Introduction to Microbiology/Prokaryotes

1. Introduction to Microbiology/Prokaryotes Dr. Cory L. Blackwell August 26, 2014

2. Changing Paradigms • Before the 1880’s it was believed that diseases came from demons and witchcraft • With the new concept of biogenesis and the realization that microorganisms can physically and chemically change organic materials, scientists/physicians began to develop The Germ Theory of Disease.

3. GERM THEORY OF DISEASE • The Germ Theory of Disease states that a particular microbe might cause a specific disease • 1865 Joseph Lister, English surgeon, began treating surgical wounds with phenol (acid) resulting in the significant reduction of infections and deaths • 1876 Robert Koch discovered that the bacterium Bacillus anthracis was present in the blood of cattle that died of the disease anthrax • Koch eventually established Koch’s Postulates

4. Koch’s Postulates • The same pathogen must be isolated in each case of the disease • Pathogen must be isolated from the diseased host and grown in a pure culture • The pathogen from the culture must cause the same disease when used to inoculate a healthy organism • Microorganism must be isolated from the newly diseased animal and be identical to the original pathogen

5. Prokaryotic and Eukaryotic Cells

6. Prokaryote or Eukaryote? Prokaryotes Eukaryotes Humans Plants Yeast Fungi Amoebas • Bacteria • Archaea

7. Prokaryote and Eukaryote • Prokaryotes and Eukaryotes have four common features • Cell membrane • Cytoplasm • Nucleic Acid • Ribosomes • Both utilize similar chemical reactions to metabolize food, build proteins, and store energy

8. Eukaryotic or Prokaryotic • Prokaryotes and Eukaryotes differ in several ways:

9. DNA Location • DNA of Eukaryotes are found in the cell’s nucleus—membrane bound organelle that contains the genetic material • DNA of Prokaryotes is not enclosed in a membrane bound organelle

10. DNA Location Prokaryote Eukaryote

11. DNA Structure • Eukaryotic DNA is bound by chromosomal proteins called histones and is found in multiple chromosomes • Prokaryotic DNA is usually takes the form of a singular circularly arranged chromosome. No histones are present

12. Prokaryotic DNA Eukaryotic DNA

13. Organelles • Eukaryotes possess membrane-enclosed organelles • Mitochondria, endoplasmic reticulum, golgi apparatus, lysosomes, nucleus, etc. • Prokaryotes are void of an membrane-enclosed organelles

14. Organelles

15. Cell Wall Composition • Prokaryotes contain peptidoglycan (complex polysaccharide) within its cell walls • Lipotechoic acids (LTA) • Lipopolysaccharides (LPS) • Eukaryotes cell wall (only in plant cells and fungi) are made of simple molecules (cellulose and chitin)

16. Cell Wall Composition Eukaryotic Cell Membrane Prokaryotic Cell Wall

17. Growth and Division • Prokaryotes divide by binary fission • Requires relatively few structure and processes • Eukaryotes divide utilizing mitosis • More complex than binary fission • Interphase, prophase, metaphase, anaphase, telophase

18. PROKARYOTES

19. Prokaryotes • Prokaryotes are subdivided into two groups • Bacteria • Archaea • Both bacteria and archaea are unicellular organisms • Although bacteria (constitutes the majority of prokaryotes) and archaea look similar, their chemical composition is different • Archaealack peptidoglycan in their cell walls • Archaea usually live in extreme environments • Methanogens • Extreme Halophiles • Hypothermophiles

20. BACTERIA

21. Bacterial Size, Shape, and Arrangement • Most bacteria range between 2 to 8 µm in length • That is roughly 1,000X less than the size of an ant • Bacteria have three different cellular shapes • Coccus“spherical” • Bacillus “rod-shaped” • Spiral “spiral-shaped”

22. Cocci • Bacterial cells that are cocci can be oval, elongated, or flat on one side

23. Cocci

24. Cocci • The cocci are also distinguished based on how the bacteria group with one another (bacterial arrangement)

25. Spatial Arrangement of Cocci • Diplo—pairs of bacteria • Strepto—chains of bacteria • Staphyl—grapelike clusters • Tetrads—groups of four • Sarcinae—cube like structures consisting of 8 bacteria

27. Bacilli • Bacilli divide only across their short axis, therefore there are less arrangement groupings • Diplo—pairs of bacteria Bacillus anthracis

28. Bacilli • Bacilli divide only across their short axis, therefore there are less arrangement groupings • Diplo—pairs of bacteria • Strepto—chains of bacteria arranged from tip to tail

