Eukaryotic Cell Reproduction PDF

Chapter 11 11.1 An Overview Eukaryotes and Overview What are eukaryotes whether humans or microbial eukaryotes posses a nucleus and othe key membrous organelles, and nearly all posses a mitochondria These organelles includes: nucleus, mitochondria enedmomebrane system, golgi and a chloroplas...

Chapter 11 11.1 An Overview Eukaryotes and Overview What are eukaryotes whether humans or microbial eukaryotes posses a nucleus and othe key membrous organelles, and nearly all posses a mitochondria These organelles includes: nucleus, mitochondria enedmomebrane system, golgi and a chloroplast. Membranous organelles includes -ER, golgi, and vacuoles (granules) Reproduction of Eukaryotic Cells: All eukaryotes have linear chromosomes and must divide by mitosis. The “ends” of linear chromosomes require special means of replication not required for most bacteria with their circular chromosomes mitosis is the process of segregating the two copies of all chromosomes gently into the daughter cells ◦ DNA replication occurs during a portion of interphase, the active state of the cell. ◦ Once complete, most enzymatic activities halt in preparation for mitosis ◦ Mitosis ensures that each daughter cell receives a full set of chromosomes In most cases mitosis involves 4 phases: (PMAT) Prophase: paired chromosomes post replication condense into short rods, in most species the nuclear envelope dissolves Metaphase: teh chromoses arrange it self along a place across the equator of the cell. Anaphase: the pairs seperate pulled by spindle fibres composed of microtubule s that contract. The separated chromosomes are pulled towards the opposite poles of the cells. Telophase: the choromosed dcondense (becomes long and thin again), and a nuclear membrane forms around each set. The cell completes division of its cytoplasm, forming two daughter cells. Many eukaryotic microbes, such as yeast, can proliferate (rapid increase in numbers) indefinitely by mitosis, a process called asexual reproduction or vegetative reproduction. Most eukaryotic organisms also have the option of sexual reproduction, which requires the reassortment of genetic material form different chromosomes. sexual life cycle diploid sex cells (2n = containing two copies of each chromosomes) to haploid sex cells (n). Two of the haploid sex cells called gametes, can join each other thru fertilization to create a diploid cell (zygote). ◦ The diploid contains two homologous of each chromosomes, two versions of the same chromosomes from each parent. The process of gamete formation requires a special modification of mitotic cell division called meiosis ◦ Includes meiosis I an meiosis II ◦ Meiosis I must be pre[receded by replication of all chromosomes during interphase. Diploid cell will have four copies of each DNA homolog. ◦ Prophase I = there will be an exchange of portions of their DNA. The process known as crossing over. ◦ Same process happens after for meiosis II leading to a result of four haploid cells. What is the consequences of alternation between haploid and diploid? In the haploid from, the Protozoa requires fewer resources, resulting in less genetic variation and fewer antigenic changes. As the Protozoa transitions to the diploid form, increased genetic diversity occurs, alllowing it to better adapt to new hosts or changing environment. ◦ Diploid forms generate novel combinations of genes that may provide an advantage when the environment changes or when parasites enter the cell. ◦ This is why in most eukaryotic organisms they maintain an option for sexual reproduction ◦ For example, the malaria parasite proliferates mainly as haploid but undergoes a brief cycle of fertilization and meiosis within the insect vector. This genetic variation in the diploid stage enhances the parasite’s ability to evade the hosts immune system and thrive in different conditions. Diversity of Microbial Eukaryotes Eukaryotes -> animal and plant Microbial eukaryotes are classified traditionally as fungi , Protozoa, and algae Fungi: hyphae (filaments of cells) and yeast (single cells) lack photosynthesis yet were considered to be a form of plant, because they grow in soil and other substrates, As a result mycology ( study of fungi) was often included in botany. Protozoa: amebas and paramecia Are motile and appear more like microscopic animals They are terms as first animals Microscopic life forms containing green chloroplast are termed as algae, and were thought to be primitive plants. Some Protozoa have chloroplast, some algae are motile with flagella. They call them collectively as protists. Protist: