Chapter 5- The eukaryotes of microbiology Flashcards
Protist
Refers to a diverse group of microscopic eukaryotic organisms. It is not considered a formal taxonomic term because the organisms it describes do not have a shared evolutionary origin. Historically, the protists were informally grouped into the “animal-like” protozoans, the “plant-like” algae, and the “fungus-like” protists such as water molds.
Plankton
An informal term used to describe microorganisms that drift or float in water.
Trophozoites
Describes protozoans during the feeding and growth part of their life cycle. They feed on small particles of food, like bacteria. Some protozoa stay in this stage, others develop into a cyst stage
Encystment
The process by which a trophozoite becomes a cyst. This occurs when environmental conditions are too harsh for a trophozoite. Eimeria is a protozoan genus that is capable of encystment
Excystment
When cysts are triggered by environmental cues to become active again.
Cyst
A cell with a protective wall.
Schizogony
The nucleus of a cell divides multiple times before the cell divides into many smaller cells. This is an asexual method of reproduction for protozoans
3 types of asexual reproduction in protozoa
Binary fission, budding, or schizogony
Merozoites
Products of schizogony, they are stored in structures called schizonts.
Syngamy
When a protozoa’s haploid gametes fuse
Conjugation
When protozoa’s gametes join to exchange DNA. It is a true form of eukaryotic sexual reproduction between two cells of different mating types. It is found in ciliates, a group of protozoans
Plasmalemma
The plasma membrane of protozoans. Some protists, including protozoans, have distinct layers of cytoplasm under the membrane. In these protists, the outer gel layer (with microfilaments of actin) is called the ectoplasm. Inside this layer is a fluid region of cytoplasm called the endoplasm. The membrane structures contribute to complex shell shapes in some protozoans
Protozoa
Nonphotosynthetic, motile organisms
that are always unicellular. They are heterotrophic. . Mitochondria may be absent in parasites or altered to kinetoplastids (modified mitochondria) or hydrogenosomes
Pellicle
A structure in the plasma membrane of protozoans, formed by bands of proteins. It adds to rigidity in the membrane
Cytostome
A specialized structure of taking in food through phagocytosis in protozoans. Oral grooves leading to cytostomes are lined with hair-like cilia to sweep in food particles
Cytoproct
A specialized structure for the exocytosis of wastes in protozoans
Holozoic
Protozoans that ingest whole food particles through phagocytosis
Saprozoic
Protozoans that ingest small, soluble food molecules
How are protists able to move?
Some have flagella or hairs (cilia) made of microtubules that they can use for movement. Others use extensions of the cytoplasm (pseudopodia) to attach the cell to the surface and cytoplasm moves into the extensions so the cell can move forward
Contractile vacuoles
Organelles that can be used to move water out of the cell for osmotic regulation (salt and water balance)
Polyphyletic
Protists are polyphyletic because they lack a shared evolutionary origin. They are all eukaryotic and are therefore all in the domain Eukarya, but protists are scattered across different taxonomic groups
Amoebozoa
A eukaryotic supergroup that includes protozoans that use amoeboid movement. Includes subgroups entamoebas and slime molds
Amoeboid movement
Actin microfilaments produce
pseudopodia. Protoplasm flows into the extensions and moves the organism.
Entamoeba
A genus that is a subgroup of the eukaryotic supergroup Amoebozoa. Includes commensal or parasitic species, including the medically important E. histolytica, which is transmitted by cysts in feces and is the primary cause of amoebic dysentery. Another member of this group
that is pathogenic to humans is Acanthamoeba, which can cause keratitis (corneal inflammation) and blindness
Slime molds
A group of organisms that is a subgroup of the eukaryotic supergroup Amoebozoa. They are classified into cellular slime molds and plasmodial slime molds.
