Exam 2 Week 7

Algae

Algae

not a taxonomic group

unicellular or filamentous photoautotrophs

lacks roots, stems, and leaves

mostly aquatic, water is necessary for growth and reproduction

Characteristics of Algae

locations depend on nutrient availability, light wavelength, surfaces to attach

pneumocyst: floating gas filled bladder providing buoyancy, with sexual and asexual reproduction

most are photosynthetic

chlorophyll a and accessory pigments are responsible for distinctive colors of algae

oomycotes: chemoheterotrophic

Brown Algae

kelp - phylum of algae

cellulose and alginic acid cell walls

multicellular and macroscopic, can reach lengths of 50 meters

produces algin, a thickener for foods

Red Kelp

phylum of algae

have branched thalli

most are multicellular

able to live at greater depths than other algae

harvested for agar and carrageenan, some produce a lethal toxin

Green Algae

phylum of algae

cellulose cell walls, unicellular or multicellular

chlorophyll a and b

stores starch

gave rise to terrestrial plants

Diatoms

phylum of algae

pectin and silica cell walls

unicellular or filamentous

stores oil and produces domoic acid, causes neurological disease

Dinoflagellates

phylum of algae

cellulose in plasma membrane

unicellular

component of plankton (large group of free floating aquatic organisms)

neurotoxins (saxitoxins) causing paralytic shellfish poisoning

ex: pfiesteria piscicida: genus of toxic finolagellate responsible for massive fish kills

Algae Functions

fix CO2 into organic molecules

produce 80% of earths O2

algal blooms: increases in planktonic algae that result in toxin release or die and consume oxygen

produce oil

symbionts of animals

Protozoa

unicellular eukaryotes

inhabit water and soil, over 50,000 species

some are normal microbiota in animals while some cause disease

ex: plasmodium: causes malaria

animal like nutrition

complex life cycles, some produce a cyst to survive adverse conditions

Trophozoite

feeding and growing form of protozoa

Schizogony

a type of protozoa asexual reproduction

multiple fissions

also can occur by fission budding

sexual reproduction is conjugation

Characteristics of Protozoa

require large amounts of water

many have outer protective pellicle, requiring specialized structures to take in food

ciliates wave cilia toward mouthlike cytosome

amebae phagocytize food

food is digested in vacuole and waste is eliminated through anal pore

Feeding Grooves (Excavate)

medically important protozoa

move by means of flagella and undulating membranes

ex: diplomonads: giardia intestinalis

ex: parabasalids: trichomonas vaginalis

ex: euglenozoa: trypamosome spp

Amoebozoa (Ameba)

medically important protozoa

move by means of pseudopods

Ciliates

medically important protozoa

move by means of cilia

Conjugation

a ciliate undergoing sexual reproduction

Diplomonads

medically important protozoa

no mitochondria, multiple flagella

Parabasalids

medically important protozoa

undulating membranes, no cyst stage

Eugleenozoa

medically important protozoa

photoautrophs or facultative chemotrophs

hemoflagellates: transmitted by bites of blood feeding insects

Giardiasis

caused by giardia duodenalis

flagella protozoan that forms cysts in feces and water, trophozoites in body

attaches to intestinal wall

acquired by ingesting cysts after person to person contact or contaminated water

shed by wild mammals, including beavers

prolonged diarrhea, malaise, weight loss, flatulence, cramps, hydrogen sulfide in stool and breath

diagnosed with microscopic exam of stool samples

Trichomoniasis

caused by trichomonas vaginalis, normal inhabitant of vagina and urethra

grown when acidity of vagina is changed

irritation and a profuse, frothy, greenish yellow, foul odor discharge

diagnosed with microscopic identification or DNA probe

Chagas Disease

caused by tryoanosoma cruzi

flagelleted protozoan

reservoir in rodents, opossums, and armadillos

endemic in central and south america

vector is reduviid bug (kissing bug), which defecates trypanosomes into human bite wounds

acute stage of disease: fever and swollen glands

20-30% progress to chronic form which can cause megasophagus and megacolon years later, death due to heart damage

therapy is difficult bc it multiplies intracellularly

Amebae

move by extending pseudopods

Entamoeba Histolyctia

type of amebae

causes amebic dysentery

Acanthamoeba

type of amebae

infects corneas and causes blindness, can infect brain (encephalitis)

