7.2.6 Importance of Protists to Humans

Protists are a diverse group that has both useful and harmful impacts for humans. Some are discussed below.

Intermediate Level

Myxomycota in Detail

Oomycota in Detail

Comparison of Myxomycota and Oomycota

Importance of Protists to Humans

Important Points

• 1. MYXOMYCOTA: Slime Molds:
• - Slime molds, specifically plasmodial slime molds, typically exist as plasmodium. It is a diploid multinucleated cytoplasmic mass wrapped in slime sheath.
• - Under unfavorable conditions for growth, for example when there is not enough water, this plasmodium develops many sporangia.
• - These sporangia are special because they make new cells called spores through a process called meiosis.
• - A sporangium (Gk. spora: seed, and angelon: vessel) is a reproductive structure that produces spores by meiosis.
• - In plasmodial slime, spores release a haploid flagellated cell or an amoeboid cell.
• - Eventually the two of them fuse to form a diploid zygote that feeds and grows, producing multinucleated Plasmodium once again.
• - Characteristics of slime molds are interesting to biologists because the life cycle involves many changes in form.
• - These different forms resemble other types of protists.
• 2. OOMYCOTA: The Water Molds:
• - Oomycetes include water molds, white rusts and downy mildews.
• - They are typically found in aquatic environments or moist terrestrial ones.
• - The members of the group are either parasites or saprotrophs.
• - Some are parasites of plants while a few aquatic oomycetes are animal parasites.
• - The cell wall in oomycetes contain cellulose unlike fungi which have chitin.
• - They have filamentous structures called hyphae as in fungi.
• - The hyphae are aseptate i.e., without intercellular cell wall and are coenocytic.
• - The life cycle of Oomycetes is characterized by both sexual and asexual reproduction.
• - The lifecycle involves the production of swimming spores called zoospores, that are produced asexually from structures called sporangia.
• - Zoospores are released into the environment and can move through water due to a single, whip-like flagellum.
• - These zoospores find suitable conditions to attach, germinate into germ tubes, and form filamentous hyphae.
• - Some Oomycetes can also produce thick-walled oospores, which serve as a survival strategy.
• - For sexual reproduction there are two types of gametangia i.e., the female gametangium called oogonium and the male gametangium called antheridium.
• - The antheridia contain numerous male nuclei, which are functional male gametes and the oogonia contain from one to eight eggs which are female gametes.
• - The movement of the contents of an antheridium into an oogonium leads to the fusion of one or more pairs of male nuclei with eggs.
• - This is followed by the thickening of the cell wall around the resulting zygote or zygotes.
• - This produces a special kind of thick walled cell called an oospore.
• - This structure gives the phylum its name i.e., phylum oomycote.
• - Common examples of oomycetes include Phytophthora infestans, Saprolegnia.
• - Saprotroph: Saprotroph, (also called as saprophyte or saprobe) are organisms that feed on nonliving and rotten organic matter known as detritus at a microscopic level.
• 3. 7.2.6 Importance of Protists to Humans:
• - Protists are a diverse group that has both useful and harmful impacts for humans.
• - Dinoflagellates: Some produce toxins harmful to marine life and can cause harmful algal blooms (red tides). The neurotoxin produced by certain dinoflagellates, such as those in the genus Alexandrium, can lead to a condition known as Paralytic Shellfish Poisoning (PSP) in humans. These toxins accumulate in shellfish when the shellfish feed on these dinoflagellates. When humans consume contaminated shellfish, the toxins can cause paralysis by blocking the transmission of nerve signals to muscles. This paralysis can extend to the respiratory muscles, potentially leading to respiratory failure if left untreated. Other dinoflagellate are primary producers in aquatic food chains and are important sources of food for small animals in the ocean.
• - Diatoms: Diatoms are major oxygen producers and a fundamental component of both marine and freshwater food webs. Additionally, their intricate silica shells, called frustules, have applications in various industries, from cosmetics and pharmaceuticals to nanotechnology.
• - Brown algae: Brown algae, including edible kelp, are a nutritious food source, especially in Asian cuisines, providing vitamins and minerals. Their alginates find extensive industrial use as thickeners and stabilizers in food and pharmaceuticals. Ecologically, brown algae, such as kelp forests, help protect coastlines from erosion, benefiting coastal communities. Additionally, they play a role in marine biodiversity.
• - Red Algae: They are important economically as their significance extends beyond their role as a food source in dishes like sushi. They are used in the cosmetics industry due to their natural pigments and potential skincare benefits. One notable product derived from red algae is agar, which is widely used in microbiology labs for growing cultures and even as a material for taking dental impressions. Red algae serve as valuable subjects in biotechnology research and offer insights into innovative applications in fields such as sustainable energy and pharmaceuticals.
• - Green Algae: They are important producers in the ecosystem. Chlorella is not only extensively being used in research in photosynthesis but also serves as a nutritious food source, offering high protein content and essential vitamins. In Taiwan and Japan dried Chlorella is sold as "health food." Additionally, green algae have garnered attention for their potential as biofuel sources, particularly in the production of sustainable energy. Their ability to convert sunlight into energy through photosynthesis makes them promising candidates for addressing future energy needs while reducing environmental impact.
• - Plasmodium: Plasmodium species are responsible for malaria, a deadly disease affecting millions worldwide. Understanding these protists is crucial for efforts to combat and prevent malaria.
• - Entamoeba histolytica: This protozoan when ingested, usually through contaminated food or water, can lead to a condition known as amoebic dysentery, a gastrointestinal disease. This parasitic infection can cause severe diarrhea, abdominal pain, and fever. If left untreated, Entamoeba histolytica infections can become life-threatening.
• - Acanthamoeba: It is a genus of amoeboid protozoa found in various environments, including soil, water, and even human-made environments like swimming pools and contact lens cases. Acanthamoeba can cause infections in humans, primarily affecting the eyes, skin, and rarely, the central nervous system. Eye infections, known as Acanthamoeba keratitis, can result from improper contact lens hygiene or exposure to contaminated water.
• - Phytophthora infestans: It is known for causing the devastating Irish Potato Famine, and this protist continues to affect potato crops globally. Potato plants infected with Phytophthora infestans show individual leaflets with small brown, dead and scarred areas. Short, specialized branches called haustoria penetrate the leaves to obtain nourishment. In addition to leaves, tubers are also infected with fallen sporangia. As a result, whole plant is killed. It can be controlled by destroying all infected plants before lifting tubers.

