microbio chapter 4

are you pro or eu

monomorphic

single shape

• most bacteria are monomorphic

pleomorphic

many shapes

coccus

sphere

bacillus

long cylinder

coccobacillus

in-between sphere and long cylinder

pairs

diplococci, diplobacilliclus

clusters

staphylococci

chains

streptococci, streptobacillius

groups of four

tetrads

cubelike groups of eight

sarcinae

glycocalyx

external to cell wall

• viscous & gelatinous

• primarily made of polysaccharide

  • made of/include polypeptide

• only synthesized in response to particular environmental cues

  • two types: capsule and slime layer

capsule

neatly organized and firmly attached to cell wall

• glycocalyx type

• contributes to virulence

  • prevents phagocytosis

  • contributes to adherence to surfaces

• retains water and protects cells from desiccation

  • serves as reserve of nutrition

slime layer

unorganized and loosely attached

• glycocalyx type

• contributes to virulence

  • allows bacteria to adhere

  • extracellular polymeric substance is critical for formation of biofilms

    • provides significant protection to bacteria within them

  • retains water and protects cells from desiccation

  • serves as reserve of nutrition

flagella

long, filamentous appendages external of cell

• only some have it

• made of flagellin protein

• rotate to propel bacteria → '“run” or “tumble”

  • three parts

    • filament

    • hook

    • basal body

• allow bacteria to move toward or away from stimuli: ability called taxis

  • flagella proteins are H antigens and distinguish among serovars

    • serovars are distinct variations within bacterial species based on surface antigens

axial filaments

also called endoflagella

• found in spirochetes

• anchored at one end of cell; beneath outer sheath

  • rotation causes cell to move like corkscrew

fimbriae

composed of pilin protein subunits

• singular: fimbria

• hairlike, short, fine, and numerous appendages

  • allow for attachment

    • involved in formation of biofilms

    • enable some bacteria to adhere to body surfaces

pili

composed of pilin protein subunits

• singular: pilus

• one or two projections, longer than fimbriae

• involved in motility (gliding and twitching)

  • main role: sex/conjugation pili involved in DNA transfer from one cell to another

bacteria cell wall

contains peptidoglycan

• maintains shape of bacteria

• prevents osmotic lysis and protects cell membrane

  • does NOT prevent plasmolysis

• targeted by some antibiotics and lysozyme

• some components contribute to pathogenicity (cause disease)

  • chemical composition of cell wall can be used to differentiate major groups of bacteria

peptidoglycan

polymer of repeating disaccharide in rows

• NAG + NAM

  • rows linked by short peptide side chains

gram-positive cell walls

thick peptidoglycan (many sheets)

• teichoic acids

  • stabilize peptidoglycan

  • carry negative charge, regulate movement of cations

  • provide antigenic specify

gram-negative cell walls

outer membrane

• made of lipopolysaccharide (LPS), lipoproteins, and phospholipids

  • O polysaccharide functions as antigen

  • lipid A is endotoxin embedded in top layer

    • porins (proteins) form channels through membrane

      • allow passage of small molecules & ions

• protects from phagocytosis and action of complement proteins (host defenses), & certain antibiotics & chemicals

thin peptidoglycan layer

• periplasmic space

  • periplasm between outer membrane and plasma membrane

    • many processes take place

  • gram-negative harder to treat due to complex cell wall structure

gram stain mechanism

crystal violet-iodine crystals form inside cell

• gram positive

  • alcohol dehydrates peptidoglycan

  • CV-I complex do not leave during decolorization step

• gram negative

  • alcohol dissolves outer membrane and leaves holes in peptidoglycan

  • CV-I washes out, cells are colorless

    • safranin added to stain cells

acid-fast cell walls

• no outer membrane

• contains some peptidoglycan

• large amounts of waxy lipid

• acid-fast genera

  • mycobacterium

  • nocardia

• stain with carbolfuchsin in acid-fast stain procedures

mycoplasma

lack cell walls

• sterols in plasma membrane protects cell from lysis

archaea

wall-less

• walls of pseudomurein

  • no peptidoglycan

lysozome

cleaves glycosidic bonds between NAM and NAG in peptidoglycan

• weakens cell wall of gram-positive bacteria

beta-lactam antibiotics

e.g., penicillin & cephalosporin

• inactivate transpeptidase (aka penicillin binding protein) → inhibits formation of peptide bridges in peptidoglycan → interferes with final stages of synthesis of the cell wall

