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Transcript
Chapter 2 - Review of general microbiology Objectives 1. Basic description of viruses, bacteria, fungi, algae, and protozoa (size, cell components) 2. Basic functions of a bacterial cell 3. Importance of the cell wall and cell membrane to a bacterial cell 4. Major differences between eubacterial and eukaryotic DNA/RNA 5. Plasmid types and function 6. Information exchange between bacteria 7. Understand the four nutritional categories and give an example of a microbe in each category Evolutionary Timeline 4.5 4.0 3.0 2.0 1.0 Billions of years 0 Viruses Viroids Prions http://www.astro.washington.edu/endsofworld/ MS2 bacteriophage 24nm ooooooooooooooooooo oooooo oooo o oooo o oo oooo oooo o o oo Polio virus 30nm oo o ooooooo oooooooo o ooo o o oooo ooooo ooo o oooo o oo oo oo Adenovirus 70nm oO Ooooooo oooooo oooo oooo ooo oooo o ooo Adenovirus DNA PPPPPP PP PPPPPP PP PPPPPPP PP Human Immunodeficiency Virus (HIV) 100nm PPPPPPPP PP Tobacco Mosaic Virus 18 x 300 nm T-4 bacteriophage 30 x 124nm IIIIIIIIIIIIIIIIIIII IIIII IIIIIIIIIIIIIIIIIII IIIII I IIIIIIIIIIIIIIIIIIIII IIII Herpes virus 125nm IIIIIIIIIIIIIIIIII IIIII Chlamydia elementary body 450nm Vaccinia virus 300 x 450 nm T-4 bacteriophage DNA E. coli bacterium 0.5-2um Viruses Bacteria A dividing gram positive bacterium Cell membrane Cell wall DNA Size – ranges from 0.3 to 3 mm in length depending on the environment 106 bacteria in a pinpoint colony 106 bacteria/gm soil required to observe significant degradation activity Bacterial Strategies for Survival Nitrosomonas Specialist vs. vs. Pseudomonas Jack-of-all-Trades Nitrosomonas europaea • Gram-negative, chemoautotroph • Specializes in ammonia oxidation. These bacteria are important in the treatment of industrial and sewage waste in the first step of oxidizing ammonia to nitrate. NH3 NO2 NO3 • Found in soil, freshwater, sewage, the walls of buildings and on the surface of monuments especially in polluted areas where air contains high levels of nitrogen compounds. • Problematic because can reduce availability of nitrogen to plants and hence limit CO2 fixation. Also may contribute significantly to the global production of nitrous oxide. • N. europaea strain Schmidt Stan Watson is now completely sequenced. 2715 predicted genes, 2.80 x 106 bp overall G+C content = 50.8% Pseudomonas aeruginosa • Gram-negative, chemoheterotroph • Versatile • Found in soil, marshes, coastal marine habitats, on plants and animals • Problematic for cystic fibrosis, burn victims, cancer, ICU patients • P. aeruginosa PAO1 is now completely sequenced. - 5570 predicted genes 6.3 x 106 bp (largest sequenced genome to date) overall G+C content = 66.6% isolated regions with lower G+C content may be result of recent horizontal gene transfer - > 500 genes are transcriptional regulators or environmental sensors. Has more than twice the number of two-component regulators than E. coli or B. subtilis. The bacterial cell as the basic unit of life What are the basic functions of a microbial cell? • ability to reproduce • ability to use food as an energy source • ability to synthesize new cell components • ability to excrete waste • ability to respond to environmental changes • ability to change through mutation What are the basic components of a microbial cell? • cell envelope cell membrane cell wall glycocalyx • appendages for motility and adhesion • nucleic acids • spores Cell surface meets the outside world Lipoteichoic acid Teichoic acid Porins Lipopolysaccharide Outer membrane Peptidoglycan Periplasmic space Proteins Cell membrane Membrane proteins Gram negative Lipids Gram positive Eubacteria have two main types of envelopes, Gram Positive and Gram Negative. Cell surface meets the outside world Lipoteichoic acid Teichoic acid Porins Lipopolysaccharide Outer membrane Peptidoglycan Periplasmic space Proteins Cell membrane Membrane proteins Gram negative Lipids Gram positive Cell wall - The cell wall is a rigid structure composed of peptidoglycan that maintains the characteristic shape of the cell. • permeable to small molecules (<15,000) Cell surface meets the outside world Cell membrane – The cell membrane is a highly selective barrier that enables cells to take in nutrients and excrete waste products Proteins = Phospholipid • passive diffusion • facilitated diffusion • group translocation • active transport R1 O CH2 R2 O CH H2C O O P O CH2 CH2 NH2 O Phosphatidylethanolamine ( where R1 and R2 are fatty acyl residues) Cell surface meets the outside world Lipoteichoic acid