MIcrobiology Module 2

Shapes: Cocci (Spherical), Bacilli (Rod-like), Vibrios (Comma-shaped), Spirilla (Spirals), or Spirochete (Cork-screw)

Cell can stick together after dividing to form pairs (Diplo), tetrads, chains (strepto), grape-like clusters (Staphylo-), filaments

Size range from 0.05 um diameter to >500um

E.Coli is a typical bacillus at 1X 3 um

Envelope contains plasma membrane (PM or CM), cell wall made of murein (type of peptidoglycan) and sometimes an S-layer

Gram (+) Positive have CM and cell

Gram (-) have CM but have thinner cell wall and another structure (OM) and the space between the 2 membranes (periplasmic space)

OM may be considered part of cell wall

Basic structure of CM is phospholipid bilayer w/fatty acids face inward and glycerol phosphates point outward toward cytoplasm or outside of cell

Hopanoids (related to cholesterol) act for fluidity buffers. Interact w/fatty acids within the membrane

• Lipid composition depend on microbe and its environment
• Fluidity determined by level of saturation of FA-at a given temperature the greater the number of double bonds (unsaturation) the more fluid the membrane

Murein: Consists of layers, each layer comprised of alternating NAG and NAM (lysozyme-sensitive linkage)

Each NAM has an attached short peptide that may be X-linked to another NAM short peptide on an adjacent layer (via transpeptidase)

Gram Positive bacteria: X-link of D-Ala is to gly interbridge, then bridge is X-linked to L-Lys. Walls have many layers (20-80nm) (10-40 layers)

Gram Negative bacteria: NO interbridges, Use DAP (Diaminopimelic Acid) linked to D-Ala and have fewer layers (2-7nm)

In Gram Positive: Crystal violet binds to CM. Ethanol hits cell wall and causes all layers to collapse. Crystal violet gets stuck in collapsed layers

Gram negative allows for ethanol to get to CM and wash out crystal violet

Teichoic Acid are covalently attached to cell wall (or lipoteichoic acids attached to CM)

Teichoic acids give negative charge to cell wall, but function is unclear

All cell walls of Gram + or - microbes protect cells from swelling excessively in hypotonic environments

Inner leaflet of OM is continuation of CM

Lipopolysaccharide (LPS) is major component of outer leaflet of OM

LPS is comprised of lipid A, core polysaccharide and O antigen

Lipid A (Endotoxin) is responsible for septic shock associated w/ Gram (-) bacterial infections

OM much more permeable to solutes than PM due to presence of porins

Found in some bacteria (Gram + and -) and archaea (can sometime take place of cell walls)

Self assembling, crystalline structures of a single protein of glycoprotein

Model systems for studies of nanotechnology

Campylobacter use them to shield cells from immune system

Extracellular structures composed of Hi MW polysaccharides or polypeptide

Only found on some microbe. Used for attachment, protection from immune system or for protection against dessication

Important virulence factors

Slime layer part of gliding non-directed) motility in some species

Glycocalyx refers to region of slime found between organisms

Closely related to Gram Positive (+) bacteria

Cell walls are non-murein always. Variable in structure

CMs contain branched lipids derived from isoprene, that are ether-linked to glycerol phosphate, no LPS in Gram Negative (-) Archaea

Hyperthermophiles contain C40 monolayers (stable at hi temp.) other archaea contain lipid bilayers or combinations, depending on environment

Flagella are most important. Most common form of prokaryotic directed motion. Used for chemotaxis

Pili (Fimbriae) are used mainly for adhesion. Buy may be used along w/slime production to create a type of twitching (non-directed) motility

Types and numbers of flagella and pili are used in classification

Monotrichous Polar Flagellation: One flagella at end of cell

Lophotrichoud Flagellation: Tuft of flagella at one end of cell

Peritrichous Flagellation: Flagella all around cell

Semi-rigid, multi-component structures. Found in both Gram positive and negative cells.

Prokaryotic and eukaryotic flagella differ

In Prokaryotes: Flagella are anchored by rings assembled in each layer of the cell envelope (Basal Body)

Flagella are assembled from inside to outside via hollow internal tube-like structure

Filament is made of flagellin subunit (H antigens used for classification)

Each flagella is semi rigid and movement occurs by turning whole structure (propeller mechanism)

Torque is generated by movement of H+ into cell using Mot proteins

Rotations of flagella can be either clockwise (backward or tumbles) or counterclockwise (forward) and can be reversed by Fli proteins

Movement is in response to conc. of repellents or attractancts in environment (chemotaxis), pH taxis, phototaxis

Axial filament/fibrils wraps around cell w/in periplasmic space

When flagella rotates, spirochetes move forward in corkscrew motion, allowing them to invade into tissues to cause disease

Short, filamentous structures (usually gram - microbes) used for attachments to substrata or to other microbes in conugation (Sex pili)

Some involved in non-directed crawling motion called twitching motility but typically not involved in locomotion

Filaments are made of proteins called pilins

Not rigid structure, area where DNA is found

Prokaryotes typically have singular chromosome but no nuclear membrane

Chromosome is condensed by proteins in special area (Nucleoid)

Transcription and translation occur simultaneously

Common extra-chromosomal circular DNAs that replicate autonomously in cytoplasm

Size varies from 1kn to over 1000kb

Copy number varies from 1 to >1000

Plasmids have auxillary (non-essential) functions

Site of translation. Prokaryotic cytoplasm is packed with ribosomes. contain 10-20X more ribosomes than eukaryotes

Prokaryotic ribosomes (70S) consist of 2 subunits, are functionally similar but structurally diff. than eukaryotic ribosomes (80S) and are differentially inhibited by antibiotics

Eukaryotic cells contain prokaryotic-type ribosomes in mitochondria and chloroplasts

ALL prokaryotes have cytoskeletal elements analogous to those found in eukaryotes

Functions: Cell division, protein localization and cell shape determination

Mbl (Similar to actin)

Found in bacteria and archaea

totally impermeable to water, but permeable to gases

Purpose if for buoyancy ( NOT STORAGE)

Usually found in photosynthetic organisms

Vary in number from several to several hundred and vary in size

Membrane delineated structures with specific functions

Include: storage granules, inclusion bodies, carboxysomes, magnetosomes

Most are separated from cytoplasm by membrane

Commonly formed and used for storage of excess organic fuel molecules

PHB (Poly-B-hydroxybuterate) is most common PHA

Glycogen inclusions also occur

PHAs are enclosed in lipid membrane to form storage vesicles

Other types of molecules (phosphate, sulfur) are also stored in granules

-some: Refer to a membrane delineated structrue

Particles containing Fe(3)O(4) or Fe(3)S($=4). Essentially contains iron

Work as magnet and allow cells to align along earth's magnetic pole

Surrounded by invaginations of CM

Carboxysomes contain high levels of enzymes used to fix CO2 into carbohydrate

Enterosomes (intestinal) contain high levels of specific enzymes involved in special metabolic pathways in gut bacteria

Specific structures found in few microbes. Critically important.

Location: Terminal, subterminal or central, characteristic of the species that make endospores

Endosporulation occurs when times get tough and cell cannot survive (Cell does not survive endospore formation)

Endospores resistant to dessication, heat, radiation, and chemicals and may survive for centuries

Endospores contain high levels of Calcium, dipicolinic acid, and SASPs (small, acid-soluble proteins) that bind to and protect DNA. Very low water content and are metabolically inactive.