Food Microbio Exam 1 flashcards

Ch 1: Intro and History

Microbiology

• Study of living organisms of microscopic size

  • Occurrence

  • Characteristics

  • Relationships

  • Control

  • Human health

  • Food and industrial technology

Microbes In Our Lives

• Some are pathogenic

• Decompose waste

• Producers in the ecosystem

• Produce fermented foods (cheese, beer, bread)

Branches of Microbiology

• Bacteriology

• Mycology

• Parasitology

• Immunology

• Virology

• rDNA technology

Classification of Microorganisms

• Three domains

  • Bacteria

    • Procaryotes

  • Archaea

    • Procaryotes

    • Lacking peptidoglycan

    • Extremophiles

  • Eukarya

    • Eucaryotes

History

• Ancestors of bacteria were first life on Earth

• First microbes observed in 1673

• 1665: Robert Hooke reported that living things were composed of little boxes, or cells; published Micrographia

• 1858: Rudolf Virchow said cells arise from preexisting cells

• Cell theory: all living things are composed of cells and come from preexisting cells

• 1673-1723

  • Anton van Leeuwenhoek: known as the “Father of Microbiology”

  • Described live microorganisms

Debate Over Spontaneous Generation

• Spontaneous Generation (Abiogenesis): The hypothesis that living organisms arise from nonliving matter; a “vital force” forms life

• Biogenesis: The hypothesis that living organisms arise form preexisting life

Theory of Biogenesis

• Louis Pasteur: father of Organic Chemistry: disproved the Spontaneous Generation theory

• S-Shaped flask kept microbes out but let air in

• Aseptic techniques: ways to avoid contamination in studies

• Aerobes: require oxygen to grow

• Anaerobes: do not need/want oxygen

• Pasteurization: heat without destroying the product; kills pathogens without affecting taste or color of milk

Germ Theory of Disease

• Joseph Lister used a chemical disinfectant to prevent surgical wound infections

• Robert Koch proved that a bacterium causes anthrax (bacillus anthracis) and provided the experimental steps, Koch’s Postulates, to prove that a specific microbe causes a specific disease

Vaccination/Immunization

• 1796: Edward Jenner inoculated a person with cowpox virus, who was then protected from smallpox

• Vaccination is derived from vacca, for cow

• The protection is called immunity

Chapter 2: Organic Chemistry Review

Chemical compounds

• All chemical compounds are either inorganic or organic

• Inorganic compounds typically lack carbon

• Organic compounds always have carbon and hydrogen

Biologically important organic building blocks

• Amino acids

• Fatty acids

• 5-carbon and 6-carbon sugars

• Nitrogenous bases

Amino acids

• Protein subunits

• structural , metabolic, energy functions

• Peptide bonds between amino acids are formed by dehydration synthesis

• Primary structure: polypeptide

• Complete Breakdown: Protein → proteose → peptone → polypeptides → peptides → amino acids → ammonia → nitrogen

Fatty Acids

• Lipid subunits

• Fats or triglycerides

• Contain glycerol and fatty acids; formed by dehydration synthesis

• Primary components of cell membranes

• Consist of C, H, and O

• Are nonpolar and insoluble in water

• Simple lipids

  • Saturated fat: no double bond

  • Unsaturated fat: one or more double bonds

• Complex lipids

  • Contain C, H, O,+ P, N, or S

  • Membranes are made of phospholipids

Monosaccharides

• Simple sugars with 3 to 7 carbon atoms

• 5 and 6-carbon monosaccharides are important in cell metabolism and structure

• Glucose: most abundant monosaccharide in nature; utilized by microbes as carbon and energy source

• Ribose and deoxyribose (5 carbon): present in RNA and DNA

• Modified monosaccharides (N-acetylglucosamine and N-acetylmuramic acid): found in bacterial cell wall

Carbohydrates

• Cell structures and energy sources, consist of C, H, O with the formula (CH2O)n

• Disaccharides are formed when 2 monosaccharides are joined in a dehydration synthesis; can be broken down by hydrolysis

• Oligosaccharides consist of 2 to 20 monosaccharides

• Polysaccharides consist of tens of hundreds of monosaccharides joined through dehydration synthesis