Remember

• - Myxomycota = slime molds.
• - Oomycota = water molds.
• - Plasmodium = diploid multinucleated mass.
• - Sporangia = produce spores by meiosis.
• - Zoospores = swimming spores.
• - Oospores = thick-walled survival spores.
• - Hyphae = filamentous structures.
• - Cellulose = cell wall of oomycetes.
• - Examples: Physarum, Phytophthora infestans, Saprolegnia.
• - Importance of protists = both useful and harmful.

Common Mistakes

• 1. Confusing Myxomycota and Oomycota – Myxomycota = slime molds; Oomycota = water molds.
• 2. Thinking slime molds are fungi – Slime molds are protists, not fungi.
• 3. Thinking water molds are fungi – Water molds are protists, not fungi.
• 4. Confusing the cell wall composition – Oomycota have cellulose in their cell walls; fungi have chitin.
• 5. Thinking all oomycetes are parasites – Some oomycetes are saprotrophs.
• 6. Confusing zoospores and oospores – Zoospores = swimming spores; Oospores = thick-walled survival spores.
• 7. Thinking plasmodium is a single cell – Plasmodium is a multinucleated mass.
• 8. Forgetting the role of meiosis in slime molds – Spores are produced by meiosis.
• 9. Confusing the importance of protists – Some are beneficial, some are harmful.
• 10. Thinking all protists are harmful – Many protists are beneficial.
• 11. Confusing the gametangia – Oogonium = female; Antheridium = male.
• 12. Forgetting the examples – Physarum, Phytophthora infestans, Saprolegnia.

