Microbiology Chapter 5

structure of eukaryotic cell

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* nucleus with linear chromosomes
* membranous organelles: ER, Golgi, vacuoles
* mitochondria
* chloroplasts

Ostreococcus tauri

smallest members of the Eukarya domain, demonstrates that even a tiny eukaryote has all of the basic structures

mitosis

process of segregating the two copies of all chromosomes evenly into the daughter cells

asexual/vegetative reproduction

the type of reproduction that takes place without the formation of gametes

many eukaryotic microbes can proliferate indefinitely by mitosis

meiosis

process of gamete formation that requires a special modification of mitotic cell division

results in 4 unique haploid cells

mitosis process

chromosomes are replicated to form identical DNA pairs beforehand

1. nuclear membrane falls apart, chromosomes condense, centrioles move to poles
2. chromosomes align at cell equator
3. DNA copies separate and move toward poles
4. nuclear membranes and centriole reform, making 2 identical daughter cells

meiosis process

replication of all genetic material → diploid 2n forms temporarily (4 copies of each homolog)

1. nuclear membrane falls apart, centrioles move to poles; duplicated chromosomes pair with homologs, forming tetrad → cross over
2. tetrads align with equator
3. homologs separates and move toward poles with DNA copies still paired
4. daughter cells form but enter a second round of division similar to mitosis
5. 4 unique gamete cells form with one copy of each chromosome, recombined from each parent

fungi and microsporidians

filaments or yeasts that lack motility, tough cell wall as made out of chitin

heterotrophs by absorptive nutrition and includes decomposers and parasites

yeasts

single celled fungi that can produce antibiotics, make food (cheese and bread)

capable of sexual and asexual reproduction → environmental conditions determine which type of life cycle it's in

form pseudohyphae from individual cells

Saccharomyces cerevisiae

yeast, used to leaven bread and brew wine/beer

yeast reproduction

haploid cell → ascus with ascospores (asexual, dividing by themselves) → haploid mating cells in contact → mating (cell fusion and nuclear fusion) → mated haploids (zygote budding)

filamentous fungi

fungi hyphae (undergo a life cycle to make spores; either septate or nonseptate) extend and form branches, producing a mycelium

chitin in cell walls

septate

one nuclei per unit

nonseptate

having no dividing walls, continuous cell with many nuclei

ascomycete life cycle

(from slides)

ascospores germinate to form hyphae (n) → cytoplasmic fusion (2n) → hyphae containing paired nuclei grow into mycelia → asci develop within fruiting body → meiosis forms linear ordered tetrads of ascospores in asci → some species pack asci in fruiting bodies

fungi sexual reproduction

1. haploid fungi form hyphae with gametes at tips (n)
2. gametes' cytoplasms fuse to to produce a cell w/ 2 distinct nuclei
3. nuclei fuse to create a diploid zygote
4. the zygote undergoes meiosis to from spores that germinate to start the haploid stage — eventually creates more haploid mycelia

fungi asexual reproduction

by mitosis, mitosis with budding, fragmentation of hyphae, formation of asexual spores by mitosis

Histoplasma capsulatum

dimorphic fungus that grows in soil exposed to bird feces or bat feces (temperature dependent)

outdoors → grows as a mycelium

inhaled into body → high body temp → turns into yeast that can multiply in the lungs, causing chronic lung histoplasmosis

Candida albicans

grows as yeast in the lungs and as filaments in soil

amoebas

2 major groups

Entamoeba histolytica

amoeba, causes amoebic dysentery (bloody diarrhea) or intestinal amoebiasis

identified by Wheatley's trichrome stain

fecal

Wheatley's trichrome stain

cytoplasm of protozoa stains green/blue

nuclear membrane and ingested RBCs (provide nutrients for amoeba) stain bright red

Entamoeba histolytica development

1. human ingests cysts (in contaminated water) which have a tough covering and can be viable for a long time
2. cells ex cyst and develop into trophozoites (active feeding state)
3. trophozoite amoebas ingest RBCs
4. some amoebas develop into dormant cysts, which exit in the feces

dormant cyst

formed when cyst runs out of food supply, viable for a long time

Naegleria fowleri

causes primary amoebic meninogoencephalitis (infection of the brain), enters through the nose

