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General Introduction to Bacteria With Special Thanks to Megan Rokop and Ms. Boehm

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Fun Facts about Bacteria Necessary to make many everyday foods including yogurt, cheese, sauerkraut, soy sauce, vinegar Used to clean up various forms of pollution including oil spills, pesticides, sewage Produce antibiotics that we can use to the fight bacteria that make us sick Produce Botox so we can all have wrinkle-free foreheads Fun Fact: Bacteria comprise about 1/20 th of your total body weight!

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Bacteria are the most abundant organisms on earth. Classification of Bacteria

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The domain Bacteria is often referred to as eubacteria The most common type of bacteria found on earth Examples: Streptococcus, Escherichia coli, Clostridium botulinum, Salmonella The domain Archaea are prokaryotic like bacteria but are not bacteria Archaea are thought to resemble the very first cells on earth Some live in extreme conditions such as the halophiles (salt lovers) in Utahs Great Salt Lake May be at least as closely related to eukaryotes as they are to bacteria

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Identification of Bacteria

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Bacteria have three basic shapes. These images are magnified by more than 10,000 times! They are all surrounded by some type of cell wall Sphere shaped: coccus Rod shaped: bacillus Spiral shaped: spirochete Bacterial Shapes

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Staining Bacteria Gram-positive Gram-negative: Thick peptidoglycan layer holds purple dye holds purple dye Double membrane doesnt hold purple dye

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Peptidoglycan Plasma Membrane Gram-Negative Gram-Positive Plasma Membrane Peptidoglycan Outer Membrane Holds Purple Dye Will Not Hold Purple Dye DNA Cell Wall Structure

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The Genetics of Bacteria

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The main DNA is a long circular loop, one single chromosome, not contained within a nucleus Many bacteria also contain plasmids, a smaller loop of DNA It is the plasmid that allows these asexual organisms to have variation, and can also make the bacteria pathogenic! Bacteria Are Prokaryotic

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Bacterial Conjugation Often it is the plasmid that contains genes that are pathogenic to humans!

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Bacterial Growth and Division

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Most bacteria divide every 20 minutes They will form bacterial colonies Bacteria divide by a process called prokaryotic fission The product from one bacterium dividing would be two genetically identical daughter cells

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Good vs. Bad Bacteria There are many different kinds of bacteria, most of which will not make you sick and may actually help you: Staphylococcus epidermidis lives harmlessly on your skin Escherichia play a nutritional role in the intestinal tract by synthesizing vitamins, especially vitamin K. Neisseria subflava lives harmlessly in most peoples mouths Fun Fact: The human body contains 20 times more microbes than it does cells! But, there are also some that can make you sick

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Strep Throat - Streptococcus pyogenes Ear Infections - Streptococcus pneumonia, Haemophilus influenzae, Moraxella catarrhalis Meningitis Neisseria meningitidis, Haemophilus influenzae Tuberculosis Mycobacterium avium, M. tuberculosis Gonorrhea Neisseria gonorrhoeae Syphilis Treponema pallidum Bacteria Can Cause Many Different Illnesses

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Food Microbiology Delicious or Dangerous?

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Food Microbiology Microorganisms are a part of the food we eat every day, specifically bacteria Most of these bacteria are harmless, non-pathogenic BUT some of these bacteria are harmful to us, pathogenic Is the food delicious or dangerous????

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Delicious Food Microbiology Yogurt has bacteria added to it that give it a slightly sour taste active yogurt cultures Lactobacillus bulgaricus and Bifidobacteria Cheeses can be fermented with various bacteria Swiss cheese -Propionibacterium Blue cheese -Penicillium roqueforti and Lactobacillus Finally, many pickled vegetables get their flavor from bacteria Sauerkraut Leuconostoc and Lactobacillus Pickles Lactic acid bacteria

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Dangerous Food Microbiology Contaminated Food Can Make You Sick Escherichia coli O157:H7 *Source: spinach, ground beef, frozen pizza * *Symptoms: vomiting, diarrhea (often bloody) Clostridium botulinum -botulism *Source: soil, water, non-acid canned foods *Symptoms: flaccid paralysis and possible death (or a smooth face ) Salmonella typhimurium salmonella *Source: eggs, chicken meat, dairy products *Symptoms: headache, chills, vomiting, diarrhea

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Facts about Foodborne Illness The CDC estimates that 76 million people get sick, more than 300,000 are hospitalized, and 5,000 Americans die each year from foodborne illness. Uncooked foods are the largest source of foodborne illness in the US (raw meat, uncooked eggs, raw vegetables, etc.)

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Case Study Outbreak of E. coli in Spinach, 2006

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What happened? There are rare cases of E. coli 0157:H7 contamination each year In late August of 2006, the CDC noticed a dramatic spike in cases The hypothesis was that this was a foodborne illness, but the source was unknown

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Who was affected? E. coli O157:H7 outbreak resulted in 205 confirmed illnesses and three deaths The contaminated spinach was found in 26 states.

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Source traced to spinach The CDC narrowed the source down to fresh spinach coming from an isolated farm in southern California Normally fresh vegetables do not harbor pathogenic bacteria The CDC, in September 2006, reported an apparent outbreak of E. coli O157:H7 linked to the consumption of bagged spinach

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How did the spinach get contaminated? Environmental risk factors for E. coli O157:H7 contamination at or near the spinach field: the presence of wild pigs in the proximity of irrigation wells used to grow produce for ready-to- eat packaging surface waterways exposed to feces from cattle and wildlife The strain of E. coli is normally found in the intestinal tract of cows, pigs and deer.

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How did the CDC identify E. coli 0157:H7? The CDC cultured the bacteria from the spinach and placed it on a food source E. coli likes to eat, such as EMB (eosin methylene blue) agar E. coli grows pink colonies on EMB agar No other bacteria will grow pink on this media. The CDC was able to distinguish the E. coli 0157:H7 strain from other E. coli strains by doing gel electrophoresis of the DNA. The genetic fingerprint will be different- do you know why?

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How could our class identify E. coli? 3 methods of potential identification methods: 1.Look at shape under the microscope 2.Gram staining 3.EMB agar 1.2. 3.

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Symptoms of E. coli 0157:H7 infection Type of enterohemorrhagic Escherichia coli (EHEC) Hemorrhagic (bloody) diarrhea Abdominal pain Kidney failure

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How does E. coli 0157:H7 make you sick? E. coli 0157:H7 produces a toxin, verotoxin, similar to a shiga toxin Verotoxin invades the cells of the intestine and inhibits protein synthesis Inhibition of protein synthesis = cell death

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How can we avoid getting sick? Cook the food E. coli 0157:H7 (on spinach) can be killed by cooking at 160 F for 15 seconds Cook meat until grey/brown in color and juices run clear to kill bacteria

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How can food contamination be prevented pre-consumer? Irradiation is one possible solution Process of irradiating foods with ionizing radiation (gamma rays or high energy electrons) to destroy microorganisms contaminating the food According to CDC, irradiation does NOT change nutritional value, composition of the food, or make the food dangerous Cool fact: astronauts eat irradiated food in space!

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Summary Bacteria are the most abundant organisms on earth Some bacteria never cause us harm and can be helpful to us (non-pathogenic) Some bacteria are harmful to us (pathogenic) Toxins produced by bacteria can damage our cells Outbreak of E. coli 0157:H7 in spinach Contamination and infection can be prevented by a variety of methods Cooking you can do at home Irradiation can be done by producers