plasma (cytoplasmic) membrane

phospholipid bilayer that encloses the cytoplasm

• membrane proteins

  • peripheral proteins and integral proteins

• fluid mosaic model

  • proteins move freely for various functions

  • phospholipids rotate and move laterally

plasma membrane functions

• selective permeability allows passage of some molecules, but not others

  • site of electron transport chain (ETC) and ATP synthase

    • contains various components that can include different types of enzymes, pigments, and other molecules for respiration and ATP

    • performs photosynthesis in photosynthetic bacteria

damage to plasma membrane

damage → leakage of cell contents

• some disinfectants damage plasma membrane

  • alcohols & detergents

• some antibiotics damage plasma membrane

  • polymyxin

passive processes

substances move from high concentration to low concentration

• no energy expended

active processes

substances move from low concentration to high concentration; energy expended

simple diffusion

movement of solute from an area of high concentration to an area of low concentration

• continue until molecules reach equilibrium

facilitated diffusion

integral membrane proteins, known as transporters, serve as specific or nonspecific channels or carriers

• transports ions and larger molecules across a membrane down the concentration gradient

osmosis

the movement of water across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration

• through lipid bilayer by simple diffusion

• through aquaporins (water channels)

iso-tonic solution

solute concentrations equal inside and outside the cell

• water is at equilibrium

  • no net movement of water

hypotonic solution

solute concentration is lower outside than inside the cell

• water moves into the cell

hypertonic solution

solute concentration is higher outside of cell than inside

• water moves out of cell

active transport

requires a transporter protein and energy (ATP)

• goes against gradient

  • allows a cell to accumulate needed materials

• can move a variety of ions as well as amino acids and sugars against the gradient

group translocation

energy is expended to chemically modify substances and transport them across the membrane

• form of active transport

• energy is provided by high-energy compound phosphoenolpyruvate (PEP)

• one of mechanisms to transport glucose into the cell

bacterial efflux

pumps in the cell membrane actively expel harmful substances out of the cell

cytoplasm

thick, aqueous, elastic, semitransparent substance inside the plasma membrane

• 80% water plus proteins, carbohydrates, lipids, and ions

  • includes DNA, ribosomes, and inclusions

cytoskeleton

series of fibers in the cytoplasm which participate in

• cell division and growth

• maintaining cell shape

• DNA movement

  • no cytoplasmic streaming in bacteria

nucleoid

distinct region within a bacterial cell that contains chromosome

• site where DNA replication and transcription occur

bacterial chromosome

typically circular thread of double-stranded DNA that contains cell’s genetic information

• supercoiled and highly structured form

• not enclosed within a nuclear envelope (membrane)

  • no associated histones

plasmids

small circular DNA that separte from the chromosome

• not located in the nucleoid

• carry genes that may encode antibiotic resistance, production of toxins; noncrucial for survival

• replicate independently of chromosomal DNA

  • may be transferred to other bacteria

ribosomes

sites of protein synthesis

• size: 70s

  • made of 50S and 30s subunits

    • each subunit made of proteins and ribosomal RNA rRNA

  • ribosomal RNA used in PCR tests

inclusions

contain reserve deposits of certain nutrients

• phosphate granules (metachromatic granules can be used in lab identification)

• polysaccharide granules

• lipid inclusions

• sulfur granules

gas vacuoles

protein-covered cylinders that maintain buoyancy

carboxysomes

contain enzymes for CO₂ fixation during photosynthesis

magnetosomes

iron oxide inclusions that aid cell movement

endospores

resting cells; produced when environmental conditions are unfavorable

• e.g., when nutrients are depleted

• resistant to desiccation, heat, chemicals, and radiation

  • survive in a dormant state for a long time

  • a survival mechanism; not a reproductive process

• produced by genera: Bacillus and Clostridium

sporulation

process of endospore formation

germination

process an endospore returns to vegetative state