Reproduction of Microorganisms
Sara Austin
•
•
•
•
•
•
Microorganisms are literally “microscopic
organisms”, which can only be seen with a
microscope.
They include bacteria, fungi and viruses.
Helpful microorganisms are used in industry
and biotechnology, but
Harmful microorganisms cause many human
diseases
Understanding their reproduction is essential
to interacting safely
We control bacteria to help us, and to try to
prevent them from harming us
Teaching Strategies
The Hook: the FiveSecond Rule –is it true?
Two college students examined food dropped on
the floor of a cafeteria for various lengths of
time, and measured bacterial growth.
http://abcnews.go.com/Video/playerIndex?id=3269384
(note 12 second commercial plays first)
Stop the video once the study is
described, and ask for
predictions from students as to
the outcome.
Curriculum Correlation
This concept is part of the SBI3C
course, within the Microbiology
strand


Three types of microorganisms
are examined: bacteria, viruses,
and fungi
These microorganisms have
different types of reproduction diagrams and life cycle graphics
are essential
Reproduction in Microorganisms
Ministry Curriculum Expectation

C3.4
By the end of the
course, students will
be able to explain the
different methods of
reproduction in
various types of
bacteria, viruses, and
fungi
Overview - Microorganism
Reproduction

Bacteria:
Binary Fission
Conjugation

Viruses:
Lysogenic cycle
Lytic cycle
Retroviruses

Fungi: Sporulation
Sexual & Asexual
Overview: Bacterial Reproduction
Binary Fission
Binary Fission: the single strand of DNA
replicates, resulting in identical genetic
material being transferred to each new cell.
Following replication of the genetic
material, the bacterium produces a cross
wall, dividing the cell in to two identical
bacteria, which may separate or remain
attached.
Animation of Binary Fission:
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::500::500::/sites/dl/
free/0073375225/594358/BinaryFission.swf::BinaryFission
Actual film of bacteria dividing by binary fission:
http://cellsalive.com/qtmovs/ecoli_mov.htm
Overview: Bacterial Reproduction
Conjugation
1- Donor cell produces pilus (cytoplasmic
projection)
2- Pilus attaches to recipient cell, brings the
two cells together
3- The mobile plasmid is nicked and a
single strand of DNA is then transferred to
the recipient cell
4- Both cells recircularize their plasmids,
synthesize second strands, and reproduce
pili. Both cells are now viable donors.
From
http://parts.mit.edu/igem07/index.php/Boston_Univers
ity/Conjugation
Overview: Viral Reproduction
Viral Replication occurs
through a Lytic cycle.
Some viruses are dormant
for some time, and
maintain a Lysogenic
cycle until activated to
enter the Lytic cycle
Overview: Viral Reproduction
LYTIC CYCLE:
Viral genetic material injected into
host cell and takes over machinery to
produce parts of future viruses.
Parts are assembled and the cell
explodes (lysis), releasing more
harmful viruses. “Virulent” viruses
undergo a lytic cycle.
Overview: Viral Reproduction
Lytic Cycle
Steps …follow the
moving yellow oval as the
steps are highlighted
• Attachment and entrance
• Synthesis of protein and
nucleic acid
• Assembly of units
• Release of new virus
particles
Overview: Viral Reproduction
LYSOGENIC
CYCLE:
Viral genetic material
remains dormant, replicated
with the host cell DNA
each time the cell divides.
“Temperate” viruses
undergo a lysogenic cycle.
At some point, the lytic
cycle is triggered.
Overview: Viral Reproduction
RETROVIRUSES contain RNA as their genetic material.
The virus contains reverse transcriptase, which it uses to make DNA
from an RNA template (this never occurs in cellular organisms).
The cell then follows the directions in the new DNA code, and the
lytic cycle is triggered.
Teaching Note:
It is worth reviewing the functions of
DNA and RNA. Viruses are
classified according to their genetic
molecule (DNA or RNA), and
whether the nucleic acid is singlestranded or double-stranded.
Overview: Viral Reproduction
Web-based Animations
Lytic Cycle animation:
http://www.courses.fas.harvard.edu/~
biotext/animations/lyticcycle.html
Lysogenic Cycle animation:
http://www.courses.fas.harvard.edu/~
biotext/animations/lysogeny.html
HIV life cycle animation:
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf
::535::535::/sites/dl/free/0072437316/12
0088/micro41.swf::HIV%20Replication
Overview: Fungal Reproduction
Fungi reproduce both asexually and sexually but always
produce spores as reproductive cells. Spores are usually
dispersed by air currents, and germinate in suitable conditions.
Animation of Fungal Reproduction
http://bcs.whfreeman.com/thelifewire/conte
nt/chp31/31020.html
Overview: Fungal Reproduction
•Haploid hyphae, found below the soil,
fuse to begin reproduction.
