Ch 27: Prokaryotes - Bacteria and Archaea

1. Ch 27: Prokaryotes - Bacteria and Archaea Great Salt Lake – pink color from living prokaryotes; survive in 32% salt • Prokaryotes are divided into two domains • bacteria and archaea • thrive in diverse habitats • including places too acidic, salty, cold, or hot for most other organisms • Most are microscopic • but what they lack in size they make up for in numbers • For example: more in a handful of fertile soil than the number of people who have ever lived

2. Single cell Some form colonies Very small 0.5–5 µm (10-20 times smaller than Eukaryotes) Lacks nucleus and most other membrane bound organelles Reproduce very quickly Asexual binary fission Genetic recombination variety of shapes spheres (cocci) rods (bacilli) spirals Cell wall More structural & functional characteristics in (Ch.27) Prokaryotes

3. Rod shaped Example: E. coli Usually solitary Sometimes chains streptobacilli Bacilli

4. Spherical Clumps or clusters (like grapes) E.g. Staphylococcus aureus Streptococci – chains of spheres Diplococci – pairs of spheres E.g. Neisseria gonnorheae Cocci

5. Streptococcus 1

6. Streptococcus 2

7. Diplococcus 1

8. Diplococcus 2

9. Spirilla – spiral shaped With external flagella Variable lengths Spirochaetes Internal flagella Corkscrew-like Boring action E.g. Treponema pallidum (Syphilis) Spiral prokaryotes

10. Cell-Surface Structures • Cell wall is important • maintains cell shape • protects the cell • prevents it from bursting in a hypotonic environment • Eukaryote cell walls are made of cellulose or chitin • Bacterial cell walls contain peptidoglycan • network of sugar polymers cross-linked by polypeptides • Archaea cell walls • polysaccharides and proteins but lack peptidoglycan

11. Gram-positive bacteria Gram-negative bacteria • Scientists use the Gram stain to classify bacteria by cell wall composition • Counter stains to differentiate between cell wall characteristics • Gram-positive bacteria • simpler walls with a large amount of peptidoglycan • Gram-negative bacteria • less peptidoglycan and an outer membrane that can be toxic 10 m

12. Thick layer of peptidoglycans Retains crystal violet Doesn’t wash out Masks red safranin Stains dark purple or blue-black Gram positive bacteria

13. Thin sandwiched layer of peptidoglycans Rinses away crystal violet Stains pink or red Gram negative bacteria (b) Gram-negative bacteria: crystal violet is easily rinsed away, revealing red dye. Carbohydrate portion of lipopolysaccharide Outer membrane Cell wall Peptido- glycan layer Plasma membrane

14. Bacterial capsule • Extra capsule covers many prokaryotes • polysaccharide or protein layer • Some also have fimbriae • stick to substrate or other individuals in a colony • Pili(or sex pili) • longer than fimbriae • allow prokaryotes to exchange DNA Bacterial cell wall Fimbriae Tonsil cell 1 m 200 nm

15. Diverse nutritional and metabolic adaptations have evolved in prokaryotes • Prokaryotes can be categorized by how they obtain energy and carbon • Phototrophs obtain energy from light • Chemotrophs obtain energy from chemicals • Autotrophs require CO2 as a carbon source • Heterotrophs require an organic nutrient to make organic compounds • Energy and carbon sources are combined to give four major modes of nutrition

16. The Role of Oxygen in Metabolism • Prokaryotic metabolism varies with respect to O2 • Obligate aerobes require O2 for cellular respiration • Obligate anaerobes are poisoned by O2 and use fermentation or anaerobic respiration • Facultative anaerobes can survive with or without O2

17. Nitrogen Metabolism • Nitrogen is essential for the production of amino acids and nucleic acids – nitrogen fixation • some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3) • Some cooperate between cells of a colony • allows them to use environmental resources they could not use as individual cells • E.g. cyanobacteriumAnabaena, photosynthetic cells and nitrogen-fixing cells called heterocysts(or heterocytes)exchange metabolic products Photosynthetic cells Heterocyst 20 m

18. Molecular systematics led to the splitting of prokaryotes into bacteria and archaea Eukaryotes Korarchaeotes Euryarchaeotes Domain Archaea Crenarchaeotes UNIVERSAL ANCESTOR Nanoarchaeotes Proteobacteria Chlamydias Spirochetes Domain Bacteria Cyanobacteria Gram-positive

20. Clades of Domain Bacteria • Fig 27.18 (27.13 in 7th ed.) • Proteobacteria • diverse & includes gram-negatives • Subgroups: α, β, γ, δ, ε • Chlamydias • Spirochaetes • Cyanobacteria • Gram positive bacteria

21. Proteobacteria • Alpha subgroup • Rhizobium • Nitrogen-fixing bacteria reside in nodules of legume plant roots • Convert atmospheric N2 to usable inorganic form for making organics (i.e. amino acids)

22. Proteobacteria Gamma subgroup • Includes many Gram negative bacteria • E. coli • common intestinal flora • Enterobacter aerogenes • Pathogenic; causes UTI • Serratia • Facultative anaerobe • Characteristically red cultures

23. Delta subgroup of Proteobacteria Slime-secreting decomposers Elaborate colonies Thrive collectively, yet have the capacity to live individually at some point in their life cycle Release myxospores from “fruiting” bodies Proteobacteria: Myxobacteria

24. Chlamydias Chlamydias • parasites that live within animal cells • Chlamydia trachomatis causes blindness and nongonococcal urethritis by sexual transmission 2.5 m Chlamydia (arrows) inside an animal cell (colorized TEM)

25. Spirochaetes • Long spiral or helical heterotrophs • Flagellated cell wall • Decomposers & pathogens • Some are parasites, including Treponemapallidum, which causes syphilis, and Borreliaburgdorferi, which causes Lyme disease

26. Cyanobacteria • “blue-green algae” • Photoautotrophic • Generate O2 as a significant primary producer in aquatic systems • Typically colonial • Filamentous • Plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis

27. Oscillatoria (Cyanobacteria) 1

28. Oscillatoria 2

29. Anabaena (Cyanobacteria) 1 • Vegetative cell • Primary metabolic function (photosynthesis) • Heterocyst • Nitrogen fixation • Akinete • Dormant spore forming cell

30. Anabaena 2

31. Anaebena 3

32. Nostoc (Cyanobacteria) 1

33. Nostoc 2

34. Gleocapsa (Cyanobacteria) 1

35. Gleocapsa 2

36. Gram positive bacteria • Gram stains – purple • Thick cell wall • Includes: • Micrococcus • Common soil bacterium • M. luteuscultures have a yellow pigment • Some Staphylococcus and Streptococcus,can be pathogenic • Bacillus • B. subtilisare relatively large rods; common “lab organism” • Bacillus anthracis, the cause of anthrax • Actinomycetes, which decompose soil • Clostridium botulinum, the cause of botulism • Mycoplasms, the smallest known cells Hundreds of mycoplasmas covering a human fibroblast cell (colorized SEM)

37. Domain Archaea

38. Archaea -- “Extremophiles” Many are tolerant to extreme environments Extreme thermophiles High and low temperature Commonly acidophilic E.g. hot sulfer springs, deep sea vents Extreme halophiles High salt concentration Often contains carotenoids E.g. Salton Sea Methanogens Anaerobic environments Release methane E.g. animal guts