Balamuthia

type of amebae

granulomatous amebic encephalitis

Apicomplexa

nonmotile

obligate intracellular parasites

medically important protozoa

apical complex is a specialized structure that facilitates entry of parasite to host cell

has a complex life cycle

ex: malaria: plasmodium with mosquito vector

Cryptosporidium

type of apicomplexa

transmitted via feces

causes waterborne illness

Babesia Microti

type of apicomplexa

transmitted by tick lxodes scapularis

causes fever and anemia in immunocompromised

Toxoplasma Gondii

type of apicomplexa

transmitted by cats

causes fecal infections

food borne and congenital transmission

Definitive Host

organism that harbors the adult, sexually mature form of a parasite

Intermediate Host

organism that harbors the larval or asexual stage of a helminth or protozoan

Reservoir

continual source of infection

Vector

arthropod that carries disease causing organisms from host to another

Plasmodium

type of apicomplexa

causes malaria

sexually reproduces in anopheles mosquito

mosquito injects a sporozoite into the bite, this undergoes schizgony in the liver, merozoites are produced

merozoites infect RBC’s forming ring stage inside the cell

RBC’s rupture and merozoites infect new RBC’s

Ciliates

move by cilia arranged in precise rows

ex: balantidium coli: only human parasite, causes dysentery

Cellular Slime Molds

resemble ameba

ingest fungi and bacteria by phagocytosis

cells aggregate to form stalks and spore caps that differentiate into spores

Plasmodial Slime Molds

mass of protoplasm with multiple nuclei

moves as a giant ameba

Cytoplasmic Streaming

protoplasm moves and changes speed and direction to distribute oxygen and nutrients

Helminths

parasitic worms

two phyla:

1. platyhelminthes: flatworms

2. nematoda: roundworms

Characteristics of Helminths

multicellular eukaryotic animals

specialized to live in hosts

lack digestive systems and have a reduced nervous system

reduced or lacking locomotion

complex reproductive system

Dioecious

life cycle

separate male and female sexes

Monoecious

life cycle

hermaphroditic

male and female reproductive systems in one animal

Trematodes

type of platyhelminths (fluke)

flat leaf shaped

ventral and oral sucker

absorb food through cuticle fluke

schistosoma: blood fluke

paragonimus: lung fluke

Cestodes (Tapeworms)

type of platyhelminths

scolex: head that has suckers for attachment

absorb food through cuticle

proglottids: body segments that contain male and female reproductive organs

Cestodes: Humans as Definitive Hosts

harbor adult sexually reproducing worms

eggs from proglottids are ingested, hatch into larvae, and bore into intestinal wall

produce cysticerci

ex: taenia solium: pork tapeworm

Cestodes: Humans as Intermediate Hosts

harbor larval hosts

eggs are ingested and hatch into intestine

larvae migrate to the liver or lungs and develop hydatid cysts

ex: echinococcus granulosus

Nematodes: Roundworms

cylindrical, has complete digestive systems

dioecious, males contain spicules

have free-living species and parasitic species

eggs and larvae are infective to humans

Ascaris Lumbricoides

type of nematode

infects human intestines

Baylisascaris Procyonis

type of nematode

raccoon roundworm

Trichuris Trichiura

type of nematode

whipworm

Enterobius Vermicularis

type of nematode

pinworm

Strongyloides

type of nematode

reemerging infection

Necator Americanus/ Ancylostoma Duodenale

type of nematode

hookworms, enter the skin and go to intestine

Dirofilaria Immitis

type of nematode

spread by mosquitos, causes heartworm

Arthropods

animals with segmented bodies, hard external skeletons, and jointed legs

have mechanical and biological (multiplies in vector) transmission

ex: Arachnida: eight legs like spiders, mites, ticks

ex: crustacea: four antennae like crabs and crayfish

ex: insecta: six legs like bees, flies, mosquitoes, and lice

Scabies

caused by sarcoptes scabiei mites

burrow in the skin to lay eggs

causes inflammatory skin lesions with intense itching

transmitted via intimate contact

Lyme Disease

caused by borreliella burgdorferi

most common tickborne disease in the US

field mice are common reservoir

nymphal stage of lxodes tick feed on mice and infect humans

tick feed on deer, deer don’t get infected

tick must attach for 2-3 days to infect human

Bedbugs

detect host from exhaled carbon dioxide

suck the hosts blood and depart to lay eggs

almost eradicated in 1900’s by DDT and pesticides

now, some are resistant and can only be killed by chemicals with toxic side effects