•The hyphae enlarge, break through the
soil as white spheres called buttons
•Buttons grow and mature, forming a
stalk and a spherical cap
•Within the cap, gills form, consisting of
many tangled, modified hyphae.
•Specialized extensions from gills
containing two haploid nuclei of different
parents fuse, then undergo meiosis to
produce four haploid spores, which are
released over several days
Prior Knowledge
Students will have some basic
concepts about microorganisms
from previous grades: the role of
microorganisms in food chains and
ecosystems, the immune system; the
exchange of genetic information;
bacteria, plant-like and animal-like
protists, fungi, and viruses.
Skills: Students should have some basic
microscope skills and be able to
recognize eukaryotic cells (plant and
animal) by their organelles.
Lesson Scope and Sequence
In many texts, the
Microbiology strand is
organized by type of
microorganism, with
reproduction integrated
(e.g., Nelson College Prep
Biology 11).
This lesson scope and
sequence offers a means to
teach all the reproductive
methods at once, to
compare them, and to relate
them to technology and
society.
Subject
Assessment
FOR/
AS/OF
Lesso
n2
Viral
Replication
Gizmo
worksheet,
Online
assessment
FOR
AS
Lesso
n3
Fungal
Reproduction
& Lab
Whole-class
wall diagram
Lab Report
FOR
AS
Lesso
n4
Comparison
Activity
Activity (DI
options)
OF
Lesso
n5
Applications
Research
Presentations
AS/OF
Students can organize a
Lesso
Intro &
FOR
comparison
ofExit
thediagram,
various
n1
Bacterial
True/false quiz AS
mechanisms
Reproduction of reproduction
Lesson Plan
Subject
Activities
Assessment
FOR
AS/OF
Lesson 1
Bacterial
Reproduction
Lecture with animations,
photos, Yeast Demo,
microscope slides
Exit diagram,
True/false quiz
FOR
AS
Lesson 2
Viral
Replication
Lecture with animations,
Gizmo: Virus Lytic
Cycle
Gizmo worksheet,
online assessment
FOR
AS
Lesson 3
Fungal
Reproduction
Dung Chamber demo,
Brief lecture with
animations, microscope
slides, mushroom lab
Whole-class Wall
diagram, lab work
sheets
FOR
AS
Lesson 4
Comparison
Activity
Class discussion for
rubric design Research,
work on products
Completed product
(DI)
OF
Lesson 5
Applications:
STSE
connections
Lecture with videos,
animations, photos
Begin research
projects: RAFT
activities
AS/OF
Demonstration
Build a dung chamber as
an attention grabber for the
content about Fungi:
•Go for a hike and find some dung from a vegetarian animal (rabbit or deer pellets)
•Put the dung in a petrie dish with a damp paper towel or sprinkle with water
•Start about four days before this lesson so that students can see some real-life
examples of the fungi as they proceed through the section content
Demonstration
Build a dung chamber as
an attention grabber for the
content about Fungi:
Within a few days moulds will begin to appear on the specimen. Most beginners are
unprepared for the extremely small size of many moulds and tend to overlook them
completely. Invariably students using moist chambers for the first time complain that
nothing is growing on their specimens, only to have an instructor point out at least half a
dozen different moulds! Be sure to examine the material with a magnification of at
least 15-20 times and with good bright illumination. Illumination is especially
important and should be focused on the area of the specimen that is under examination.
From http://website.nbm-mnb.ca/mycologywebpages/Moulds/Isolation.html
Other Demonstrations
Mouldy Bread Demo:
Keep mouldy bread sealed in clear container – do not open!
From Nelson Biology 11 College Preparation text p.141, eacher’s
Resource p.247
Mushroom Dissection Lab/Demo
www.biologyjunction.com/Mushroom%20
Dissection%20Lab.doc
Yeast Fermentation Demo
http://cccmkc.edu.hk/~sbjbiology/CERT%20BIO/Energetics/Res
piration/Yeast%27s%20fermentation%
20%28demo%29.htm
Peer Activity
Student Exploration:
Virus Lytic Cycle
Release a lytic virus in a group of
cells and observe how cells are
infected over time and eventually
destroyed. Data related to the
number of healthy cells, infected
cells, and viruses can be recorded
over time to determine the time
required for the virus to mature within
a cell.
http://www.explorelearning.com/index.cfm?met
hod=cResource.dspDetail&ResourceID=448
Handout
Students will receive a set
of handouts as they
progress through the
lessons, briefly outlining
the various steps of the
reproductive cycles of
Viruses, Fungi and
Bacteria.
A brief overview handout is
available in the summary
document.
