1 / 20

Ch. 27: Bacteria and Archaea

Ch. 27: Bacteria and Archaea. Modern/regular/eubacteria and the ancient methanogens Prokaryote  cells with cell membranes, cytoplasm/cytosol, DNA in the form of one circular chromosome and many plasmids, and 70s ribosomes. Shapes are cocci, bacilli, spirillum

Download Presentation

Ch. 27: Bacteria and Archaea

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Ch. 27: Bacteria and Archaea • Modern/regular/eubacteria • and the ancient methanogens • Prokaryote  cells with cell membranes, cytoplasm/cytosol, DNA in the form of one circular chromosome and many plasmids, and 70s ribosomes. • Shapes are cocci, bacilli, spirillum • May have cell wall, flagella, cilia and other structures

  2. Adaptations • Adaptations to extremes of climate from freezing to boiling to acidic and salty. (species specific ranges) • Salt tolerant up to 32% • Hot springs - thermophiles • Near frozen waters at arctic • Acid conditions; 0.03 pH !! – acidophiles • 3 million Rads of radiation

  3. Fig. 27-1

  4. Structure and functions contribute to success • Unicellular but may aggregate into colonies • Cell walls; Gram positive and gram negative based on peptidoglycans and lipids • Capsules; waxy layer that helps avoid antibiotics • Fimbriae (like velcro) and pili (trade plasmids) • Motility; cilia and flagella and taxis; roughly 50% are capable of movement – at relatively fast speeds • Plasmids

  5. Fig. 27-3 Carbohydrate portion of lipopolysaccharide Outer membrane Peptidoglycan layer Cell wall Cell wall Peptidoglycan layer Plasma membrane Plasma membrane Protein Protein Gram- positive bacteria Gram- negative bacteria 20 µm (b) Gram-negative: crystal violet is easily rinsed away, revealing red dye. (a) Gram-positive: peptidoglycan traps crystal violet.

  6. Internal and Genomic Organization • Not usually any internal, membrane-bound structures • May have specialization built into PLASMA MEMBRANE • 70s ribosomes; smaller than eukaryotic, solid (erythromycin and tetracycline) • Nucleoid region • One, circular chromosome, hundreds of genes, fills central portion, • Many plasmids – copies of frequently or currently used genes

  7. Adaptations of reproduction • Binary fission – one cell divides into 2 those into 4 those into 8, etc. • Can occur every hour at optimal conditions, some species every 20 minutes, typical is 24 hours • 1 bacteria could create a colony outweighing Earth in 3 days…. Obvious checks and balances here. • Nutrient supply • Toxins/ poison selves • Competition • Space - pressure

  8. Bacterial Populations • They are very small organisms 0.5 – 5 mm ( eukaryotic are 10-100 mm) • They reproduce by binary fission • They have very short generation times • ENDOSPORES can survive harsh conditions and survive for centuries • MSU study looked at 20,000 generations in 8 years – evidence of evolution • Simpler – but not inferior or primative • On Earth for over 3.5 billion years now

  9. Diversity • Three events lead to diversity • Rapid reproduction • Most variety in sexually reproducing species is from arrangement/ shuffling of alleles during meiosis • Insertions, deletions, base pair substitutions • Mutations still very RARE, but sheer numbers of organisms and time per generation means more are expressed • Mutation • More variety in ribosomal RNA between 2 strains of E.coli than between human and platypus • Genetic recombination • Next page

  10. Genetic Recombination • Transformation • Bacteria are able to absorb genetic information from their surroundings • Transduction • Bacterial genes are also spread between bacteria populations by viruses known as bacteriophages • Conjugation • Pili bridge bacteria and they trade plasmids • F factor and R factor

  11. Phage DNA A+ B+ Fig. 27-11-4 A+ B+ Donor cell A+ Recombination A+ A– B– Recipient cell A+ B– Recombinant cell

  12. F plasmid Bacterial chromosome Fig. 27-13 F+ cell F+ cell Mating bridge F– cell F+ cell Bacterial chromosome (a) Conjugation and transfer of an F plasmid Recombinant F– bacterium A+ Hfr cell A+ A+ A+ F factor A– A+ A– A+ A– A– F– cell (b) Conjugation and transfer of part of an Hfr bacterial chromosome

  13. Metabolic adaptations (table 27.1)

  14. Metabolism • Oxygen Metabolism • Obligate aerobes • Obligate anaerobes • Facultative anaerobes • Nitrogen Metabolism • N is essential for amino acids • Atmospheric N isn’t highly useable • Microbes ‘fix’ nitrogen into nitrate, nitrites and ammonium ions that are useable • Metabolic Cooperation • Colonies of cells that fix nitrogen and produce oxygen so that neighboring area is hospitable • Ocean floor and dental plaque 

  15. Molecular Systematics • Previously bacterial classification (systematics) used motility, shape, nutrition and gram staining • Molecular systematics has drastically changed the classification – • Much more diverse than assumed • 6000+ species/strains ID and named • A soil sample could contain over 10,000 species • Horizontal transfers of genes blur “root” for this region of the tree of life • Two main branches are Archaea and Bacteria

  16. Groups of Bacteria Eukarya Archaea Bacteria

  17. Subgroup: Alpha Proteobacteria Alpha Beta Gamma Proteobacteria Delta Fig. 27-18a 2.5 µm Epsilon Rhizobium (arrows) inside a root cell of a legume (TEM) Subgroup: Beta Proteobacteria Subgroup: Gamma Proteobacteria 1 µm 0.5 µm Thiomargarita namibiensis containing sulfur wastes (LM) Nitrosomonas (colorized TEM) Subgroup: Delta Proteobacteria Subgroup: Epsilon Proteobacteria B. bacteriophorus 5 µm 2 µm 10 µm Fruiting bodies of Chondromyces crocatus, a myxobacterium (SEM) Helicobacter pylori (colorized TEM) Bdellovibrio bacteriophorus attacking a larger bacterium (colorized TEM)

  18. CHLAMYDIAS SPIROCHETES Fig. 27-18i 2.5 µm 5 µm Chlamydia (arrows) inside an animal cell (colorized TEM) Leptospira, a spirochete (colorized TEM) GRAM-POSITIVE BACTERIA CYANOBACTERIA 1 µm 50 µm 5 µm Hundreds of mycoplasmas covering a human fibroblast cell (colorized SEM) Streptomyces, the source of many antibiotics (colorized SEM) Two species of Oscillatoria, filamentous cyanobacteria (LM)

  19. Positive Roles of Bacteria • Decomposers • Symbioses • Mutualism • Commensalism – normal flora • (parasitism – not positive) • Chemical recycling • Nitrogen • Oxygen • Carbon • Research and Technology • Food (cheese) and beverages • Waste water treatment • Genetic engineering

  20. Negative Impacts of Bacteria • Parasitic bacteria that cause disease are called PATHOGENS • Opportunistic • Exotoxins and endotoxins

More Related