A1258150322ROnur

1
Y/M period 1 Fri, Oct 4

• Bacteria vs. Fungi
• Cell size
• Growth condition
• pH
• Temperature
• aw
• Yeasts vs. Molds
• Yeasts Molds
• uni-cellular multi-cellular
• non-filamentous filamentous
• Significance in food
• Spoilage
• Fermentation

2
Y/M period 1 Fri, Oct 4
Our menu today Juice

• Why juice is chosen for enumeration of yeasts
  molds?
• Fresh juice vs. Frozen concentrate

3
Y/M period 1 Fri, Oct 4

• Media
• Acidified Potato Dextrose Agar
• PDA (nonselective) tartaric acid
• low pH inhibits most bacteria permits
  growth of fungi
• Antibiotic Plate Count Agar
• PCA (nonselective) antibiotics
  (chloramphenicol tetracyclin)
• antibiotics prevent bacterial growth by
  inhibiting protein synthesis
• Petrifilm (for Yeasts Molds)
• nutrients antibiotics indicator dye
• yeasts blue-green or off-white color,
  small, defined colonies
• molds blue in color or natural pigmentation
• larger, diffused colonies

4
Y/M period 1 Fri, Oct 4
I. Juice sample preparation
II. Media preparation
1. Label empty plates
Tartaric acid
Antibiotic
2. Add selective agents
2 ml
1.85 ml
Ab-PCA
Acid-PDA
3. Pour plates
Bring annotated flowchart (Figure 3.1) on monday
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6
Y/M period 3 Mon Oct 14

• Colony counting
• Count yeasts and molds separately
• molds larger, fuzzier
• yeasts similar to bacterial colony
• Use reasonable judgement for overwrapping
  colonies
• Follow counting rules

7
Y/M period 3 Mon Oct 14

• Microscopic Examination
• Yeast
• Pick 3 colonies w/ different colony morphologies
  from any plate (abo-PCA or acid-PDA)
• Prepare heat-fix smear
• Crystal violet stain for 60 sec
• Examine cell morphology using oil-immersion lens
  (100X)
• Mold
• Pick 3 colonies w/ different colony morphologies
  from any plate (abo-PCA or acid-PDA)
• A drop of lactophenol cotton blue dye on a slide
• Gently touch the surface of mold colony with
  tape
• Place the tape on the slide
• Examine the slide (10X)

8
Y/M period 3 Mon Oct 14
Features of Fungal Phyla
Guarro et al., 1999 (Clin. Microbiol. Rev. 12454)
9
Y/M period 3 Mon Oct 14

• Observation of demonstrated slides
• Rhizopus sp.
• Penicillium sp.
• Aspergillus sp.
• Budding yeast (Saccharomyces cerevisiae)
• a bacterium

molds

• Yeast vs. Bacterium
• Compare colony morphologies of a bacterium vs. a
  yeast
• Compare cell morphologies of a bacterium vs. a
  yeast
• Compare the demonstrated yeast vs. the yeast from
  the sample
• Examination of Mold
• Examine mold colony morphologies
• Examine mold mycelium structures
• Compare the demonstrated molds vs. the mold from
  the sample