Bio 265 lecture

Suggested

Textbook

Antoni van Leeuwenhoek-Dutch

The Early Years of Microbiology - Late 1600s

Reproduction of Leeuwenhoek’s microscope

Specimen holder Lens Antoni van

Leeuwenhoek

Changed the way

we see our world

Began making and

using microscopes

Examined water

and observed tiny

“animalcules”

The Early Years of Microbiology

By the end of the 19th century, “animalcules” were called

microorganisms (microbes)

The Debate over Spontaneous Generation

Spontaneous generation: The hypothesis that living

organisms arise from nonliving matter

Biogenesis: The hypothesis that living organisms arise

from preexisting life

mid-1800s

Louis Pasteur

conducted experiments

that demonstrated the

theory of biogenesis

The Golden Age of Microbiology

Steam escapes from open end of flask.

Infusion is heated.

Infusion sits; no microbes appear.

Months

Air moves in and out of flask.

Infusion remains sterile indefinitely.

Dust from air settles in bend.

When the “swan-necked” flasks remained upright, no microbial

growth appeared

When the flasks were tilted and the liquid touched the dust in their

necks, these flasks became cloudy with microbes

Pasteur’s Experiments

The Golden Age of Microbiology

The Germ Theory of Disease

Late 1800s

Robert Koch proved that a

bacterium caused anthrax

Provided the experimental

steps, known as “Koch’s

postulates”

To demonstrate that a specific

microbe causes a specific

disease

The Golden Age of Microbiology

The Golden Age of Microbiology

Koch’s Postulates

“Suspected causative agent” must be found in every case of the disease and be absent from healthy hosts

“Agent” must be isolated and grown outside the host

When the “agent” is introduced into a healthy host, the host must get the disease

Same “agent” must be found in the diseased experimental host

Koch isolated rod-shaped

bacteria (Bacillus anthracis)

in the blood of cattle that had

died of anthrax

Isolation of bacteria on solid media and the concept of

pure culture

Bacterium 1

Bacterium 2

Bacterium 3

Bacterium 4

Bacterium 5

Bacterium 6 Bacterium 7

Bacterium 8

Bacterium 9

Bacterium 10

Bacterium 11

Bacterium 12

Koch received the Nobel prize in 1905 after his publications on

the cause of tuberculosis – Mycobacterium tuberculosis

The Golden Age of Microbiology

Gram’s Stain – 1884

Danish scientist Hans Christian Gram developed a staining technique

Involves the applications of a series of dyes

Some microbes are left purple, called Gram-positive

Other microbes are left pink, called Gram-negative

Gram staining

What are the organisms

studied by microbiologists?

Prokaryotes Bacteria Archaea

Eukaryotes

Fungi Protozoa Algae Helminths

Eukaryotic-human cheek cells

Prokaryotic-bacterial cells

Viruses (too small to be seen with a simple microscope!)

Unicellular organisms

Lack a nucleus

Reproduce asexually

Include:

Bacteria*

Cell walls contain peptidoglycan

Archaea

Cell walls lack peptidoglycan

Often found in extreme environments

Not known to cause disease in humans

Prokaryotes: Bacteria and Archaea

Haemophilus influenzae

Prokaryotes - Bacteria

Proteus vulgaris

Vibrio cholerae

Staphylococcus aureus

Prokaryotes - Bacteria

Escherichia coli

Borrelia burgdorferi

Streptococcus pneumoniae

Eukaryotic (have membrane-bound nucleus)

Obtain food from other organisms

Possess cell walls

Molds are multicellular, grow as long filaments, and reproduce by sexual and asexual spores

Yeasts are unicellular, reproduce by budding, fission, or sexual spores

Fungi

Penicillium chrysogenum Saccharomyces cerevisiae

The discovery of antibiotics - 1929

Alexander Fleming

discovered the first

antibiotic

He observed that

Penicillium fungus made

an antibiotic (penicillin)

that killed S. aureus

Penicillin was tested

clinically and mass

produced

Effects of penicillin on a bacterial “lawn” in a petri

dish

Fungus colony (Penicillium)

Zone of inhibition

Bacterial colonies (Staphylococcus)

Disc impregnated with antibiotics are placed onto inoculated

plates

The clear zone around a disc indicates that bacterial growth

has been affected (bacterial cell are inhibited or killed)

Understanding the role of antibiotics

You will learn more

about this method

in the lab

Single-celled eukaryotes

Similar to animals in nutrient needs and cellular structure

Live freely in water; some live in animal hosts as parasites

Asexual (most) and sexual reproduction

Capable of locomotion by

Pseudopodia

Cilia

Flagella

Protozoa

Trypanosoma gambiense

Giardia lamblia

Protozoa

Parasitic worms

Taenia: tapeworm

Most of these worms are not

microscopic as adult

Microscopic eggs and immature

stages can be found in blood, fecal,

and urine samples

Ascaris lumbricoides

Viruses infecting a

bacterial cell

Viruses

Viruses are acellular parasites

Replicate only when they are

within a living host cell

Can be seen with an electron

microscope (1932)

Can infect

plants

animals (human body included)

bacteria (bacteriophages)

The system of nomenclature for organisms currently in use

was established by C. Linnaeus, Swedish botanist, ~ 1753

Organisms have Latin names

Binomial nomenclature assigns each organism two names

Genus (genera) is the first name and it is capitalized

Species name follows and it is not capitalized

Both names are italicized (italics)

Esherichia coli

E. coli

Nomenclature (binomial nomenclature)

Principles of Taxonomy

Organisms are grouped into a series of categories (taxa) that make up the taxonomic hierarchy:

A particular species belongs to a given genus, family, order,

class, phylum, … domain

Domain Kingdom Phylum Class Order Family Genus Species

Taxonomic levels of the bacterium Shigella

The three Domains of life - based on comparative analysis

of the nucleotide sequences of ribosomal RNA (rRNA)

The domain bacteria includes all of the pathogenic prokaryotes

3.5 billion years ago

How do we distinguish and identify

different bacteria (prokaryotes)?

