unit 1 test

Binary Fission

Cell division where one parent cell splits into two equal daughter cells.

Budding

Cell division where the parent cell divides asymmetrically. Example: Hyphomicrobium.

Exponential Growth

The growth rate, or rate of increase in cell numbers or biomass, is proportional to the population size at a given time.

Nt= N0 x 2n

Nt= total number of cells, N0 = original number of cells, n= number of rounds of binary fission

Lag phase

Bacteria are preparing their cell machinery for growth

Log phase

Growth approximates an exponential curve (straight line, on a logarithmic scale)

Stationary Phase

Cells stop growing and shut down their growth machinery while turning on stress responses to help retain viability

Death phase

Cells die with a 'half-life' similar to that of radioactive decay, a negative exponential curve

Lag phase characteristics

Metabolically active, but no increase in number of cells occurs, cells are adapting and inducing necessary enzymes and length varies with species and conditions

Exponential (log) Phase characteristics

Population doubles each generation, primary metabolites are synthesized and all cellular constituents made at constant rates. Cells are most susceptible to antibiotics.

Primary metabolites

Made during exponential growth; examples include amino acids, nucleic acids and simple lipids

Stationary Phase characteristics

Growth curve horizontal, population growth ceases, new cells made at same rate as old cells die (growth rate = death rate), secondary metabolites are made at beginning

Death phase characteristics

Exponential, 99% of population dies, prolonged decline – 1% population mutates according to environment

Secondary metabolites

Antibiotics

Continuous Culture

All cells achieve a steady state, which allows detailed study of bacterial physiology.

Chemostat

Ensures logarithmic growth by constantly adding and removing equal amounts of culture media

Millimeter (mm)

Unit of measurement equal to 10^-3 meters.

Micrometer (µm)

Unit of measurement equal to 10^-6 meters.

Nanometer (nm)

Unit of measurement equal to 10^-9 meters.

Microbes

Organisms and acellular agents too small to be seen by the unaided eye.

Robert Hooke

First to build a compound microscope and coined the term 'cell'.

Antonie van Leeuwenhoek

First to observe single-celled microbes with single-lens magnifiers, calling them “small animals.”

Spontaneous Generation

The discredited theory that living organisms could arise from non-living matter.

Francesco Redi

Scientist who demonstrated that flies do not spontaneously generate from decaying meat.

Lazzaro Spallanzani

Scientist who showed that boiled broth would only become cloudy with microbes if exposed to the air.

Louis Pasteur

Scientist who definitively disproved spontaneous generation with his swan-necked flask experiment.

Germ Theory

The theory that many diseases are caused by microbes.

Chain of Infection

Transmission of a microbe to cause disease.

Pure Culture

A culture containing only a single type of microbe.

Colonies (microbial)

Distinct populations of microbes grown from a single cell.

Robert Koch

Developed postulates to establish a link between a specific microbe and a disease.

Koch's 1st Postulate

First postulate: Microbe must be present in every case of the disease and absent from healthy organisms.

Koch's 2nd Postulate

Second Postulate: Microbe must be isolated and grown in pure culture.

Koch's 3rd Postulate

Third Postulate: The same disease must result when the isolated microorganism is inoculated into a healthy host.

Koch's 4th Postulate

Fourth Postulate: The same microorganism must be isolated from the second diseased host.

Helicobacter pylori

The bacterium suspected to cause stomach ulcers, later confirmed by Barry Marshall.

Edward Jenner

Deliberately infected patients with matter from cowpox.

Florence Nightingale

First to use medical statistics to demonstrate the significance of mortality due to disease.

Ignaz Semmelweis

Ordered doctors to wash their hands with chlorine, an antiseptic agent, to reduce mortality rates.

Joseph Lister

Developed carbolic acid to treat wounds and clean surgical instruments.

Alexander Fleming

Discovered that Penicillium mold generated a substance (penicillin) that kills bacteria.

Howard Florey and Ernst Chain

Purified penicillin, leading to the first commercial antibiotic.

Sergei Winogradsky

Among the first to study microbes in natural habitats, discovering lithotrophs and developing enrichment cultures.

Lithotrophs

Microbes that obtain energy from inorganic compounds.

Resolution

The ability to distinguish small objects close together.

Magnification

An enlarged image of an object.

Contrast

The difference in color intensity between an object and its background.

Compound microscope

Microscope where the image is formed from more than 2 lenses.

Condenser

Collects and directs lights in a bright-field microscope.

Refraction

Bending of light as it passes through an object that slows its speed.

Dark-field optics

Enable microbes to be visualized as halos of bright light against darkness. Light shines at an oblique angle. Only light scattered by the sample reaches objective.

Fluorescence microscopy

For specimens with added dye, or naturally photosynthetic microbes; Shows bright colored (fluorescent) image of the object, protein, or structure.

Fluorophores

Chemical compounds that absorb/emit light of specific wavelengths. Can be a dye or protein.

Electron Microscopy (EM)

Microscopy in which electrons are used instead of a light beam.

