MBIOS 101 1nd Edition Lecture 11 Outline of Last Lecture 1. Bacteria are able to grow in diverse environments2. Growth Requirementsa. Temperatureb. pHc. Osmotic pressured. Oxygen requirementse. Food source3. Bacterial Growth curvea. Lag phaseb. Log phasec. Stationary phased. Death phase Outline of Current Lecture – 1. How do we calculate bacteria growth?2. Growth in environments – Milka. Streptococcus lactis b. Lactobacillusc. Yeasts and moldsd. Pseudomonas and spoilage organisms Current Lecture – The Bacterial Growth Curve1. How do we calculate how much bacteria have grown?a. Egg Salad Sandwich Examplei. The egg salad sandwich sits for 4 hours at 80 degrees Fii. Replicates once every 20 minutesiii. E. Coli has an inoculation of 10 cell organismsiv. Formula: Nt=No+2nv. To find n: n=60/20*4hrs=12These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.vi. So Nt=10*2012=40,960 organisms vii. Is this safe to eat?viii. Most likely this is okay most E. coli strains are okay and this in terms of bacterium is a decently small sample size2. Growth in environmentsa. Most environments have more than one type of bacteria growingb. Example Milk i. Primary Organisms in milk1. Streptococcus lactisa. Likes pH 7 (milk is pH 7)b. Loves lactose (a lot of lactose in milk)c. Because of this environment it thrives, overloads the system and starts to died. The waste products of streptococcus lactis makes the moreacidic2. Lactobacillusa. Likes a pH of 6.8b. So it waits to grow until streptococcus makes the milk more acidicc. Then it is grows, overloads the system and starts to grow d. The waste products make the milk even more acidic3. Yeasts and moldsa. Start to grow in the acidic environment – like pH of 4 b. Their waste products make the pH of the milk start to return to pH 74. Pseudomonas and spoilage organismsa. Likes pH of 7 b. Eats protein of milkc. This causes the milk to start curdling d. These organisms produce odor and so this gives old milk that nasty smelle. Their job is to decompose the milk f. Bacteria is important for this reason – to decompose
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