algae + Protozoa (not animals, plant, fungi) Plants show close genetic relationship with “primary algae”, green algae that evolved from a common chloroplast bearing ancestor. Animals most closely related to fungi. this is a surprise because animals are thought to be more similar to protists that have motility. Major groups of microbial eukaryotes includes: These groups are considered as true microbes, even if there are some that are macroscopic forms. fungi ◦ They have absorptive nutrition, digesting many complex plant polymers. Most are non-motile ◦ Microsporidians are spore-forming organisms closely related to fungi. Amebas ◦ Single called protist of highly variable shape that form pseudopods, locomotor extensions of cytoplasm enclosed by the cell membran e. Ciliates are single celled protists with short, whiplike motility organelles called cilia. Most are free living, but some are human parasites Trypanosomes and metamonads ◦ Flagellated protists with complex parasitic life cycles involving developmental stages within host Algae ◦ Are protists containing chloroplasts that conduct photosynthesis, related to those of plants. ◦ Some algae are single-celled, whereas others grow as filaments or sheets. ◦ Dinoflagellates possess chloroplast obtained by their ancestral cells via endosymbiosis of green algae. Some other multicellular parasites are not considered as microbes, although they are considered as mites and worms. These invertebrate animals have fully different organ systems, sometimes comparable in complexity to those of vertebrates. The dynamics of transmission and infection of invertebrate parasites parallel those of microbial pathogens. Therefore, these animals parasites are often covered by health professionals under the category of “eukaryotic microbiology: helminths ◦ Are multicellular worms, including the nematodes (roundworms), custodies (tapeworms), and trematodes (flukes). Arthropods ◦ Include insects such as fleas and lice, as well as no insects such as mites. Worms and arthropods are a major source of morbidity and mortality worldwide. a quarter of worlds population is paratizied by worms. 11.2 Fungi and Microsporidians Fungi Fungi recycle wood and leaves, including substances, such as lignin, that animals cannot digest. many are saprophytes (live on dead organisms) They decompose animal bodies they produce antibiotics such as penicillin and contribute to food products such as beer and cheese. Mycorrhizae (mycorrhiza) underground fungal filaments, extend root systems or trees, forming a nutritional internet, that interconnect s plant commiunities. Candida albicans and Candida auris some fungi are pathogens that threaten the lives of humans, animals, and plants Normally carried by most people, but can kill a susceptible patients. C.auris is a deadly pathogen spreading in hospitals. Is resistant to nearly all antifungal agents and has a mortality rate of 35% Yeast are single celled fungi Advantage of rapid growth and dispersal in aqueous environment. Baker’s yeast, Saccharomyces cerevisiae, is used to leaven bread and to brew wine and beer. Candida albicans ◦ Important members of human vaginal biota. ◦ Also an opportunistic pathogen, causing infections such as thrush in the mouth of patients with aids. ◦ Some fungi can grow as yeast or as filamentous fungi, depending on the environment. ‣ These are known as dimorphism fungi ‣ This includes blastomyces dermatitidis = causes blastomycosis a type of pneumonia ‣ B.dermatitidis grows as yeast within the infected lung, in culture and in soil environment it forms multicellular filaments Pneumocystis jirovecii ◦ Yeast form ascomycete Cryptococcus neoformans ◦ A yeast form basidiomycete, S.cerevisiae ◦ Some yeast are asexual, some alternate between diploid and haploid, forms a life cycle known as alternation of generations. ◦ Both haploid and diploid forms are single cells. ◦ The haploid cells undergo several generations of mitosis and budding. ◦ This asexual reproduction is referred to as vegetative growth. ‣ At some point, however, various stress conditions, such as nutrient limitation may lead to haploid cells to develope into gametes. ‣ The gametes are two mating types. Cells of two mating type s may fertilize each other by fusing together and combining their nuclei to make a diploid zygote, ‣ The diploid cells - may undergo vegetative budding and reproduction. ‣ Under stress the 2n cell may undergo meiosis, regenerating haploid cells. The haploid progeny possess chromosomes reasserted and recombined from those of parental gametes. Filamentous Fungi Aspergillus is a filamentous fungus of the