MicroBiology Ch 3 Flashcards

All bacterial cells possess

- A cell membrane

- Cytoplasm

- Ribosomes

- A cytoskeleton

- One (or a few) chromosome(s)

Most bacterial cells possess:

- A cell wall

- A surface coating called a glycocalyx

Some but not all bacterial cells possess

- Flagella, pili, and fimbriae

- An outer membrane

- Plasmids

- Inclusions

- Endospores

- Intracellular membranes

Pleomorphism

variations in size and shape among cells of a single species

Spherical (s. coccus, pl. cocci)

Rod-shaped (s. bacillus, pl. bacilli)

Comma-shaped (s. vibrio, pl. vibrios)

Spiral (s. spirillum, pl. spirilla)

Pleiomorphic (varied shapes)

Hyphae (branching filaments of cells)

Mycelia (tufts of hyphae)

a network of branching, thread-like structures called "hyphae" that make up the vegetative body of a fungus

Thiomargarita namibiensis

up to 700 μm in diameter

Epulopiscium fishelsoni

200‒700 μm x 80 μm

mycoplasma

some cells are only 0.2 μm in diameter

Appendages

Structures such as legs and antennae that extend from the body wall.

flagella, pili and fimbriae

Cell envelope

• The plasma membrane and all surrounding layers external to it

• Capsules or sheaths, cell wall, plasma membrane

• Composed of two or three basic layers:

- Cell wall

- Cell membrane

- Outer membrane in some bacteria

Cytoplasm

A jellylike fluid inside the cell in which the organelles are suspended

inclusion bodies, nucleoid, ribosomes

Flagella - Prokaryotic Propellers

• Bacterial locomotion

• Three distinct parts

• Comprised of many proteins

• 360 degree rotation

Monotrichous

Single flagellum

Lophotrichous

Small bunches or tufts of flagella

Amphitrichous

Flagella at both poles of the cell

Peritrichous

Flagella dispersed randomly over the surface of the cell

Chemotaxis (Bacterial Movement)

• Bacteria move in response to chemical signals

• Receptors bind extracellular molecules, which triggers flagellum to rotate

Runs (Bacterial Movement)

smooth linear movement toward a stimulus

Tumbles (Bacterial Movement)

flagellar rotation reverses, causing the cell to stop and change its course

Fimbriae

used for attachment

Pili

used for attachment and genetic exchange during conjugation

Glycocalyx

• Composed of polysaccharides, proteins or both

• Varies in thickness

• Used to avoid phagocytosis and for adhesion (biofilms)

Capsule

• Bound more tightly to the cell, denser and thicker than a slime layer

• Visible by negative staining

• Produces a sticky(mucoid) character to colonies

• Encapsulated bacterial cells generally have greater pathogenicity

Peptidoglycan Cell Wall

• Repeating framework of long glycan (sugar) chains cross-linked by short peptide (protein) fragments

• Present in most bacteria

• Provides strength to resist rupturing due to osmotic pressure

Gram Positive Cell

• Thick peptidoglycan

• Teichoic acid, lipoteichoic acid

• One membrane

Gram Negative Cell

• Thin peptidoglycan

• Lipopolysaccharide

• Two membranes

• Porins

Acid-Fast Bacteria

• Mycobacterium sp. and Nocardia sp.

• Contain mycolic acid (a wax)

• Modified Gram-positive structure

• Must use the acid-fast stain to ID important pathogens causing:

- Tuberculosis

- Leprosy

Cell-Wall Deficient Bacteria

• Cell membrane stabilized by sterols, is resistant to lysis(i.e. Mycoplasma pneumoniae)

• Other cell-wall deficient types called L forms are linked to infections

Lipopolysaccharide

• Located in the outermost layer of the outer membrane (OM) in gram-negative bacteria

• Lipid A (endotoxin) stimulates fever and shock

Cytoplasmic Membrane

• A lipid bilayer with proteins embedded

• Provides a site for reactions

• A major action of the cell membrane is to regulate the passage of nutrients into and out of the cell

The Cytoplasm

• 70-80% water

• Soluble proteins, salts, carbohydrates

• Site of nearly all chemical reactions

• Contains the DNA in the nucleoid

Bacterial DNA

• DNA of most bacteria exists in the form of a single circular bacterial chromosome

• DNA is aggregated in a dense area of the cell called the nucleoid

Prokaryotic Ribosome

•Two subunits(30S and 50S)

•Total size is 70S (versus 80S in eukaryotes)

•60% rRNA and 40%protein

•Translates mRNA into proteins

Inclusions or Granules: Storage Bodies

• Non-membrane bound granules

• Usually for storage of nutrients

The Cytoskeleton

• Peptidoglycan layer determines shape of many bacteria

• Others use protein fibers composed of actin and tubulin to alter cell shape

Bacterial Endospores

• Dormant bodies

• Heat resistance due to calcium and dipicolinic acid content

• Cortex, spore coats protect against radiation and chemicals

• Metabolically active vegetative cells can undergo sporulation

• Sporulation is not a reproductive function for most bacteria

• When spores of Clostridium sp. are embedded in a wound with dead tissue, they can germinate, grow, and release toxins

Archaea

• Prokaryotic microorganisms

• Many are found in extreme environments (i.e. psychrophiles)

• Different from members of the domains Bacteria and Eukarya in terms of: cell structure, metabolism, genetics

Bergey’s Manual of Systemic Bacteriology

For studying prokaryotic relationships and origins

Bergey's Manual of Determinative Bacteriology

Identify/differentiate unknown microbial species

Organizes the prokaryotes into four major divisions based on cell wall structure:

- Gracilicutes

- Firmicutes

- Tenericutes

- Mendosicutes

Gram-negative cell walls and thus are thin-skinned

Gracilicutes

Gram-positive cell walls that are thick and strong

Firmicutes

Lack a cell wall and thus are soft

Tenericutes

Archaea with unusual cell walls

Mendosicutes

Subspecies, strain, or type

Terms used to designate bacteria of the same species that have differing characteristics

Serotype

Refers to representatives of a species that stimulate a distinct pattern of antibody (serum) responses in their hosts

Plasmid

• Can replicate independently

• Extrachromosomal DNA

• Physically separated from chromosomal DNA