1. Bacterial Form and Function
Microbiology- Ch. 4 pp

2. Structure of a Prokaryotic Cell

3. Prokaryote Structures:
Appendages- flagella, pili, fimbrae
Cell envelope- glycocalyx, cell wall , cell membrane
Cytoplasm- ribosomes, granules, nucleoid/chromosome.

4. Bacterial Appendages:
Pili (pl), pilus (s)
Only found in gram negative bacteria
hollow, hairlike structures of protein larger and more sparse than fimbriae.
allow bacteria to attach to other cells.
sex pilus, - transfer from one bacterial cell to another- conjugation.
fimbriae (pl) fimbria (s)
Adhesion to cells and surfaces
Responsible for biofilms.
Pathogenesis of gonococcus and E.coli
Flagella (pl), flagellum(s)
Motility-
long appendages which rotate by means of a "motor" located just under the cytoplasmic membrane.
Bacteria may have one, a few, or many flagella in different positions on the cell.
All spirilla, half of bacilli, rare cocci
Advantages- chemotaxis-positive and negative.

5. Motility- Flagella vary in number and arrangement. Polar arrangment-
Monotrichious- 1 flagellum at one end
Fastest; Pseudomonas -example
Lophotrichious- tuft at one end
Amphitrichious- bipolar
Peritrichious-
Multiple flagella; randomly dispersed around the bacterial cell
E.coli -example

6. Structure of flagella allows for 360 degree filament rotation

7. Flagellar arrangements

9. Detection of Motility Stab line in semisolid motility agar
growth out from the streak line indicates motility.
A= motile; B=nonmotile
Motility plate
Hanging drop- from actively
growing culture
18-24 hrs old.
directional movement
vs. “brownian movement

10. Bacterial Surface Structure- cell envelope Bacteria have some or all of the following structures:
Glycocalyx- capsule or slime layer
layer of polysaccharide (sometimes proteins)
Different composition in certain bacteria-
Streptococcus pneumoniae- capsule- tighter
Slime layer- looser, washes off
protects the bacterial cell from phagocytosis
associated with pathogenic bacteria -Staphylococcus aureus.
Glycocalyx- colonize nonliving materials- plastics, catheters, medical devices.
Cell wall –
peptidoglycan (polysaccharides + protein),
Support and shape of a bacterial cell.
The three primary shapes in bacteria are:
coccus (spherical),
bacillus (rod-shaped)
spirillum (spiral).
Mycoplasma are bacteria that have no cell wall and therefore have no definite shape.

13. 2. Cell wall –
peptidoglycan (polysaccharides + protein)
Repeating glycan chains (N acetyl glucosamine and N acetyl muramic acid) with crosslinked peptides.
Support and shape of a bacterial cell.
The three primary shapes in bacteria are:
coccus (spherical),
bacillus (rod-shaped)
spirillum (spiral).
Mycoplasma are bacteria that have no cell wall and therefore have no definite shape.

15. Differences in Cell Wall Structure
Basis of Gram Stain Reaction
Hans Christian Gram- 1884
Differential Stain
Gram Positive vs Gram Negative Cells
Gram Positive Cells-
Thick peptidoglycan layer with embedded teichoic acids
Gram Negative Cells-
Thin peptidoglycan layer, outer membrane of lipopolysaccharide.

16. Gram Stain Reaction Hans Christian Gram- 1880s
Divides bacteria into 2 main groups-
Gram positive
Gram negative
Also- gram variable
Gram nonreactive
Gram positive bacteria
many layers of peptidoglycan and teichoic acids.
Form a crystal violet-iodine-teichoic acid complex
Large complex,difficult to decolorize

18. Gram negative cells Gram variable cells Very thin peptidoglycan
No teichoic acids
Alcohol decolorizer readily removes the crystal violet.
Alcohol also dissolves the lipopolysaccharide of the cell wall.
Gram variable cells
Some cells retain crystal violet; some decolorize and take up the safranin
4 factors-
Genetics- variable amount of teichoic acid.
Age of culture- older cultures have variable amount of teichoic acid
Growth medium- necessary nutrients not available
Technique-
smear not thin or evenly made.
Staining procedure not done correctly- decolorizer left on too long.