ascomycete group Filaments of aspergillus typically grow in soil or indoors as basement mild or on air conditioning coils. It forms spores that can reach significant concentrations, where it can b e taken into the lung and may cause allergic reactions. in patients with impaired immune function, they may germinate and grow into fungus balls, that require surgical removal. In franks case, the infection was community acquired. Frank’s predisposing conditions had allowed the fungal infection to take hold. Many fungi grow as multicellular branched filaments Hyphae they undergo a life cycle that produced spores for dissemination Inhalation of fungal spores cna lead to aspergillosis and histoplasmosis (dangerous for immunocompromised patients). Other fungi cause skin infections such as ringworm and athletes foot (tinea pedis) The fungi most commonly found in humans or in or local environments include: Ascomycetes (form asci, pods of eight spores) Aspergillus = plant saprophyte; produces aflatoxin; infects lungs of immunocompromised patients Blastomyces = blastomycosis; opportunistic infections of the skin Candida = yeast infections; thrush; opportunistic Histoplasma = histoplasmosis, lung disease Trichophyton = ringworm and athletes foot and skin infections Basidiomycetes (mushrooms and mycorrhizae) Cryptococcus = opportunistic infections of patients with AIDS Zygomycetes (saprophytes, insects pathogens, and mycorrhizae) mucor = solid mold; opportunistic infections Microsporidia (related to fungi) encephalitozoon = opportunistic infections of patients with AIDS Hyphae have though cells that are composed of chitin chitin is acetylated amino polysaccharide stronger than steel. There are multiple hydrogen bonds between fibres. It’s grows by extending multinucleated cells. As a fungal hypha extends. It’s nuclei divide mitotically without cell division.. the hyphae form branching tufts called mycelium, ◦ The mycelium may grow large enough to be seen as fuzzy colony or puffball. ◦ As the hypha extends its chitinous cell wall enables it to penetrate softer materials, such as plant or animal cells. the biosynthesis of chitin provides a target for antifungal agents such as nikkomycin Z. Another drug target is the membrane lipid ergosterol an analog of cholesterol not found in animals or plants. Ergosterol biosynthesis is inhibited by antifungal agents called triazoles Most fungal forms are nonmotile (with the exception of chytridiomycete zoospores). Fungi cannot ingest particlulate food, as do protists. This is because their cell walls cannot be part and re-form like the flexible pellicle of amebas and ciliates does. ◦ Instead, fungi secrete digestive enzymes and then absorb the broken-down molecules form their environment. Filamentous fungi can expand at great length by asexual division (mitosis) eventually, however, they run out of nutrients, and the cells undergo meiosis to form gametes. The gametes develop into spores for dispersal. ◦ Example of spore-forming life cycle is that of ascomycete fungi such as aspergillus or morchella In an ascomycete, the tips of the diploid mycelium undergo meiosis and develop into haploid ascospores within pods called asci. ◦ The ascopores dispersed until they germinate in a region of fresh resourced, ◦ Each ascus undergoes celll division to form a haploid mycelium, which is male or female. ◦ The male and female structures fuse, followed by migration of all the male nuclei into the female structure ◦ The paired nuclei then undergo several rounds of mitotic division while migrating into the growing mycelium ◦ In the mycelia tips, the paired nuclei finally fuse (becoming 2n) and re-form a diploid mycelium ◦ Overall, the diploid-haploid life cycle enables a fungus to respond genetically to environment change by reassorting its genes through meiosis and fertilization, ◦ Rene assortment provides new genotypes, some which may increase survival in the changed environment. Some fungi pack their asci (or other spore-producing forms) into a larger structure called fruiting body. ascomycete such as aspergillus and penicillium mold form relatively small fruiting bodies called conidiophores, that disperse airborne spores. Conidiopore-forming ascomycetes are the major type of mold associated with dampness in human dwellings; they caused massive damage to homes flooded in teh wake of hurricane Katrina. The fruiting bodies of other ascomycete fungi can be impressively large and edible as prized foods. Morels and truffles form large, mushroom-like fruiting bodies whose ascospores are dispersed by animals attracted by their delicious flavour. The famous