Features of Viruses

obligatory intracellular parasites require living host cells to multiply

contain DNA or RNA and a protein coat

multiply within living host cell, using hosts synthesizing machinery

no ribosomes or ATP generating mechanism

Host Range

the spectrum of host cells a virus can infect

most viruses infect only one specific cell type determined by specific host attachment sites and cellular factors

animal cells have receptor on plasma membrane

Bacteriophages

viruses that infect bacteria

phage receptor site may be part of bacterial cell wall or fimbriae or flagella

Viral Structure

virion: complete fully developed viral particle

nucleic acid DNA or RNA can be single or double stranded, linear or circular

has capsid, capsomeres, envelope, and spikes

Capsid

protein coat made of capsomeres (protein subunits)

Envelope

present on some viruses, external to the capsid

composed of lipid, protein, and carbohydrates

partially formed from the plasma membrane of host when the virus buds from the cell

Spikes

found on some enveloped viruses

made of carbohydrates and proteins

may be used for attachment

Nucleic Acid

viral genome is DNA or RNA, never both

viral genome may be single stranded or double stranded

may be linear or circular or segmented

total amount varies from a few thousand to 250,000 nucleotides

Helical Viruses

hollow, cylindrical capsid that is helical

ex: virus that causes rabies and ebola

Polyhedral Viruses

many sided

most are icosahedron (20 triangular facets and 12 corners)

ex: adenoviruses and poliovirus

Enveloped Viruses

most are roughly spherical

Complex Viruses

complicated viruses

ex: bacteriophage

Virus Taxonomy

baltimore classification system: based on viruses nucleic acid and how its mRNA is produced

seven groups referred to as realms

genus name ends in -virus

family named end in -viridae

order named end in -ales

Viral Species

a group of viruses sharing the same genetic information and ecological niche (host)

Growing Bacteriophages in the Lab

grown in bacteria

viruses must be grown in living cells

form plaques, which are clearings on a lawn of bacteria on the surface of agar

each plaque corresponds to a single virus, can be expressed as plaque-forming units (PFU)

Growing Animal Viruses in living Animals

mice, rabbits, guinea pigs

some human viruses cannot be grown in animals, or can be grown but may not cause disease in animals

Growing Animal Viruses in Embryonated Eggs

virus injected into the egg

viral growth is signaled by changes or death of the embryo

used to grow viruses for some vaccines

Primary Cell Lines

tissues are treated with enzymes to separate cells

Cytopathic Effect (CPE)

viruses are detected via visible changes or deterioration of monolayer cells

Cell Cultures - Growing Animal Viruses

may use diploid cell lines

derived from human embryos - can be maintained for 100 generations

often used for cultivation or rabies virus for vaccine development

Continuous Cell Lines - Growing Animal Viruses

derived from transformed (cancerous) cells

can be maintained indefinitely

ex: HeLa cell line

Viral Identification

cytopathic effects observed on cell culture

serological tests like ELISA, virus is detected and identified by reaction with antibodies

nucleic acid tests: PCR

Viral Multiplication

for a virus to multiply it must…

1. it must invade the host cell

2. it must take over hosts metabolic machinery

a single virion can give to several or to thousands of similar viruses in a single host cell

has one step growth curve

Lytic Cycle

phage causes lysis and death of host cell

ex: tequatrovirus (t-even bacterophages) that infect E. coli

Lysogenic Cycle

phage DNA is incorporated in the host DNA

phage conversion

specialized transduction

Lytic Cycle Steps

1. attachment: phage attaches by the tail fibers to the host cell

2. penetration: phage lysozyme opens the cell wall, tail sheath contracts to force the tail core and DNA into cell (similar to hypodermic syringe)

3. biosynthesis: production of phage DNA and proteins, host cell protein synthesis is halted

4. maturation: assembly of phage particles

5. release: phage lysozyme breaks the cell wall

Bacteriophage Lambdavirus

infection with lambda virus may initiate a lytic or lysogenic cycle

Lysogeny

phage remains latent, no lysis of host cell

phage DNA incorporates into host cell DNA

Prophage

inserted phage DNA

when host cell replicated its chromosome, it also replicated prophage DNA