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Ch 27: Prokaryotes - Bacteria and Archaea Great Salt Lake – pink color from living prokaryotes; survive in 32% salt Prokaryotes are divided into two domains.

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Presentation on theme: "Ch 27: Prokaryotes - Bacteria and Archaea Great Salt Lake – pink color from living prokaryotes; survive in 32% salt Prokaryotes are divided into two domains."— Presentation transcript:

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 Prokaryotes 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)

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

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

5 Streptococcus 1

6 Streptococcus 2

7 Diplococcus 1

8 Diplococcus 2

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

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 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 Gram-positive bacteria 10  m Gram-negative bacteria

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

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

14 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 Bacterial capsule Tonsil cell 200 nm Fimbriae 1  m

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 CO 2 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 O 2 – Obligate aerobes require O 2 for cellular respiration – Obligate anaerobes are poisoned by O 2 and use fermentation or anaerobic respiration – Facultative anaerobes can survive with or without O 2

17 Nitrogen Metabolism Nitrogen is essential for the production of amino acids and nucleic acids – nitrogen fixation – some prokaryotes convert atmospheric nitrogen (N 2 ) to ammonia (NH 3 ) – Some cooperate between cells of a colony allows them to use environmental resources they could not use as individual cells – E.g. cyanobacterium Anabaena, 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 Crenarchaeotes Nanoarchaeotes Proteobacteria Chlamydias Spirochetes Cyanobacteria Domain Bacteria Domain Archaea UNIVERSAL ANCESTOR Gram-positive

19

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

21 Alpha subgroup Rhizobium – Nitrogen-fixing bacteria reside in nodules of legume plant roots – Convert atmospheric N 2 to usable inorganic form for making organics (i.e. amino acids) Proteobacteria

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

23 Proteobacteria: Myxobacteria 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

24 Chlamydias parasites that live within animal cells Chlamydia trachomatis causes blindness and nongonococcal urethritis by sexual transmission Chlamydias 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 Treponema pallidum, which causes syphilis, and Borrelia burgdorferi, which causes Lyme disease

26 Cyanobacteria “blue-green algae” Photoautotrophic – Generate O 2 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. luteus cultures have a yellow pigment – Some Staphylococcus and Streptococcus, can be pathogenic – Bacillus B. subtilis are 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


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