2 1 Light microscopy Compound light microscope 9 11 2015 Two sets of lenses form the image o Objective lens and ocular lens o Total magnification objective ocular o 2000X maximum magnification Bright field scope o Specimen because of differences in contrast density between specimen and Resolution the ability to distinguish two adjacent objects as separate and distinct o Resolution is determined by wavelength of light used and numerical aperture of surroundings lens o Limit of resolution for light microscope 0 2 um Prepare a smear spread culture Improve contrast in light microscopy Differential stains gram stain Differential stains separate bacteria into groups Grain stain is used in microbiology o Bacteria can be divided into major groups gram positive and gram negative o Gram positive purple gram negative red after staining Phrase contrast microscopy o Phrase ring amplifies differences in refractive index of ell and surroundings o Improves contrast of a sample without use of a stain Dark field microscopy o Light reaches specimen from sides and scattered light Marine biological lab Osamu Shimomuru isolated from jellyfish CSLM o Computerized microscope coupled with a laser source to generate a 3D image o Computer can focus the laser on single layers of specimen o Different layers can be compiled for a 3 D image o Resolution is 0 1 um for CSLM Electron Microscopes use electrons instead of photons to image cells and structures o Two types of electron microscopes TEM SEM Not considered cells No metabolic abilities of their owns Rely completely on biosynethetic machinery of infected cell Infect all types of cells 10nm diameter smallest virus Viruses SEM pressure ticks survive under a high pressure Eukaryotes vs Prokaryotes Check from lecture Viruses Not cells Genomes bacteria and eukary both have genomes Full complement of genes Circular DNA chromosomes Specimen is coated with small heavy metals Example observation of live ticks haemaphysalis flava by SEM under high vacuum o DNA unifies to form nucleoid region o Prokaryotes have small amounts of extra chrmosomal DNA called plasmids antibiotic resistance o Eukaryotic DNA is linear and found within the nucleus Associated with proteins to fold of DNA More than one chromosome Two copies of each chromosome Cell division nucleus divided by mitosis During sexual reproduction genome is halved by meiosis Ecoli genome o 4 64 million base pairs o 4300 genes o 1900 different kinds of proteins o 2 4 million protein molecules Human cell o 1000x more DNA per cell than E coli o 7x more genes than E coli Evolution Phylogeny Process of change over time in new varieties and species of organism Looking for evolutionary relationships between organisms Comparing genetic info in different specimens rRNA rRNA sequencing can define lineages of cells called domains bacteria archaea eukarya archaea are more closely related to eukarya than bacteria Lynn Margulis mitochondria DNA beginning of eukaryotic cells develop endosymbiosis theory critical for understanding the evolution of eukaryotic cells endosymbiosis mitochondria and chloroplasts took up residence