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Microbial Growth - Coggle Diagram
Microbial Growth
Biofilms
Quorum Sensing- chemical signal communication between bacteria in biofilm, coordinates grouping
Planktonic Bacteria- free floating single cells, move independently, susceptible to antis, and attach and form biofilms!!
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Purpose: share nutrients, share plasmid/DNA, protect from environment
Prevention: incorporating antimicrobials, identifying and studying chemical signaling, and adding lactoferrin to bind to iron to inhibit motility
Measurement/Techniques
Preservation- short term (refrigeration) and long term (deep freezing and freeze drying-lyophilization)
Count Techniques
Viable Plate Count- counts living cells, most frequently used- 24-48 hours, one bacteria grows to one colony
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Direct Microscopic Count using Petroff-Hauser Cell Counter: inexpensive, quick, counts both live and dead cells with high bacteria count
Estimate with Spectrophotometer- absorbance vs. time and match with plate counts set up at same time with same culture. indirect estimate with 10-100 million bacteria required
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Requirements
Physical
Osmotic Pressure- solute concentration within and surrounding the cell. Heat fixing prevents abrupt change in osmotic pressure during staining
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Temperature- organisms are classified by the temperature range they live in- most die in extreme heat and slow growth in cold
Danger Zone- 40 F - 140 F - rapid growth and toxin production (E. Coli, Salmonella, Campylobacter)
STAPHYLOCOCCUS AUREUS- carried in nose and skin + halophilic (likes 7.5% salt) and high osmotic pressure. Heat tolerant and produces endotoxin to survive boiling
BACILLUS CEREUS- psychotroph that lives in fridge conditions, large gram positive bacillus, found in soil and vegetation, forms endospores that are not killed off by heat and germinate as food cools + release endotoxin
CHEMICAL
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Oxygen Requirement- aerobic organisms require but anaerobic do NOT (facultative prefer one but can live with other
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Anaerobic Chamber- palladium catalyst pellets, methylene blue indicator, envelope with sodium bicarbonate
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