Chapter 1 The structure and function of prokaryotes

1. Chapter 1 The structure and function of prokaryotes EUKARYOTES PROKARYOTES BACTERIA ARCHAEA

2. 1.Differences between prokaryotes/eukaryotes 2.Shape and arrangement 3.Procaryoic cell organization

3. Prokaryotes (Bacteria) • Eubacter "True" bacteria • human pathogens • clinical or environmental • one kingdom • Archaea • Environmental organisms • second kingdom

4. Eukaryotes • Other cell-based life e.g. • plants • animals • fungi

5. Differences between prokaryotes/eukaryotes 1. The prokaryotic cell, in contrast to the eukaryotic cell, is not compartmentalized. Nuclear membranes, mitochondria, endoplasmic reticulum, Golgi body, phagosomes and lysosomes are not present. 2. Prokaryotes generally possess only a single circular chromosome. Since there is no nuclear membrane, the chromosome is bound to a specific site on the cell membrane - the mesosome. 3. Prokaryotic ribosomes are 70S (S stands for Svedberg unit, a measure of size), whereas eukaryotic ribosomes are larger (80S). Prokaryotic ribosomal subunits are 30S and 50S (eukaryotic are larger). The 30S ribosome has 16S RNA, whilst the 50S ribosome contains 23S and 5S RNA. Ribosomal RNA is larger in eukaryotes (e.g. 18S versus 16S rRNA). 4. Bacterial membranes generally do not contain sterols (甾醇)(e.g. cholesterol).

6. Prokaryotic Cell (versus Eukaryotic Cell) • Not compartmentalized • Cell membranes lack sterols (e.g. cholesterol) • Single circular chromosome • Ribosomal are 70S with • subunits 30S (16S rRNA) • 50S (5S & 23S rRNA)

7. Bacteria versus Archaebacteria • Eubacteria • peptidoglycan (murein) • muramic acid • Archaebacteria • pseudomurein • no muramic acid

8. Bacteria versus Archaebacteria • 16S rRNA • sequence very different

9. An overiew of procaryotic cell structre 1.size:width×length E.coli(average): 1.1-1.5m × 2.0-6.0  m ? The smallest: Nanobacteria: 0.05-0.2 m ? monsteous microbe: >10-50 m

10. 2.Shape and arrangement Coccus or Cocci Rod Spirillum or Spirilla Spirochete Budding and appendaged Filamentous

11. Streptococcus

12. Bacillus gram

13. Spirillum

14. cocci/coccus Individual Diplococci Long chain: one plane Tetrads: two planes Cubical packets of eight cells: three planes Grapelike form: random planes Sarcina Staphylococcus

15. Rod(bacillus/bacilli): Length-to-width ratio The shape of the rod’s end: flat; rounded; cigar-shaped; bifurcated;分叉 Arrangement: Single: many Pairs: Chain: Curved: Vibrios

16. Other shapes: Spirilla: rigid Spirochetes:flexible Long multimucleate filaments: Actinomycetes

17. Procaryoic cell organization

18. Structure of the cytoplasmic membrane Phospholipids bilayer+protein, 5-10nm thick Prokaryotes Membrane Stabilizers: hydrogen bonds hydrophobic interactions Mg2+, Ca2+, hopanoids

19. Many bacterial membrane Strengthening Agents: Hopanoids类何帕烷 Eukaryotes membrane stabilizer: Sterol (a) General structure of a sterol; (b) The structure of cholesterol; (c) The structure of the hopanoid diploptene.

20. Functions of the Cytoplasmic Membrane 1. Permeability barrier -prevents leakage and function as gate way for transport of nutrients into and out of the cell. 2. Protein anchor- site of many proteins involved in transport, bioenergetics, and chemotaxis. 3. Energy conservation- site of generation and use of the proton motive force. The cytoplasmic membrane is selectively permeable and contains specific carrier proteins that participate in the transport process Selectively Permeability: nonpolar and fat-soluble such as fatty acids, alcohols and benzene (permeable); charged molecules such as organic acids, amino acids and inorganic salts (impermeable, must be specifically transported) Carrier Proteins: or Membrane Transport Proteins: Uniporters, Symporters and Antiporters

21. Mesosome: invaginationa of the plasma membrane in the shape of vesicles, tubules, or lamellae. Functions: 1.cell wall formation during division. 2.play a role in chromosome replicaton and distribution to daughter cells.

22. The cytoplasmic matrix: substance lying between the plasma membrane and the nucleoid. Protoplast: the plasma membrane and everything within.

23. Making Wall-less forms • Result from action of: • enzymes lytic for cell wall • antibiotics inhibiting peptidoglycan biosynthesis • Wall-less bacteria that don’t replicate: • spheroplasts (with outer membrane)? • protoplasts (no outer membrane). ? • Wall-less bacteria that replicate • L forms Naturally Wall-less GenusMycloplasma

24. INCLUSIONS Within the cytoplasm of procaryotic (and eucaryotic) cells are several kinds of reserve deposits, known as inclusions. Some inclusions are common to a wide variety of bacteria, whereas others are limited to a small number of species and therefore serve as a basis for identification. Among the more prominent bacterial inclusions are the following: Carbon storage polymers – PHB and glycogen Phosphate polymers Sulfur Granules Gas Vacuoles

25. Polyhydroxybutyric acid (PHB) A Vibrio species PHB is a lipidlike compound - one of the most common inclusion bodies in prokaryotic organisms. PHB is commonly found as a storage material and unique to bacteria Glycogen is a starchlike polymer of glucose subunits. Glycogen granules are usually smaller than PHB granules.

26. Polyphosphate granule in a bacterial cell A Pseudomonas species Many microorganisms accumulate granules of polyphosphate, which are large reserves of inorganic phosphates that can be used in the synthesis of ATP

27. The sulfur globules inside the cells of purple sulfur bacterium Chromatium buderi Some bacteria, including many photosynthetic bacteria, accumulate elemental sulfur granules as a result of their metabolism.

28. Gas vacuoles (blue) and storage granules (red) in the cyanobacterium Microcystis The formation of gas vacuoles by aquatic bacteria provides a mechanism for adjusting the buoyancy of the cell.Many aquatic cyanobacteria use their gas vacuoles to move up and down in the water column.

29. Magnetosomes Magnetic particles of Fe3O4 Isolated from Aquaspirillum magnetotacticum

30. Ribosomes:protein synthesis Procaryotic: 70S (50S 30S) Eucaryotic: 80S ( 60S 40S) What is S: Svedberg unit. This is the unit of the sedimentation coefficient, a measure of the sedimentation velocity in a centrifuge; the faster a particle travels when centrifuged, the greater its Svedberg value or sedimentation coefficient. The sedimentation coefficient is a function of a particle’s molecular weigh, volume, and shape.

31. The Nucleoid Usually procaryotics contain a single circle of double-stranded DNA. But some: a linear DNA chromosome Recently: Vibrio cholerae: >one chromosome. Nucleoid: 60% DNA, 30% RNA, 10% protein (by weight) Exceptions: 1. Pirellula: a single membrane 2. Gemmata obscuriglobus: two membrane

32. Arrangement of DNA in Prokaryotes

33. DNA Supercoiling To package the DNA into the cell requires that the DNA be supercoiled. There are over 50 supercoiled domains in the E. coli chromosome, they are stabilized by association with the structural proteins.

34. Plasmids: ds, circular or linear DNA, exist and replicate independently of the chromosome or may be integrated with it, not required for host growth and reproduction. • extrachromosomal DNA • multiple copy number • coding pathogenesis and antibiotic resistance factors • bacterial replication