Principles of Microbiology
Biological and
Physical Sciences
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Objective
Identify the basics facts of microbiology in
relation to Preventive Medicine
2
Overview
Definition
Cells
Groups of Microorganisms
Microbial Growth
Role of Microorganisms
Disease Process
3
Microbiology Definition

Study of very small living
organisms.
 Too small to be seen unaided
 Need a light microscope or
an electron microscope to see
them
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Microbiology Definition
Size comparison
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Cells
Smallest
unit of living matter
capable
of independent life
self-reproduction
Contains
DNA and RNA
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Types of Cells – Simple Cells
 No
nucleus/specialized organelles
 Genetic
 Cell
material on single circular chromosome
wall is usually present
 chemically
complex
 gives cell shape
 has staining characteristics
 Size
ranges (1-10 um in diameter)
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Types of Cells-Complex Cells

Highly organized
Specialized membrane
bound
 Defined nucleus



Genetic informationlinear chromosomes
Cell wall
May or may not be
present
 Chemically simple when
present


If present - Size range
(10-100 um in diameter)
Groups of Microorganisms
Simple - Bacteria
 Size--0.20-2.0
um in diameter, 2-8 um in length
 Three basic shapes--coccus, bacillus, spiral
Coccus (round)
Bacillus (rod)
Spiral
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Simple - Bacteria
Shapes
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Simple - Bacteria
 Staining
characteristics--stains cell
wall
Positive
= purple = thick cell wall
Negative = red/colorless = thin
cell wall
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Simple - Bacteria
Staining characteristics
 Provides
information for treatment
different antibiotic therapies for gram positive vs.
gram negative bacteria

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Antibiotics
 Substance
that kill bacteria

Many man-made

Most interfere with
cell wall formation

Adaptation “mutations”
by bacteria results in
resistance
Testing antibiotics
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Endospores
 Bacterial
resting structures--survival mode
 Produced

under adverse environmental conditions
High temperatures, no water, and toxic chemicals
 Can
remain dormant for years
 Important in food and medical care industries
 resist
normal processes used to kill bacteria
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Examples of Bacteria
 Tuberculosis--Mycobacterium
 Sexually
tuberculosis
Transmitted Diseases

Neisseria gonorrhea -- Gonorrhea
 Chlamydia trachomatis -- Chlamydia
 Treponema pallidum -- Syphilis
M. Tuberculosis
colonies
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Viruses
 Simple

noncellular entities (parasite)
Cannot reproduce by self (alone)
Polio Virus

Can’t metabolize energy or proteins

Parasite--organism that derives its nutrients
from a living host without providing any benefit in return

Consist of either DNA or RNA--not both

Core surrounded by a protein coat (capsid)
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Viruses
 Size

range (20-300 nanometers)
Smallest microorganisms
 Multiply

in cells of particular species
Infect animals, plants, and bacteria
 May
or may not have an envelope
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Viruses
Virus attaches to host cell
Releases genetic instructions
Into host cell
Recruits host cell’s enzymes
Assemble into new viruses
New viruses break free of
host cell
Viruses
 Characterized

by shape
Helical, Polyhedral, Spherical, and Complex
Helical (coiled tubes)
Polyhedral (many sided)
Complex (combination)
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Examples of Viral Diseases
 Influenza--Respiratory
Infection
 HIV--Bloodborne and Sexually Transmitted
 Hepatitis B--Hepatic (Liver) Infection
Influenza Virus
HIV
Hepatitis B Virus
Budding out of a human immune cell
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Complex Microorganisms
- Fungi
 Unicellular
(yeasts) or multicellular (mushrooms)
 Plantlike, but cannot photosynthesize
 Absorb nutrients from environment
 Decompose organic material
 Some are parasites of plants and animals
 Examples
 Yeasts
 Molds
Penicillin mold
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Harmful Effects of Fungi
Economic Effects

Molds cause spoilage--fruits, vegetables, grains
 Cause diseases in plants--wheat, potatoes, elms
Diseases Caused by Fungi

Infections of hair, skin, and internal organs
 Foodborne illnesses (rare)--aflatoxins in peanuts
Ringworm
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Harmful Effects of Fungi
Diseases Caused by Fungi
Fungal foot
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Complex Microorganisms Protozoa
 Found
in soil, water, intestinal tracts of animals
 Size range (3-100 um)
 Unicellular
 Classified
animals
by means of movement
 Flagellates--long,
whiplike extensions
 Ciliates--shorter hairlike extensions
 Pseudopodia--blunt, lobe-like projections
 Some
are incapable of movement--must be
carried/transported--plasmodium causes malaria
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Protozoa
 Cysts
are produced under adverse conditions
for survival outside a host
 Lack
of nutrients, water, and oxygen
 Temperatures aren’t suitable
 Presence
of certain toxic chemicals
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Protozoal Diseases
Amoebic
Dysentery
•Amoebae
feeds on red blood
cells
•Human-to-human transmission
through cysts passed through
feces to mouth (ingestion)