20. Gram nonreactive cells
Have peptidoglycan but have very waxy- thick lipids –waterproof, dyes cannot enter either.
Examples- Mycobacterium- tuberculosis and leprosy.
Alternative staining- acid fast stain-

21. Cell wall deficient forms Figure 4.17
L- forms ( Lister Institute where discovered)
Bacteria loses cell wall during the life cycle
Result of a mutation in cell wall forming genes
Induced by treating with lysozyme or penicillin which disrupts the cell wall
Protoplast-
G + bacterium with no c. wall, only a c. membrane
Fragile, easily lysed
Spheroplast-
G – bacterium loses peptidoglycan, but has outer membrane
Less fragile but weakened.

22. Surface structures continued:
Outer membrane
This lipid bilayer is found in Gram negative bacteria and is the source of lipopolysaccharide (LPS) in these bacteria
LPS is toxic and turns on the immune system.
Not found in Gram positive bacteria.

23. Cell membrane Located just beneath cell wall Very thin
Lipid bilayer, similar to the plasma membrane of other cells. Transport of ions, nutrients and waste across the membrane
Typical
30-40% phospholipids
60-70% proteins
Exceptions-
Mycoplasma- sterols
Archaea- unique branched hydrocarbons

25. Mesosome Extension of cell membrane Gram-positive bacteria-prominent
Folding into cytoplasm – internal pouch
Increases surface area.
Gram-positive bacteria-prominent
Gram negative bacteria- smaller,harder to see.
Functions-
Cell wall synthesis
Guides duplicated chromosomes into the daughter cells in cell division.

26. Photosynthetic Prokaryotes
Cyannobacterium- dense stacks of internal membranes with photosynthetic pigments.

27. Functions of Cell Membrane
Carries out functions normally carried out by eukaryote organelles.
Site for energy functions
Nutrient processing
Synthesis
Transport of nutrients and waste
Selectively permeable
Most enzymes of respiration and ATP synthesis
Enzyme synthesis of structural macromolecules
Cell envelope and appendages
Secretion of toxins and enzymes into environment.

28. Cell cytoplasm Encased by cell membrane Dense, gelatinous
Prominent site for biochemical and synthetic activities
70-80% water- solvent
Mixture of nutrients- sugar, amino acids, salts
Building blacks for cell synthesis and energy

29. Bacterial chromosome Singular circular strand of DNA
Aggregated in a dense area- nucleiod
Long molecule of DNA tightly coiled around protein molecules.
Plasmids-
Nonessential pieces of DNA
Often confer protection- resistance to drugs
Tiny, circular
Free or integrated
Duplicate and are passed on to offspring
Used in genetic engineering

30. Ribosomes Site of protein synthesis Thousands 70S
Occurs in chains –polysomes
70S
2 smaller subunits
30S and 50S

32. Inclusions If nutrients abundant- stored intracellularly Granules-
Crystals of inorganic compounds not enclosed by membranes
Sulfur granules- photosynthetic
Polyphosphate- corynebacterium
Metachromatic- Mycobacterium

33. Bacterial Internal Structures
Endospores
inert, resting, cells produced by some G+ genera: Clostridium, Bacillus and Sporosarcina
have a 2-phase life cycle:
vegetative cell – metabolically active and growing
endospore – when exposed to adverse environmental conditions; capable of high resistance and very long-term survival
Features of spores- size, shape, location=identification
sporulation -formation of endospores
hardiest of all life forms
Forms inside a cell- functions in survival
not a means of reproduction
withstands extremes in heat, drying, freezing, radiation and chemicals
germination- return to vegetative growth

35. Endospores
Resistance linked to high levels of calcium and dipicolinic acid
Dehydrated, metabolically inactive
thick coat
Longevity verges on immortality - 25,250 million years.
Resistant to ordinary cleaning methods and boiling
Pressurized steam at 120oC for minutes will destroy

36. Bacterial Shapes, Arrangements, and Sizes
Variety in shape, size, and arrangement but typically described by one of three basic shapes:
coccus - spherical
bacillus – rod
coccobacillus – very short and plump
vibrio – gently curved
spirillum - helical, comma, twisted rod,
spirochete – spring-like

38. Bacterial Shapes, Arrangements, and Sizes
Arrangement of cells is dependent on pattern of division and how cells remain attached after division:
cocci:
singles
diplococci – in pairs
tetrads – groups of four
irregular clusters
chains
cubical packets
bacilli:
palisades