Cellular slime molds
The cellular slime molds exist as individual amoeboid cells that periodically aggregate into a mobile slug. The aggregation of cells forms a “fruiting body”, which can produce haploid spores
Plasmodial slime molds
Large, multinucleate amoeboid cells that form reproductive stalks to produce spores that divide into gametes
Chromalveolata (4)
A eukaryotic supergroup united by similar origins of its members’ plastids. Includes the apicomplexans, ciliates, diatoms, and dinoflagellate
Apicomplexans
A member of the supergroup Chromalveolata. They are parasites that can be intracellular or extracellular. They have an apical complex at one end of the cell, where organelles, vacuoles, and microtubules are concentrated. This concentration of structures allows the parasite to enter host cells. Apicomplexans have complex life cycles that include an
infective sporozoite that undergoes schizogony to make many merozoites, and requires transmission between multiple hosts. The genus Plasmodium is an example of this group. Another example is Toxoplasma gondii, which causes toxoplasmosis and can be transmitted from cat feces, unwashed fruit and vegetables, or from undercooked meat.
Toxoplasmosis can be associated with serious birth defects
Ciliates
Located within the supergroup Chromalveolata. They are a diverse group characterized by cilia on their cell surface. Cilia can be used for locomotion or feeding. These organisms have a micronucleus and a macronucleus. Balantidium coli is the only parasitic ciliate that affects humans by causing intestinal illness, although it rarely causes serious medical issues except in the immunocompromised
Micronucleus
Diploid, somatic, and used for sexual reproduction by conjugation.
Macronucleus
Derived from the micronucleus- the macronucleus becomes polyploid (multiple sets of duplicate chromosomes), and has a reduced set of metabolic genes.
How do ciliates reproduce?
Through conjugation. Two cells attach to each other, and the diploid micronuclei undergo meiosis in each cell. Eventually, one haploid micronucleus and the macronucleus are left in each cell. The haploid micronucleus undergoes mitosis. s. The two cells then exchange one micronucleus each, which fuses with the remaining micronucleus present to form
a new, genetically different, diploid micronucleus. The diploid micronucleus undergoes two mitotic divisions, so each cell has four micronuclei, and two of the four combine to form a new macronucleus. The chromosomes in the macronucleus replicate until it’s polyploid, and the two cells separate. The two cells are now genetically different from each other and from their previous versions.
Oomycetes
Similar to fungi, but have several different characteristics. Located within the supergroup Chromalveolata. They have cell walls of cellulose (unlike the chitinous cell walls of fungi) and they are generally diploid, whereas the dominant life forms of fungi are typically haploid. One example is Phytophthora, the plant pathogen found in the soil that caused the Irish potato famine
Excavata
A eukaryotic supergroup. Includes primitive eukaryotes and parasites with limited metabolic abilities. These organisms often have a depression on the cell surface, called an excavate. Includes the subgroups Fornicata, Parabasalia, and Euglenozoa.
Fornicata
Part of the supergroup Excavata. They have flagella, but no mitochondria. One example is Giardia lamblia, which causes diarrheal illness and can be spread through cysts from feces that contaminate water
supplies
Parabasalia
Part of the supergroup Excavata. Live in animals as part of an endosymbiotic relationship. They live in the intestines of animals like termites and cockroaches. They have basal bodies and modified mitochondria (kinetoplastids). They also have a large, complex cell structure with an undulating membrane and often have many flagella. Includes pathogens such as Trichomonas vaginalis, which causes the human sexually transmitted disease trichomoniasis. In women, it causes vaginal discomfort and can cause complications in pregnancy.
Euglenozoa
Part of the supergroup Excavata. Can be photosynthetic, but others are not. Includes members of the genus Euglena and trypanosomes, which are parasitic pathogens.
Stigma
Eyespot that is used to sense light
Euglena
A genus of protozoa that are typically not pathogenic. Their cells have 2 flagella, a pellicle, a stigma, and chloroplasts for photosynthesis. The pellicle of Euglena is made of a series of protein bands surrounding the cell, it supports the cell membrane and gives the cell shape.