truffles grow underground, where human collectors traditionally use muzzled pigs to detect and unearth them. Quick Look at Other: helminths (parasitic worms) ◦ Many human pathogens ◦ Includes organisms like roundworms (nematodes), tapeworms (cestodes), and flukes (trematodes) ◦ They are highly prevalent worldwide and cause diseases such as schistosomiasis, ascariasis, and filariasis Fungi ◦ Includes yeasts, molds, and dimorphic fungi ◦ Pathogenic fungi include candida, aspergillus, and cryptoccocus (athletes foot to life threatening systemic infections) Apicomplexnas ◦ Many human pathogens ◦ Theses protozoans include plasmodium (causes malaria), toxoplasma gondiim and cryptosporidium. ◦ They are responsible for serious deisease like malaria, toxoplasmosis, and cryptosporidiosis Trypanosomes ◦ Several human pathogens ◦ Includes species like trypanosomiasis Bruce I (causes African sleeping sickness) and trypanosome Cruze (chagas disease), these Protozoa are transmitted by insects and cause severe systemic diseases Amebas ◦ Several human pathogens ◦ Includes entamoeba histolytica (ameobiasis), and free-living amoebae like naegleria Fowler I (primary amoebic meningoencephalitis) ◦ Most amebas are not pathogenic to humans. Metamonads ◦ Some human pathogens ◦ Includes giardia lamblia (giardiasis) and trachoma as vaginalis (trochomoniasis) Arthropods ◦ Few direct human pathogens, but many are vectors. ◦ Some arthropods (e.g., scabies mites, lice) directly infect humans. ◦ Most arthropods (like mosquitoes, ticks, and fleas) are vectors for other pathogens. Ciliates ◦ Few human pathogens. ◦ The primary human pathogen is Balantidium coli (balantidiasis). Microsporidia ◦ Few human pathogens. ◦ These are obligate intracellular parasites that can cause disease, especially in immunocompromised individuals (e.g.,Enterocytozoon bieneusi), but they are relatively rare compared to other eukaryotic pathogens. Algae ◦ Few human pathogens. ◦ Algae are mostly non-pathogenic to humans. However, some species, like Prototheca (a rare algal pathogen), can cause protothecosis in immunocompromised individuals. Toxic algal blooms (typically cause poisoning rather than infection). 11.3 Protozoa: From amebas to trypanosomes Amebas are voracious predators, consuming other protists and bacteria. two major groups ◦ Lobed amebas with large, bulky pseudopods -> cytoplasmic stream ‣ More familiar kind ‣ Have pseudopods that extend lobes of cytoplasms through cytoplasmic streaming Cytoplasmic streaming is the flow of nutrients through the cytoplasm, mediated by actin proteins ‣ Most are free living in soil or water, where they pray on bacteria or small arthropods ‣ Important in aquatic ecosystems. ‣ Some ameabas are slime molds where they are covered in fruiting bodies ‣ Some types causes dysentery and meningitis. ◦ Filamentous amebas with thin needle like pseudopods ‣ Some amebas with needle like pseudopods, such as formaminiferans (forams) ‣ Form inorganic shells made of calcium carbonate Fossil formaniniferan shells are common in rock formations derived from ancient seas. Diseases causing amebas: Ameabas are usually ingested in the form of cyst (Entamoeba histolytica = intestinal illness, common in developing world, lead to malnutrition and death.) Dormant cells encased in a tough coating. They can remain viable for many weeks in contaminated water. The ingested cysts (non metabolic = more resistant, same with endospore) can reach the intestine, where they can “excyst” and develop into trophozoites (they are metabolic) ◦ It will not turn into an active site until it passes the intestine. ◦ That’s why they start colonization in the colon ◦ Ameabas with pseudopods that phagocytose prey. In the internal lumen and bloodstream ◦ The ameabas ingest RBC (erythrocytes) ◦ As they run out of food they become dormant cyst, which exit through the oral fecal route ◦ In several cases they may invade the liver, lungs and other organs. ‣ Which organism stays in the liver? (E.Histolytica) creates abseses = pus Dysentery caused by different pathogens and viruses, which is why they should be identified correctly to issue correct medication. Shigella ◦ May be detected by immunological tests To diagnose the presence of ameabas and other intestinal parasites requires microscopy because their cell size and shape are distinct Wheatley’s trichrome stain ◦ Reveals parasite amounts human cells and fecal material ◦ Cytoplasm of Protozoa stain green/ blue ◦ Nuclear membrane and ingested RBC stains bright red ◦ Cyst forms of ameabas stains blueish purple ◦ Closely related nonpathogen Entamoeba dispar and E.histolytica