Food Microbiology: Delicious or… Boehm 2010 …Dangerous? Presentation by: Ms. Boehm, Wellesley High School, MA General Introduction to Bacteria 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 1/20th of your total body weight! Classification of Bacteria •Bacteria are the most abundant organisms on earth. •Of the three major domains of classification, bacteria take up two. •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 is often referred to as archaebacteria •Archaea are thought to resemble the very first cells on earth •They are more rare and live in extreme conditions Identification of Bacteria Bacterial Shapes Sphere shaped: coccus Rod shaped: bacillus Spiral shaped: spirochete •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 Staining Bacteria Gram-negative: Double membrane doesn’t hold purple dye Gram-positive Thick peptidoglycan layer holds purple dye Cell Wall Structure Gram-Negative Gram-Positive Holds Purple Dye Will Not Hold Purple Dye DNA Outer Membrane Peptidoglycan Plasma Membrane Peptidoglycan Plasma Membrane The Genetics of Bacteria Bacteria Are Prokaryotic •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! Bacterial Conjugation Often it is the plasmid that contains genes that are pathogenic to humans! Bacterial Growth and Division Bacterial Growth and Division • 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 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 people’s 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… Bacteria Can Cause Many Different Illnesses •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 Food Microbiology Delicious or Dangerous? 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????” 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 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 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.) 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. 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 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 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