fruit juices. The spores can survive pasteurization treatments and heat can activate the spores to begin growth and cause contamination. Magnification*: x2,400 Type: SEM

Spirillium = spiral shaped Leptospira interrogans Leptospirosis is the most widespread bacterial infection in the world, affecting both animals and humans. It is a bacterial infection passed from animals to humans by way of contaminated urine. Leptospirosis is also know as hemorrhagic jaundice, infectious jaundice, mud fever, caver’s flue & many other names.

Review: The three basic shapes of bacteria are? Caption: Photocomposite of the three common types of bacterial morphology - coccus, bacillus, spirillum. These spherical, rod and sprial shaped morphologies are typical of such genera as: Streptococcus / Staphylococcus, Escherichia / Bacillus and Leptospira / Spirillum. Magnification*: x800 Type: SEM

Identifying Prokaryotes cont. Cell Walls – Eubacteria can be identified by the thickness of their cell walls. A Gram stain tells them apart. Gram-positive bacteria: have thick peptidoglycan walls. Gram-negative bacteria: have much thinner cell walls inside an outer lipid layer.

Gram Positive vs. Gram Negative

Movement – Prokaryotes can be identified by whether they move & how they move. Many forms have flagella for movement. Some bacteria have pili, which allow them to attach to other things. Pili Flagella

Identifying Prokaryotes cont. How they obtain energy Autotrophic What does this mean? Photoautotrophs (e.g. cyanobacteria or blue-green algae) Cyanobacteria Cyanobacterium (Nostoc spp.). Gram-negative, oxygenic, photosynthetic, filamentous cyanobacterium (prokaryote). Note the thylakoids (photosynthetic membranes - green), polyhedral bodies (purple) and lipid bodies (pink). Lichens often are associated with Nostoc in a symbiotic relationship. Specialized cells in the Nostoc filament, called heterocysts, fix atmospheric nitrogen gas into amino acids and thus progressively enrich the soil with nitrogen for plant growth. Magnification*: x4,560 Type: TEM Thylakoids… but No Chloroplasts!

Identifying Prokaryotes cont. Chemoautotrophs – Don’t require sunlight for enery (e.g. methanogens or halophiles) Methylomonas methanica - Methylotrophic bacteria (methylotrophs) are bacteria capable of growth on single carbon compounds (such as methane, methanol, etc.) These compounds act as the sources of carbon and energy to sustain growth.

Identifying Prokaryotes cont. Heterotrophic What does this mean? Chemoheterotrophs – Must take in organic (carbon) molecules for both energy & a supply of carbon. Photoheterotrophs – Use sunlight for energy, but need organic compounds as a carbon source.

Metabolism By diffusion Obligate aerobes - Must have oxygen to live (e.g. Mycobacterium tuberculosis) Tuberculosis (TB) is a disease caused by bacteria called Mycobacterium tuberculosis*. The bacteria usually attack the lungs. But, TB bacteria can attack any part of the body such as the kidney, spine, and brain. If not treated properly, TB disease can be fatal. TB disease was once the leading cause of death in the United States. TB is spread through the air from one person to another. The bacteria are put into the air when a person with active TB disease of the lungs or throat coughs, sneezes, speaks, or sings. People nearby may breathe in these bacteria and become infected. In the early 1900s, TB killed one out of every seven people living in the United States and Europe. Starting in the 1940s, scientists discovered the first of several medicines now used to treat TB. As a result, TB slowly began to decrease in the United States. But in the 1970s and early 1980s, the country let its guard down and TB control efforts were neglected. This led to an increase in the number of TB cases between 1985 and 1992. However, with increased funding and attention to the TB problem, there has been a steady decline in the number of persons with TB since 1993. But TB continues to be a problem. For example, the number of TB cases is still declining, but the speed of decline has slowed since 2003. Multidrug-resistant TB (MDR TB) remains a concern, and extensively drug-resistant TB (XDR TB) has become an important issue. And, racial and ethnic minority populations and foreign-born individuals continue to account for a large number of TB cases in the United States.

Obligate anaerobes - Can not live in the presence of oxygen e.g. Clostridium botulinum spores can be found in honey and this is why children less than 12 months old should not be fed honey. What is botulism? Botulism is a rare but serious paralytic illness caused by a nerve toxin that is produced by the bacterium Clostridium botulinum. There are three main kinds of botulism. Food borne botulism is caused by eating foods that contain the botulism toxin. Wound botulism is caused by toxin produced from a wound infected with Clostridium botulinum. Infant botulism is caused by consuming the spores of the botulinum bacteria, which then grow in the intestines and release toxin. All forms of botulism can be fatal and are considered medical emergencies. Food borne botulism can be especially dangerous because many people can be poisoned by eating a contaminated food. What kind of germ is Clostridium botulinum? Clostridium botulinum is the name of a group of bacteria commonly found in soil. These rod-shaped organisms grow best in low oxygen conditions. The bacteria form spores which allow them to survive in a dormant state until exposed to conditions that can support their growth. There are seven types of botulism toxin designated by the letters A through G; only types A, B, E and F cause illness in humans. What are the symptoms of botulism? The classic symptoms of botulism include double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, and muscle weakness. Infants with botulism appear lethargic, feed poorly, are constipated, and have a weak cry and poor muscle tone. These are all symptoms of the muscle paralysis caused by the bacterial toxin. If untreated, these symptoms may progress to cause paralysis of the arms, legs, trunk and respiratory muscles. In food borne botulism, symptoms generally begin 18 to 36 hours after eating a contaminated food, but they can occur as early as 6 hours or as late as 10 days.

