1. Bacterial Classification
Assoc.Prof.Dr.Yeşim Gürol
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2. In this lesson Describe bacterial classification: List taxon levels
Define taxonomy and identification
Describe principles of taxonomy
Explain classification of bacteria

3. Taxonomy
Is the science of classification, especially of living organisms, to facilitate research and communication. Organisms are arranged into taxonomic categories or taxa (singular: taxon), to show degrees of similarities between organisms.

4. Criteria that drive taxonomy
Although genomic analysis has become the final determinant of taxonomy,demonstration of phenotypic features remains the primary means of applying these classifications in diagnostic microbiology.

5. Based on certain shared genotypic and phenotypic characteristics bacteria are classified into: • Family • Genus • Species • Strain

6. Genus (plural genera) refers to a group of
bacterial organisms that share in common
several structural, biochemical and physiological traits
Species refers to a subgroup of organisms
within a genus that share more specific traits
among themselves.
The term strain refers to a pure culture made up of descendants of a single isolation

7. Bacterial classification is based on several major properties
Gram staining (and other stains)
Morphology
Metabolic behavior
Infection patterns
Intracellular vs extracellular
Antigenic composition
DNA sequence

8. Natural classification scheme that reflects major differences in cell wall structure and to some extent the mechanisms involved in disease.
Gram positive (blue): single membrane consisting of a thick peptidoglycan layer – no lipopolysaccharide

9. Gram negative (pink): inner and outer membranes, with outer membrane having lipopolysaccharide molecules

10. Property discovered by Christian Gram 1883, a Danish botanist, while attempting to differentiate bacteria from human tissue by different staining methods. He noted differences in stain retention by bacteria..

15. Gram positive cocci
in clusters
Gram positive cocci
in chains

16. Gram negative cocci
Gram negative rods

17. Morphology
Rods or cocci
Curved or spiral
Filamentous

18. Metabolic properties may influence ability type of disease caused but not the only factor
Aerobe versus anaerobe (microaerophilic, facultative aerobes)
Anaerobes have a greater propensity to cause abscesses
Brain, lung, liver, intra-abdominal abscesses

19. Some correlation between morphology and disease
Spiral bacteria---Treponemes, Borrelias, Leptospiras, Spirillium tend to cause systemic diseases

20. Pathogenic filamentous bacteria
Actinomyces, Nocardia, Mycobacteria tend to cause chronic diseases
Gram positive bacteria, Staphylococcus more likely to cause skin infections, Streptococci skin and pneumonia

22. The ultrastructure of Escherichia coli (E
The ultrastructure of Escherichia coli (E. coli) as an example of a prokaryote
                                                                                    

23. The general size of a prokaryotic cell is about 1-2 um.
Note the absence of membrane bound organelles
There is no true nucleus with a nuclear membrane
The ribosome's are smaller than eukaryotic cells
The slime capsule is used as a means of attachment to a surface
Only flagellate bacteria have the flagellum
Plasmids are very small circular pieces of DNA that maybe transferred from one bacteria to another.

28. How does an experienced physician approach bacterial diseases?
Organ system approach
Which bacteria cause disease in a certain location
Gram stain approach
What does the gram stain show--used to treat empirically before cultures are completed
Requires that one is able to get a gram stain which is not always the case

29. Organ system approach Meningitis
Pneumococci, Meningococci, Hemophilus influenzae, Listeria
Sinusitis
Pneumococci, H. influenzae, Moraxella
Acute otitis media
Pharyngitis
Group A streptococci
These are all aerobic bacteria

30. Now add in the Gram stain
Gram negative rods seen in CSF in meningitis
H. influenzae
Gram positive cocci in meningitis
Pneumococcus
Gram positive cocci in sinusitis
Pneumococcus or Staphylococcus
Gram stain may suggest the organism --clusters or diplococci?

31. Pneumonia Pleural cavity Endocarditis Pneumococcus, Staphylococcus
Pneumococcus, H. influenzae
Pleural cavity
Pneumococcus, Staphylococcus
Endocarditis
Streptococcus, Staphylococcus, Enterococci

32. Pneumonia-sputum gram stain
Gram positive diplococci as predominant organism
Likely organism Pneumococcus--the most common gram positive cocci found in pneumonia
Therapy
Endocarditis-blood culture positive
Gram positive cocci on the stain
Maybe Streptococci, Enterococci, or Staphylococci
Treatment decision made on this basis- Vancomycin +

33. Bacteria Archae Eukarya
The three phylogenetic lineages of cells (Domains according to comparative rRNA sequences)
Bacteria
Archae
Eukarya

35. Bacteria :Prokaryotic
Archae :Prokaryotic
Eukarya :Eucaryotic

39. Eukaryotic (Greek for true nucleus)
Prokaryotic (Greek for primitive nucleus)

40. Procaryotic cells
Bacteria
Archae

41. Bacteria The smallest cells Visible only with the aid of a microscope
The smallest bacteria: Mycoplasma,Chlamydia and Rickettsia micrometer
Larger bacteria: many microns in length

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

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

45. 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 sircular DNA
diploid genome haploid genome

46. Eucaryote Prokaryote Cytoplasmic Structures Mitokondria + -
Golgi bodies
Endoplasmic
reticulum
Ribosomes 80S(60S+40S) S(50S+30S)
membrane with sterols no sterol

47. Differences between Procaryotes
Bacteria differ:
-morphology (size, shape, stainig characteristics)
-metabolic
-antigenic and
-genetic characteristics

48. Procaryotic cells
Size: micrometer(μm)
meter

49. Size:
-the smallest bacteria:
Mycoplasma : 0.3 μm
Nanobacteria: μm
Escherichia coli:2-6 μm
Spirochetes: 500 μm
red blood cell:7 μm

52. Capsule:unstained part

53. Spore:unstained part

54. Dark-field (Treponema pallidum-Syphilis_Frengi)

66. Biochemical reactions are used to classify

68. Sequencing