Presentation on theme: "Chapter 2 - Review of general microbiology"— Presentation transcript:
1Chapter 2 - Review of general microbiology ObjectivesBasic description of viruses, bacteria, fungi, algae, and protozoa (size, cell components)Basic functions of a bacterial cellImportance of the cell wall and cell membrane to a bacterial cellMajor differences between eubacterial and eukaryotic DNA/RNAPlasmid types and functionInformation exchange between bacteriaUnderstand the four nutritional categories and give an example of a microbe in each category
2Evolutionary Timeline Oxygen atmosphere formsMicrobes appearEarth formsDinosaursHumansBillions of years
5Bacteria A dividing gram positive bacterium DNACell membraneCell wallSize – ranges from 0.3 to 3 mm in length depending onthe environment106 bacteria in a pinpoint colony106 bacteria/gm soil required to observe significantdegradation activity
6Bacterial Strategies for Survival Nitrosomonas vs PseudomonasSpecialist vs Jack-of-all-Trades
7Nitrosomonas europaea Gram-negative, chemoautotrophSpecializes in ammonia oxidation. These bacteria are important inthe treatment of industrial and sewage waste in the first step ofoxidizing ammonia to nitrate.NH NO NO3Found in soil, freshwater, sewage, the walls of buildings and on thesurface of monuments especially in polluted areas where air containshigh levels of nitrogen compounds.Problematic because can reduce availability of nitrogen to plants andhence limit CO2 fixation. Also may contribute significantly to the globalproduction of nitrous oxide.N. europaea strain Schmidt Stan Watson is now completely sequenced.2715 predicted genes, 2.80 x 106 bpoverall G+C content = 50.8%
8Pseudomonas aeruginosa Gram-negative, chemoheterotrophVersatileFound in soil, marshes, coastal marine habitats,on plants and animalsProblematic for cystic fibrosis, burn victims,cancer, ICU patientsP. aeruginosa PAO1 is now completely sequenced.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 recenthorizontal gene transfer- > 500 genes are transcriptional regulators or environmentalsensors. Has more than twice the number of two-componentregulators than E. coli or B. subtilis.
9The bacterial cell as the basic unit of life What are the basic functions of a microbial cell?ability to reproduceability to use food as an energy sourceability to synthesize new cell componentsability to excrete wasteability to respond to environmental changesability to change through mutationWhat are the basic components of a microbial cell?cell envelopecell membranecell wallglycocalyxappendages for motility and adhesionnucleic acidsspores
10Cell surface meets the outside world Eubacteria have two main types of envelopes, Gram Positive and Gram Negative.
11Cell 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)
12Cell 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 productspassive diffusionfacilitated diffusiongroup translocationactive transport
13Cell surface meets the outside world Fig. 2.12How does the cell membrane fit into the cell envelope?
14Flagella Appendages 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.FlagellaAppendagesFimbriae
15Nucleic acids – A,T (U), C, G DNA (gene)transcriptionRNAtranslationenzymeBacteria – DNA1 closed circular chromosomeplasmid(s)RNA16s-rRNA16s-rDNA gene now used for classificationEukaryotes – DNADNA is found within a membrane-bound nucleusDNA synthesis and RNA transcription occur in the nucleusRNA18s-rRNARNA translation (protein synthesis) occurs in the cytoplasm
16The 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.
17Types of plasmidsLow-copy –number plasmids 1-2 copies/cell, usually > 10 kbHigh-copy-number plasmids 10 – 100 copies/cell, usually < 10kbRelaxed plasmids not dependent on initiation of cell replicationStringent plasmids synchronized with replication of chromosomeConjugative plasmids self-transmissible between same/differentspecies, tra genesNon-conjugative plasmids not self-transmissibleIncompatible plasmids cannot exist in together in the same cellInc P plasmids exist in a wide variety of bacteriaPlasmid functionCryptic plasmids no known function (most)Resistance plasmids protect against antibiotics, metals, bacteriophageDegradative plasmids encode biodegradation of unusual metabolitesPlant interactive plasmids mediate interaction between bacteria and plants(Sym, Ti plasmids)Miscellaneous plasmids involved in a variety of functions, RNAmetabolism, conjugation, bacterial cellenvelope alteration
18Information exchange between bacteria can occur in three ways: ConjugationTransformationTransduction
22How was information transfer achieved? Case Study 3.1How was information transfer achieved?DiGiovanni et al Appl. Environ. Microbiol. 62:
23Bacterial 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.
25Microbial Nutrition CO2 C(H2O) Autotrophs (CO2) Carbon source Heterotrophs (organic carbon)Carbon sourceEnergy sourcePhototroph (light)Chemotroph (chemical)CO2C(H2O)PhotosynthesisOxidation of inorganicsRespirationLight energy is harnessed through photosynthesisChemical energy is harnessed through oxidation of organic/inorganicsubstances
26Nutritional classification Viruses – living or nonliving?Eubacteria –Archaebacteria –Cyanobacteria –Algae –Fungi –Protozoa –photoautotrophicphotoheterotrophicchemoautotrophicchemoheterotrophicphotoautotrophicchemoautotrophicchemoheterotrophicphotoautotrophicphotoautotrophicchemoheterotrophicchemoheterotrophicphotoautotrophicphotoheterotrophic
27Viruses Eubacteria Archaebacteria Cyanobacteria Algae Fungi Protozoa Discussion QuestionsVirusesEubacteriaArchaebacteriaCyanobacteriaAlgaeFungiProtozoaBased 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?