are indistinguishable. (EH is more common tho) Can be avoided by careful fluid consumption. Only drink filtered water, avoid fresh produced that may have been washed by contaminated water. Healthy host can eliminate amoebic infection within 2 weeks. Repeated infections can cause malnutrition Can also lead to chronic carrier status and can lead to systemic infections involving the liver, lungs and other organs, ◦ Systemic infections are difficult to treat and can be lethal. ◦ Drug paromomycin specifically targets the small subunit RNA of microbial eukaryotes ◦ Metronidazole - targets anaerobic Protozoa and bacteria. Other diesease involving amebas Primary amoebic meningoencephalitis infection of the brain and meninges Caused by Naegleria Fowleri and balamuthia mandrillaris (5-7 days) ◦ The amebas may enter the body through the nose during swimming in contaminated water. ◦ Stiff neck = meningise ◦ Fever = meninges (spef.) and brain ◦ Sezuires, confusions, and headache = brain Same cycle the nose is warmer - which is an ideal environment ◦ They will turn into flagellated trophozoite = easier to move around ◦ They will attach to the respiratory epithelium, release enzymes to break immune Barriers to cross teh cribriform plate. ◦ This will allow them to pass the bloodstream in order to colonize the brain immediately ‣ Harder to reach with medication ‣ Starts replication in olfactory bulb and jump to the brain immediately Acanthamoeba may contaminate contact lens cleaning solutions Causing keratitis Free living soil ameabas Layer of the eye is avascular, harder for the medication to reach the cell ◦ There is no path (blood) to reach the pathogens host ameabas free-living ameabas can play as host for other pathogens ◦ Legionella pneumophila = legionellosis =fatal penumonia ‣ Often contaminate water supplies, air ducts, dental irrigation solutions. The host ameabas enable the pathogen’s persistence and transmission to human host. Predators and Parasites Ciliates are covered with cilia ◦ Short hairlike organelles composed of microtubles ◦ The beating cilia propel a stream of prey to the oral groove Consume algae and smaller protists They are consumed by ameabas Balantidium coli ◦ Cause of dysentery Powered by ATP hydrolysis ◦ The cilia beat in coordinated waves that maximize the efficiency of motility Cilia serve two functions: ◦ Cell propulsion ‣ Coordinated waves of beating cilia ‣ Usually covering the cell surface, propel the cell forward ◦ Food acquisition. ‣ By generating water currents into the mouth of the cell, a ring of cilia around the mouth brings food into the cell. Paramecium ◦ One of the best-studied ciliates ◦ Feed on bacteria by trapping them in the oral groove and the consuming therm through enzymes within digestive vacuoles. ◦ They can also take up smaller particles through endocytosis by specialized pores in their cortex parasomal sacs. ◦ They are consumed by larger ciliates such as didinium. Alveolate ◦ Ciliates Complex cell form ◦ Referring to the flattened vacuoles called alveoli within the outer cortex ◦ Some alveoli contain plates of stiff material such as protein, polysaccharide, or mineral. ◦ Without a rigid cell walls, how do ciliates maintain osmotic balance? ‣ Ciliates generally grow in aqueous solutions with salt and organic concentrations that are lower than those of their cytoplasm. ‣ Water concentration outside is higher, and water tends to run into the cell. ‣ Excess water is expelled by a connective vacuole, which withdraws water from the cytoplasm or contracts to expel it. ‣ Contractile vacuoles are widespread among protists and algae, but their mode of action has been studied mostly in paramecia. ‣ As water enters the cell from a low-solute environment, the contractile vacuole takes up the water through an elaborate network of intracellular channels and then contracts to expel the water through a pore, thus preventing osmotic shock and lysis. Like other eukaryotes that have nuclei containing chromosomes that undergo division by mitosis and generate gametes by meiosis. They maintain two types of nuclei: ◦ Micronucleus ‣ Genes maintain genetic fidelity for sexual reproduction ◦ Macronucleus ‣ Contains multiple gene copies that express gene products throughout the large cell ◦ During asexual reproduction, both micro nuclear and macro nuclear chromosomes undergo replication For sexual reproduction ◦ Ciliate undergoes conjugation ‣ During, two paramecia of opposite mating types form cytoplasmic bridge. ‣ Within each conjugating cell, the 2n micronucleus undergoes meiosis to form four n game tic nuclei.  ‣ three out of four of the gametic nuclei disintegrate, as dies the macronucleus. ‣ The haploid micronuclei undergo mitosis, forming two daughter micronuclei ‣ Daughter micronuclei from each cell are exchanged across the cytoplasmic bridge and then fuse with their respective counterparts, restoring a 2n micronucleus to each cell. ‣ The bridge cells come apart, and each micronucleus generates a new macronucleus. ‣ The new macronucleus now expresses gene products. Flagellates possessing paires of flagella ◦ Long, whiplike organelles ◦ Powered motion is powered by ATP Apicomplexans form a major group of parasites of humans and other animals. Their anme is derives from the apical complex = specialized structure that facilitates entry of the parasite into a host cell. They are alveolates possessing an elaborate cortex composed of alveoli, pores, and microtubules. But they have undergone extensive reductive evolution, losing their flagella and cilia. parasitic protists may have life cycles involving multiple hosts ◦ Malaria parasite (plasmodium) ‣ Alternates between the human host and the anopheles mosquito ‣ Definitive host = the host where the parasites matures and may reproduce sexually ‣ Mosquito is the definitive host of malaria ‣ Then alternate host (human) is called the intermediate host = supports asexual proliferation of the parasite and is required for transmission to the next insect host. Plasmodium falciparum and plasmodium vivax = main cause of malaria ◦ Carried by mosquitoes and transmits to humans after penetrating skin Life cycle includes development stages in the mosquito Followed by transmission to human host = where parasites undergo stages in the liver and in the blood. In the liver, the transmitted parasites develop into merozoite form = invades RBCs, ◦ Merozoites first contact a RBC through interaction between its apical complex (the structure penetrating tip of the cell) and receptor protein on the RBC ◦ The apical complex contains a pair of score your organelles that ar escaped by a ring of microtubels and that inject enzymes that aid entry of the parasite,. ◦ The tip of the apical complex penetrates teh host cell, enabling secretion of lipids and enzymes that facilitate invasion. ◦ Eventually, the entire merozoite enters the host cell, leaving no traces of the parasite (ring stage) becomes invisible to the immune system until its progeny burst out. Some progeny are then picked up by mosquitoes, where they undergo a sexual life cycle and are transmitted to new hosts. Malaria parasites acquire resistance rapidly and no longer respond to drugs ◦ The life cycle and molecular properties of P.falciparum have been studied extensively for clues t o the development of new antibiotics and vaccines, toxoplasmosis ◦ Toxoplasma Gondii = carried by cates and transmissible to humans ◦ Asymptomatic in humans because of our immune system, but can harm fetus. ◦ Can enter the brain, where it can alter host behaviour ‣ Can cause cases of schizophrenia Babesiosis ◦ Babesia microti = spread by deer ticks, same agents that spread Lyme disease. ◦ Can spread through blood contact and transfusions ◦ Multiple within RBCs ◦ Can mimic symptoms of Lyme disease and are often misdiagnose. Waterborne apicomplexans ◦ Cryptosporidium parvum ‣ Watery diarrhea ‣ Obligate intracellular pathogen, generates cyst form transmitted by fecal-oral route ‣ Resists chlorination = causes major outbreaks of intestinal disease ◦ Cyclospora - danger for immunocompromised patients ‣ Occasional outbreaks from recalls contaminated produce Trypanosomes and Metamonads Euglenids are group of protists that have whiplike flagella and chloroplast arising from secondary endosymbiosis, similar to dinoflagellates but mor distantly related. Some of the euglenids, however, lost their chloroplasts and evolved into obligate parasites called trypanosomes Trypanosomes consists of an elongated cell with a single flagellum They have a unique organelle called “kinetoplast”, which evolved as a specialized mitochondrion that provides energy for the flagellum. Trypanosomiasis ◦ Also known as African sleeping sickness = major killer of humans and livestock ◦ Trypanosoma Brucei = carried by tsetse fly ‣ Multiplies in the bloodstream of the host animal, causing repeated cycles of prolific action and fever that causes increasing drowsiness -> death, if untreated. Anti genetic variation - the ability to generate numerous different versions of its coat protein and thereby evade antibodies of the host immune system. ◦ It’s genome includes 200 different active versions of its variant surface glycoprotein (VSG), the antigen that induces