Classification Why do we classify or separate different organism into groups? Aristotle suggested plant and animal Kingdoms. Why did this system work in 375 BC? Why doesn’t it work today? Modern day taxonomy relies on molecular, structural and evolutionary characteristics. Examples – Binomial Nomenclature –Each organism is assigned a two word Latin name. Genus, species Homo sapiens, Homo sapiens Bacillus anthracis, Bacillus anthracis Classifications of Microbes Prokaryote o Bacteria o Archea Eukaryote o Planta o Animalia o Fungi o Protista 1 Kingdom Animalia Eukaryotic Multicellular No cell wall Consumer (mouth) Typically motile Examples – Kingdom Planta Eukaryotic Typically mulitcellular, some unicellular and colonial Cell wall – made of cellulose Producer No movement Examples – Kingdom Fungi Eukaryotic Unicellular or multicellular Cell walls – chitin Non-motile Consumer (no mouth), dead feeder, parasite Examples – Domain Protista Eukaryotic Unicellular and colonial Two distinct groups o Plant – like characteristics Green Algae Diatoms Euglena Dinoflagellates Brown and red algae 2 o Animal – like characteristics Ameboids Flagellates Ciliates Sporozoans (no movement) Domain Bacteria Prokaryotic Cell walls, peptidoglycan Unicellular, some colonial Parasite, dead feeder May be motile Examples – Domain Archea – Prokaryote Unicellular or colonial Non-motile No cell wall Specialized producer Examples – How do we classify plants and animals? How is bacterial classification different from that of plants and animals? What characteristics do we use to classify bacteria? Cell wall composition Morphology 3 o o Shape Coccus Bacillus Spiral (vibrio, spirillum) Arrangement of cells Diplo- Strepto- Staphylo- Differential staining o Gram stain o Endospore stain Oxygen requirements DNA base pair comparison = A/T vs. C/G Biochemical tests – what kind of media will they grow on? Eukaryotic cell structure No cell walls Membrane bound organelles o Mitochondria o Nucleus o Centriole o Endoplasmic Reticulum RER SER o Golgi Body o Vacuole o Peroxisome Non membrane bound organelles o Ribosome 4 Prokaryotic Cell Structure Outside the cell wall o o Glycocalyx Negative staining technique Capsule Slime layer Flagella Gives motility towards food (chemotrophic), light (phototropyic) o Monotrichous Lophotrichous Amphitrichous Peritrichous Fimbrae – provide attachment, G- bacteria 5 o Pili – used to share DNA segments, a form of sexual reproduction o Cell wall – responsible for cell shape, controls osmotic movement. Made up of several materials, depending on species. Peptidoglycan typical component Some bacteria have lipid in their cell wall, special cell wall staining techniques Gram staining procedure How to “stick the bacteria to the slide” Adhere to clean, dry slide. Air dry Flame, twice Crystal violet Gram’s iodine Alcohol Safranin (a counterstain) Gram positive cells Gram negative cells Inside the cell wall o o Plasma membrane Selectively permeable membrane Fluid mosaic model Hydrophobic unit Hydrophilic unit Proteins Glycoproteins Cytoplasm o Cytosol + organelles DNA – one single, circular DNA 6 o o Plasmid – small, circular DNA Replicates independent of DNA Small number of genes (<10) Carries information unnecessary to daily life Ribosome site of protein synthesis composed of rRNA + proteins o Inclusions – reserve storage (fat, lipids, etc.) o Endospore – in bacteria they are formed in response to environmental stress, lack of nutrients, never reproductive structures, mostly in G+ 7