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 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 ID o toxic to mammalian hosts Periplasm just underneath the outer membrane o above and below the petidoglycan Gram cell wall o import reaction site for a large varied pool of substances that o houses secreted degradative enzymes enzymes are stored temp enter and leave the cell 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 small o replicates even when the cell doesn t o circular o dsDNA o 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 o The molecular machine that assembles amino acids into proteins o 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 to offspring Ribosomes cells Endospores o withstand hostile conditions and facilitate survival o dormant bodies produced by the bacterial bacillus clostridium and sporosarcina endospore o two phase life cycle that shifts between vegetative cell and an o the vegetative cell is the metabolically active and growing phase o when exposed to certain environmental signals it forms and endospore by a process called sporulation o the spore exists in an inert resting condition that is capable of high resistance and very long term survival o metabolically inactive o dormant cell type produced mainly by Bacilllus and Clostridium o extraordinary resistant to heat dessication toxic chemicals starvation response UV almost everywhere o 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 a baby 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 mins o 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 divide o EX No 100 o Duration time 30 min o Elapsed time 10 hours o Nt No X 2n o 100 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 in the 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 Metabolizes by aerobic respiration when oxygen is present but in its absence it adopts an 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 oxygen at all Don t utilize oxygen gas but can survive and grow in its presence these anaerobes are not harmed by oxygen mainly b c they posses alternate mechanisms for breaking down peroxide and superoxide Certain lactobacilli and streptococci use mangense ions and peroxidases to perform this task