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various microbial eukaryotes
- i. Fungi
- ii. Protozoa
- iii. Helminths
types of non-living infectious agents (all are different)
- i. viruses
- ii. viriods
- iii. prions
Fungal General Characteristics
- eukaryotic cells
- (all fungi )reproduce sexualy and nonsexually)
- heterotrophic (use organic compounds a carbon source; they can’t make their own sugars(FOOD); no photosynthesis)
Fungi facultative anaerobes example
Fungi saprophytes - obtain nutrients by
decomposing dead & decaying matter important in ecosystems as decomposers
- hyphae can be coenocytic NO SEPERATION NO CROSS WALL (undivided network of branching tubes) or have SEPTA (cross walls).
- CAN BE MULTI AND UNICELLULAR ARE ROD SHAPE
Fungus have cell wal;s composed of
- •cellulose, chitin (contains nitrogen - also found in the
- exoskeletons of insects, crayfish, etc.), or a combination of the two.
Fungi asexual reproduction
- Occurs by elongation of hyphae, budding, or asexual spore production
- Only contain one genome
- Budding is one cell copying its genome and seppararing (like yeast)
(Fungi) Asexual Spores are products of a type of cell division called
mitosis (one cell divides to form 2 daughter cells that are identical to one another and to the original parent cell).
Types of asexual spores
Fungi Sexual Reproduction Occurs by
producing sexual spores, which form following sexual fusion of gametes (similar to sperm & eggs)
Types of sexual reproducing fungi
Underground one filament fungi are known as
- Imperfect fungi, group not known much about only that they reproduce asexual and are temporary grouping
- untill more info is known
Yeasts vs. Molds
- •Yeast are nonfilamentous and unicellular
- •Molds are filamentous and multicellular
Fungi key points
- •Fungi are eukaryotes
- •Fungi are heterotrophs
- •Can reproduce via asexual and/or sexual reproduction
- •Can cause human diseases
- •Many different types of fungi
- •Humans usually acquire fungal disease from nature; they are not highly contagious.
- •Fungi are a leading cause of nosocomial infections (hospital aquire infections)
- Fungal infections are a major problem in immune suppressed people.
- Fungal infections are often mistaken for bacterial infections, with fatal consequences.
- •Systemic (most dangerous)
- •Opportunistic (most dangerous)
Superficial mycoses infection of outerlayer of skin
- Pityriasis versicolor--pigmented lesions on torso
- Tinea nigra--gray to black macular lesions often on palms
- Black piedra--dark gritty deposits on hair
- White piedra--soft whitish granules along hair shaft
- All are diagnosed by microscopy and are easily treated by topical preparations
Three genera of dermatophytes:
- -cause infections of skin and its appendages
Systemic fungal disease is most often associated with four organisms
- 1.Coccidioides immitis
- 2. Histoplasma capsulatum
- 3.Blastomyces dermatitidis
- 4.Paracoccidioides brasiliensis (S. America)
Infection caused by inhalation of spores
•Coccidiodes immitis is considered to be the most virulent of fungal pathogens.
- •Fungal infections that do not normally cause disease in
- healthy people, but do cause disease in people with weakened immune defenses (immunocompromised people).
prime importance in the occurrence of vaginal candidiasis
Local factors such as pH and glucose concentration (under hormonal control)
Protozoa General Characteristics:
- Unicellular eukaryotes.
- Limited to a moist environment because they lack a cell wall
Fungi reproduce asexually by
- 1.fission (one cell divides to form 2 identical daughter cells and budding
- 2.schizogony (multiple fission).
Sexual reproduction occurs by
- 1.conjugation: the fusion of vegetative cells
- 2.fusion of specialized gametes called gametocytes.
- Some have complex life cycles
- Requiring multiple hosts and changing their morphology
- Plasmodium uses the mosquito as an intermediate host
- active, motile, feeding stage of protozoans; parasitic stage
- that causes the disease in the host
resistant, inactive stage; how diseases are usually transmitted by the fecal-oral route; usually more useful than trophozoites for lab identification
Classification based on mode of
locomotion or motility
- Move by means of pseudopodia or "false feet"
- Temporary extensions of the cell body caused by protein filaments of the cytoskeletonpushing on the cell membrane)
- Feed on algae, bacteria, and other protozoans by phagocytosis.
Mastigophora or Zoomastigophora
- Move by means of flagella
- Some can also have pseudopodia
- Many are disease-causing species
- Some are parasites
- Move by means of cilia
- Cilia are short, hairlike projections of cytoplasm composed of pairs of microtubules surrounded by cell membrane.
