LECTURE 1- GRAM +: - rubber car tire (last longer)- strong, tough, insoluble- Thick homogenous sheath of peptidoglycan ranging frm 20 to 80nm in thickness. also contains tightly bound acidic polysaccharides including: teichoic acid directly attached to pptidolycan and lipoteichoic acid. - Teichoic Acid: a polymer of ribitol or glycerol and phosphate embedded in peptidogylcan sheath (project outward from peptidoglycan layer- immunogenic- lipoteichoic acid: project inward from peptidoglycan layer to cytoplasmic memberane ( anchor) similar in structure but is attached to lipids in the plasma membrane- These molecules appear to function in cell wall maintenance and enlargement during cell division. They also move cations into and out of the cell and stimulate a specific- Immune response (antigencicity). - The cell wall of GRAM + bacteria is often pressed tightly against the cell membrane with very little space between them, but in some cells, a thin periplasmic space is evident between the cell membrane and the cell wall. - Periplasmic: around, the fluid substances of a cell.- Gram – cell wall- resistance to certain antibiotics - more complex I morphology b/c it is composed of an outer membrane and a thinner shell of peptidoglycan- thin peptidolycan layer : no peptide inter-bridge - Outer Membrane: unique structure: bilayer of phospholipids (inner). Lipoplysaccharide (outer)- Prions: span the outer membrane (size exclusion): protects from some antibiotics - Lipopolysaccharides (LPS)o immunegetic o heat stable endotoxin composed of : elicits all the symptoms of a bacterial infection o different types of LPS: species IDo toxic to mammalian hosts - Periplasm: just underneath the outer membraneo above and below the petidoglycano import reaction site for a large varied pool of substances that enter and leave the cell o houses secreted degradative enzymes (enzymes are stored temp. in periplasm) Bacterial Chromosomes!!- Single: where one gene goes so do all the others (there is little variation) - Circular: easier to replicate than linear (humans have linear) - dsDNA: like ours: replicates like ours - supercoiled: allows a larger bacterial cell - Plasmids : o very smallo replicates even when the cell doesn’to circularo dsDNAo nonessential pieces of DNA. these tiny strands exist apart from the chromosome, although at times they can become intregtated into it. o during bacterial reproduction they are duplicated and passed on to offspring. - Ribosomes: o The molecular machine that assembles amino acids into proteinso comprised of 54 proteins and 3 RNA o sufficiently different from eurkarytoic ribosomes o target of many antibiotics o there are antibiotics that are affective without disrupting human cells - Endospores : o withstand hostile conditions and facilitate survivalo dormant bodies produced by the bacterial bacillus, clostridium and sporosarcina o two- phase life cycle that shifts between vegetative cell and an endospore. o the vegetative cell is the metabolically active and growing phaseo when exposed to certain environmental signals, it forms and endospore by a process called sporulationo the spore exists in an inert, resting condition that is capable of high resistance and very long-term survival o metabolically inactiveo dormant cell type produced mainly by Bacilllus and Clostridium (starvation response) o extraordinary resistant to heat, dessication, toxic chemicals UV :almost everywhereo can remain dormant for 100 years o botulism, tetanus gas gangrene, anthrax o major stimulus for endospore formation is the depletion of nutrients: animo acids. o once this stimulus has been received by the veg. cell it converts to a committed sporulating cell called sporangium LECTURE2 - Stages of Cell Growth 1. Lag Phase: period of adjustment no increase in cell number (caused by different or fresh media) . An early “flat” period on the graph when the population appears not to be growi or is growing at less than the exponential rate. 2. Log (exponential ) phase: cell number doubles every generation (caused by unlimited nutrients) 3. Stationary Phase: no net increase/decrease in cell number (cell divisions = cell deaths) (caused by depleted nutrients/build-up of toxic by-products) (don’t change ababy’s diaper) 4. Death Phase: net decrease in cell number- cell deaths > cell divisions (exp also) (caused by prolonged stationary phase) - Bacterial Growth Rate: grows in about 20 mins. divides quickly- Exponential Growth: o doubles every generation o generation time about 20 minso ( Nt = N0 X 2n ) o Nt – the number of bacteria at a certain time (what you try to calculate)o N0 – the number of bacteria at the beginning o n - the number of times the bacteria divideo EX: No = 100 o Duration time = 30 mino Elapsed time = 10 hours o Nt = No X 2n o100 x 2 to the 20th o= 104,000,000 o EX: Lets assume that only 10 bacteria fell into the Chicken Salad at 11:00 AM and it remained covered the whole time (yeah right!).o How many are there by 5:00 PM ???o 11:00 AM to 5:00 PM is 6 hours; 3 20 minute generations per hour(60min/20min); so 6 X 3 = 18 generations (n)o Nt = 10 X 218 = 2.62 MILLION !!!o (that’s 2,620,000)- Temperature Requirements:- Psychrophiles: -5 to 15 degrees C (many Pseudomonas)- Mesophiles: 25 to 45 degrees C ( E. Coli and all human pathogens) (room temp) - Thermophiles: 45-70 degrees (Lactobacillus delbruekii- yogurt) - Hyperthermophiles: 70-110 degrees C ( Pyrolobusfumarimii- ocean vents) - Oxygen Requirements: - Obligate aerobes: require the level of oxygen normally present in air (pseudomonas). Cannot grow without oxygen - Obligate anaerobes: require the absence of oxygen (clostridium). lack the enzymes for processing toxic oxygen, they cannot tolerate any free oxygen inthe immediate environment and will die if exposed to it- Facultative anaerobes: can grow in presence OR absence of oxygen but grow faster with oxygen (E. coli. uses 2 different types of metabolism). Metabolizesby aerobic respiration when oxygen is present. but in its absence, it adoptsan anaerobic mode of metabolism such as fermentation. (gram – intestinal bacteria and staphylococci) - Microaerophiles: require reduced levels of oxygen (heliobacter pylor ex:ulcers). does not grow at norma atmospheric concentrations of oxygen but requires a small amount of it in metabolism. - Aerotolerant: grow equally well in the presence as in the absence of oxygen (streptococcus pyogenes) b/c they don’t use