the immune response ◦ In effect, the trypanosome overwhelmed the host immune system by continually generating new antigenic forms until the host repertoire of antibodies is exhausted. Diagnosis requires microscopic detection of the parasite in centrifuged blood. The parasite invade many body systems, causing cardiac and kidney dysfunction. In a late stage, the trypanosomes cross the blood - brain barrier, invading the central nervous system. Neurological impairment leads to distruption of the sleep cycle - hence sleeping sickness To infect human host ◦ They need to interconvert among several different forms of its life cycle ◦ Many forms: ‣ Slender form = proliferates in the bloodstream of a human or other mammal (definitive host) ‣ Stumpy form = does not proliferate in the mammal; it needs to be ingested by the asexual stage. ‣ Only the stumpy form can survive the tsetse midgut to develop into the forms that can grow there (procyclic and epimastigote) ‣ The salivary gland can transmit the parasite to the next host, where the slender form develops again. Metamonads are group of flagellated parasites distantly related to other Protozoa. Giardia intestinalis ◦ Cause of intestinal giardiasis ◦ Is a frequent nemesis of infant day care Centers, significant proportions of caregivers are carriers. ◦ Is also endemic in wildlife and contaminates freshwater streams crossed by bears and other animals, ◦ The parasoites can contaminate community water supplies and is endemic in some Russian cities they are noted for their anaerobic metabolism and their complete absence of mitochondria, lost through reductive evolution; Their metabolism requires the anaerobic intestinal environment of their host. Another common Trichomonas vaginalis ◦ Cause of trichomoniases, one of the most common sexually transmitted infections. ◦ Grows in the urethra and in the vagina. ◦ Men rarely report symptom, but women may experience pain on urination. ◦ Untreated infections lead to complications during pregnancy.. 11.5 Invertebrate Parasites: Helminthes and Arthropods What kinds of parasites are actually multicellar animals? infectious parasites include many invertebrate animals, primarily worms and arthropods. Although they are a=not strictly microbes, some require a microscope to visualize. Their infection cycles resemble those of microbial pathogens. Helminths parasitic worms Wormlike invertebrates that do not share a unique clade. They cause tremendous global burden of morbidity and mortality. Are multicellular animals that possess fully differentiated organs. Although they are invertebrates, their body plans have surprising complexity Caenorhabditis elegant ◦ Free-living soil nematodes ◦ Serves as a major does system for the study of human development. ◦ Many of the worms genes have homologous on the human genome that are involved in vital processes related to neural development, aging and cancer. They include 3 categories: ◦ Nematodes: (roundworms) ‣ Cylindrical, with digestive tube that ends in an anus ‣ They are migratory hermaphrodityes in their reproductive forms ‣ Although a few are male ‣ Pinworms Small white nematodes of species Enterobius vermicularis They infect only humans, most prevenlent helminth infection in the US and Europe Commonly ingested by sucking dirty1ngers. ◦ In the small intestine the larvae hatch and grow, abrosbing nutrients from host (they usually gets unnoticed unless there are large numbers) ◦ The female worms migrate to the anus, where they release their eggs. ◦ Their perinatal movement of worms causes irritation, leading to scratching of anus. ◦ In the process the host fingernails pick up eggs for transfer elsewhere. When left untreated, they can lead to complication ◦ Malabsorption of nutrients and anorexia ◦ Secondaryry bacterial infection may occur at the perianal site or at the vulva where the worms may migrate by mistake All family must be treated Toxocara infects 14% of people contacted mainly from dogs ◦ Toxocariasis commonly contracted mainly from dogs ◦ Can lead to blindness ◦ Pets should receive monthly medication ‣ Hookworms Are common in tropical regions around the world, Unlike pin worms, hookworm larvae grow in the soil, feeding soil microbes until they penetrate the host skin Often through the sole of the feet, They travel through the blood until they penetrate the alveoli in the lungs and then are coughed up to the throat and ingested. Within the small intestine lining and suck blood. Their offspring then exit in the feces. Can cause anemia and protein insufficiency ‣ Trichinella spiral lips The cause of trichinosis Is spiral in shape form