Life on Earth through the ages: ● The first cells ○ First self-replicating entities may not have been cells ○ Last Universal Common Ancestor (LUCA): ■ Common ancestral cell from which all cells descended ■ First division between bacteria and archaea → then to eukarya ■ No oxygen until 2-3 BYA - cyanobacteria - eukaryotes don’t appear until 2 BYA until then it was bacteria and archaea ● Research is still happening with the differentiation of microbial structures ○ Evidence from 3.7 billion years ago   Phylogeny ● Evolutionary relationships between organisms ● Relationships can be deduced by comparing genetic information in the different specimens● Cells → isolate dna from each organism →  make copies of rRNA gene by PCR → sequence DNA → analyze sequence →  generate phylogenetic tree ● Archaea is close to humans than bacteria ● Eukaryotic microorganisms were the ancestors of multicellular organisms ● Where do viruses belong? ○ They are not cells iClicker 3) Among eukarya, bacteria and archaea, which one is evolutionary more distant from the other two? A) Bacteria Microbial Life ● Microorganisms exist in nature in populations of interacting assemblages called microbial communities ○ Microbes found in almost every environment imaginable ○ Global estimate of 5 x 1030 cells iClicker 4) Most prokaryotic cells reside …. A) In the oceanic and terrestrial subsurfaces - do not find it on the surface - we interact with the minority of microbes on the planet Microorganisms as disease agents ● Can be both beneficial and harmful to humans ● Control of infectious disease during last centuryChapter 1- cont. 9/11/17 ● Microorganisms and the human gastrointestinal (GI) tract ○ High numbers of microorganisms occur in colon and oral cavity Sequencing DNA - for every HUMAN gene in your body, there are 360 microbial genes Microorganisms, energy and the environment ● The role of microbes in production of biofuels ○ Using cellulose from plant materials needs to be digested into glucose, and then fermented into ethanol Antonie van Leeuwenhoek (1632-1723) - father of microbiology : the first to describe bacteria ● Made is own microscope - looked at diarrhea in microscope ○ Found eukaryotic parasite- GIARDIA - need to boil water in Rocky Mountain ● Further progress required development of more powerful microscopes Louis Pasteur (1822-1895) - father of experimental microbiology ● Disproved theory of spontaneous generation ○ Argues by showing that tilting the medium to collect dust + microbes which was stuck in the swan neck - the liquid goes bad and microbes grow in the medium ○ The medium can still support the growth of microbes - oxygen is needed to support the growth ● Led to development of methods for controlling the growth of microorganisms (aseptic technique) Robert Koch (1843 - 1910) - the father of medical microbiology ● Developed the idea of how we can demonstrate a pathogen ● Collect sample from sick animal - have to be able to culture these microbes on the plate to purify it iClicker 7- which of the following situations would prevent Koch’s postulates from being satisfied? A) The suspected pathogen cannot be grown in pure culture ● As long as you can culture pathogen in pure level 3 medium, and inoculate in animal and show the disease then you can still satisfy Koch’s postulate ● Being a virus doesn’t prevent you from satisfying Koch’s postulate either iClicker 8- Koch’s postulates cannot be used to determine the cause of Black Death