Bacterial morphology, metabolism and growth

1. Bacterial morphology, metabolism and growth Dr Ömer Küçükbasmacı

2. Cell • Fundemental unit of living things (smallest bacterium-largest plants-animals)

3. Bacteria • The smallest cells • Visible only with the aid of a microscope • The smallest bacteria: Chlamydia and Rickettsia-0.1-0.2 micrometer • Larger bacteria: many microns in length

4. A newly described species • Hundred of times larger than the average bacterial cell • Is visible to the naked eye Diversity!

5. Most bacterial cells • Approximately 1 micrometer in diameter • Visible by light microscope • Resolution: 0.2 micrometer

6. Microscopes • Light: • Bright-field • Dark-field (Treponema pallidum-Syphilis_Frengi) • Fluorescence • Phase contrast (details of the living cell) • Electron

7. Staining • Simple • Differential: Gram and Acid-fast stain Gram-stain: cell wall Acid fast stain: Mycobacterium • Negative stain: Indian ink (capsule) • Special staining

8. Animal and plant cells • Much larger • Ranging from 7micrometer (red blood cells) • To several feet (certain nerve cell)

9. Each cell • Genetic basis for reproduction (DNA genome) • Biochemical machinery (genetic information is transcribed in mRNA and mRNA translated in proteins) • The machinery for energy production and biosynthesis • This is all packaged by a membrane.

10. Each cell • Replicates by cell division.

11. Cells • Eukaryotic (Greek for true nucleus) • Prokaryotic (Greek for primitive nucleus)

13. Eucaryotes • Animals • Plants • Fungi

14. Procaryotes • Bacteria • Blue-green algae

15. Major characteristics of Eucaryotic and prokaryotic cell Eucaryote Prokaryote • Size >5 μm 0,5-3 μm • Nuclear structure : Nucleus classic membrane no membrane Chromosomes strands of DNA single circular DNA diploid genome haploid genome

16. Major characteristics of Eucaryotic and prokaryotic cell Eucaryote Prokaryote • Cytoplasmic Structures Mitokondria + - Golgi bodies + - Endoplasmic reticulum + - Ribosomes 80S(60S+40S) 70S(50S+30S) Cytoplasmic membrane with sterols no sterol

17. Major characteristics of Eucaryotic and prokaryotic cell Eucaryote Prokaryote • Cell wall -/composed of kitin complex structure (protein, lipits and peptidoglycans) • Reproduction sexual and asexual asexual (binary fission) • Movement complex flagellum simple flagellum (If present) (If present) • Respiration via mitokondria via cytoplasmic membrane

18. Bacteria • Lack nucleus membrane and membrane bound organelles • A smaller ribosome • Peptidoglycan cell wall which protects it from environtment with low osmotic pressure, at temperature extremes (both hot and cold), dryness and with very dilute and diverse energy sources. • They have evolved their structures and functions to adopt these conditions.

19. Differences • Between Eukaryotes and prokaryotes

20. Differences between Prokaryotes • Bacteria differ: -morphology (size, shape, stainig characteristics) -metabolic -antigenic and -genetic characteristics

21. Size • They are diffucult to differentiate by size

22. Shape • Spherical: coccus (Staphyloccus) • Rod-shaped: bacillus (Escherichia) • Snakelike: spirillum (Treponema) • Branched filamentous (Nocardia and Actinomyces) ( Clusters: diplococcus (Neisseria) chains (Streptococcus) grapelike (Staphylococcus) )

23. Bacterial shape Sperical (coccus) Rod-shaped Spiral Spiral or spirillum Helix or spirochete

24. Bacterial arrangement Diplococcus Chains: streptococcus Clusters: staphylococcus Packets of eight:sarcina

25. Treponema by dark-field microscopy

26. Gram stain • Two major classes of bacteria are distinguished: • Gram-positive and • Gram-negative bacteria • Except: • Mycobacteria (waxy outer shell , distinguished by acid fast stain) • Mycoplasmas(no peptidoglycan)

29. Bacterial Ultrastructure • Internal structure • External structure • Gram-positive and gram-negative bacteria have -Similar internal structure -But different external structure

30. Cytoplasm • DNA chromosome • mRNA • Ribosomes • Proteins • Metabolites

31. Bacterial chromosome • Unlike eukaryotes • A single • Double stranded circle • Not in a membrane bound nucleus • In a discrete area called nucleoid

32. Bacterial chromosome • Unlike eukaryotes • No histons

33. Plasmids • Smaller • Circular • Extrachromosomal DNAs • Not usually essential for cellular survival • Most commonly found in gram-negative bacteria • Often provide a selective advantage: resistance to antibiotics

34. Lack of a nuclear membrane • Simplifies the requirements and • Control mechanisms for the synthesis of proteins

35. Ribosomes • Unlike the eukaryotic 80S(40S+60S)ribosome • Bacterial 70S chromosome (30+50S) • Proteins and RNA of the ribosome are significantly different • Major targets for antibacterial drugs

36. Cytoplasmic membrane • Lipid bilayer • Similar to eukaryotic membranes • But no sterols (cholesterol) Exception: Mycoplasmas

38. Cytoplasmic membrane • Responsible for many functions • Attributable to organelles in eukaryotes: -electron transport -energy production (mitokondria in eukaryotes)

39. Cytoplasmic membrane • Transport proteins: uptake of metabolites release of other substances • Ion pumps: to maintain a membrane potential • Enzymes

40. Mesosome • A coiled cytoplasmic membrane • An anchor to bind and pull apart daughter chromosomes during cell division.

41. Cell wall • Distinguishes gram-positive and gram-negative bacteria

42. The cytoplasmic membrane in most prokaryotes surrounded by • Rigid peptidoglycan (murein) layer • Except: Archaebacteria (pseudoglycan and pseudomurein) and mycoplasmas (no cell wall) • Peptidoglycan provides rigidity and determines the shape of a bacteria • Gram-negative bacteria. + outer membranes

43. Gram positive bacteria • Thick multilayered cell wall • Consisting mainly of peptidoglycan

44. Gram positive bacteria • Peptidoglycan • Sufficiently porous(allows diffusion of metabolites to the plasma membrane) • Essential for structure, replication, for survival

45. Peptidoglycan • During infection • İnterferes with phagocytosis • Stimulates lymphoctes • Pyrogenic activity (induces fever)

46. Peptidoglycan • Degraded by lysozyme • Enzyme in human tears, mucus (produced by bacteria and other organisms) • Degrades the glycan backbone of the peptidoglycan which protects it from osmotic pressure changes

47. Protoplast • Removal of cell wall with lysozyme • Lysis unless it is osmotically stabilized

48. Gram-positive cell wall • Peptidoglycan + • Teicoic acid • Lipoteichoic acid • Complex polisaccarides (C polysaccharides) • M protein of streptococci • R protein of staphylococci

49. Gram-positive bacteria • Teicoic acid : covalently linked to peptidoglycan • Lipoteichoic acid : anchored in the cytoplasmic membrane • Common surface antigens • Distinguish bacterial serotypes • Promote attachment to other bacteria and to spesific receptors on mammalian cell surfaces (adherence)

50. Gram positive-bacteria • Teicoic acid: important virulance factors • Lipoteicoic acid are shed into media and host • Although weaker • Can initiate endotoxic-like activities.