  • Starch, glycogen, dextran, and cellulose are polymers of glucose that are covalently bonded differently

  • Chitin in shrimps

Nitrogenous bases

• Nucleotide subunits: heterocyclic amines

• Pyrimidines: thymine and cytosine

• Purines: adenine and guanine

Nucleic acids

• Consists of nucleotides, which consist of:

  • Pentose, Phosphate group, Nitrogenous base (purine or pyrimidine)

DNA

• Deoxyribose nucleic acid

• Has deoxyribose

• Double helix

• A bonds w T

• C bonds w G

RNA

• Ribonucleic acid

• Has ribose

• Is single stranded

• A bonds w U

• C bonds w G

ATP

• Adenosine Triphosphate

• Has ribose, adenine, and 3 phosphate groups

Chapter 3: Observing Microbes

1 um = 10^-6 m = 10^-3 mm

1 nm = 10 ^-9m = 10^-6 mm

1000 nm = 1 um

.001 um = 1 nm

Light Microscopy

• Use any kind of microscope that uses visible light to observe specimens

• Types of light microscopy

  • Compound light

  • Darkfield

  • Phase-contrast

  • Differential interference contrast

Compound light microscope

• Image from objective lens is magnified by ocular lens

• Total magnification = objective lens x ocular lens

Compound light microscopy

• Resolution: the ability of the lens to distinguish two points

  • Shorter wavelengths of light provide greater resolution

• Refractive index: a measure of the light-bending ability of a medium

  • Immersion oil is used to keep light from bending

• d (resolution) = lenda (wavelength) / 2NA (numerical aperture) 

• 100x objective lens is also known as oil immersion lens

• 40x objective lens is also known as high dry lens

Differential interference contrast microscopy

• Accentuates differentiation of the light with two beams

Fluorescence Microscopy

• Uses UV light

• Fluorescent substances absorb UV light and emit visible light

• Cells may be stained with fluorescent dyes (fluorochromes)

Confocal microscopy

• Cells strained with fluorochrome dyes

• Short wavelength blue light used to excite the dyes

• The light illuminates each plane in a specimen to produce a 3D image

  • Up to 100 um deep

Electron microscopy

• Uses electrons instead of light

• The shorter wavelength of electrons gives greater resolution

Transmission (TEM) vs Scanning (SEM)

• At top of microscope there is an electron gun 

• Special condenser and objective lens that are electromagnetic needed

• Transmission used to study cell structure

  • Stained with heavy metals (lead, uranium) to allow electrons to be absorbed by the section of specimen

• Scanning: when electron beams hit specimen, they will scatter and are collected by an electron collector, form an amplified image, and puts it on a viewing screen (no eyepiece)

  • Used to study cells from the outside (the surface); stained with gold or palladium

Preparation of Specimens for Light Microscopy

• Unstained cells have little contrast with the surrounding medium and are hard to observe

• Smear: a thin film of a solution of microbes on a slide

  • A smear is usually fixed to attach the microbes to the slide and to kill the microbes

• Staining: coloring the microbe with a dye that emphasizes certain structures

Specimen Preparation

• Suspension in liquid

  • Wet mount

  • Hanging drop

• Fixed and stained smears

Motility

• The ability of microbes to move

Brownian movement

• Friction of live cells

Stain

• Stains consist of a positive and a negative ion

• In a basic dye, the chromophore is a cation (positive)

• In an acidic dye, the chromophore is an anion (negative)

• Bacterial cells are typically negatively charged

• Staining the background instead of the cell is called negative staining

Simple stains

• Use of a single basic dye

• A mordant may be used to hold the stain or coat the specimen to enlarge it

Differential stains

• Used to distinguish between bacteria

  • Gram stain

  • Acid-fast stain

Special stains

• Used to distinguish parts of cells

  • Capsule stain

  • Endospore stain

  • Flagella stain

Chapter 4: Cells

Bacterial Cells

• Average size of .2-1.0 um x 2-8 um

• Most bacteria are monomorphic

• A few are pleomorphic

Basic shapes of cells

• Bacillus (rod shaped)

  • Vibrio

• Coccus (spherical)

