Microbiology Module 3

Source of carbon precursor molecules w/electrons that are either already hi-energy or can be energized.

Movement of hi energy electrons leads to production of ATP and/or proton motive force (PMF)

Sources of nitrogen, sulfur, phosphorous, iron and others also required to make all cellular bldg blocks from precursors

Microbes vary in ways in which they obtain nutritional requirements. Used in classification

• CARBON SOURCE:
• Autotrophs: CO2 sole or principal biosynthetic carbon source
• Heterotrophs: Reduced, preformed, organic molecules from other organisms

• ENERGY SOURCE
• Phototrophs: Light
• Chemotroph: Oxidation of organic or inorganic cmpnds

• ELECTRON SOURCE
• Lithotrophs: Reduced inorganic molecules
• Organotrophs: Organic molecules

Uptake of nutrients require special transporters since CM is impermeable to most substances.

Active transport move solutes into cell against conc. gradient, requires an energy source

Facilitated diffusion (passive) is not a major mechanism for prokaryotic transport because it requires environment in which conc. of nutrients is higher outside the cell relative to inside

Cells use energy from electron transfers to generate gradients (respiration) and then use gradients for active transport

Symport (Sugars, amino acids, anions) occurs when H+ or Na+ and solute both move into cell together

Antiport occurs when H+ and another cation are transferred in opposide directions

• NOT used by "fermenting" microbes
• (cannot generate ion gradients)

Sugars, amino acids and many other things transported using this mechanism

Contain nucleotide binding domain

Many related ABC transporters all use ATP as driving force but differ in which solute-binding proteins (Periplasmic binding proteins) interact with the membrane-spanning channel

Mechanism for transporting sugars into the cell

Also called Phosphoenolpyruvate Sugar Phosphotrasferase system (PTS)

Transported sugar is phosphorylated as soon as it reaches the cytoplasm, sugar-P cant get back out. PEP is initial energy source

Fermentative bacteria that cannot use symport can use these systems

Refers to the determination of number of cells within a population

Direct methods use microscope to count individual cells (Petroff-Hausser counting chamber)

Plating techniques count live cells after each cell in a culture has grown to form a colony on an agar plate

Total conc. of cell mass is measured using a spectrophotometer to assess light scattering

Growth curves are obtained and used to generate growth rates and doubling times under diff. environmental conditions. Used for Classification

Microbes can be stained prior to counting

Requires a microscope and special slides with grids

Immediate answers can be obtained

Both lives and dead microbes are usually counted

Microbes in a culture scatter light and amount of scattered light is a measure of total cellular mass

Rapid and common technique that is used when a culture must be manipulated at a given cell density during its growth

For counting live cells.

Takes time and effort. Results in 24-48 hours

Usually used to verify results from other quicker methods

Used to measure viability in antibiotic-type experiments

Usually plotted as log [cells] vs. time

Lag phase is seen when new cultures are inoculated from non-growing cells

Log (exponential) phase is used to generate growth rates under diff. conditions

Stationary approx 10^9 cells/ml, happens when cells stop dividing or when growth is balanced by death

Death phase may be seen using dilute and plate method

Osmotic conc, pH, temperature, oxygen levels, pressure

Osmotolerant: able to grown in wide range of hypotonicity

Halophiles: Grow best under high levels of salt in environment

Acidophiles: Love acidic environment

Psychrophiles: Grow best with very cold condition

Psychrotrophs: Can grow in cold but prefer warmer temperatures

Mesophiles: Grow on body temperature

Thermophiles: 60-80 degrees

Hyperthermophiles: 80+ degrees

Obligated aerobe: Need oxygen to grow

Facultative Anaerobe: Does not require oxygen for growth, but growth is facilitated in the presence of oxygen

Aerotolerant aerobe: Dont care about having or not having oxygen

Obligate anaerobe: Requires absolutely no oxygen

Microaerophiles: Requires small amount of Oxygen

Barophiles: require high hydrostatic pressures

Life likely evolved at higher temps --> thermophiles (that is the norm environment)

Enzymes and proteins from thermophiles function in same reactions and in same ways, but a few AA differences allow proteins to remain folded at higher temps

Higher numbers of specific ionic bonds are important for protein structures in thermophiles and hyperthermophiles

Ionic bonds independent of temperature for bond strength

CMs of thermophilic bacteria are high in saturated FAs and hopanoids to maintain integrity of lipid bilayer

C40 units ether-linked to glycerol phosphate are used by hyperthermophiles (all archaea)

DNA positively supercoiled in hyperthermophiles

• Psychrophiles have CMs w/higher numbers of PUFAs and hopanoids to maintain fluidity
• (negatively supercoiled DNA)