Giardiasis
•Parasite
found in small intestine
of mammals
•Cyst can survive in environment
until ingested
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Protozoal Diseases
 Malaria--Plasmodium
vivax
 Complex
life cycle
 Involves red blood cells, liver of humans, and
intestinal tract of female mosquitoes
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Complex Microorganisms
- Algae
 Pigmented
plants
 Unicellular
or multi-cellular
 Photosynthesize--converts CO2 to O2
 Mostly aquatic
 Prefer lots of light (radiant energy)
 Example:
Red Tides (Red Algae Gonyaulax)
 Produce
toxin that causes paralytic shellfish
poisoning
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Microbial Growth
Physical Requirements
 Physical Aspects
Light, temperature, and pH
May be less stringent for survival vs.
growth
 Chemical
Aspects
Water, carbon, oxygen, and other
minerals
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Physical - Light
Light-Energy Source
 Photosynthesis
 Light
used as an energy source
 Exposure
to direct sunlight can kill
 UV light used on TB bacteria
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Physical - Temperature
Based on preferred range
 Mesophiles (moderate loving microbes)
200- 400 C/680 – 1040F
Most pathogens
 Thermophiles (heat loving microbes)
Above 450C/1130F
spoilage organisms
 Psychrophiles (cold loving microbes)
00- 200C/30 - 680F
Spoilage in refrigeration
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Physical – pH level
pH--refers to alkalinity or acidity in solution
 Best
growth in pH 6.5 - 7.5 (neutral range)
 Few grow in acid pH below 4.0
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Chemical - Water
Water--microorganisms are 80-90% water
 Hydrophilic--need
lots of moisture for growth
 Hydrophobic--grow
best with little water
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Chemical - Carbon
Carbon

Some microorganisms
rely on carbon dioxide
as source of carbon

Other microorganisms
use organic material as
source of carbon
Chemical - Oxygen

Aerobic--need oxygen to
live
 Anaerobic--live without
oxygen
 Facultative--anaerobes
that survive with
or without oxygen
 Obligate anaerobesdie when exposed to
oxygen
Control of Microbial Growth
Bacteria grow FAST!
• In ideal circumstances, some common
bacterial cells can divide and double every 20
minutes
Control of Microbial Growth
 Physical
 Heat,
cold, drying, and radiation
 Chemical
 Destroy
Methods
or limit growth on body surfaces
 Sterilization
 Destruction
of all microorganisms
 Both physical and chemical control
 Radiation
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Physical Methods - Heat
Most practical, efficient and inexpensive
Time and temperature
Types
Boiling (1000C) - kills most cells and viruses
within 10 minutes
Pasteurization – high temperature/short time
Autoclaving – steam under pressure
Dry Heat – direct flame, incineration
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Physical Methods - Cold
Refrigeration (00-70C)--inhibits growth
Slows most microbial growth
But may Not Kill them
Freezing--No growth or reproduction, but
may still survive!
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Physical Methods - Drying
 Without
water, cannot grow, but may live
 Curing--High
concentration of salt and sugar
results in loss of water (dehydration)
 Freeze
drying--removes water by high vacuum
at low temperatures
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Physical Methods - Radiation
 Non-ionizing
radiation--low penetration
used on surfaces / in the air (UV light)
 Ionizing
radiation
 Sterilize
pharmaceuticals, and
medical/dental instruments
 Used in foods (generally not
accepted by public)
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Chemical Methods
of Control

Disinfection--process that
destroys, neutralizes, or inhibits
pathogenic organisms

Disinfectant--chemical agent
used on inanimate objects to
destroy pathogens, but not
necessarily viruses or
endospores

Few chemicals
achieve sterility
Staphylococcus
aureus
Antiseptic--chemical agents
used on living tissue

Sanitation – reduce to safe
levels
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Chemical Methods - Types
Halogens -- used alone or combined in solution
 Iodine--inactivates enzymes and other cellular proteins
 Chlorine--acidifies environment
Soaps and Detergents
 Decrease surface tension--aids in mechanical removal of
microorganisms
 Handwashing--most important means for preventing
transfer of microorganisms
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Chemical Methods - Principles of
Disinfection
Properties and Concentration of chemical used
(Read the instructions!!)
 Presence
of organic matter (May need additional
scrubbing)
 Temperature
 Role
(hotter= more effective)
of microorganism (positive or negative)
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Positive Roles
 Microorganisms
are beneficial to humans
 Degrade
dead plants and animals
 Recycle chemical elements used by living cells
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Positive Roles
 Useful
in food production--cheese and yogurt
 Industry--insulin, vaccines, antibiotics, and
bioremediation for pollutants
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Positive Roles
 Living
animals have normal flora
 “Normal flora” are microorganisms that
colonize an animal without causing disease
 Compete with pathogenic microorganisms
Normal skin flora
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How Microorganisms Cause
Disease
– ability to produce disease
 10% of microorganisms are opportunists -cause disease under specific circumstances
 3% of microorganisms are true pathogens
 Pathogenicity
 Virulence
– degree of pathogenicity
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How Microorganisms Cause
Disease
Virulence -- degree of pathogenicity
 Infectivity -- ability to enter host and avoid host
defenses

Invasiveness -- ability to enter tissue of a host and
flourish

Toxigenicity -- ability of microorganism to produce a
poison
 Exotoxins--produced by bacteria and released
 Enterotoxins--toxins that act on intestinal cells
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Disease Processes
 Exposure
to organism
 Incubation Period -- No Symptoms
 Microorganism
multiplies and overcomes host
defense
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Disease Processes
 Illness
 Local
-- presence of signs/symptoms
infection -- pathogen is confined to single
area
 Systemic infection -- pathogen invades tissues
and/or is carried by lymphatic and/or circulatory
system throughout body
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Disease Processes
 Illness

Disease may be acute, chronic, or both
Acute--rapid onset followed by rapid recovery
Chronic--slow onset, long duration
 Both--rapid
onset followed by long-lasting disease
process
 Recovery,
Disability, or Death
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NATURAL COURSE OF
DISEASE
Usual Time
of Diagnosis
Pathologic Onset of
Exposure Changes Symptoms
Stage of
Susceptibility
Stage of
Subclinical Disease
Stage of
Clinical Disease
Incubation Period
Stage of Recovery
Disability or Death
Objective
Identify the basics facts of microbiology in
relation to Preventive Medicine.
54
Summary
Definition
Cells
Groups of Microorganisms
Microbial Growth
Role of Microorganisms
Disease Process
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QUESTIONS?
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