Acanthamoeba keratitis

causes corneal infection, commonly results from improperly cleaned contact lenses

ciliates

protists with cilia (short, hairlike organelles composed of microtubules) to capture prey → consume algae and smaller protists

consumed by amoebas

most are free

conjugation

sexual reproduction for a ciliate

1. 2 paramecia of opposite mating types form a cytoplasm bridge
2. micro nucleus (2n) undergoes meiosis
3. 3 of 4 meiotic products disintegrate, leaving one micro nucleus (n)
4. haploid micronuclei replicate and divide (mitosis)
5. haploid micronuclei exchange over cytoplasmic bridge, macronuclei disintegrate
6. haploid micronuclei fuse, becoming diploid 2n
7. macronucleus reforms

oral groove

a depressed region around the mouth of some ciliate protozoans, such as Paramecium

digestive vacuole

contains digestive enzymes in ciliates to digest nutrients

contractile vacuole

cell structure in ciliates to expel excess water out

Stentor

stalked, ciliated predator

cilia draw prey into mouth, found in wastewater treatment community

parasomal sac

pores that take in substances for ciliates

amoebas

heterotrophic protists with amorphous shape

motile with pseudopods → cytoplasmic streaming to extend in direction they want to move

apicomplexans

intracellular parasites with complex life cycles; form a major group of humans and other animals

apical complex enables attachment and penetration of host cell

apical complex

a specialized structure that facilitates entry of the parasite into a host cell

malaria

transmitted by Plasmodium spp. and is a mosquito vector

toxoplasmosis

Toxoplasma gondii, food borne and congenital transmission

definitive host

a host where the parasite matures and replicates sexually

intermediate host

a host that gives food and shelter to immature stages of a parasite, supports proliferation

Plasmodium life cycle

1. female Anopheles mosquito takes a blood meal (injects sporozoites)
2. enters exoerythocytic cycle → infected liver cell
3. schizont forms
4. schizont ruptures, releasing merozoites
5. enters erythrocytic cycle (asexual multiplication) → immature trophozoite (ring stage)
6. either matures and forms a schizont that also ruptures
7. or becomes gametocytes (P. vivax, P. ovale, P. malariae)
8. enters sporogonic cycle → mosquito takes blood meal (ingests gameocytes)
9. microgamete enters macrogamete
10. forms ookinete
11. ookinete becomes oocyst
12. oocyst ruptures and releases sporozoites → cycle restarts

ookinete

motile, elongated zygote of Plasmodium

schizogony

asexual reproduction by multiple fission; produce thousands of trophozoites called merozoites

hypozoites

stays in liver from exo

ring stage

young trophozoite in blood cell → diagnostic feature

advantages of growing a mycelium

1. enables coordinated expansion into a food resource such as a host tissue
2. enables it to avoid being engulfed by amoebas or host macrophages

advantages of growing as a single

celled yeast

Enterobius vermicularis (lifecycle)

1. eggs on perianal folds → larvae inside eggs mature within 4

Taenia solium (lifecycle)

1. eggs or gravid proglottids in feces → passed into environment
2. cattle and pigs become infected by ingesting vegetation contaminated by the eggs/gravid proglottids
3. oncospheres hatch, penetrate intestinal wall and circulate to musculature
4. oncospheres develop into cysticerci in muscle
5. humans infected by ingesting raw/undercooked meat

slime molds

fungus

plasmodial slime molds

a type of protist, commonly seen on decaying forest litter and rotting wood

play an important role as de composers and recyclers of nutrients in food web

Dictyostelium discoideum (lifecycle)

1. plasmodium mature fruiting body generates spores → meiosis
2. mature fruiting body releases spores (n)
3. spore germinates
4. germination gives rise to amoeba which divide to form more individual cells
5. two amoebas fuse to form a zygote (2n)
6. zygote grows and undergoes meiosis and multiple rounds of mitosis
7. new haploid amoebas are released
8. amoebas aggregate into a structure aka a slug
9. slug migrates at a rate of 2mm per hour
10. migration stops and aggregate forms a fruiting body at the end of a stalk

haploid form

(n), this form of the parasite requires fewer resources and generates fewer varieties of coat proteins

diploid form

(2n), this form generates novel combinations of genes that my provide a new advantage when the environment changes or when the parasite enters a new host

thus, most eukaryotes will maintain the option of alternating between this form and haploid form