Suggested Labs
Mushroom Dissection Lab
www.biologyjunction.com/Mu
shroom%20Dissection%20La
b.doc
Examination of Lichen
http://lichens.science.oregonstate.edu/lab/L
ABMATERIALS.htm
Websites for Lesson Planning
www.who.int/csr/don/en/
http://science.nelson.com/0176265252/teac
hweblinks_ch02.html
http://serendip.brynmawr.edu/sci_edu/wald
ron/
http://www.lessonplanet.com/lessonplans/microorganisms
http://www.tes.co.uk/taxonomySearchResu
lts.aspx?keywords=micro-organisms
http://serc.carleton.edu/microbelife/index.ht
ml
Potential Areas of Difficulty
Students may think there were no effective treatments for diseases
because they were undiagnosed in the past – but anti-infective
agents been used for thousands of years. The Chinese recognized
that mouldy soybean curd was effective against skin infections.
Scabies was treated with sulfur. Mercury was used to treat
syphilis.
Viruses represent an example of the “which came first” riddle. Viruses seem to
be a stage between abiotic and biotic organisms, yet they must have appeared
after cells, as viruses cannot reproduce on their own. A decimal numbering
system is also used for viral classification (e.g., H1N1). It was decided years ago
that viruses would not use Latinized binomial terms.
Students may think that mushrooms growing on trees only benefit nutritionally –
but in fact, mushrooms can use trees to gain a better, sunnier position in a shady
environment like a rain forest. Sometimes fungi climb tress and vines to release
their spores from as high a position as possible.
From Nelson Biology 11 College Preparation,
Teacher’s Guide, Unit 2 Section Support, pp 165266
Potential Areas of Difficulty
Pathogenic organisms and the diseases they cause do not remain static.
The incidence of new of changing diseases caused by bacteria, viruses,
and protozoa are increasing.
If moulds are so ubiquitous, why are we not affected by all of them?
Moulds are opportunistic organisms: they infect humans at sites of lesions,
or when immunodeficient, or during serious diseases such as cancer or
diabetes.
Gene therapy diagrams look straightforward and reliable, but gene therapy
is still experimental and controversial. Some stunning success stories, and
some devastating failures.
From Nelson Biology 11 College Preparation,
Teacher’s Guide, Unit 2 Section Support, pp 165266
Visual Aids
The Hook: the Five-Second Rule –is it true?
http://abcnews.go.com/Video/playerIndex?id=3269384
Viral Geometry and Structural Diversity
film
http://www.microbeworld.org/
These fun soft microorganisms are sure
to be popular with students and lead to
good discussions and inquiries.
The geometric structures of viruses are
beautiful and can be used, along with
genomic information, to identify them.
(3 minutes 22 seconds)
http://www.hhmi.org/biointeractive/dis
ease/viral_diversity.html
Prepared Microscope Slides of Microorganisms
Available from science suppliers such as Boreal
Safety Considerations
Students should wash hands before
handling (to prevent contamination)
and after handling (for safety) all
organic material.
Proper microscope procedures
should be reviewed.
Mouldy bread should remain
covered when examined by
students.
Mouldy dung should be disposed of
by the teacher, wrapped, with care.
Internet use carries its own
safety hazards. Students must
be supervised to ensure they
remain on-task on lessonfocused sites.
Evaluation Instruments:
Comparison/Explanation
Students create a comparison of reproductive strategies
of bacteria (binary fission), fungi (spores, nuclear
fusion), and viruses (lysogenic and lytic cycles).
Students develop this by examining teacher-provided
charts/posters/diagrams/videos (and do online research as
needed) illustrating the life cycle and reproductive
strategy of a representative from each of bacteria, fungi,
and viruses.
Evaluation Instruments:
Comparison/Explanation
Students choose the form of this comparison, as long as
critical information is present: a song, a poem, a letter, a
set of resumes, a business plan, a poster, an
advertisement, a graphic organizer, a commentated
video/podcast, a script.
The rubric for all products is the same: students are being
evaluated on their ability to explain the different methods of
reproduction in various types of bacteria, viruses, and fungi.
Students and teachers can together develop a rubric to
evaluate the products.
Evaluation Instruments:
RAFT Activity (STSE)
Choose
one:
Role
Audience
Format
Topic
Anaerobic
Bacteria
Other anaerobic
bacteria
Travel Guide
Journey through
the waste
treatment plant
Insulin
Biotechnology
Technician
His parents
Letter
My job: What it
is and why it
matters
Crop Disease
Forecasting
Expert
Farmer
E-mail
How to prevent
potato blight
World AntiDoping Agency
(WADA)
International
Olympic
Committee
(IOC)
Recommendatio
n Report
Olympic Policy
on Gene Doping
GeneticallyModified food
The Public
Complaint
People don’t
trust me – why?
Practical and Societal Implications:
Microorganisms and Human Disease
Harmful microorganisms are the
cause of disease and decay that is
not due to structural problems or
mutations in humans. Many
microorganisms also cause disease
and decay in crops and farm animals.