of its cysts made by the worm larvae embedded in muscle Transmitted from eating raw or undercooked pork. Bear meat and horse meat can also carry T. Spiralis They mature in the intestinal mucosa, mate, and produce progeny larvae. The larvae now encyst in the host musclesm where they cause pain and eventually death. ‣ Filariasis worms Grow within the blood, lymph, or subcutaneous fatty tissue Biting flies, or aquatic arthropods. They reproduce in large numbers, which enables transmission to new hosts. Bruges Malayi ◦ Large numbers of worms in the lymphatic system may block the lymphatic ducts, leading to swelling of the body parts (elephantiasis) Onchocerca volvulus = river blindness  Dracunculus Medinensis = Guinea worm disease, painful blister on the skin until they are released outside into water. ‣ Roundworms Ascaris lumbricoides - can grow to relatively large size within the human digestive tract and their effects may be lethal ◦ Worms cause infections by ingestions of eggs from soild. ◦ The eggs develop within the digestive tract, where they increase in size indefinitely and can obstruct the intestine. ◦ Worms may invade the lungs or other organs, causing life-threatening damage. ◦ Within the intestine, the worms produce eggs that exit the anus, ◦ Defecation outdoors in soild may lead to transmission to other people who unknowly pick up the eggs on hands or feet. ◦ trematodes ‣ Flukes ‣ Most species require a mollusk as their primary host. ‣ Flatworms = they have an internalized mouth. “Throat”, and digestive tube, but the tube ends in one or more pouches called cecum. ‣ Because the worm lacks an anus, it must expel its wastes back out the mouth. ‣ They have two sucker - one near its mouth and one on the ventral side of the body. The mouth sucker ingests nutrients from the host. ‣ Different fluke species have different attachment to different internal organs ‣ Liver fluke Clonorchis sinensis The fluke arises from eggs ingested by a snail, where the larvae then penetrate the skin and flesh of a fish, where they develop into a secondary form. Eating raw fish, the parasite will attach to a person’s bile duct where it grows and mature. Producing eggs that exit through the bowel and anus. Prolonged growth of the fluke is associated with secondary infections and predisposition to cancer, ◦ cestodes ‣ Tapeworms are transmitted through larvae embedded in uncooled meat ‣ Taenia solium (pork), taenia saginata (beef), and diphyllobothrium (fish) ‣ Infections with fish tapeworms are common in Asia and South America. = raw fish and ceviche has led to increase of incidents. ‣ Tapeworms are flatworms (Platyhelminthes), their worm form is different from both flukes and roundworms, ‣ Composed of a head and successive segments, which form out of the head and then are gradually pushed down in a tail that may grow 2-15 meters. ‣ Scolex - head of the tapeworm, has special sucker device ‣ Each segment contains both male and female reprodcutive organs. Which may cross-fertilize each other ‣ Tapeworm segments packed with offsprings pass out through the anus of the host,where some other host may ingest them ‣ They may grow for many years inside the digestive tract without the notice, until some of the offspring migrate to the muscle, brain, or liver. ‣ They may forms cyst, leading to muscle pain and neurological symptoms such as seizures Arthropods invertebrate animals with an exoskeleton and jointed appendegas They include insects and arachnids (spiders and mites) Free-living, but some are parasites with complex life cycles. Some are ectoparasites = attaching to the surface of a human or other vertebrate Others are parasites that burrow into the flesh Some arthropods parasites suck blood and then fall off Some inject their eggs to develop for many weeks or months inside the host. Arachnid parasites members of the arachnid group Acari - are eight-legged mites and ticks The include many species that are parasites of animals and plants throughout terrestrial habitats. Most people have dermodex mites living in their hair follicles and facial pores. Mites ◦ Mange (in animals) ◦ Scabies (in animals or humans) - a condition also known as acariasis -most often caused by human itch mite (sarcoptes scabiei) ◦ The mites attach to the skin using specia, mouthparts and cutting surfaces on their forelegs ◦ Eggs hatch to larvae, which attach to hair follicles and feed causing inflammation Ticks ◦ Lyme disease and other bacterial infection ◦ Babesiosis ◦ Flaviviruses insect parasites ◦ Six legged, and with or without wings ◦ Lice are wingless ectoparasites ◦ Bedbugs (cimex lectularius)