Biology 203 1st Edition Lecture 7Outline of Last Lecture I. The Three Domains of LifeII. What are viruses?III. What do they do?IV. Do viruses exhibit the traits that unify earth’s living organisms?V. Where do they come from?VI. 2014-2015 Ebola OutbreakOutline of Current Lecture I. Similarities between Bacteria and ArchaeaII. BacteriaIII. ArchaeaCurrent LectureI. Similarities and Differences between Bacteria and Archaeaa. Both lack a nucleus, and are smaller than eukaryotesb. Called prokaryotes (“before nucleus”)c. Both are approximately 1/10 the size in diameter of a eukaryotic celld. They do have DNA: a single, circular chromosome in most typese. They also have ribosomes for protein synthesisf. Have plasma membranes, cell walls and a diversity of external structuresi. In Bacteria, cell wall is made of peptidoglycanii. In Archaea, the plasma membrane contains isopreneiii. Various members of both groups have flagella to moveiv. Needlelike fimbrae and sticky secretions allow Bacteria and Archaea to adhere to their substrates (including other cells)II. Bacteriaa. Why care about Bacteria?i. They had a 2 billion year head start on eukaryotic cellsii. They still outnumber eukaryotes, even in ourselves (bodies)iii. There are ~1000 bacteria cells for every human cell in your bodyiv. There are more bacteria in your mouth than there are mammals on the planetv. They have always been there, and it’s good for you that they areb. Metabolic DiversityThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.i. Aerobic, anaerobic (alternative oxygen acceptors such as sulfate)ii. Heterotrophic, autotrophicc. Locomotioni. Flagella ii. Axial fibrilsiii. Glidingd. Chemical communicatione. Bioluminescencef. Bacteria are hideously undercountedi. The definition of “bacterial species” is very fuzzy; no sexual reproduction as we know itii. A common “species” definition among bacteria is “Average Nucleotide Identity” (ANI) – how well two sequences matchiii. Bacteria are different species if they have less than 94% ANIiv. Two strains of E. coli have about 98% ANI, so are considered the same speciesv. Humans and chimps have about 98.5% ANI, but are in different generag. Bacteria live in almost habitat and have a huge variety of growth forms (spirochete, cocci, rods, filaments, and stalked)h. Gram-negative vs. Gram-positive bacteriai. Identified by applying a pigmented chemical called Gram stainii. Gram-negative cells have two membranes and a cell wall in the space between the membranesiii. Gram-positive cells have a single membrane, and a very thick cell walliv. The gram stain targets the peptidoglycan in the cell walls of bacteria. If the bacteria is gram-positive, it will hold the stain. The gram-negative bacteria have thicker membranes which will not hold the stain.i. Most Bacteria are heterotrophic, using respiration or fermentationj. Bacteria can also fix atmospheric nitrogen, providing an essential nutrient for all lifeIII. Archaea: a second domain of prokaryotes, closely related to the Eukaryaa. Traits that unite Archaea and Eukarya:i. Cell wall composition is NOT peptidoglycanii. Aspects of DNA packaging, replication, repair, and translation differ from Bacteriaiii. Certain enzymes differ from those in Bacteriaiv. DNA homology of multiple other genesb. What are Archaea like?i. They look and act a lot like Bacteria – smaller than Eukaryotes: no nucleus, circular chromosomeii. Also have a cell wall, but no peptidoglycaniii. Some big differences in the chemistry of their membrane phospholipids1. Glycerol in the phosphate head is a mirror image of that in Bacteria and Eukarya2. Hydrophobic chains in the interior are made of isoprene, not fatty acidsiv. Some have stranger shapes: squares, sheets, threads or almost-amoeboidc. What is up with those square cells?i. Cells like this are found only in organisms that live in very salty environmentsii. Water “wants” to leave the cells, to dilute the surrounding concentrated solutioniii. Cytoskeleton is shaped like a cubeiv. Plasma membrane and cell wall are “shrink-wrapped” down onto the cytoskeletond. Archaea are classically known as “Extremophiles” that live in extremely harsh environments, but many also live in “mesophilic” environments like the open ocean or in soile. Archaea affect us in some ways, but generally not in a bad wayf. Methanogenic Archaea make methanei. Methanogens are very important to decomposition in anaerobic environmentsii. They use CO2 produced by heterotrophic decomposers as an electron acceptor, reducing it to methaneiii. Source of swamp gas, and methane that comes out of