Transcript Lab #2
Lab #2 Bacteriology & the Archaea 2.5 µm 1 µm Subgroup: Beta Proteobacteria Nitrosomonas Subgroup: Gamma Proteobacteria 0.5 µm Chromatium Subgroup: Delta Proteobacteria 5 µm – 5 well-established groups • alpha • beta • gamma • delta • epsilon – newer groups being discovered today – e.g. zeta Rhizobium (arrows) 10 µm • 1. Proteobacteria: diverse group of gram negative bacteria Subgroup: Alpha Proteobacteria Bdellovibrio bacteriophorus Chrondromyces crocatus Subgroup: Epsilon Proteobacteria 2 µm Bacterial Groups PROTEOBACTERIA Heliocobacter pylori Bacterial Groups • 1. Proteobacteria: – a. alpha: live in close association with eukaryotes • Rhizobium – lives in nodules within the roots of legumes – convert atmospheric N2 into compounds that the plants can use (nitrogen fixation) • some strains can cause tumors in plants – Agrobacterium – used to genetically modify plants root nodules Bacterial Groups • 1. Proteobacteria: – b. beta: nutritionally diverse • Nitrosomonas – soil bacteria that plays a role in N2 recycling by oxidizing ammonium (NH4) into nitrites (NO2-) Bacterial Groups • 1. Proteobacteria: – c. delta: slime secreting myxobacteria • when the soil dries out – they form into aggregations called fruiting bodies & release spores into the environment for the establishment of new colonies in better environments • Bdellovibrio bacteria “charge” at other bacteria at speeds equivalent to 240km/hr • drills into its prey using its flagella and digestive enzymes Bacterial Groups • 1. Proteobacteria: – d. gamma: includes many well-known strains of gram-negative bacteria • autotrophic & heterotrophic species • include the older classification known as purple-sulfur bacteria (e.g. Thiomargarita namibiensis) – obtain energy by oxidizing H2S producing sulfur as a waste • many heterotrophic strains are pathenogenic (e.g. Legionella, Salmonella and Vibrio cholerae) • non-pathenogenic strain = E. coli Vibrio cholerae Bacterial Groups • 1. Proteobacteria: – e. epsilon: many are pathenogenic to humans and other animals • includes Campylobacter = blood poisoning • Helicobacter pylori = stomach ulcers – f. zeta: relatively new classification Helicobacter pylori Bacterial Groups • 2. Gram positive bacteria: rival proteobacteria in diversity 2 major subgroups based on cell shape: cocci and bacillus most decompose organic matter in soil two strains of Actinomycetes cause leprosy and tuberculosis Streptomyces used by pharmaceutical companies to produce antibiotics numerous strains are very pathogenic: Bacillus anthracis, Clostridium botulinum, Staphylococcus and Streptococcus GRAM-POSITIVE BACTERIA 5 µm – – – – – Streptomyces Mycoplasmas covering a human fibroblast cell Bacterial Groups • 3. Chlamydias – move through rotation provided by internal flagella-like filaments – Treponema pallidum – causes syphilis – Borrelia burgdorferi – causes Lyme disease – Leptospira – causes leptospirosis (field fever) 2.5 µm • 4. Spirochetes CHLAMYDIAS Chlamydia (arrows) SPIROCHETES 5 µm – can only survive in animal cells – depend on their hosts for ATP – Chlamydia trachomatis – cause of nongonococcal urethritis (most common STD) Leptospira Bacterial Groups • 5. Cyanobacteria – photoautotrophs – only prokaryotes with plant-like, oxygen-generating photosynthesis – abundant components of fresh water and marine phytoplankton 50 µm CYANOBACTERIA Oscillatoria Bacterial classification – colony morphology • bacterial colonies grow from single cells • colony is composed of millions of bacteria • each colony has a characteristic size, shape, consistency, texture and color • common colony shapes: – – – – punctiform = each colony is less than 1mm round filamentous – often confused with fungus (which is more “fuzzy”) irregular Bacterial classification – cell morphology • • • • bacilli (rod) cocci (spherical) spirilla or spiral many bacterial cells adhere to each other and form clusters or chains • under some environments – many different species may associate with each other – creating a community called a biofilm • biofilms are usually found where nutrients are plentiful – soils, water pipes, surface of your teeth Gram staining – both Gram-positive and Gramnegative bacteria take up the same amounts of crystal violet (CV) and iodine (I). – CV-I complex is trapped inside the Gram-positive cell by the washing of the bacteria with 95% ethanol • results in dehydration and limits the loss of CV-I complex = PURPLE STAIN – thin peptidoglycan layer of the gram negative bacteria does not impede extraction of the CV-I complex – plus the outer membrane limits the amount of CV-I complex that can reach the PG layer = CLEAR STAIN Gram Staining • • • • • • • • • 1. Place a slide with a bacterial smear on a staining rack. 2. STAIN the slide with crystal violet for 1-2 min. 3. Pour off the stain and rinse with water thoroughly. 4. Flood slide with Gram's iodine for 1-2 min. 5. Pour off the iodine and rinse with water thoroughly. 6. Decolorize by washing the slide briefly with acetone (2-3 seconds) or 95% ethanol 7. Wash slide thoroughly with water to remove the acetone/ethanol 8. Flood slide with safranin counterstain for 2 min. 9. Wash with water. 10. Blot excess water and dry http://www.youtube.com/watch?v=OQ6C -gj_UHM