Microbial Growth A. Microbial Reproduction 1. binary (transverse) fission A) parent cell enlarges and duplicates all its genetic material B) DNA copies move to opposite ends of parent and attach to a section of the cell membrane as it begins to pinch together at the center

Microbial Growth C) new cell wall forms between daughter cells D) cells separate or may remain attached forming chains/clusters 1) Strepto – chains 2) Staphylo – clusters 3) Diplo – groups of 2 4) Tetrads – groups of 4 5) Sarcina (Packets) – cube-shaped packets of 8

Microbial Growth 2. Generation Time A) time necessary to complete binary fission B) average is minutes 1) ranges from 5-10 min to days 2) food-borne pathogens take min

Microbial Growth 3. Bacterial Growth Curve A) shows the predictable pattern of bacterial growth

Microbial Growth B) 5 phases 1) lag phase a) period of slow or no growth b) cells are producing the molecules necessary for growth 2) log (exponential) phase a) period of optimal growth and reproduction b) will continue as long as there are sufficient nutrients and space

Microbial Growth 3) stationary phase a) cell death balances out cell reproduction b) caused by: i) decreased nutrients ii) accumulated wastes iii) increased cell density

Microbial Growth 4) death phase a) cell death outpaces cell reproduction b) caused by depletion of nutrients c) 99% of viable cells die 5) phase of prolonged decline a) the “fittest” cells can survive on the nutrients released by dying cells b) can last for months to years

Microbial Growth 4. Calculating Population Size A) population growth is exponential 1) 2  4  8  16  32  64  128… B) population size can be calculated 1) N t = (N o )2 n a) N t = final number of cells b) N o = original number of cells c) n = number of divisions 2) examples

Microbial Growth B. Microbial Nutrition 1. all life requires 3 groups of nutrients A) macronutrients (major elements) – needed in large quantities 1) includes S, C, H, N, O, P B) micronutrients (trace elements) – needed in small quantities 1) includes Co, Zn, Cu, Mn, K, Ca, Na, Mg, and Fe

Microbial Growth C) essential nutrients (growth factors) – small organic molecules that cannot be produced by the cell 2. Nutrient Sources A) Carbon 1) necessary for all cell products 2) obtained from organic sources or CO 2 (inorganic)

Microbial Growth B) Nitrogen 1) necessary for the production of DNA, RNA, ATP, and amino acids 2) most bacteria obtain N by consuming DNA, RNA, ATP, and amino acids 3) some obtain N from inorganic sources a) NO 3 - (nitrate), NO 2 - (nitrite) & NH 3 (ammonia)

Microbial Growth 4) a select few bacteria can obtain N from air (N 2 ) a) they must convert it to NH 3 (N fixation) before it can be used

Microbial Growth C) Oxygen 1) necessary for biomolecule production and energy-releasing reactions 2) no real limitations on sources a) can be obtained from organic sources, inorganic sources, or directly from air (O 2 )

Microbial Growth D) Hydrogen 1) obtained from any organic source as well as many inorganic ones 2) necessary for: a) maintaining pH b) forming H bonds c) biomolecule production d) energy source for redox reactions

Microbial Growth E) Phosphorous 1) necessary for the production of DNA, RNA, ATP, and phospholipids a) usually obtained via these sources 2) very scarce in nature a) found primarily as PO 4 -3 (phosphate ion) and H 3 PO 4 (hydrogen phosphate) in rocks and ocean mineral deposits

Microbial Growth F) Sulfur 1) necessary for the production of select amino acids and is vital for tertiary protein structure 2) obtained by consuming sulfur- containing organic molecules 3) also found in rock and sediment deposits often as SO 4 (sulfate)

Microbial Growth G) Micronutrients & Growth factors 1) obtained by consuming molecules containing them C. Nutritional Classifications of Microbes 1. Energy Source A) phototrophic B) chemotrophic

Microbial Growth 2. Carbon Source A) autotrophic B) heterotrophic 3. Energy & Carbon Sources A) photoautotrophic 1) photosynthetic orgs 2) considered the primary producers 3) ex. cyanobacteria

Microbial Growth B) chemolithoautotrophic 1) very unique 2) do not require sunlight or organic molecules a) ex. methane-producing bacteria (methanogens) – obtain energy by removing electrons from inorganic molecules and using them to bond C & H

Microbial Growth C) photoheterotrophic 1) also very rare 2) some can use chemicals as well as light for energy (facultative) 3) ex. purple and green bacteria D) chemoheterotrophic 1) majority of microbes 2) obtain C and energy from organic sources

Microbial Growth 3) many carry out cellular (aerobic) respiration 4) 2 categories a) saprobic – feed on dead organic matter i) considered free-living b) parasitic – feed on cells/tissue of living host 5) Saprobes a) primary decomposers

Microbial Growth b) some can carry out phagocytosis and ingest dead matter c) most cannot phagocytize i) cell walls prevent it ii) must release enzymes to digest matter then absorb the digested particles iii) 2 classifications of saprobes (a) obligate saprobes (b) facultative parasites

Microbial Growth 6) Parasites a) range from viruses to worms b) 3 types i) ectoparasites – ex. fungal skin infections ii) endoparasites – ex. parasitic worms iii) intracellular parasites – ex. viruses c) pathogen – parasite which usually causes disease or death d) obligate parasite

Microbial Growth D. Non-Nutritional Classifications of Microbes 1. Temperature A) all microbes have 3 critical temps 1) minimum temperature 2) maximum temperature 3) optimal temperature B) Classifications

Microbial Growth 1) Psychrophilic a) opt. temp between -5–15 o C b) cannot grow above 20 o C c) found in frigid ocean waters 2) Psychrotrophic a) opt. temp from 20–30 o C b) common cause of food spoilage c) found in cool soil and water

Microbial Growth 3) Mesophilic a) accounts for vast majority of medically important microbes b) opt. temp of 25–45 o C i) human pathogens usually 35–40 o C c) found in soil, water, plants and animals d) some can withstand short periods of higher temp = thermoduric

Microbial Growth 4) Thermophilic a) opt. temps above 45 o C i) usually 45–70 o C b) some can survive up to 100 o C i) temp at which most enzymes are destroyed c) found in hot springs, compost heaps and water heaters

Microbial Growth 5) Hyperthermophilic a) opt. temp from 70–110 o C b) usually Archaea c) found in hydrothermal vents in the ocean floor i) a newly discovered bacteria can survive up to 130 o C

Microbial Growth 2. Gas Requirements A) Obligate aerobe 1) require O 2 to survive B) Facultative anaerobe 1) grow best in presence of O 2 but can survive without it C) Obligate anaerobe 1) cannot use or survive in the presence of O 2

Microbial Growth D) Microaerophile 1) require small amounts of O 2 but larger amounts will inhibit growth E) Aerotolerant anaerobe 1) cannot use O 2 but can survive in its presence F) Capnophile 1) grow best in environments with high CO 2

Microbial Growth 3. pH Requirements A) Neutrophilic 1) prefer pH of 5–8 a) human pathogens usually 6.5– 7.5 2) don’t grow well in extremes a) inhibits enzyme function

Microbial Growth B) Acidophilic 1) grow best at pH below 5.5 2) ex. Helicobacter & Lactobacillus C) Alkalophilic 1) grow best at pH above 8.5 2) found in alkaline lakes and soils

Microbial Growth 4. Osmotic Pressure (Salt Concentration) A) most microbes prefer isotonic or hypotonic environments B) 2 main classifications 1) Osmotolerant a) can survive up to 10% NaCl 2) Halophilic a) require at least 9% NaCl but optimal is ~25% b) ex. Staphylococcus