Lecture 25

• food and water borne bacterial diseases

  cholera

  listeriosis

  botulism

  e.coli and salmonella typhimurium infections

  generally prevented and controlled by sanitation measures, antitoxins and antibiotic therapy
• E.coli O157:H7

  gram negative

  enterohemorrhagic e.coli

  infectious dose <100 (for other strains ID>1000000)

  carriers: cattle, swine
• E. coli toxin

  AB toxin

  binds glycolipid receptors on kidney and intestinal cells, enters

  cleaves human rRNA

  hemolytic uremic syndrome (Itus, kidney failure)

  toxin genes on prophage

  what conditions activate prophage? UV light, stress
• foods not only serve as important vehicles for disease transmission, but can be transformed by microbes into gastronomic delights

  kimchi and sauerkrat = Leuconostoc

  Natto = soybeans fermented with Bacillus natto
• Microbial fermentations play an important role in the food industry including the production of yogurt, cheese, chocolate and alcoholic beverages

  – major fermentations used are lactic, propionic and ethanolic
• fermentation: consequence of life without air

  Glucose -> 2 pyruvate, ATP via substrate level phosphorylation

  pyruvate -> lactic acid, ethanol, propionic acid
• yogurt production - lactic acid bacteria

  Lactobacillus, streptococcus: starter culture

  lactose (in milk) hydrolyzed to glucose, fermented to lactic acid
• contamination with what microbe is a major concern in yogurt production

  Listeria, Cryptosporidium, Campylobacter, Brucella, Escherichia coli and Salmonella.
• cheese production

  lactococcus starter culture and enzyme renin added to promote coagulation (milk to curd)

  ripening: more microbes added (curd to cheese)

  propionibacterium for swiss cheese

  penicillium (fungus) for blue and brie
• probiotics

  microbes added to diet to improve health

  ex: lactobacillus, bifidobacterium
• potential benefits of probiotics

  vitamin production

  improved digestion

  pathogen inhibition

  evidence for positive and lasting benefits not well established
• prebiotics

  compounds (fiber) that promote growth of beneficial microbes
• extreme probiotics

  UMN researchers have begun transplanting bacteria from a donors healthy colon to treat pseudomembranous colitis, a crippling disease responsible for over 5000 deaths/year caused by Clostridium difficile
• kombucha tea

  fermented tea using bacteria (bacillus) and yeast (saccharomyces)

  scoby

  symbiotic colony of bacteria and yeast
• how is beer made?

  malting and mashing

  plant enzymes breakdown complex starches and proteins

  hops: antibacterial flavor

  yeast members of eukarya: saccharomyces
• ginger beer

  usually non alcoholic, traditional production involved fermentation of ginger spice and sugar with saccharomyces and lactobacillus
• wine


  grape juice (must) with sugars

  yeast: saccharomyces ethanol fermentation
• industrial microbiology

  microbial growth and product production occurs in bioreactors that can hold over 100,000 liters
• biofuels

  fuels from biological material

  cargill expands its corn based ethanol business by opening a plant in fort dodge iowa with capacity to grind 150,000 bushels of corn daily

  corn -> bacteria, yeast fermentation -> ethanol
• antibiotics are secondary metabolites

  secondary metabolites not required for growth and are usually made by microbes under limiting conditions following active growth