Reproduction of Microorganisms• 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

Sara Austin

Teaching Strategies

The Hook: the Five-Second 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

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

Ministry Curriculum Expectation

Overview - Microorganism Reproduction

Bacteria:Binary Fission

Conjugation

Viruses:

Lysogenic cycle

Lytic cycle

Retroviruses

Fungi: SporulationSexual & Asexual

Overview: Bacterial ReproductionBinary 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.mcgraw-hill.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 ReproductionConjugation

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_University/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 ReproductionLytic Cycle

• Attachment and entrance

• Release of new virus particles

• Assembly of units

• Synthesis of protein and nucleic acid

Steps …follow the moving yellow oval as the steps are highlighted

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 ReproductionRETROVIRUSES 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 single-stranded or double-stranded.

Overview: Viral ReproductionWeb-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.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120088/micro41.swf::HIV%20Replication

Overview: Fungal ReproductionFungi 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/content/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 KnowledgeStudents 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 SequenceIn 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.

Students can organize a comparison of the various mechanisms of reproduction

Subject Assessment FOR/AS/OF

Lesson 1

Intro & Bacterial Reproduction

Exit diagram,True/false quiz

FORAS

Lesson 2

Viral Replication

Gizmo worksheet,Online assessment

FORAS

Lesson 3

Fungal Reproduction & Lab

Whole-class wall diagramLab Report

FORAS

Lesson 4

Comparison Activity

Activity (DI options)

OF

Lesson 5

Applications Research Presentations

AS/OF

Lesson PlanSubject Activities Assessment FOR

AS/OF

Lesson 1 Bacterial Reproduction

Lecture with animations, photos, Yeast Demo, microscope slides

Exit diagram,True/false quiz

FORAS

Lesson 2 ViralReplication

Lecture with animations, Gizmo: Virus Lytic Cycle

Gizmo worksheet, online assessment

FORAS

Lesson 3 Fungal Reproduction

Dung Chamber demo, Brief lecture with animations, microscope slides, mushroom lab

Whole-class Wall diagram, lab work sheets

FORAS

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

Mushroom Dissection Lab/Demo

www.biologyjunction.com/Mushroom%20Dissection%20Lab.doc

Yeast Fermentation Demo

http://cccmkc.edu.hk/~sbj-biology/CERT%20BIO/Energetics/Respiration/Yeast%27s%20fermentation%20%28demo%29.htm

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

Peer Activity

Student Exploration: Virus Lytic Cycle

http://www.explorelearning.com/index.cfm?method=cResource.dspDetail&ResourceID=448

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.

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

Examination of Lichenhttp://lichens.science.oregonstate.edu/lab/LABMATERIALS.htm

Mushroom Dissection Lab

www.biologyjunction.com/Mushroom%20Dissection%20Lab.doc

Websites for Lesson Planning

www.who.int/csr/don/en/

http://science.nelson.com/0176265252/teachweblinks_ch02.html

http://serendip.brynmawr.edu/sci_edu/waldron/

http://www.lessonplanet.com/lesson-plans/microorganisms

http://www.tes.co.uk/taxonomySearchResults.aspx?keywords=micro-organisms

http://serc.carleton.edu/microbelife/index.html

Potential Areas of DifficultyStudents 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 165-266

Potential Areas of Difficulty

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 165-266

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.

Visual Aids

The Hook: the Five-Second Rule –is it true?

http://abcnews.go.com/Video/playerIndex?id=3269384

These fun soft microorganisms are sure to be popular with students and lead to good discussions and inquiries.

http://www.microbeworld.org/

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 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 lesson-focused 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)

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?

Choose one:

Practical and Societal Implications: Microorganisms and Human Disease

Examples of familiar human diseases include:

Bacteria: salmonella, tetanus, typhoid, cholera, gangrene, bacterial dysentery, diphtheria, tuberculosis, bubonic plague, meningococcal meningitis, pneumococcal pneumonia

Viruses: rabies, influenza (flu), measles, mumps, polio, rubella (german measles), chicken pox, colds, warts, cold sores

Fungi: athlete's foot, ringworm

www.who.org

Communicable disease surveillance site

http://www.phac-aspc.gc.ca/id-mi/index-eng.php

Canadian Public Health Agency

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.

Practical and Societal Implications:Biotechnology

Related Possible Activities:

Act 5.6.1 Students view a video or visit a local factory highlighting the importance 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

Industry:

Preventing microorganism growth in food handling facilities (Maple Leaf meats - contamination)

Hormone production, Food production

Waste management

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 teacher-provided 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

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

http://www.pbs.org/opb/intimatestrangers/

Animation of Binary Fission:

http://highered.mcgraw-hill.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

http://serendip.brynmawr.edu/sci_edu/waldron/

Gizmo: Viral Lytic Cycle

http://www.explorelearning.com/index.cfm?method=cResource.dspDetail&ResourceID=448

http://www.peteducation.com/article.cfm?c=18+1803&aid=2956

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 YeastStudents 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-OStudents 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/waldron/

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.

Have the teacher-librarian identify resources with appropriate reading level when research is required.

Advise ESL/ESD staff in advance when significant written work is required.

Permit the use of a translation dictionary on assessments.

Have students keep a science dictionary of terms using pictures and first language words.

Provide additional time on assessments for dictionary use and processing language.

From SBI3C Course Profile, www.curriculum.org