Sara Austin
Concept: Microorganism Reproduction
OUTLINE: CONCEPT PRESENTATION:
Microorganism Reproduction
Background Information (Handout):
BACTERIAL REPRODUCTION:
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.
Bacterial 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.
VIRAL REPRODUCTION:
LYTIC CYCLE:
Viral genetic material injected into host cell and takes over
machinery to produce parts of future viruses. Parts are
assembl
ed and
the cell
explode
s (lysis),
releasing more harmful viruses. “Virulent” viruses
undergo a lytic cycle.
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.
RETROVIRUSES contain RNA as their genetic material.
The virus contains reverse transcriptase, which it the
Sara Austin
Concept: Microorganism Reproduction
directions in the new DNA code, and the lytic cycle is triggered.
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.
•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
Sara Austin
Concept: Microorganism Reproduction
Advance Preparations:
Teachers should prepare in advance any demonstrations (bread mold and dung chamber – start dung
chamber 4 days in advance of use), handouts with web links for research, worksheets, and microscopes
and slides for examination of prepared specimens. Teachers should generate quiz questions, exit diagram
blanks, whole-class wall diagram (fungal reproduction), materials for mushroom lab.
Special Materials:
Need to collect herbivore dung (try rabbit owners?)
Buy mushrooms for dissection
Bread for mould study
Specimen slides of various microorganisms
Curriculum Emphasis:
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
Specific 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
Lesson Sequence Outline:
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
Wholeclass 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
Sara Austin
Concept: Microorganism Reproduction
Student Difficulties/Misconceptions:
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.
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.
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.
Teaching Ideas/Strategies:
Build interest using the many available animations, photographs, video clips and real microscope slides.
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
Student
Exploration: Virus
Lytic Cycle Gizmo
(explorelearning.com)
Release a lytic virus in a group of cells and observe how cells
are infected over time and eventually destroyed. Data
Sara Austin
Concept: Microorganism Reproduction
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. Student exploration sheets and online assessment
provided, along with teaching notes and vocabulary pages.
Evaluation Procedures:
Assessment for and as learning proceeds with student tasks in Lessons 1 to 3:
Lesson 1:
Lesson 2:
Lesson 3:
True/False Quiz – Bacterial Reproduction
Exit Diagram – Bacterial Reproduction
Gizmo worksheet and online assessment – Viral Reproduction
Whole-class Wall Diagram – Fungal Reproduction
Lab Worksheet – Fungal Reproduction
Assessment of learning in Lessons 4 and 5:
Lesson 4: Reproduction Comparison using DI Products - 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. 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.
Lesson 5: Applications: RAFT Activity – Students create authentic products demonstrating their ability to
relate the reproduction of bacteria, viruses and fungi to STSE.
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 Anti-Doping Agency
(WADA)
International Olympic
Committee (IOC)
Recommendation
Report
Olympic Policy on Gene
Doping
Genetically-Modified food
The Public
Complaint
People don’t trust me –
why?
Sara Austin
Concept: Microorganism Reproduction
Applications and Societal Issues:
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. Biotechnology: bacterial vectors are used extensively for gene transfer,
viral vectors are being studies as means for medical therapies, and microorganisms themselves are being
used as probiotics to replenish gastrointestinal tract and compete with other dangerous microorganisms
to reduce their effects. The extensive use of antibiotics in soaps and other products as well as in
treatment has led to concerns about their overuse and the resultant antibiotic-resistant strains.
Biotechnology in Industries – Emphasis is on both preventing microorganism growth in food handling
facilities (Maple Leaf meats - contamination), and on the use of microorganisms to manufacture products
(Hormone production - insulin, Food production – yogurt, beer, breads). Microorganisms are also used to
process waste in waste management facilities.
Selected Annotated References:
Di Giuseppe et al., Nelson Biology 11: College Preparation (2003) Nelson, Toronto.
Student Text, Teacher’s Resource and website:
http://science.nelson.com/0176265252/teachweblinks_ch02.html
Communicable disease surveillance site
www.who.org www.who.int/csr/don/en/
Canadian Public Health Agency
http://www.phac-aspc.gc.ca/id-mi/index-eng.php
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.hhmi.org/biointeractive/disease/viral_diversity.html
Gizmo: Viral Lytic Cycle
http://www.explorelearning.com/index.cfm?method=cResource.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://cellsalive.com/qtmovs/ecoli_mov.htm
Disease Outbreak News – World Health Organization
http://www.who.int/csr/don/en/
A nice overview and summary of bacteria, viruses and fungi. The website is for pet diseases, but human
diseases are also mentioned.
http://www.peteducation.com/article.cfm?c=18+1803&aid=2956
Biology4kids: A simple, whimsically-written website that explains the various types of micro-organisms in
simple language, but does include terminology appropriate for high school students. Quizzes available.
Advertising is a bit distracting
http://www.biology4kids.com/files/micro_main.html
Sara Austin
Concept: Microorganism Reproduction