Quick Revision

• MYXOMYCOTA: Slime Molds:
• Slime molds, specifically plasmodial slime molds, typically exist as plasmodium. It is a diploid multinucleated cytoplasmic mass wrapped in slime sheath.
• Under unfavorable conditions for growth, for example when there is not enough water, this plasmodium develops many sporangia.
• These sporangia are special because they make new cells called spores through a process called meiosis.
• A sporangium (Gk. spora: seed, and angelon: vessel) is a reproductive structure that produces spores by meiosis.
• In plasmodial slime, spores release a haploid flagellated cell or an amoeboid cell.
• Eventually the two of them fuse to form a diploid zygote that feeds and grows, producing multinucleated Plasmodium once again.
• Characteristics of slime molds are interesting to biologists because the life cycle involves many changes in form.
• These different forms resemble other types of protists.
• OOMYCOTA: The Water Molds:
• Oomycetes include water molds, white rusts and downy mildews.
• They are typically found in aquatic environments or moist terrestrial ones.
• The members of the group are either parasites or saprotrophs.
• Some are parasites of plants while a few aquatic oomycetes are animal parasites.
• The cell wall in oomycetes contain cellulose unlike fungi which have chitin.
• They have filamentous structures called hyphae as in fungi.
• The hyphae are aseptate i.e., without intercellular cell wall and are coenocytic.
• The life cycle of Oomycetes is characterized by both sexual and asexual reproduction.
• The lifecycle involves the production of swimming spores called zoospores, that are produced asexually from structures called sporangia.
• Zoospores are released into the environment and can move through water due to a single, whip-like flagellum.
• These zoospores find suitable conditions to attach, germinate into germ tubes, and form filamentous hyphae.
• Some Oomycetes can also produce thick-walled oospores, which serve as a survival strategy.
• For sexual reproduction there are two types of gametangia i.e., the female gametangium called oogonium and the male gametangium called antheridium.
• The antheridia contain numerous male nuclei, which are functional male gametes and the oogonia contain from one to eight eggs which are female gametes.
• The movement of the contents of an antheridium into an oogonium leads to the fusion of one or more pairs of male nuclei with eggs.
• This is followed by the thickening of the cell wall around the resulting zygote or zygotes.
• This produces a special kind of thick walled cell called an oospore.
• This structure gives the phylum its name i.e., phylum oomycote.
• Common examples of oomycetes include Phytophthora infestans, Saprolegnia.
• Saprotroph: Saprotroph, (also called as saprophyte or saprobe) are organisms that feed on nonliving and rotten organic matter known as detritus at a microscopic level.
• 7.2.6 Importance of Protists to Humans:
• Protists are a diverse group that has both useful and harmful impacts for humans.
• Dinoflagellates: Some produce toxins harmful to marine life and can cause harmful algal blooms (red tides). The neurotoxin produced by certain dinoflagellates, such as those in the genus Alexandrium, can lead to a condition known as Paralytic Shellfish Poisoning (PSP) in humans. These toxins accumulate in shellfish when the shellfish feed on these dinoflagellates. When humans consume contaminated shellfish, the toxins can cause paralysis by blocking the transmission of nerve signals to muscles. This paralysis can extend to the respiratory muscles, potentially leading to respiratory failure if left untreated. Other dinoflagellate are primary producers in aquatic food chains and are important sources of food for small animals in the ocean.
• Diatoms: Diatoms are major oxygen producers and a fundamental component of both marine and freshwater food webs. Additionally, their intricate silica shells, called frustules, have applications in various industries, from cosmetics and pharmaceuticals to nanotechnology.
• Brown algae: Brown algae, including edible kelp, are a nutritious food source, especially in Asian cuisines, providing vitamins and minerals. Their alginates find extensive industrial use as thickeners and stabilizers in food and pharmaceuticals. Ecologically, brown algae, such as kelp forests, help protect coastlines from erosion, benefiting coastal communities. Additionally, they play a role in marine biodiversity.
• Red Algae: They are important economically as their significance extends beyond their role as a food source in dishes like sushi. They are used in the cosmetics industry due to their natural pigments and potential skincare benefits. One notable product derived from red algae is agar, which is widely used in microbiology labs for growing cultures and even as a material for taking dental impressions. Red algae serve as valuable subjects in biotechnology research and offer insights into innovative applications in fields such as sustainable energy and pharmaceuticals.
• Green Algae: They are important producers in the ecosystem. Chlorella is not only extensively being used in research in photosynthesis but also serves as a nutritious food source, offering high protein content and essential vitamins. In Taiwan and Japan dried Chlorella is sold as "health food." Additionally, green algae have garnered attention for their potential as biofuel sources, particularly in the production of sustainable energy. Their ability to convert sunlight into energy through photosynthesis makes them promising candidates for addressing future energy needs while reducing environmental impact.
• Plasmodium: Plasmodium species are responsible for malaria, a deadly disease affecting millions worldwide. Understanding these protists is crucial for efforts to combat and prevent malaria.
• Entamoeba histolytica: This protozoan when ingested, usually through contaminated food or water, can lead to a condition known as amoebic dysentery, a gastrointestinal disease. This parasitic infection can cause severe diarrhea, abdominal pain, and fever. If left untreated, Entamoeba histolytica infections can become life-threatening.
• Acanthamoeba: It is a genus of amoeboid protozoa found in various environments, including soil, water, and even human-made environments like swimming pools and contact lens cases. Acanthamoeba can cause infections in humans, primarily affecting the eyes, skin, and rarely, the central nervous system. Eye infections, known as Acanthamoeba keratitis, can result from improper contact lens hygiene or exposure to contaminated water.
• Phytophthora infestans: It is known for causing the devastating Irish Potato Famine, and this protist continues to affect potato crops globally. Potato plants infected with Phytophthora infestans show individual leaflets with small brown, dead and scarred areas. Short, specialized branches called haustoria penetrate the leaves to obtain nourishment. In addition to leaves, tubers are also infected with fallen sporangia. As a result, whole plant is killed. It can be controlled by destroying all infected plants before lifting tubers.

60-Second Revision

• Myxomycota = slime molds.
• Oomycota = water molds.
• Plasmodium = diploid multinucleated mass.
• Sporangia = produce spores by meiosis.
• Zoospores = swimming spores.
• Oospores = thick-walled survival spores.
• Hyphae = filamentous structures.
• Cellulose = cell wall of oomycetes.
• Examples: Physarum, Phytophthora infestans, Saprolegnia.
• Importance of protists = both useful and harmful.
• Warning: Myxomycota = slime molds; Oomycota = water molds. Slime molds and water molds are