Microbiology & Parasitology Lecture M1

Microbiology

The study of microorganisms, a large and diverse group of microscopic organisms that exist as single cells or cell clusters

Robert Hooke

Reported that life’s smallest structural units were “cells,”

First to observe cells on cork

Cell Theory

States that all living things are composed of cells

Anton Van Leeuwenhoek

Father of Microbiology;

First to observe live microorganisms, called them “animalcules”

Spontaneous Generation

Abiogenesis

The belief that living organisms could arise from nonliving matter (abiogenesis)

Biogenesis

Concept that living cells arise only from preexisting cells

Francesco Redi

First experiment for Abiogenesis;

Performed experiment with meat and jars to refute spontaneous generation

John Needham

Claimed microorganisms arose spontaneously from heated broth

Vital Force

John Needham claimed this is needed for abiogenesis to occur

Lazzaro Spallanzani

Disproved Needham’s results, showed microbes came from air

Rudolf Virchow

Proposed biogenesis, stating cells arise from preexisting cells

Louis Pasteur

Disproved spontaneous generation using swan;

Coined the word vaccine; Turned a bacteria into a vaccine for fowl cholera

insert type of fermentation

Pasteurization

Heating process to kill bacteria in beverages and milk

Germ Theory of Disease

States that specific microorganisms cause specific diseases

Joseph Lister

Father of Antiseptic Surgery;

Introduced antiseptic surgery using phenol

Robert Koch

Proved microorganisms cause disease, developed Koch’s postulates

Koch’s Postulates

Criteria to establish that a specific microorganism causes a specific disease

Anthrax

Bacillus anthracis

Vaccination

Process of conferring immunity by inoculation with a vaccine

Edward Jenner

Developed smallpox vaccine using cowpox material; world’s first vaccine.

John Tyndall

Developed Tyndallization (fractional sterilization) to kill spores

Tyndallization

Fractional Sterilization;

allows the destruction of heat-resistant endospores through the introduction of a gap between treatments.

Ignaz Semmelweis

Introduced handwashing to prevent puerperal fever, Father of Handwashing

Chemotherapy

Treatment of disease using chemicals (synthetic drugs or antibiotics)

Paul Ehrlich

Developed Salvarsan for syphilis treatment

Alexander Fleming

Discovered penicillin

Howard Florey & Boris Chain

Purified penicillin for clinical use (antibiotic)

Rene Dubos

Discovered antibiotics tyrocidine and gramicidin

Rebecca Lancefield

proposed a classification system for streptococci based on certain components in the cell walls of bacteria,

Dmitri Iwanowski

Discovered viruses in tobacco plants

Wendell Stanley

Studied viral structure and chemistry

George Beadle & Edward Tatum

Demonstrated gene relationship with enzymes

Oswald Avery, Colin Macleod, Maclyn McCarty

Established DNA as hereditary material

Joshua Lederberg & Edward Tatum

Discovered bacterial conjugation

James Watson & Francis Crick

Proposed double helical structure and replication of the DNA.

Francois Jacob & Jacques Monod

Discovered mRNA and gene regulation

Paul Berg

Developed recombinant DNA technology

Microorganisms

Minute living things too small to be seen by the naked eye, including bacteria, fungi, protozoa, algae, and viruses

Bacteria

Unicellular, prokaryotic organisms with peptidoglycan cell walls, reproduce by binary fission

Archaea

Unicellular prokaryotes, distinct from bacteria in biochemistry and evolution

Fungi

Eukaryotic organisms (yeasts, molds, mushrooms) that absorb nutrients from the environment

Protozoa

Unicellular eukaryotes, classified by locomotion

Algae

Photosynthetic eukaryotes producing oxygen and carbohydrates

Viruses

Acellular, consist of nucleic acid (DNA or RNA) inside a protein coat, obligate intracellular parasites