Trypanosomes
A group of parasitic pathogens. Includes T. brucei, which causes African trypanosomiasis (African sleeping sickness) and Chagas disease. These diseases are spread by insect bites. T. brucei is spread through a bite by a tsetse fly. The early symptoms include confusion, difficulty sleeping, and lack of coordination. Left untreated, it is fatal. Chagas disease affects either the heart tissue or the tissues of the digestive system. Untreated cases can eventually lead to heart failure or significant digestive or neurological disorders.
2 groups of parasitic helminths
Roundworms (Nematoda) and flatworms (Platyhelminthes)
Helminths
Worms- about half are parasitic and some are important human pathogens
Monoecious
Helminths that have both male and female reproductive organs (in a single individual)
Dioecious
Having either male or female reproductive organs
Phylum Nematoda (roundworms)
These unsegmented worms have a full digestive system even when parasitic. Some are common intestinal parasites, and their eggs can sometimes be identified in feces or around the anus of infected individuals. Pinworm infections and hookworm infections are an example
Phylum Platyhelminthes (flatworms)
This group includes the flukes, tapeworms, and the turbellarians, which include planarians. The flukes and tapeworms are medically important parasites
Flukes
Non segmented flatworms that have an oral sucker (and sometimes a
second ventral sucker) and attach to the inner walls of intestines, lungs, large blood vessels, or the liver. They have complex life cycles that often use multiple hosts. One example is Schistosomiasis, which is a serious parasitic disease. The parasites are found in freshwater snails, and immature forms burrow through the skin into the blood. They migrate to the lungs, then to the liver and, later, other organs. Symptoms include anemia, malnutrition, fever, abdominal pain, fluid buildup
Tapeworms
Segmented flatworms that may have suckers or hooks at the scolex (head region). Tapeworms use these suckers or hooks to attach to the wall of the small intestine. The body of the worm is made up of segments called proglottids that contain reproductive structures. Proglottids detach when gametes are fertilized and they contain eggs.
Tapeworm life cycle
Tapeworms often have an intermediate host that consumes the eggs, which then hatch into a larval form called an oncosphere. The oncosphere migrates to a particular tissue or organ in the intermediate host, where it forms cysticerci. After being eaten by the definitive host, the cysticerci develop into adult tapeworms in the host’s digestive system. Humans are infected by eating undercooked meat
Mycoses
Illnesses caused by fungi. Some pathogenic fungi are opportunistic, meaning that they mainly cause infections when the host’s immune defenses are compromised and do not normally cause illness in healthy individuals
Why are fungi important?
They act as decomposers in the environment, and they are critical for the production of certain foods such as
cheeses. Fungi are also major sources of antibiotics, such as penicillin from the fungus Penicillium.
Hyphae
Filaments composing certain fungi, such as molds. Hyphae can form a tangled network
called a mycelium and form the thallus (body) of fleshy fungi.
Molds
Multicellular fungi composed of hyphae
Septate hyphae
Hyphae that have walls between the cells
Coenocytic hyphae
Hyphae that lack walls and cell membranes between the cells
Yeasts
Unicellular fungi
Budding yeasts
Yeasts that produce asexually. The new yeast cell buds off of a smaller daughter cells. The cells that are created sometimes stick together as a chain (pseudohypha)
Dimorphic fungi
Fungi that have more than one appearance during their life cycle- they can appear as yeasts or molds. They change in response to environmental factors like temperature or nutrient availability. These fungi can more easily survive in diverse environments. C. albicans is one example, and is associated with vaginal yeast infections, oral thrush, and candidiasis of the skin
Chitin
The molecule that makes up fungal cell walls
Fungal cell membranes are made up of
Ergosterols. Ergosterols are often exploited as targets for antifungal drugs
How do fungi reproduce sexually?
The hyphae of haploid fungi have gametes at their tips. The tips can either have a + or - mating type. The cytoplasms of one + and one - type gamete fuse in an event called plasmogamy. This produces a dikaryotic cell. Then, the nuclei fuse in an event called karyogamy to produce a diploid zygote. The zygote will undergo meiosis to form spores that germinate and start the haploid stage. This eventually creates more haploid mycelia
Dikaryotic cell
A cell with 2 distinct nuclei
How do fungi reproduce asexually?
