Ch. 27: Bacteria and Archaea

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