Lecture 7 Microbial Growth Flashcards
Solutes such as salts and sugars ____ the availability of water to microbes.
Decrease
Availability of ___ affects growth of all cells.
This is expressed as?
Water
water activity (Aw) ex.) higher [solute] ---> lower Aw
Hypotonic Solution
Solute conc. inside (intracellular) > Solute conc. outside (extracellular)
Isotonic Solution
Solute conc. inside (intracellular) = Solute conc. outside (extracellular)
Hypertonic Solution
Solute conc. inside (intracellular) < Solute conc. outside (extracellular)
What is a Halophile?
Name the two examples from lecture.
Osmophiles that live in high[Salt]
ex. ) - Halobacterium (member of the archaea)
- Staphylococcus
- Human skin
- Mannitol Salt Agar used to isolate
What are microbes that can grown under pH of 0-6?
Acidophiles
What are microbes that can grow under pH of 8-12
Alkaliphiles
What is the pH range of Escherichia coli?
pH 2-9 10million fold difference
How do Halophiles live in a high salt environment?
They use compatible solutes like KCl. Keeps intracellular solute conc. high with out interfering with growth or metabolism.
What are nutrients?
Substances used in biosynthesis and energy release - required for growth.
What is 95% of the microbial cell weight made of?
Macronutrients (or macroelemets)
C,O,H,N,S,P,Fe
What is the the other 5% of the cell weight made of?
Micronutrients (or trace elements)
Co, Cu, Zn, Mn
What is the form of nitrogen that microbes can use?
Ammonia (NH3) or Nitrate (NO3)
What is Nitrogen fixation?
N2 reduced to ammonia (NH3)
Rhizobium and Azotobacter
Rhizobium - in symbiosis with plants
Azotobacter - free living in soil
How does food for microbes enter the cell?
- at high rates
- across membranes
- selective fashion
- often against concentration gradient
Passive and Active transport systems used.
Describes Passive Transport
- no energy required
- requires gradient from [higher] to [lower]
Passive Diffusion
Only small molecules and certain gases
Facilitated Diffusion
- Uses membrane carrier proteins
ex) Aquaporins - form H2O channels
Active Transport
- Energy - dependent
- Moves nutrients against gradient
- ATP or proton motive force used
Describe Primary Active Transport : ABC Transporters
- ) After binding solute, the solute-binding protein approaches ABC transporter.
- ) Solute-binding protein attaches to transporter and releases solute. Energy released by hydrolysis of ATP drives movement of solute across membrane.
different types of ABC Transporters
- Uptake ABC - move nutrients in
- Export ABC - also called Multidrug Efflux Pumps, moves substances out
- In bacterial cells - move antibiotics out, bacteria become resistant to antibiotic
- In cancer cells - move anticancer drugs out, tumor becomes resistant
Describe Secondary Active Transport and name the example from lecture.
- Uses potential energy of ion gradients
- Electron transport across membrane generates proton (H+) gradient
- Can use gradient to do work !
Example Lac Permease
- Membrane protein, moves lactose in powered by proton also moving in
Active Transport : Group Translocation and name the example from lecture.
- Nutrient chemically altered
- Energy from phosphoenolpyruvate attaches P to sugars
- Phosphoenolpyruvate - key intermediate in Glycolysis
- Metabolic pathway that converts glucose to pyruvate
REVIEW FIG. 3.14
Describe Iron Uptake
- Microbes release siderophores to acquire Fr
What are Siderophores and name the example from lecture
- Fe complex then transported into cell often using ABC
Enterobactin : An Escherichia coli siderophore
Describe Siderophore-iron complex transport into a gram - negative bacterial cell.
- ) E. coli synthesizes and secretes an iron-binding enterochelin that bind Fe3+
2a. ) The complex is transported to the periplasm through an outer membrane protein (FepA) and is transported into the cell by an ABC transporter that includes a periplasmic solute-binding protein (FepB) and the integral membrane proteins FepC, G, and D. - ) Inside the cell, the iron is released and reduced to Fe2+
What is Metabolism
All the chemical reactions in a cell
What Catabolism
Breakdown of complex molecules into smaller ones with release of benefit for Anabolism - reactions that build cells.