African Trypanosomiasis (lifecycle)

1. tsetse fly takes blood meal (injects metacyclic trypomastigotes)
2. injected metacyclic trypomastigotes → bloodstream trypomastigotes → carried to other sites
3. trypomastigotes multiply by binary fission in various body fluids
4. circulating trypomastigotes in blood during acute phase, usually undetectable in latent pahse
5. tsetse fly takes blood meal (ingests bloodstream trypomastigotes)
6. transform into procyclic trypomastigotes in vector midgut, multiply by binary fission
7. procyclic trypomastigotes leave midgut → epimastigotes
8. epimastigotes multiply in salivary gland → metacyclic trypomastigotes

cycle restarts

trypanosomes

vector

T. brucei

trypanosome, causing sleeping sickness

L. donovani

trypanosome, transmitted by sandflies

causes leishmaniasis

T. cruzi

trypanosome, causes Chagas' disease

metamonads

flagellated parasites that lack mitochondria → look for anaerobic environments (aka in intestines)

Giardia lamblia

example of metamonad, common in daycare

Aspergillus

(ascomycetes) plant saprophyte, produces aflatoxin, infects lungs of immunocompromised patients

Blastomyces

(ascomycetes) blastomycosis, opportunistic infections of skin

Candida

(ascomycetes) yeast infections, thrush, opportunistic

Geomyces

(ascomycetes) white

Histoplasma

(ascomycetes) histoplasmosis, lung disease

Magnaporthe

(ascomycetes) rice blast, the most important disease of rice farming

Penicillium

(ascomycetes) grows on bread and fruits, original source of penicillin

Saccharomyces

(ascomycetes) ferments beer and bread dough

Stachybotrys

(ascomycetes) black mold, contaminates dwellings

Trichophyton

(ascomycetes) ringworm and athlete's foot skin infections

Cryptococcus

(basidomycetes) opportunistic infection of patients with AIDS

Nucor

(zygomycetes) soil mold, opportunistic infections

algae

protists that conduct photosynthesis by using chloroplasts

either green or red

green algae

photosynthetic autotrophs that have chlorophyta (pigment)

can be unicellular or multicellular

red algae

photosynthetic protist that has rhodophyta (red pigment)

dinoflagellates

major group of marine algae, essential to marine food chains

flagella wraps around the organism to provide a whip

Karenia brevis

dinoflagellate that is responsible for the red tide

helminths

parasitic worms: nematodes, trematodes, cestodes

nematodes

(roundworms) cylindrical with a digestive tube that ends in an anus

trematodes

(flukes) oval

cestodes

(tapeworms) parasitic flatworms, absorbing nutrients through their skin

sucker head structure grows a long "tail" of segments containing male and female reproductive structures

segmented

pinworms

small, white nematodes of the species Enterobius vermicularis

infections occurs via self

hookworms

enter body through bare foot

travel through blood to lungs → penetrate alveoli → host coughs → parasite moves to throat and gets ingested → latch onto intestinal lining and suck blood → offspring exit host feces

Ancylostoma duodenale, Necator americanus

examples of hookworms

Ascaris lumbricoides

(roundworm), eggs ingested from soil → increase in size in digestive tract

worms can invade lungs and other organs → life

flatworms

(platyhelminthes) have an internalized mouth, pharynx, digestive tube which ends in one or more pouches aka caeca

expels wastes back out mouth + has 2 suckers (mouth and ventral side) for sticking

tapeworms

transmitted as larvae in uncooked meat (different species in different meats)

composed of a head and successive segments

may grow 2

gravid proglottids

mature tapeworms that produce eggs

Taenia solium

(cestode) found in undercooked pork

Taenia saginata

(cestode) found in undercooked beef

Diphyllobothrium latum

(cestode) found in undercooked fish

Clonorchis, Opisthorchis

(trematodes) infect liver

Fasciolopsis buski

(trematodes) infects intestines

Paragonimus westermani

(trematodes) infects lungs

Schistosoma mansoni, S. haematobium, S. japonicum

(trematodes) snails that burrow through skin to reach host

Echinococcus granulosus

(cestode) infects dogs

Trichuris trichiura

(nematode) human whip worm

Toxocara canis, T. cacti

(nematode) found in dogs/cats

Trichinella spiralis

(nematode) contracted by consuming undercooked meat