Summary MICROIMM 2500B Micro MIDTERM 2 NOTES very helpful notes , scored an A midterm

MICROIMM 2500B Micro MIDTERM 2 NOTES Lecture 1: Introduction to Bacteriology - There are not that many bacteria that are actually pathogenic; most bacteria are beneficial - Prokaryotes: the smallest, simplest and most abundant cells on earth; includes bacteria and archaea - Lack a nucleus and complex organelles - Viruses outnumber the amount of prokaryotes - Bacteria can grow fast - bacteria reproduce by binary fission - 4 stages of growth: lag, log phase, stationary growth, and then death - Some bacteria are very slow at growing and they can cause disease. E.g. Tuberculosis - Bacteria classification by shape - Coccus looks like a sphere - Rods can also be called visills - Spirillium are spiral shaped ones - Bacteria classification by oxygen utilization - Obligate aerobe: require oxygen for growth - Obligate anaerobe: oxygen is toxic for growth - Facultative anaerobe: can use oxygen if present and grow better with it, but can also grow without oxygen - Aerotolerant anaerobe: doesn’t use oxygen but oxygen is not toxic - Microaerophile: grow best with low levels of oxygen - Can have two strains of bacteria that look the same but can have a completely different genome Gram Stain - Two general types of bacteria - Gram positive = purple - Gram negative = pink - Don’t stain for mycoplasma because they don’t stain as a result of weird cell envelopes - Don’t stain for mycoplasma because they don’t have cell walls 1. Put cells onto slide which is slightly hot to make sure that they are there 2. Stain the slide with a crystal violet 3. Put iodine onto the slide as well so that the purple will get into some of the cells 4. Wash the cells on the slide with a pray bottle of ethanol - This causes the purple to come off of the gram negative and the gram positive would get it stuck in their thick cell wall - The cell wall of the gram + is very thick while that of the gram – is very thin 5. Counter stain with safrinin so that the gram negative are pink Gram positive and gram negative cell envelopes - The peptidoglycan is a thick layer on the gram positive - It is the same thing as the cell wall - The gram negative has 2 membranes: an outer membrane and a cytoplasmic membrane - There is still a peptidoglycan structure in between the membranes that is separated by the periplasmic space - Both have a cytoplasmic membrane - Lipopolysaccharide is a part of the gram – - Teichoic acids and lipoteichoic acids are part of gram + - Gram positive cell wall: can be forty layers or so thick Bacterial cell walls (peptidoglycan) - Rigid structure - Prevents osmotic lysis - This structure is unique for bacteria so it can be a target for antibiotics - If you get rid of the cell wall, it will die from exposure to enzymes and blow up - Backbone is an alternating backbone of G and M all the way around the bacterial cell - Between the M, there is a peptide linkage - Crystal violet gets stuck in the meshwork not allowing it to be washed out  looks purple - Gram-negative cell wall - Some antibiotics that we use to kill bacteria cannot get across the outer membrane - Thin peptidoglycan in the middle Lipopolysaccharide (Endotoxin) - Endotoxin because it is part of the outer membrane - O-specific polysaccharide (also called O-antigen) - Antigenic and highly variable - At the top it sticks out - Different gram negatives have different O antigens - Core polysaccharide - Lipid A - N-Acetylglucosamine disaccharide - Fatty acid groups - Recognized by the innate immune system  septic shock - If there is too much release of LPS, the immune system can be over stimulated, which can cause a cytokine storm  can put you in sepsis and shock (hyper inflammatory condition) - Component that is buried in the membrane - Amphipathic Primary Functions of the Cytoplasmic Membrane - Permeability barrier: prevents leakage and functions as a gateway for transport of nutrients into and out of the cell - Protein anchor: site of many proteins involved in transport - Energy conversion: site of generation and use of the proton motive force - Around the membrane it will set up this protein gradient, which by the movement of protons into the cell can make ATP