BMS 212 W4
BMS 212 W4 BMS 212
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This 3 page Class Notes was uploaded by Brandon Czowski on Sunday February 14, 2016. The Class Notes belongs to BMS 212 at Grand Valley State University taught by Dr. Leonard in Winter 2016. Since its upload, it has received 26 views. For similar materials see Microbiology in Biomedical Sciences at Grand Valley State University.
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Date Created: 02/14/16
BMS 212 Week 4 Chapter 6: Microbial Nutrition Require: macronutrients: large quantities of C,H, O, N and P,K,Mg, (Fe for metabolism); obtained from • enzymes and nucleic acids • micronutrients: smaller amounts, “trace elements”; Zn, Mo, Mn, Cr; needed for enzyme function • Growth factors: amino acids, NADH, vitamin B6 (organic nutrients) Non-organic nutrients are needed for bacterial growth Bacteria can produce amino acids, allowing them to produce their own nutrients Classiﬁed based on source of carbon/energy: Carbon source: • • Autotrophs: acquires carbon from inorganic sources (CO2) • Heterotrophs: carbon from organic sources • Energy source: • Phototrophs: energy from sunlight • Chemotrophs: energy from bond breaking (redox reactions) Four Basic groups 1. Photoautotrophs: plants, algae, cyanobacteria 2. Chemoautotrophs: bacteria and some archaea that are able to ﬁx nitrogen 3. Photoheterotrophs: green/purple non sulfur bacteria 4. Chemoheterotrophs: aerobic respiration, anaerobic, and fermentation (most pathogens) When performing redox reactions, hydrogens are required for hydrogen bonding that occurs, hydrogen atoms and electrons can be obtained from organic/inorganic sources Organotrophs: organic sources of hydrogen/electrons Lithotrophs: inorganic sources provide hydrogen/electrons Environmental Inﬂuences on Bacterial growth - Temperature: most bacteria have optimal temperatures to grow, but if it becomes too hot growth can stop and cause disfunction or unfolding • Psychrophiles—cold blooded (below 15 degrees celsius), slow growth • Mesophiles—body temp. (35-37 degrees celsius), both facultative and thermoduric organisms - facultative psychrophiles: ﬂexible to temperatures, allows them to grow at body & room temperature, but at a much slower rate in cooler areas - thermoduric organisms: favors optimal temperature but able to tolerate higher temps for short periods of time • Thermophiles—heat loving (above 45 degrees celsius) • Hyerthermophiles—extreme conditions (greater than 60 degrees celsius); hot springs, thermal sea beds - Oxygen requirement: use thioglycollate test, which reduces O2 to H2O to test is organisms growth based on oxygen availability obligate aerobes: require O2 to grow • • Obligate anaerobes: cannot grow with O2 (becomes poisoned) • Facultative anaerobes: ﬂexible and able to grow with/without oxygen present • Aerotolerant anaerobes: do not use oxygen for growth, also not poisoned by it - Toxic forms of oxygen: formed as byproducts of aerobic respiration, microbes that don’t use oxygen produce them in the presence of O ; al2 contain extra electron pair/radical making them more reactive, the microbes must have ability to produce enzymes Singlet oxygen— O 1 2- • BMS 212 Week 4 • Superoxide—O : su2eroxide dismutase detoxiﬁes with 2 protons to give H2O2 and oxygen gas 2- • Peroxide anion—O 2 : catalase detoxiﬁes H2O2 to Water and oxygen gas; peroxidase (doesn’t create O2 as product) detoxiﬁes H2O2 and NADH to water and NAD + • Hydroxyl radial (OH): single electron makes it very reactive - pH inﬂuence • acidophiles: grow best in acid pH conditions • neutrophiles: grow best in neutral pH (most common pathogens) • alkalinophiles: grow best in alkaline pH - Physical effects of water • osmotic pressure: pressure required to stop the ﬂow of water across a semi-permeable membrane (high osmotic pressure—> hypertonic—water leaving cell) - halophiles: grow best in high salt concentrations, non-pathogenic, obligate/facultative - osmophiles: grow best in high osmolarity in some solution other than salt - barophiles: need high barometric/atmospheric pressure (deep sea organisms) Ecological relationships: organisms live in association with different species antagonist relationship: one beneﬁts and one is harmed in the association (parasitism) synergistic relationship: members can live separately, but beneﬁt when associated (bioﬁlms) symbiotic relationship: both organisms beneﬁt from relationship, one rarely lives without the other (bacteria in rumen of cows stomach, rhizobium—utilizes nitrogen, and pea plant) *synergistic and symbiotic relationships are both beneﬁcial Growth of Microbes Microbes grow by using binary ﬁssion and measured by using generation time, the time it takes for one bacteria to become 2; each passing of a generation time resulting in doubling amount of cells Bacteria can grow arithmetically (straight slope) or logarithmically (increasing 10 fold)— dependent on the type of organism, nutrients that are available, and temperature 4 phases of microbial growth 1. Lag phase: slow growth while adapting to environment, inoculating a new culture 2. Log phase: maximum rate of growth, rapid chromosome replication, growth and reproduction, all generally same shape/size (antibiotics work the best in this phase because bacteria is growing the most) 3. Stationary phase: growing slows due to decrease in nutrients and increase in waste; no net change of # of cells (# dying = # new cells) 4. Death phase: cells are dying faster than being produced Measuring Microbial Growth • Incubation required Viable plate count: accuracy is dependent on the media bacteria is grown and technique; • colony count ranges from 30-300, need to create serial dilutions to ﬁnd original amount • Membrane ﬁltration: sample of bacteria gets ﬁltered in ﬂask attached to vacuum, the ﬁlter is placed on agar for bacteria to grow • Without Incubation • Petroff-Hausser counter: (hemocytometer) good for large numbers of colonies but unable to distinguish dead and alive cells and challenging with multiple species present; view bacterial suspension under oil immersion lens to count cells in grid, allows calculation of original amount • Turbidity with Spectrophotometer: this method requires a standard curve to be generated with a hemocytometer; measures absorbance of the sample (higher absorbance corresponds to higher turbidity) but loses sensitivity to lag and stationary phase BMS 212 Week 4 • Coulter-counter: machine that measures the disrupted electrical ﬁeld caused from bacterial growth (bacterial growth tends to clump); better for less dense populations composed of larger cells; cannot distinguish dead or alive cells; generally used for yeast/eukaryotes • Flow Cytometry: utilizes light sensitive detector with ﬂuorescent tags that label/separate populations of bacteria while also distinguishing dead and alive cells; very accurate
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