- Multinucleate organisms
- Macronucleus controls cell functions and asexual reproduction.
- Micronucleus is also involved with sexual reproduction.
Apicomplexa or Sporozoa
- Basically nonmotile.
- All have an infectious, sporelike stage (sporozoite) that is often transmitted to new hosts by an insect vector.
- All are parasitic (obligate parasites - cannot live apart from the host).
- Some have elaborate life cycles, changing body form (trophozoite, sporozoite, merozoite)
- Life cycle includes schizogony (multiple fission).
Several serious human diseases:
- Chaga’s disease
- African sleeping sickness
(African sleeping sickness)
- Flagellated protozoans
- TseTse fly carries
- --Systemic: multiplies in blood
- --Progresses to neurological stage, infects central nervous system → meningoencephalitis
- --Loss of consciousness. Hence, the SLEEP part.
Malaria caarried by the
- Anopheles Mosquito
- ----Plasmodium. falciparum– most virulent and prevalent
(insects) that convey a parasite from host to host
Protozoas are unicellular
- Reside in humans, but do not usually replicate there
- Not intracellular
- Most infected individuals carry few, immune system not heavily engaged, level of immunity generated is often poor
Concentration of sensory receptors toward the anterior end
Flatworm sexual reproduction
Most are monoecious (Male & Female) both reproductive organs in same animal
Sexual reproduction in roundworms
Dioceious (Seperate Sexes)
Types of Helminths
Flat and round worms
- Most are free living
- Marine and Freshwater
- Predator, Scavengers, or Parasitic
- Some have regenerative capabilities
Trematodes + Cestodes =
Flatworms = Platyhelminthes
- All parasitic of vertebratesHave complex life cycles that include sexual and asexual phasesThey require at least 2 kinds of organisms to complete the cycle They reach sexual maturity in a primary or definitive host (always a vertebrate), their larval stages develop or become encysted in an intermediate host (usually an invertebrate).
- Intestinal parasites of vertebratesNo digestive system like in trematodes & nematodesThey absorb nutrients through their tegument!
- Scolex (head) with suckers and/or hooks (for attachment)
- Proglottids (body units - each one has male and female reproductive organs)
- 1.immature proglottids (closest to the scolex)
- 2.mature proglottids (next closest to the scolex)
- 3.gravid proglottids (furthest from the scolex - in these proglottids, the uterus is filled with eggs).
- The gravid proglottids break off and are passed in the definitive host's fecesLarval forms hatch when the eggs are ingested by the intermediate hostLarvae then encyst in the intermediate host (called a cysticercus or bladder worm)Adult worms usually develop in the definitive host when raw or poorly cooked infected meat is eaten.
larvae encyst in the intermediate host (called a
cysticercus or bladder worm
What part of the body may harbor cysticerci.
Every organ in the body
When a cysticercus dies, it releases
toxins and usually causes a severe allergic reaction, which is sometimes fatal.
- Nematodes are everywhere!!!! They are freeliving in soil, fresh & salt water, & are parasitic in plants and animals.Dioecious (separate sexes).
- a nonliving cuticle, which is secreted by the epidermis and is resistant to the
- digestive enzymes of the hosts.More highly developed than flatworms.Adults do not latch onto the host like the tapeworms
roundworms in the small intestine
trematode worm causing debilitating infection
Tapeworm of cattle and pigs
roundworm of pigs causing Trichinosis
3 major species:
- –S. mansoni (intestinal mesenteric veins) –S. japonicum (intestinal mesenteric veins) –S. haematobium (urinary bladder veins
Snails release 300-3000
cercariae (free swimming larvae)
Cercariae secrete digestive
digestive enzymes and bore into skin
- •½ the eggs can remain: invade intestinal wall, liver, or bladder → hemorrhage
- Unexcreted eggs induce
- cell-mediated delayed type hypersensitvity. Large granulomas are formed and walled off by fibrous tissue
- Granulomas often obstruct venous blood flow to the liver or bladder.
- Survive for up to 20 years evading attack of localized cellular buildup of immune andinflammatory cells
- (Pork Tapeworm)
- Humans can be infected with the adults by consuming rare pork containing cysticerci larvaeLarvae then develop into adults in digestive tract of the human.
