Presentation on theme: "Chapter 2 - Review of general microbiology Objectives 1.Basic description of viruses, bacteria, fungi, algae, and protozoa (size, cell components) 2.Basic."— Presentation 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
Billions of years Earth forms Microbes appear Dinosaurs Oxygen atmosphere forms Humans Evolutionary Timeline
Viruses Viroids Prions
DNA Cell wall Cell membrane A dividing gram positive bacterium Bacteria Size – ranges from 0.3 to 3 m in length depending on the environment 10 6 bacteria in a pinpoint colony 10 6 bacteria/gm soil required to observe significant degradation activity
Bacterial Strategies for Survival Nitrosomonas vs. Pseudomonas Specialist vs. 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. NH 3 NO 2 NO 3 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 CO 2 fixation. Also may contribute significantly to the global production of nitrous oxide. N. europaea strain Schmidt Stan Watson is now completely sequenced predicted genes, 2.80 x 10 6 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 predicted genes x 10 6 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 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 What are the basic functions of a microbial cell?
Cell surface meets the outside world Eubacteria have two main types of envelopes, Gram Positive and Gram Negative.
Cell surface meets the outside world 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 passive diffusion facilitated diffusion group translocation active transport
Cell surface meets the outside world How does the cell membrane fit into the cell envelope? Fig. 2.12
Appendages Flagella Fimbriae 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.
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 10 6 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 plasmids1-2 copies/cell, usually > 10 kb High-copy-number plasmids10 – 100 copies/cell, usually < 10kb Relaxed plasmidsnot dependent on initiation of cell replication Stringent plasmidssynchronized with replication of chromosome Conjugative plasmidsself-transmissible between same/different species, tra genes Non-conjugative plasmidsnot self-transmissible Incompatible plasmidscannot exist in together in the same cell Inc P plasmidsexist in a wide variety of bacteria Plasmid function Cryptic plasmidsno known function (most) Resistance plasmidsprotect against antibiotics, metals, bacteriophage Degradative plasmidsencode biodegradation of unusual metabolites Plant interactive plasmidsmediate interaction between bacteria and plants (Sym, Ti plasmids) Miscellaneous plasmidsinvolved 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
How was information transfer achieved? DiGiovanni et al Appl. Environ. Microbiol. 62: Case Study 3.1
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
Microbial Nutrition Carbon source Energy source Autotrophs (CO 2 ) Heterotrophs (organic carbon) Phototroph (light) Chemotroph (chemical) CO 2 C(H 2 O) Light energy is harnessed through photosynthesis Chemical energy is harnessed through oxidation of organic/inorganic substances Photosynthesis Oxidation of inorganics Respiration
Viruses Eubacteria Archaebacteria Cyanobacteria Algae Fungi Protozoa Based on size which microbial groups might you find at the soil surface? At 100 ft below the surface? Based on nutritional requirements which microbial groups might you find at the soil surface? At 100 ft below the surface? Discussion Questions