• Spiral

  • Spirillum

  • Spirochete

Cell arrangements

• Pairs: diplococci, diplobacilli

• Clusters: staphylococci

• Chains: streptococci, streptobacilli

Unusually shaped bacteria

• Star shaped

• Rectangular bacteria

Structure of a prokaryotic cell

Glycocalyx

• Outside cell wall

• Usually sticky

• Capsule: neatly organized

• Slime layer: unorganized and loose

• Extracellular polysaccharide allows cell to attach

• Capsules prevent phagocytosis

Flagella

• Outside cell wall

• Made of chains of flagellin

• Attached to a protein hook

• Anchored to the wall and membrane by the basal body

• Flagella arrangements

  • Peritrichous

  • Monotrichous and polar

  • Lophotrichous and polar

  • Amphitrichous and polar

Fimbriae and pili

• Fimbriae allow for attachment

• Pilli

  • Facilitate transfer of DNA from one cell to another

  • Gliding motility

  • Twitching motility

Cell Wall

Peptidoglycan

• Polymer of disaccharide

  • N-acetylglucosamine (NAG)

  • N-acetylmuramic acid (NAM)

• Linked by polypeptides in gram-positive bacteria

Gram positive bacterial cell wall

• Teichoic acids

  • Lipoteichoic acid links to plasma membrane

  • Wall teichoic acid links to peptidoglycan

• May regulate movement of cations

• Polysaccharides provide antigenic variation

Gram negative cell wall- outer membrane

• Lipopolysaccharides, lipoproteins, phospholipids

• O polysaccharide antigen

• Lipid A is an endotoxin

• Porins (proteins) form channels through membrane

Cell wall comparison

• Gram positive

  • Thick peptidoglycan

  • Teichoic acids

• Gram negative

  • Thin peptidoglycan

  • Outer membrane

  • Periplasmic space

Gram stain

• Positive: purple

• Negative: Pink/Red

Gram stain mechanism

• Crystal violet iodine crystals form in cell

• Gram positive

  • Alcohol dehydrates peptidoglycan, decreasing pore size and permeability

  • CV-I crystals trapped, further decreasing the pores in the peptidoglycan

• Gram Negative

  • Alcohol dissolves outer membrane and leaves holes in peptidoglycan

  • Less peptidoglycan so pores remain large even after alcohol step

  • CV-I washes out

Damage to cell wall

• Lysozyme digests disaccharide in peptidoglycan

• Penicillin inhibits peptide bridges in peptidoglycan

• Protoplast is a wall-less cell

• Spheroplast is a wall-less (some remnants remain) gram negative cell

  • Protoplasts and spheroplasts are susceptible to osmotic lysis

Plasma or Cell Membrane

• Phospholipid bilayer

• Peripheral proteins, integral proteins

• Membrane is viscous as olive oil

• Proteins move to function

• Phospholipids rotate and move laterally

• Selective permeability allows passage of some molecules

• Enzymes for ATP production

• Damage to the membrane by alcohols, quaternary ammonium (detergents), and polymyxin antibiotics cause leakage of cell contents

Movement of materials across membranes

• Simple diffusion: movement of a solute from an area of high concentration to an area of low concentration

• Facilitated diffusion

  • Solute combines with a transporter protein in the membrane

• Osmosis

  • The movement of water across a selectively permeable membrane from an area of high to low concentration

  • Osmotic pressure: The pressure needed to stop the movement of water across the membrane

• Principles of osmosis

  • Isotonic: no movement of water

  • Hypotonic: water moves into cell; causes lysis (burst)

  • Hypertonic: water moves out of cell; causes plasmolysis (shrink)

• Active Transport: requires a transporter and ATP

• Group Translocation: requires a transporter protein and PEP

Cytoplasm

• The substance inside the plasma membrane

  • Chromosome

  • Ribosomes

  • Plasmids

  • Inclusion bodies

The Prokaryotic Ribosome

• Site of protein synthesis

• 70S: 50S + 30S subunits

Inclusion bodies

• “Storage molecules”

Endospores

• Resting cells

• Resistant to desiccation, heat, chemicals

• Bacillus, Clostridium

• Sporulation: Endospore formation

• Germination: return to vegetative states

Spore coat: dipicolinic acid-calcium-peptidoglycan complex