Microbiolgy Lecture 3

The doubling time is 20 minutes at 37^oC. The bacteria have been incubating for 8 hours, which means there will be doubling taking place 3 times an hour. So there will be (8 hrs x 3) = 24 doubling moments taking place.There will be 24 generations of bacteria after 8 hours.

• 5000 x 224 = N_t
• N_t  = 83,886,080,000
• or 8.388 x10¹⁰

Utilizing the equation N_t=N_o x 2ⁿ

• N_t=population size at specified time
• N_o= initial population size
• n= # of generations

Aerobe: organism that grows in the presence of oxygen

Obligate aerobe: requires atmospheric oxygen (20% O2) for growth and metabolism

Microaerophile :requires O2 for metabolism, but at very low concentrations

Anaerobe: organism that grows in the absence of oxygen

Obligate anaerobe:cannot grow in the presence of oxygen

Facultative anaerobe: able to use both pathways; therefore, does not require O² , but grows better in its presence–

Aerotolerant: does not require O² but can withstand the presence of O²; grows just as well in and out of the presence of O²

Obligate aerobe : Top growth

Facultative anaerobe: Full column

Obligate anaerobe: bottom growth

Microaerophile : Middle growth

Aerotolerant : Full column

• Catalase:
• Peroxidase:
• Superoxide Dismutase:
• Superoxide dismutase & catalase:
• Superoxide reductase:

–Cytochromes: proteins involved in electron transport and redox reactions

-Siderophores: organic molecules that bind to Fe3+ making it possible for the cell to take up iron

Hydroxamic acid: strongly chelates iron–

Enterobactins: produced by enteric bacteria like E. coli and Salmonella

Differ in the wavelengths at which light is absorbed

Cyclic photophosphorylation–the electrons return to the chlorophyll after passing through the electron transport chain

Non-cyclic photophosphorylation–the electrons are used to reduce NADP and electrons are returned to chlorophyll from H2O and H2S

• Oxygenic = Chlorophyll
• Anoxygenic=Bacteriochlorophyll

• Oxygenic = water as electron donor
• Oxyegnic= produces oxygen
• Oxygenic = frequently aerobic

• It binds to Mg2+
• Absorbs light red and blue light; transmits green light

680nm and 660nm 

680nm is the most common

680nm

Eucaroytes: Occurs in thykaloid membranes within the chloroplast

Procaryotes: Occurs in thykaloid membranes within the cell

Sulphur

Blue and Green bacteria

Purple bacteria: invagination of the cytoplasmic membrane–

Heliobacteria: cytoplasmic membrane (unique)–

Green bacteria: both cytoplasmic membrane and membrane-enclosed structures called chlorosomes

• -Most widespread; associated with chlorophyll or bacteriochlorophyll
• –Hydrophobic pigments firmly embedded in the membrane
• –Oxygenic photosynthesis: Typically yellow, green, red, brown

–Anoxygenic photosynthesis: Typically red, purple, pink, green, yellow, brown

–Do not function in ATP synthesis

–Transfer light to the reaction centers•Reaction centers are a complex of pigments used to harvest light and generate ATP

–Act as photoprotective agents from toxic oxygen species (e.g. singlet oxygen)

Phycobilins/Phycobiliproteins–Present in cyanobacteria and red algal chloroplast

–Red (phycoerythrin) or blue (phycocyanin) pigments

–Allophycocyanin (red pigment)•Occur in aggregates called phycobilisomes, attached to the photosynthetic membranes

Usually seen in serratia

•Osmotolerant: to grow over a wide range of water activity or osmotic concentration.

•Halophile:require high levels of NaCl  to grow; usually above 0.2M

• Acidophile: pH 0 and pH 5.5
• Neutrophile:  pH 5.5 and pH 8.0
• Alkalophile: pH 8.5 and pH 11.5

Neutrophiles are usually in our bodies

Helicobacter pylori would be an acidophile

• Psychrophile– 0-15^_oC
• Psychrotroph– 20-30^oC; minimum range:
• 0-7oC; maximum: 35^oC.
• Mesophile–o20-45^oC
• Thermophile–55-65^oC
• Hyperthermophile (extreme thermophile):80-113oC

Mesophiles

Barotolerant–able to grow at different ranges of hydrostatic pressures

Barophile–Grows more rapidly at high hydrostatic pressures