1. Bacterial Cell Structure and Function
Lecture

2. The Three Domains of Life Microbiological focus
Archaea – The Extremophiles
Bacteria- Cyanobacteria and eubacteria
Eukarya – Protozoans, fungi, and worms

3. Prokaryote and Eukaryote Cells

5. The Structure of the Prokaryote Cell
Small size ( 0.5 to 2um)
Large surface area to volume ratio
A variety of shapes
Outer cell wall- very thick made of specialized molecules
Cell membranes may have a different constituency of molecules from eukaryote cells
Ribosomes smaller
No organelles, no nuclear membrane
1 ds circular loop of DNA

6. Shapes of the Bacteria
Bacillus
Coccus
Vibrio
Spirillum
Spirochete
Pleiomorphism- Some bacterial shapes vary within a culture. This can occur when the nutrients are used and wastes have built up

7. Bacterial Shapes

8. Bacillus- E. coli
Fluorescent stain
Freeze fracture

9. Public enemy # 1- Anthrax

10. Streptococcus pyogenes- strep throat

11. Staphylococcus

12. Arrangement of bacteria
Groups of two- diplo
Chains- strepto
Large groups- like grape clusters- staphylo
Division on 3 planes- sarcinae- 8 cells arranged in a cube
Division on two planes produces tetrads

13. Cell Morphology

14. Staphylococcus

15. Diplococcus

16. Streptobacilli

17. Spirillum

18. Spriochetes

19. Cell Walls Peptidoglycan
the single most important molecule in the cell walls of bacteria
One immense- covalently linked molecule
The molecule forms a chain- the constituents are sugar-amino molecules( glucosamines)

20. Peptidoglycans - Cell Wall

21. Gram Positive Bacteria- Cell walls
The cell wall is made of Teichoic acid- glycerol+ phosphates+ribotol which an alcohol sugar. These polymers extend beyond the cell even beyond the capsule
Gram Negative Bacteria- Cell Walls
The outer membrane found primarily in Gram-negative bacteria is a bilayer that forms the outermost layer of the cell wall and is attached to the peptidoglycan by lipoproteins molecules.

23. Gram-negative cell wall

24. Endotoxin The Cell Membrane
LPS- this is actually a part of the outer cell membrane and can b be used to help to identiry Gram- bacteria. It is also important to the cell wall and is usually not released until a bacterium is dead. It consists of polysaccharides and lipid A
Endotoxin
The toxins gram negative bacteria release are from this portion of the cell membrane. Gram negative bacteria release endotoxin and the result is fever, the dilation of blood vessels, so the blood pressure drops and causes other related effects.

25. Gram-Positive Bacteria
The cell wall has a thick layer of peptidoglycan 20 to 80um thick
60-90% of the cell wall is peptidoglycan
Except for the strptococci most gram positive bacterial cell walls contain very little protein

26. Gram-negative Bacteria
The wall of a Gram-negative bacterium is thinner but more complex than a Gram-positive bacterium
Only10 to 20 % of the cell wall is peptidoglycan- the remainder consists of various polysaccharides, protein, lipids.
The cell wall contains an outer membrane- the LPS

27. The Periplasmic Space
The periplasmic space is between the outer surface of the cell wallo and the cell membrane
Enzymes and toxins remain in the periplasmic space in sufficient concentrations to help destroy substances that might harm the bacterium.

28. The Cell Membrane
The cell membrane consists of molecules called phospholipids.
Phospholipids have two long tails consisting of hydrocarbon chains ( HYDROPHOBIC)
Phospholipids have a phosphate head (HYDROPHILIC)
The membrane is formed by a double layer of these molecules
The membrane also contains PROTEINS

29. Membrane structure

30. Internal Structure
Ribosomes- consist of ribonucleic acid ( RNA) and protein. They are abundant in the cytoplasm as
POLYRIBOSOMES

31. Nucleoid Region- Central
The nucleoid region contains 1 ds ciruclar loop of DNA.
The DNA may be attached to the cell membrane as well at some point
There may be RNA associated with the DNA

32. Chromatophores- photosynthetic bacteria+
Molecules of life
Chromatophores are derived from the cell membrane. They contain pigments used to capture light energy for the synthesis of sugars. Nitrifying bacteria also may have these internal membranes.
They contain the enzymes necessary for the energy transformation process of photosynthesis

33. The Nucleoid Region

34. Mesosomes- Bacteria
Bacterial cells have large infoldings in their membranes.

35. Mesosomes
Mesosomes provide the surface area for all of the chemical reactions in the cell
respiration
metabolic processes
Freeze fracture

36. Inclusions
Small bodies in the cytoplasm- some are called granules
Glycogen
pyrrophosphate granules- volutin
Metachromatic granules
Variable colors

37. Endospores
Vegetative cells of bacteria like Bacillus or Clostrium produce resting stages
These spores are designed for survival and not reproduction.
These are formed within cells
They are resistant to heat, drying,acids,bases,disinfectants, and radiation

38. Spore formation
Spores form when nutrients are depleged form a culture
Few spores are formed when nutrients are plentiful and environmental conditions are favorable.

39. Spore Structure
An endospore consists of a core, surrounded by a cortex, a spore coat and in some species a thin layer called the exosporium
spore

40. How do spores survive ?
They contain dipicolinic acid and a large number of calium ions.
These materials contribute to heat resistance
The lose water content enables them to survive.

41. They are indestructible
Endospores have survived over 10,000 years
Special methods may be used to skill them during sterilization
When conditions are favorable they can still germinate

42. Flagella
Bacteria that are motile have appendages called flagella
A bacteria can have one or many flagella
monotrichous
amphitrichous
lophotrichous
peritrichous

43. What is this type of bacteria ?

44. The diameter of a prokaryote’s flagellum is about one-tenth of that of a eukaryote
It is made of flagellin
The basal region has a hook like structure and a complex basal body
The basal body consists of a central rod or shaft surrounded by a set of rings
Gram negative bacteria have a pair of rings embedded in the cell membrane and another pair of rings associated with the peptidoglycan and lipopolysaccharide layer of the cell wall. Gram positive have one ring.

45. Turns like a mixer
Flagellar motion
Flagella rotate like twirling L- shaped hooks such as a dough hook on a kitchen rotor- or a mixer

46. Twiddling ? HHMM!
When flagella bundle together they rotate counterclockwise and the bacteria run
When the flgella rotate clockwise the flagellar bundle comes apart and the bacteria twiddle- tumble randomly

47. Chemotaxis
Sometimes bacteria move toward or away from substances in their environment. This is called chemotaxis
Concentrations of most molecules in the environment form a gradient.
When a bacteria is running a long an increasing gradient if reduces the frequency of its twiddles

48. PILI
Attachment pili-
These are structures on the surface of the bacteria that aid the bacterium in atttching to surfaces
These acid the bacterium by allowing colonization of the mucus membranes of organisms.
Some bacteria adhere to red blood cells by attachment pil and cause red blood cells to clum- this is hemagglutination

49. SEX PILI- Conjugation
Conjugation pili or sex pili are found only in certain groups of bacteria.
This structure exists exclusively for the transfer of DNA between bacteria
The DNA passes between bacteria tend to develop antibiotic resistance

50. Bacterial Slime Layer or Capsule