By mitosis, mitosis with budding, fragmentation of hyphae, and
formation of asexual spores by mitosis.
Asexual spores
Specialized cells that can have unique characteristics for survival, reproduction, and dispersal. Fungi exhibit several types of asexual spores
Glomeromycota
Obligate symbionts. They must be associated with plant roots to survive. The fungi receive carbohydrates from the plant and the plant benefits from the increased ability to take up nutrients and minerals from the soil. Includes mycorrhizal fungi
Chytridiomycetes
Small fungi that are generally aquatic and have flagellated, motile gametes. Specific types are implicated in amphibian declines around the world
Zygomycota
Have coenocytic hyphae and haploid nuclei. . They use sporangiospores for asexual reproduction and zygospores for sexual reproduction. They are crop pathogens and include bread molds. Mucor is a genus of fungi that can potentially cause necrotizing infections in humans
Zygospores
Used for sexual reproduction. They have hard walls formed from the fusion of reproductive cells from two individuals
Ascomycota
Include fungi that are used as food, like edible mushrooms, human pathogens, and sources of food spoilage like bread molds. They have septate hyphae and ascocarps. Some use sexually produced ascospores as well as asexual spores called conidia. Some produce an ascus. Species in the genus Aspergillus are important causes of allergy and infection, and are useful in research and in the production of certain fermented alcoholic beverages. The fungus Aspergillus flavus, a contaminant of nuts and stored grains, produces an aflatoxin that is both a toxin and the most potent known natural carcinogen. Neurospora crassa is used in genetics research
Ascocarps
Cup-shaped fruiting bodies found in ascomycota
Ascus
Contains ascospores within an ascocarp
Medically important ascomycetes
A large number of species in the genera Trichophyton, Microsporum, and Epidermophyton are dermatophytes, pathogenic fungi capable of causing skin infections such as athlete’s foot, jock itch, and ringworm. Blastomyces dermatitidis is a dimorphic fungus that can cause
blastomycosis, a respiratory infection that, if left untreated, can become disseminated to other body sites, sometimes leading to death. C. albicans is another example, it is part of the normal microbiota but can cause vaginal and other yeast infections
Saccharomyces yeasts
Unicellular ascomycetes with haploid and
diploid stages. This and other Saccharomyces species are used for brewing beer.
Basidia
Club shaped structures that are characteristic of Basidiomycota. They produce basidiospores (spores produced through budding) within fruiting bodies called basidiocarps
Basidiomycota
Have basidia. They are important as decomposers and as food. Cryptococcus neoformans can cause serious lung infections in immunocompromised people. Another example are certain mushrooms, like the poisonous mushroom Amanita phalloides, known as the death cap. The deadly toxins produced by A. phalloides have been used to study transcription
Microsporidia
Unicellular fungi that are obligate intracellular parasites. They lack
mitochondria, peroxisomes, and centrioles. However, their spores produce a polar tubule that pierces the membrane of a host cell so the fungus can enter. One example is Enterocystozoan bieneusi, which can cause symptoms such as diarrhea, cholecystitis (inflammation of the gallbladder), and in rare cases, respiratory illness
Algae
Autotrophic protists that can be unicellular or multicellular. Algae produce 70% of the oxygen and organic matter and aquatic environments. Some types are eaten by humans and other animals. They are also the source of agar
Algal blooms
Occur when algae grow quickly and produce dense populations, and can produce high concentrations of toxins that
impair liver and nervous-system function in aquatic animals and humans.