Specimen Staining

Adding a stain/dye to the microbe itself to Increase visibility, preserve sample, and highlight morphological features.

Fixation

Internal and external structures preserved in position.

Basic Dyes

Dyes with a positive charge that bind to negatively charged molecules (Nucleic Acid, Surface of Bacteria).

Acidic Dyes

Dyes with a negative charge and bind to positively charged molecules, used often for cellular structures or background.

Simple Stains

Color added to cells but not background.

Differential Staining

Stains one kind of cell but not another.

Gram Stain

Distinguishes bacteria based on cell-wall properties into two groups: Gram-positive (or) Gram-negative.

Peptidoglycan

Rigid structure that lies just outside the plasma membrane; composed of sugars/amino acids.

Iodine

Traps Crystal Violet in Gram + bacteria cell walls; Mordant used Gram Staining.

Bacteria

Single celled microorganisms with peptidoglycan cell walls and lacking a membrane-bound nucleus, found in various environments.

Pili

Long, thick structures (1-2 per cell) involved in DNA transfer (sex pili) and motility.

Fimbriae

Short, thin, hairlike structures (up to 1000 per cell) evenly distributed or at the poles, primarily for attachment.

Capsule (Glycocalyx)

Outer layer composed of polysaccharides, aiding in adherence to surfaces and resistance to phagocytosis.

Flagellum

External helical filament with a rotary motor that propels the cell, used for swimming and swarming motility.

Cell Membrane

Defines the existence of a cell; consists of a phospholipid bilayer with proteins.

Hopanoids

Reinforcing agents in bacterial membranes, similar to sterols in eukaryotic membranes.

Membrane Proteins

Contribute to structural support, detection of environmental signals, secretion of virulence factors, communication signals, ion transport, and energy storage.

S-Layer (Surface Layer)

Crystalline layer of thick subunits, either protein or glycoprotein, found in many Gram-positive and Gram-negative bacteria and archaea; contributes to cell shape and protects against osmotic stress.

Nucleoid

Region in prokaryotic cells where DNA is organized into loops or domains, supercoiled by DNA-binding proteins.

Plasmids

Circular DNA strands that replicate independently, often carrying unique genes such as antibiotic resistance.

Cell Wall (Sacculus)

Confers shape and rigidity to the cell and protects the cell membrane.

Mycoplasmas

Prokaryotes that have a cell membrane with no cell wall.

Glycan

A disaccharide unit that has an attached peptide of four to six amino acids.

Peptidoglycan Structure (Murein)

Meshlike polymer of identical subunits forming long strands, consisting of two alternating sugars: N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), and amino acids.

Peptidoglycan

Unique to bacteria, and the enzymes responsible for its biosynthesis make excellent targets for antibiotics.

Penicillin

Targets transpeptidase, the enzyme that cross-links the amino acids in peptidoglycan.

Firmicutes

Gram-positive bacteria that have multiple layers of peptidoglycan threaded by teichoic acids.

Teichoic Acid

Glycerol or ribitol phosphodiester chains that are negatively charged cross-threads that help retain basic dyes.

Proteobacteria

Gram-negative bacteria that have thin layers of peptidoglycan and an outer membrane.

Lipopolysaccharides (LPS)

In outer membrane act as endotoxin; when released, overstimulates immune cells, causing a cytokine storm.

Porins

Allow the passage of nutrients and are also the site of antibiotic entry in the outer membrane of Gram-negative bacteria.

Genus Mycobacterium

Contain mycolic acids (fatty acids) linked to arabinogalactan (a polysaccharide) linked to peptidoglycan.

Genus Mycoplasma

Lack cell walls and are pleomorphic. Cannot synthesize peptidoglycan. Sterols may stabilize plasma membrane; smallest bacteria capable of self-reproduction.

Mycoplasma gallisepticum

Chronic respiratory disease in chickens.

Mycoplasma pneumoniae

Primary atypical pneumonia in humans, also known as 'Walking pneumonia'.

Essential Nutrients

Nutrients a microbe cannot make for itself, but must gather from its environment.

Macronutrients

Nutrients needed in large quantities (Carbon, Magnesium, Nitrogen, Iron, Phosphorus, Potassium, Hydrogen, Calcium, Oxygen, Sulfur)

Micronutrients

Nutrients needed in small quantities (Cobalt, Copper, Manganese, Molybdenum, Nickel, Zinc)

Enriched media

Complex media to which specific blood components are added.

Selective media

Media that favor the growth of one organism over another.

Differential media

Media that exploit differences between two species that grow equally well.

Rickettsia Prowazekii

Agent of Typhus Fever, endemic in flying squirrels, spread through arthropods (lice feces), only grows in eukaryotic cytoplasm.

Heterotrophs

Rely on other organisms for carbon.

Autotrophs

Can reduce CO2 for carbon.

Phototrophy

Energy triggered by light.

Chemotrophy

Energy from oxidation-reduction reactions.