Helminths

Multicellular parasitic worms, including flatworms and roundworms

Cocci

Spherical Bacteria

Bacilli

Rod shaped bacteria

Spirochetes

Spiral shaped bacteria

Spirillum

Bacteria that is spiral and has a flagella

Diplo

pair of bacteria

Streps

Chain of bacteria

Staph

Cluster or bacteria

Polysaccharide

An extracellular polymer covering the entire bacterium

EPS

Extracellular polymeric substance

Capsule

condensed, well-defined layer and excludes particles

Slime Layer

loosely associated with the cell and does not exclude particles

Biofilm

mixture of different microorganisms that are held together and protected by glue

Glycocalyx

Used as an antigen in certain vaccines

Flagella

Long, threadlike appendages that move the bacteria towards nutrients and other attractants

Chemotaxis

ability of bacteria to move in a particular direction in response to a chemical stimulus

Monotrichous

Single polar flagellum

Lophotrichous

Multiple polar flagellum

Amphitrichous

Single flagellum found at each of two opposite poles

Peritrichous

Multiple flagella distributed over the entire cell

Axial Filament

Unique structure found in spirochetes for their motility

Fimbriae and Pili

Rigid, shorter, hairlike filaments

Adhesins

located at the tips of pili and responsible for the attachment properties

Fimbriae

L “fringes”

Pili

L “hairs”

Ordinary pili

for motility, adherence of symbiotic and pathogenic bacteria to host cells

Sex pili

bacterial DNA transfer

Cell Wall

Provides rigid support and allows the cell to withstand media of low osmotic pressure

Peptidoglycan

Also known as murein and mucopeptid

Plasma (Cytoplasmic) Membrane

composed of a phospholipid bilayer that do not contain sterols.

Mesosome

It serves as the origin of the transverse septum that divides the cell in half.

GRAM- POSITIVE CELL WALL

Have a thicker peptidoglycan layer in their cell wall; has teichoic acids; lack an outer membrane; has polysaccharides; stain purple or blue in Gram staining; tend to be more susceptible to antibiotics due to absence of outer membrane

GRAM-NEGATIVE CELL WALL

Have a thinner peptidoglycan layer in their cell wall; no teichoic acids; have an outer membrane; contain lipopolysaccharides (LPS), porins, and periplasma; LPS (endotoxin) due to Lipid A; stain pink or red in Gram staining; generally more resistant to antibiotics due to presence of outer membrane

Mycoplasma

Cell wall lacking bacteria containing sterol membrane; hydrophilic

Mycobacterium

Contains mycolic acid; acid-fast microorganism; hydrophobic, waxy

Plasma (Cytoplasmic) Membrane

Composed of a phospholipid bilayer without sterols

Functions of Plasma Membrane

Selective permeability and solute transport; electron transport and oxidative phosphorylation; excretion of hydrolytic exoenzymes and pathogenicity proteins; synthesis of precursors of the cell wall; bearing of receptors and proteins for chemotaxis and sensory transduction

Mesosome

Invagination of the plasma membrane; plays a role in cell division; origin of transverse septum for cell division

Cytoplasm

Amorphous matrix with ribosomes, nutrient granules, metabolites, and plasmids; inner nucleoid region containing DNA

Nucleoid

Region in cytoplasm where DNA is located; Feulgen positive; no nuclear membrane or mitotic apparatus; circular; prokaryotic

Plasmid

Extrachromosomal, double-stranded circular DNA; replicates independently of bacterial chromosome; F plasmid for conjugation; R plasmid for antibiotic resistance

Ribosome

Site of protein synthesis; bacterial ribosomes are 70S (30S + 50S subunits); antibiotic targets include cell wall, ribosome, cell membrane, and nucleic acids

Granules

Storage areas for nutrients; common inclusion body is poly-beta

Transposon

Also called jumping genes; DNA pieces that move between bacterial DNA, plasmids, or bacteriophages

Endospores

Resting cells formed in adverse conditions; resistant to heat, dehydration, radiation, and chemicals (due to dipicolinic acid); formed by sporulation

Properties of Endospores: Core

Contains complete chromosome, protein-synthesizing apparatus, and energy

Properties of Endospores: Spore Wall

Innermost layer surrounding the inner spore membrane

Properties of Endospores: Cortex

Thickest layer of the spore envelope

Properties of Endospores: Coat

Keratin-like protein with many disulfide bonds

Properties of Endospores: Exosporium

Paracrystalline basal layer and hairlike outer region