Facultative anaerobes - Can grow with or without O2 but do better without O2 (e.g. Escherichia coli) What is Escherichia coli? Escherichia coli (abbreviated as E. coli) are a large and diverse group of bacteria. Although most strains of E. coli are harmless, others can make you sick. Some kinds of E. coli can cause diarrhea, while others cause urinary tract infections, respiratory illness and pneumonia, and other illnesses. Still other kinds of E. coli are used as markers for water contamination—so you might hear about E. coli being found in drinking water, which are not themselves harmful, but indicate the water is contaminated. It does get a bit confusing—even to microbiologists. E. coli that is harmless to humans colonizes the lower intestinal tract and is commensalistic.

Reproduction Asexual Binary fission - splitting into two equal cells. (*Not Mitosis) E. Coli undergoing binary fission.

Reproduction Sexual reproduction Conjugation - Exchange of genetic information. This exchange increases genetic diversity of bacteria populations. Caption: E. coli - Gram-negative, facultatively anaerobic, rod prokaryote; strains undergoing conjugation via a pilus. Bacterial conjugation is the ability to transfer DNA between strains of bacteria (via a pilus). It allows a new mutation to spread through an existing population. It is believed that this process led to the spread of toxin synthesis from Shigella to E. coli (O157:H7). Harmful E. coli strains can cause urinary tract infections, traveler's diarrhea, nosocomial infections, meningitis, peritonitis, mastitis, septicemia and gram-negative pneumonia.. It causes a variety of skin and wound infections such as scalded skin syndrome, scarlet fever, erysipelas and impetigo.

Reproduction Spore formation Spores are special structures that allow a bacteria to remain dormant and protected until environmental conditions become favorable to live. Clostridium botulinum forming spores Caption: Clostridium botulinum forming spores.

Treatment of bacterial diseases Antibiotics are usually made from fungi or other bacteria. why? Examples: Penicillin, Streptomycin, tetracycline, and sulfa drugs. Problems with Antibiotics Antibiotic resistance. Kills off good bacteria as well as bad. Inhibits body's natural immunity. Pasteurization and sterilization (UV & alcohol) help prevent the spread of disease. http://www.fda.gov/fdac/features/2004/504_milk.html Got Milk? Make Sure It's Pasteurized By Linda Bren Pasteurization, since its adoption in the early 1900s, has been credited with dramatically reducing illness and death caused by contaminated milk. But today, some people are passing up pasteurized milk for what they claim is tastier and healthier "raw milk." Public health officials couldn't disagree more. Drinking raw (untreated) milk or eating raw milk products is "like playing Russian roulette with your health," says John Sheehan, director of the Food and Drug Administration's Division of Dairy and Egg Safety. "We see a number of cases of foodborne illness every year related to the consumption of raw milk." More than 300 people in the United States got sick from drinking raw milk or eating cheese made from raw milk in 2001, and nearly 200 became ill from these products in 2002, according to the Centers for Disease Control and Prevention. Raw milk may harbor a host of disease-causing organisms (pathogens), such as the bacteria campylobacter, escherichia, listeria, salmonella, yersinia, and brucella. Common symptoms of foodborne illness from many of these types of bacteria include diarrhea, stomach cramps, fever, headache, vomiting, and exhaustion. Most healthy people recover from foodborne illness within a short period of time, but others may have symptoms that are chronic, severe, or life-threatening. People with weakened immune systems, such as elderly people, children, and those with certain diseases or conditions, are most at risk for severe infections from pathogens that may be present in raw milk. In pregnant women, Listeria monocytogenes-caused illness can result in miscarriage, fetal death, or illness or death of a newborn infant. And Escherichia coli infection has been linked to hemolytic uremic syndrome, a condition that can cause kidney failure and death. Some of the diseases that pasteurization can prevent are tuberculosis, diphtheria, polio, salmonellosis, strep throat, scarlet fever, and typhoid fever. Pasteurization and Contamination The pasteurization process uses heat to destroy harmful bacteria without significantly changing milk's nutritional value or flavor. In addition to killing disease-causing bacteria, pasteurization destroys bacteria that cause spoilage, extending the shelf life of milk. Milk can become contaminated on the farm when animals shed bacteria into the milk. Cows, goats, and sheep carry bacteria in their intestines that do not make them sick but can cause illness in people who consume their untreated milk or milk products. But pathogens that are shed from animals aren't the only means of contamination, says Tom Szalkucki, assistant director of the Wisconsin Center for Dairy Research at the University of Wisconsin-Madison. Cows can pick up pathogens from the environment just by lying down--giving germs the opportunity to collect on the udder, the organ from which milk is secreted. "Think about how many times a cow lays down in a field or the barn," says Szalkucki. "Even if the barn is cleaned thoroughly and regularly, it's not steamed. Contamination can take place because it's not a sterile environment."

Antibiotics 3 min video