Pyrenoids
Structures in the chloroplasts of algae that store starch
Algae cell chloroplasts
The chloroplasts have different numbers of membranes, which is probably because of an endosymbiotic event. Primary chloroplasts have two membranes—one from the original cyanobacteria that the ancestral eukaryotic cell engulfed, and one from the plasma membrane of the engulfing cell. With secondary chloroplasts, another cell engulfed a green or red
algal cell that already had a primary chloroplast within it. The engulfing cell destroyed everything except the
chloroplast of its original cell, leaving three or four membranes around the chloroplast. Different algal groups have different pigments, which are reflected in common names such as red algae, brown algae, and green algae
Dinoflagellates
Algae that fall in the supergroup Chromalveolata. They are mostly marine organisms and are found in plankton. They can be phototrophic, heterotrophic, or mixotrophic. The photosynthetic species use chlorophyll a, chlorophyll c2, or another photosynthetic pigment. They have 2 flagella. Some have a hard outer covering called theca. Some produce neurotoxins that can cause paralysis in humans or fish through contact with water
Red tide
A harmful algal bloom that occurs when a population of dinoflagellates becomes dense. Red tides cause harm to marine life and to humans who consume contaminated marine life. Major
toxin producers include Gonyaulax and Alexandrium, both of which cause paralytic shellfish poisoning
Stramenopiles
Algae that fall in the supergroup Chromalveolata. They use chlorophyll a, chlorophyll c1/c2, and fucoxanthin as photosynthetic pigments. They use chrysolaminarin as a storage carbohydrate. Includes the golden algae (Chrysophyta), the brown algae (Phaeophyta), and the diatoms (Bacillariophyta)
Frustules
Outer cell walls of crystallized silica, found in diatoms (fungi)
Diatoms
A type of fungi. They have frustules- their fossilized remains are used to produce diatomaceous earth, which has a range of uses such as filtration and insulation. Additionally, diatoms can reproduce sexually and asexually, and the male gametes of centric diatoms have flagella providing directed movement to seek female gametes for sexual reproduction
Brown algae (Phaeophyta)
Multicellular marine seaweeds. They have leaf-like blades, stalks, and structures called holdfasts that are used to attach to
substrate. However, these are not true leaves, stems, or roots. They use chlorophyll a, chlorophyll c1/c2, beta carotene, and fucoxanthine as photosynthetic pigments. They use laminarin as a storage carbohydrate
Archaeplastids
Include the green algae (Chlorophyta), the red algae (Rhodophyta), another group of green algae (Charophyta), and the land plants. Like land plants, the Charophyta and Chlorophyta have chlorophyll a and chlorophyll b as photosynthetic pigments, cellulose cell walls, and starch as a carbohydrate storage molecule. The Charaphyta are the most similar to land plants because they share a mechanism of cell division and an important biochemical pathway
Why are lichens important?
Lichens are not pathogenic. However, they are an important part of most terrestrial ecosystems. Lichens contribute to soil production by breaking down rock, and they are early colonizers in soilless environments such as lava
flows. The cyanobacteria in some lichens can fix nitrogen and act as a nitrogen source in some environments. They have been used in foods and to extract chemicals as dyes or antimicrobial substances. Some are sensitive to pollution and have been used an environmental indicators
Lichen
A combination of two organisms: a fungus and either a green alga or cyanobacterium, which live in a symbiotic relationship. Lichens can be found on almost any surface or as epiphytes
Epiphytes
An organism that can grow on another plant
How does the symbiotic relationship work between two organisms that make a lichen?
The fungus can obtain photosynthates from the algae or cyanobacterium and the algae or cyanobacterium can grow in a drier environment than it could otherwise tolerate- both organisms would benefit in this case. However, the relationship may be controlled parasitism because the photosynthetic organism grows less well than it would
without the fungus.
Structure of licens
Have a body called a thallus, an outer, tightly packed fungal layer called a cortex, and an inner, loosely packed fungal layer called a medulla. Lichens use hyphal bundles called rhizines to attach to the substrate.
3 major types of lichens
- Crustose lichens
- Foliose lichens
- Fruticose lichens
Crustose lichens
Lichens that are tightly attached to the substrate, and therefore have a crusty appearance
Foliose lichens
Lichens with leaf-like lobes that have a second cortex below the medulla. They may only be attached at one point in the growth form
Fruticose lichens
Lichens with rounded structures and an overall branched appearance
