Bio 3400 - Lecture 5

• Filamentous temperature-senesitive proteins
• FtsZ - Ring around centre
• ZipA - Connects FtsZ to membrane
• FtsA - Recruits other cytoplasmic proteins
• FtsK - Mediates separation of chromosomes

Facilitate location of FtsZ

• Prokaryotic shape determining factor
•  - Simple cytoskeleton (Bacteria and Archaea)
•  - Not found in coccus
•  - Loacalizes peptidoglycan synthesis

• Shape-determining protein produced by vibrio-shaped cells of Caulobacter crescentus
•  - Found on concave surfaces

• Cocci - From FtsZ ring
• Rod-shapes - From points along length

• Carrier molecule that plays a major role in insertion of peptidoglycan precursors
•  - Nonpolar, easy membrane passage

• g = t/n
• t = duration of exp. growth
• n = No. of generations during exponential growth period

• 1. Slow growth at first while numbers increase
• 2. Exponential growth while nutrients are present
• 3. Stabilized growth as nutrients become limiting and waste builds up
• 4. Death

• Continuous
• Chemostat

• Too low - Membrane gelling, slow transport
• Too high - Protein denaturation, membrane collapse, thermal lysis

• Psychrophiles - Very cold temperature optima
• Psychrotolerant - Organisms that can grow at 0°C, though their optimum is somewhat higher

• More α helices than β sheets
• More polar and less nonpolar residues
• Decreased interactions between protein domains
• Antifreeze proteins
• Accumulation of compatible solutes
• Upregulation of peptidoglycan synthesis

• Thermophiles - Growth optima between 45°C and 80°C
• Hyperthermophiles - Optima greater than 80°C

• Heat tolerant protein folding
• Increased ionic bonds between acidic and basic residues
• Di-inositol phosphate, diglycerol phosphate

Membranes rich in saturated fatty acids

Lipid monolayer rather than bilayer

• Neutrophiles - pH 6-8
• Acidophiles - pH <6; sensitive membranes
• Alkaliphiles - pH >9; Na⁺ motive force (not H⁺)

Still ~neutral with some variation (4.6-9.5)

Halotolerant (0%-5% NaCl), halophile (5%-7% NaCl), extreme halophile (>15% NaCl)

Compatible solutes

Aerobes, facultative organisms (take it or leave it), microaerophiles (only small amounts), aerotolerant (live with it, but don't use it)

Killing or removal of all viable organisms

Limiting microbial growth

Treatment of an object to make it safe to handle

Removes all pathogens, but not necessarily all microorganisms

Controlled heat to reduce microbial load in heat-sensitive liquids

• -static; Inhibits growth only
• -cidal; Kills only viable cells
• -lytic; Kills eveything