29. Bacilli • Coccobacilli—combination of rod and oval shapes Brucellamelitensis

30. Spiral • Spiral bacteria form twists and are never found in a straight conformation • Spiral bacteria come in three varieties: • Vibrio • Spirillum • Spirochete

31. Vibrioare in the shape of curved rods Vibrio cholera

32. Spirilla have a helical “corkscrew” shape • Have rigid bodies Camplyobacterjejuni

33. Spirochetes are helical in nature • Bodies are FLEXIBLE • Difference between spirilla and spirochetes Treponemapallidum

34. Bacterial Shapes • Bacterial shape is determined by heredity • If the parent cells are of a certain shape their progeny will be of similar shape • Most bacteria are monomorphic, or maintain a single shape • Although the environment may play a role in changing a bacterium’s shape • When a bacterium’s shape is altered it is referred to as pleomorphic(Corynebacterium) • Leads to difficulty in identifying bacteria

35. Critical Thinking • The name of a bacterium is often associated with its shape. Draw these organisms based on their names • Streptococcus pneumoniae • Staphlycoccusaureus • Bacillus anthracis • Vibrio cholera

36. Functional Anatomy of Prokaryotic and Eukaryotic Cells

37. External Cell Wall Structures • The cell wall is a crucial component of the bacteria • There are several structures that line the outside of the cell wall that have a variety of functions

38. Glycocalyx • Glycocalyx—substance that is secreted on the surface of the cell walls by prokaryotes • Glycocalyx (sugar coat) is a sticky, gelatinous polymer that is composed of a polysaccharide, polypeptide, or both • If the glycocalyx is organized and firmly attached to the cell wall, it is referred to as a capsule • Inversely, if the glycocalyx is unorganized and loosely attached it is called a slime layer

39. Glycocalyx Capsule Slime Layer

40. Glycocalyx • The glycocalyx serves a variety of functions • Helps prevent the phagocytosis (ingestion by immune cells) of bacterial cells, thus aiding in their pathogenicity • Forms biofilms that not only shield the bacteria from external stimuli (salt concentrations or antibiotics) but also aid in the communication between the bacteria • Helps anchor bacteria to specific surfaces • Can also be used as a source of nutrients for the bacterial cells

41. Flagella • Some prokaryotes have flagella which are long filamentous appendages that aid in bacterial motility (ability of a bacteria to move by itself) • H antigen—flagellar protein that aids in distinguishing serovars of bacteria • Serovars—variations within a species • The type of flagella can be categorized based on its arrangement on the bacteria

42. Flagella • Atrichous—bacteria that lacks flagella • Peritrichous—distributed all around the cell • Monotrichous—single flagellum at one end • Lophotrichous—several flagella at one end • Amphitrichous—flagella at both ends

44. Flagella Movement • The movement of the flagella propels the bacteria towards a favorable environment or away from an unfavorable environment • This movement is referred to as taxis • Chemotaxis—movement towards a chemical • Phototaxis—movement towards light

45. Other Bacterial Projections • Axial Filaments—bundles of filaments that arise at the end of the cell beneath the outer sheath. Spiral around the entire cell • Bacteria with axial filaments move in a corkscrew shape motion

46. Other Bacterial Projections • Fimbriae—small hair-like appendages that adhere to each other and surfaces. Involved in forming biofilms • Placement is either at the ends of the bacteria or around the entire bacteria

47. Other Bacterial Projections • Pili—appendages that are involved in motility and DNA transfer • The transfer of DNA from one bacteria to another is termed conjugation • The sex pili (F+) binds to the recipient bacteria and injects genetic material Sex Pilus (F+)

48. Bacterial Cell Wall • The cell wall is a complex, semi-rigid structure that surrounds the underlying, fragile plasma membrane • Major function of the cell wall is to prevent bacteria cells from rupturing due to osmotic pressure • They also help the bacteria to maintain its shape. • Point of anchor for the external appendages

49. Cell Wall Composition • The main component of the bacterial cell wall is a macromolecule called peptidoglycan • Peptidoglycanconsists of repeating a disaccharide attached to polypeptides to form a lattice around the cell

50. Cell Wall Composition • The cell wall, depending on its composition, exhibits different characteristics • Because of this, bacteria can be placed in two different groups: Gram-Positive bacteria and Gram-Negative bacteria • The major difference between Gram-Positive and Gram-Negative bacteria is the peptidoglycan composition • G(-) have an outer membrane, inner membrane, and contain periplasm • G(+) lack outer membrane and do not contain periplasmic space