Using Phenotype to Identify Prokaryotes

Colony morphology/appearance

Red pigment of Serratia marcescens

“Fried egg” appearance

of Mycoplasma colonies

Microscopic analysis

Important initial step in the process of identification

Size

Shape (morphology)

Staining characteristics

Gram stain differentiate Gram positive/negative

Acid-fast stain

Special stains

Presence/absence of certain cell structures such

as flagella and endospores

Using Phenotype to Identify Prokaryotes

Sputum

Male urethra

secretions

Culture characteristics

Escherichia coli

EMB medium

MacConkey

Haemophilus influenzae

Culture characteristics

Chocolate agar plate

Staphylococcus aureus Culture characteristics

MSA medium

Using Phenotype

to Identify Prokaryotes

Biochemical tests

Laboratory technicians

use biochemical tests to identify pathogens

Tests rely on pH

Indicators/addition of reagents ….

Commercial

biochemical tests allow for series of tests with a single inoculation

Serology

Based on specific interaction between antibodies/surface

molecules, allows for rapid detection of numerous organisms

Using Phenotype to Identify Prokaryotes

Streptococcus pyogenes

is the causative agent of

strep throat

Target molecules are

carbohydrates of the cell

wall

Agglutination test-overview

5 volumes

CASE STUDIES FROM DAILY LIFE

The following case studies illustrate how microbiology is part

of our everyday lives:

Special Delivery

Ivan Goes to Chicago

Hamburger Havoc…..

The Hospital Can Be Dangerous!

Did You Wash Your Hands?

Special Delivery (2001)

Letters contaminated

with a fine white

powder

Spores of Bacillus

anthracis

Gram stain of B. anthracis

Cause inhalation anthrax – A form of

pneumonia that can lead to respiratory

failure and death

B. anthracis is a potential weapon of

bioterrorism

Ivan Goes to Chicago

Ivan has contracted multi-drug

resistant tuberculosis

(Mycobacterium tuberculosis)

He travels from Russia - through

NY (JFK) - to Chicago

On the plane he experiences severe

coughing spasms because he has

active disease

Acid fast stain of

Mycobacterium

He goes to the

county hospital for

treatment

In the waiting room

he begins to cough

He is expelling

infectious

M. tuberculosis

In the hospital people may be debilitated from being ill or

immunocompromised

Ivan Goes to Chicago

Hamburger Havoc…

You bring your daughter to her

favourite hamburger restaurant

Your daughter experiences:

diarrhea

vomit

severe abdominal cramping

her stool has blood in it

The doctor finds her anemic and in renal failure (she is put on

dialysis)

The child has been infected by enterohemorrhagic bacteria called

Escherichia coli found in improperly processed ground meat

Escherichia coli

The hospital can be dangerous!

Uncle Harry went to the hospital for a hip operation

The operation went well but when you go to the hospital to bring

uncle Harry home

You find that he has been

transferred to intensive care in a

room with a sign outside that

reads: MRSA Authorized

Personnel Only

Uncle Harry has contracted a

nosocomial infection (hospital-

acquired) and dies few days later S. aureus is associated with

nosocomial pneumonia

MRSA:

Methicillin-resistant

Staphylococcus

aureus

VRSA:

Vancomycin-resistant

Staphylococcus

aureus

Thousands of people die each year in US from nosocomial infections

(increase in antibiotic resistance among bacteria)

Intensive care

The hospital can be dangerous

Did You Wash Your Hands?

1800s, an hospital in Vienna, in which thousands of children

were born each year

Puerperal fever (childbed fever) caused by b-hemolytic

streptococcus killed hundreds of mothers each year

In the wing where these deaths were most prevalent, only

doctors and medical students delivered babies

The battle of Dr. I. Semmelweis

Dr I. Semmelweis figured out that

doctors and medical students had directly moved from performing

autopsies to the delivery room without properly washing their

hands

SEM - Chains of streptococci

Did You Wash Your Hands?

When they began to wash

their hands thoroughly with

chlorinated lime water

The number of deaths

caused by this infection

dropped to about 1%

Why is microbiology relevant to health care?

Infectious disease accounts for a large percentage of health

care

New diseases are appearing (emerging diseases)

Diseases we thought were eradicated are reappearing (re-

emerging diseases)

Resistance to antibiotics that were effective is increasing

The potential for bioterrorism has become fact

Not all microorganisms are pathogens!

Only a tiny fraction of microorganisms (bacteria, viruses,

fungi, parasites) out of thousands of species cause disease

Many bacteria and some fungi are part of the normal

microbiota of our body, which colonize skin and mucosal

surfaces

Most of the time these organisms are harmless and in some

cases they provide us with benefits

We use microbes to produce antibiotics, food, beverages (beer

and wine)!