- Largest intestinal nematode (round worm) in humans.Disease is called ascariasis Eggs can remain viable even in preservative! Females are longer; males are shorter & have a hooked posterior end
Two types of helminths (worm-like parasites):
Most common route of infection caused by Helminths is by
Eating uncooked meat
- General characteristicsLife cycleGrowing virusViral infectionsOther acellular organisms
- Obligate intracellular parasites (can reproduce/replicate only inside a host cell)Not cellsConsist of nucleic acids (DNA or RNA) in a protein coat, called a capsid (no cell membrane)
Virus insert themselves into a host
host cell & direct the host cell's metabolic machinery to make more virus
Viruses can attack
all cellular organisms
Characteristics of living things:
- 1. reproduction2. metabolism3. organized as cells, contain all organic molecules (lipids, enzymes, nucleic acids, carbs)4. evolution & adaptation to changing environments.
What characteristics do viruses have
- They can evolveThey contain some macromoleculesThey direct their own reproductionHowever, they are not cells - they do not have cytoplasm, a cell membrane, organelles, ribosomes, or a nucleus. They have DNA or RNA, unlike prokaryotic and eukaryotic cells, which have both. In addition, they lack a metabolism of their own (they cannot produce ATP, etc.) - raw materials and driving force (ATP & reducing power) are supplied by the host cell.
Viruses are classified by
- StructureHost range
- Life cycles
Basic structure of a virus is a
nucleic acid surrounded by a protein capsid
Describe a virion
- A complete viral particle (= capsid + nucleic acid + envelope if it is present)
Viruses store their genetic info in the
Viruses protein coat that surrounds the nucleic acid is called
the constituent protein molecules making up the capsids are called
3 basic shapes based on how the capsomeres are arranged
proteins fit together as a spiral to form a rod-shaped structure
- proteins are arranged in equilateral triangles that fit together to form a geodesic dome-shaped structure; some appear almost spherical; you may have seen
- architectural structures that have this shape
combination viruses with a helical portion (tail) attached to a polyhedral portion (head); ex. many bacteriophages; may also have a tail sheath (participates in injecting the viral nucleic acid into the host cell), plate, pins, & tail fibers (help virus attach to host cell).
Viruses that lack envelopes are called
Envelopes also help viruses infect new cells by
Fusion of the envelope with the host's cell membrane
Viral specificity is determined by whether or not a virus can
- Attach to a cell
- Attachment depends on the presence specific receptor sites
Examples of receptor sites are
Proteins, LPS’s, glycolipids, or glycoproteins.
Lytic Cycle: Replication
- a. Adsorption - the virion attaches itself to aspecific receptor site on the surface of the host cell.
- b. Penetration - the viral nucleic acid penetrates the host cell
- c. Uncoating - removing the capsid & enveloped. Viral Synthesis (Latent Period) (also
- called biosynthesis) - more viral components
Virus remains latent for many cellular generations by becoming
integrated into a host cell's chromosome (the integrated viral DNA is called a prophage
Produce population of bacteria infected with the prophage occurs by
Cultivating Animal Viruses is done more economical & efficient by
Embryonated chicken eggs
measles virus causes the membranes of neighboring cells to
fuse, creating giant, multinucleated cells. (Infection that can be seen under the microscope
large group of RNA viruses; includes
- (Human Immunodeficiency Virus) which causes AIDS (acquired immune deficiency syndrome); infects T cells (type of white blood cell).
Retro means "backward." This virus uses the enzyme
enzyme reverse transcriptase to make DNA from its RNA. This DNA can be integrated into the host cell's chromosome
AZT (azidothymidine), which is used against
HIV, helps stop reverse transcription by targeting the enzyme reverse transcriptase
uncontrolled growth of tissue (cells are dividing out of control); most are benign (non-life threatening); some are malignant (they spread or metastasize to surrounding tissues).
malignant tumors that metastasize to surrounding tissues
Tumors and Cancer Causes
Most human cancers arise form genetic mutations or cellular damage caused by environmental factors (chemicals - nicotine, pesticides; radiation - UV, X-rays, etc.; diet). About 15% are attributed to viral infections.
Viruses and Cancer Examples:
- Human T-cell leukemia (blood cancer), Epstein-Barr virus causes Burkitt's lymphomaHepatitis B virus causes hepatocellular carcinoma (liver cancer)Human papillomavirus causes skin & cervical cancers.Kaposi’s sarcoma – thought to be associated with herpesvirus
- Viroids: circular molecule, dont produce proteins, cause plant disease
- Prions: Infectious agent composed only of protein, affect CNS,
eukaryotes that can cause mycoses
unicellular animal-like eukaryotes
are multicellular parasites
Viruses, viroids and prions are
are acellular infectious agents