Examples of familiar human diseases include:
Bacteria: salmonella, tetanus, typhoid, cholera,
gangrene, bacterial dysentery, diphtheria,
tuberculosis, bubonic plague, meningococcal
meningitis, pneumococcal pneumonia
www.who.org
Viruses: rabies, influenza (flu), measles, mumps,
polio, rubella (german measles), chicken pox,
colds, warts, cold sores
Communicable disease surveillance site
Fungi: athlete's foot, ringworm
http://www.phac-aspc.gc.ca/id-mi/indexeng.php
Canadian Public Health Agency
Practical and Societal Implications:
Biotechnology
Industry:
Preventing microorganism growth Related Possible Activities:
in food handling facilities (Maple Act 5.6.1 Students view a video or visit
Leaf meats - contamination)
a local factory highlighting the importance
Hormone production, Food
production
Waste management
of microbes in development of consumer
products - e.g., edible fungi, bacteria
converting milk to yoghurt and cheese,
moulds adding flavour to Roquefort and
Camembert cheeses, antibiotics (zones of
inhibition on agar), methanogens to create
fuels from manure.
From SBI3C Course Profile, www.curriculum.org
Practical and Societal Implications:
Biotechnology
Biotechnology: bacterial vectors are
used extensively for gene transfer
Viral vectors for medical therapies
Probiotics: to replenish
gastrointestinal tract
Act 5.6.2 Cooperative Learning - Using teacherprovided resources, students investigate the uses
and development of microbes in the areas of
biotechnology and genetic engineering. This may
include bacteria as vectors for cloning and as hosts
for protein production (insulin and growth
hormone), retroviruses as vectors for gene therapy
(ADA and SCID), research on viroids, large scale
use of fungicides and pesticides on diversity using
a variety of electronic and print media. Students
may present their findings.
From SBI3C Course Profile, www.curriculum.org
Internet Sites
Communicable disease surveillance site
www.who.org
http://www.pbs.org/opb/intimatestrangers/
http://www.peteducation.com/article.cf
m?c=18+1803&aid=2956
www.who.int/csr/don/en/
Canadian Public Health Agency
http://serendip.brynmawr.edu/sci_edu/waldr
on/
http://www.phac-aspc.gc.ca/id-mi/index-eng.php
Gizmo: Viral Lytic Cycle
Viral Geometry and Structural Diversity film
The geometric structures of viruses are beautiful and can be
used, along with genomic information, to identify them.
(3 minutes 22 seconds)
http://www.explorelearning.com/index.cfm?method=cReso
urce.dspDetail&ResourceID=448
Animation of Binary Fission:
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::500::500::/sites/dl
/free/0073375225/594358/BinaryFission.swf::BinaryFission
Actual film of bacteria dividing by binary fission:
http://www.hhmi.org/biointeractive/disease/viral_dive
rsity.html
http://cellsalive.com/qtmovs/ecoli_mov.htm
Suggestions for Other Student Labs
Is Yeast Alive?
Students evaluate whether the little brown grains of yeast
obtained from the grocery store are alive by testing for
metabolism and growth.
Alcoholic Fermentation in Yeast
Students learn about the basics of aerobic cellular respiration
and alcoholic fermentation and design and carry out
experiments to test how variables such as sugar concentration
influence the rate of alcoholic fermentation in yeast. In an
optional extension activity students can use their yeast
mixture to make a small roll of bread.
Moldy Jell-O
Students design experiments to determine how substrate and
environmental conditions influence growth of common molds.
All can be found with Student
Handouts and Teacher Preparation
notes at:
http://serendip.brynmawr.edu/sci_edu/wa
ldron/
Accommodations
Ensure that peer helpers are available when students are working in small groups.
Provide handout sheets with specific skill instructions.
Help students create data charts into which they record information.
Advise special education staff in advance when students are working on major assignments.
Record key words on the board when students are expected to make their own notes.
Allow students to report verbally to a scribe (teacher or student) who can then help in note
making.
Permit students a wide range of options for recording and reporting their work to utilize student
strengths (e.g., drawings, diagrams, flow charts, concept maps).
Timelines may need to be extended to give students more time to process language and put their
thoughts into words.
Where an activity requires reading, give it in advance to students or provide a selection of
materials at different reading levels.
From SBI3C Course Profile, www.curriculum.org
ESL/ELL Accommodations
Where an activity requires
reading, give it in advance to
students.
Permit the use of a translation
dictionary on assessments.
Have students keep a science
Have the teacher-librarian
dictionary of terms using
identify resources with
pictures and first language
appropriate reading level when words.
research is required.
Provide additional time on
Advise ESL/ESD staff in
assessments for dictionary use
advance when significant
and processing language.
written work is required.
From SBI3C Course Profile, www.curriculum.org