15: PROTOZOA
- Page ID
- 157077
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- Identify medically important protozoa, such as Entamoeba histolytica, Giardia lamblia, Trichomonas vaginalis, Trypanosoma spp., Plasmodium spp., and Balantidium coli.
- Associate each organism with the disease it causes and/or tissues, organ systems affected.
BACKGROUND
Protozoa are one of the two major groups within the Kingdom Protista, along with algae. Like all protists, protozoa are made up of eukaryotic cells (cells that contain a true nucleus and membrane-bound organelles). While algae are often described as “plant-like” due to their ability to photosynthesize, protozoa are considered more “animal-like” because they must consume other organisms for food.
The name "protozoa" literally means “first animals”, and these organisms often resemble tiny animals in behavior and lifestyle. Many protozoa are pathogens in humans or animals and understanding them is essential in clinical microbiology.
Unlike algae, protozoa cannot photosynthesize, so they must find and absorb nutrients from their environment. Since they are single-celled, they do not have mouths or intestines. Instead, they absorb nutrients through their cell membrane or ingest food particles using a process called endocytosis (a method by which a cell surrounds and takes in material from its environment).
Historically, protozoa were grouped based on how they move. Today, modern classification also uses DNA sequencing and rRNA typing (methods that analyze genetic material), but for the purposes of this lab, we will focus on their method of movement. The four major groups are:
- Flagellates – move using long whip-like flagella
- Amoeboids – move by extending parts of their body called pseudopods (“false feet”)
- Ciliates – are covered in short, hair-like cilia that beat in unison to allow movement
- Apicomplexans – are obligate intracellular parasites (they must live inside a host cell and cannot move on their own); they use a specialized structure called an apical complex to invade host cells
Some protozoa can form cysts (dormant, protective forms that survive harsh environments). These cysts help them survive outside a host and allow transmission from one host to another.
Examples of Medically Important Protozoa
- Entamoeba histolytica is an amoeboid organism that causes amoebic dysentery, a serious intestinal disease. The amoeba invades the large intestine and consumes red blood cells. It is spread by ingestion of food or water contaminated with feces and is a major public health concern in many parts of the world, though less common in the United States.
- Giardia lamblia is a flagellated protozoan that causes giardiasis, an intestinal infection. It is often contracted by drinking water contaminated by animal feces or through direct person-to-person contact in childcare settings.
- Trichomonas vaginalis is a flagellated protozoan responsible for the sexually transmitted disease trichomoniasis (commonly called “tric”).
- Trypanosoma species cause diseases such as African sleeping sickness. These protozoa have a single flagellum attached to an undulating membrane (a wave-like membrane that helps in movement). They are typically spread through the bites of infected insects like the tsetse fly.
- Plasmodium, a member of the Apicomplexa group, causes malaria—the most common protozoan infection worldwide. These parasites live inside red blood cells and are spread by the bite of an infected mosquito, which also serves as the site for the organism’s sexual reproduction. At least four Plasmodium species infect humans.
- Balantidium coli, a ciliate, is the only ciliated protozoan known to infect humans. Though rare, it can cause intestinal illness in immuno-compromised individuals. It is named after its location—the colon—just like Escherichia coli (E. coli), although the two are very different organisms.
MATERIALS (Per Group of 1)
Prepared slides of the following organisms:
METHODS/PROCEDURES
1. Make accurate drawings off all slides listed at the magnifications listed in the table above.
2. Make note of any features such as flagella, cilia, nucleoli, intracellular, etc. that will help you identify the organisms on the lab exam.
Print a hard copy to bring to lab (PDF).
👉 If you are filling this out on a digital iPad or tablet please note put your name here and take a screen shot.
You are also welcome to print the PDF and turn in a physical copy of the following.
Exercise #18 Protozoa
NAME ______________________
EXPECTATIONS
Which protozoan do you think will be an intracellular pathogen?
RESULTS
CONCLUSIONS
1. What visual evidence on the microscope slides suggests that Plasmodium and Trypanosoma are parasitic organisms? Describe how their appearance and location relative to host cells support this conclusion.
2. How does the ability to form cysts help protozoa survive outside the host? How might this affect sanitation practices?
3. If you were testing a water sample for protozoan contamination, which species from today’s lab might you expect to find and why?
4. What would you expect to see if a sample contains both protozoa and bacteria? How would you tell the difference between them under the microscope?