Teichoic acid Porins Lipopolysaccharide Outer membrane Peptidoglycan Periplasmic space Proteins Cell membrane Membrane proteins Fig. 2.12 Gram negative Lipids Gram positive How does the cell membrane fit into the cell envelope? Cells can have flagella that allow them to move over short distances (um) either toward nutrients or away from inhibitory substances. Cells can have fimbriae that aid in attachment of cells to surfaces. Flagella Appendages Fimbriae Nucleic acids – A,T (U), C, G DNA (gene) transcription RNA translation enzyme Bacteria – DNA • 1 closed circular chromosome • plasmid(s) RNA • 16s-rRNA • 16s-rDNA gene now used for classification Eukaryotes – DNA • DNA is found within a membrane-bound nucleus • DNA synthesis and RNA transcription occur in the nucleus RNA • 18s-rRNA • RNA translation (protein synthesis) occurs in the cytoplasm The chromosome of a bacterial cell contains approximately 3 x 106 base pairs. If stretched out, the chromosome is 1 mm in length. In actively growing cells there are 2 to 4 copies of the chromosome since several replicating forks can occur at the same time. Bacterial cells also contain small circular pieces of DNA called plasmids. Types of plasmids Low-copy –number plasmids 1-2 copies/cell, usually > 10 kb High-copy-number plasmids 10 – 100 copies/cell, usually < 10kb Relaxed plasmids not dependent on initiation of cell replication Stringent plasmids synchronized with replication of chromosome Conjugative plasmids self-transmissible between same/different species, tra genes Non-conjugative plasmids not self-transmissible Incompatible plasmids cannot exist in together in the same cell Inc P plasmids exist in a wide variety of bacteria Plasmid function Cryptic plasmids no known function (most) Resistance plasmids protect against antibiotics, metals, bacteriophage Degradative plasmids encode biodegradation of unusual metabolites Plant interactive plasmids mediate interaction between bacteria and plants (Sym, Ti plasmids) Miscellaneous plasmids involved in a variety of functions, RNA metabolism, conjugation, bacterial cell envelope alteration Information exchange between bacteria can occur in three ways: 1) Conjugation 2) Transformation 3) Transduction 1) Conjugation Pilus 2) Transformation Transformation Donor cell Cell lysis and free DNA Recipient cell bacterial cell 3) Transduction Transduction lytic cycle phage transducing phage transduced cell Case Study 3.1 Soil + 2,4-D Soil + 2,4-D + JMP134 AlcaligeneseutrophusJM P134 80kbplasm idpJP4encodes genesfordegradationof 2,4-D Slow, incomplete degradation of 2,4-D over a 4 week period. Complete degradation of 2,4-D in 4 weeks JMP134 was not recovered after 1 week. Three indigenous strains that degraded 2,4-D increased in numbers the next 4 weeks. All three strains carried the pJP4 plasmid. How was information transfer achieved? These results indicate that there was gene transfer between the JMP134 and indigenous microorganisms. There are two possible mechanisms of gene transfer which may explain these results. DiGiovanni et al. 1996. Appl. Environ. Microbiol. 62:2521-2526. Bacterial spore formers: Gram positive bacteria can form spores that are very resistant to heat, UV, and nutrient stress. Spores can even withstand autoclaving. As a result, soil must be autoclaved three times on consecutive days to achieve complete sterilization. This allows spores to germinate in between autoclaving events. Eukaryotes Fungi Algae Protozoa Ribosomes Mitochondrion Endoplasmic reticulum Nucleus Nucleolus Cell wall Golgi apparatus Storage vessicles Microbial Nutrition Autotrophs (CO2) Carbon source Heterotrophs (organic carbon) Phototroph (light) Energy source Chemotroph (chemical) CO2 Photosynthesis Respiration Oxidation of inorganics C(H2O) • Light energy is harnessed through photosynthesis • Chemical energy is harnessed through oxidation of organic/inorganic substances Nutritional classification Viruses – living or nonliving? Eubacteria – photoautotrophic photoheterotrophic chemoautotrophic chemoheterotrophic Archaebacteria – photoautotrophic chemoautotrophic chemoheterotrophic Cyanobacteria – photoautotrophic Algae – photoautotrophic Fungi – chemoheterotrophic Protozoa – chemoheterotrophic photoautotrophic photoheterotrophic Viruses Eubacteria Archaebacteria Cyanobacteria Algae Fungi Protozoa Discussion Questions Basedononsize nutritional Based which requirements which microbial groups mightmicrobial you groups you find at find at themight soil surface? Atthe soilftsurface? 100 ft below 100 below theAtsurface? the surface?
