• Microbiology- Ch. 4 pp 87-101

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

• 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.

• 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

allows for 360 degree filament rotation

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

cell envelope
Bacteria have some or all of the following structures:
1. 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.
1. 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.

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.

• 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.

• 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

• Gram negative 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.

• 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-

• 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.

•
– 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.

• 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

Extension of cell membrane
– 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.

• Cyannobacterium- dense stacks of internal membranes with photosynthetic pigments.

• 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.

• 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

• 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

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

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

• 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

• 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 120 o C for 20-30 minutes will destroy

• 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

• 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:
• chains
• palisades