Eukaryotic cells notes

Protein Synthesis: Assembly line

Nucleus, endoplasmic reticulum, and Golgi apparatus:

–   A segment of DNA containing the instructions for producing a protein is copied into RNA, and this RNA transcript is passed out through the nuclear pores directly to the ribosomes on the endoplasmic reticulum

–   Specific proteins on the RER are deposited in the lumen and transported to the Golgi apparatus

–   Proteins in the Golgi apparatus are chemically modified and packaged into vesicles to be used by the cell or secreted out to the cell, or used for growth and repair of cell

–   Some exist in either form – dimorphic – characteristic of some pathogenic fungi.

FUNGAL NUTRITION

•       All are heterotrophic (need an organic nutrient source)

•       Majority are harmless saprobes - living off dead plants and animals

•       Some are parasites - living on the tissues of other organisms

•       Ideal growth temperature 20^o-40^oC (68^oF-104^oF)

•       Extremely widespread distribution in many habitats

FILAMENTOUS (HYPAE)

•       Filamentous fungi: organized into a mass of hyphae called mycelium;cottony, hairy, or velvety texture

–   Vegetative hyphae – digest and absorb nutrients

–   Reproductive hyphae – produce spores (different from endospores) for reproduction

FUNGAL IDENTIFICATION

•       Macroscopic and microscopic observation of:

–    Spore-forming structures and spores

–    Hyphal type

–    Colony texture and pigmentation

–    Physiological characteristics

–    Genetic makeup

•       Isolate on medium and inspected micro & macroscopically

–   Hyphae type, colony texture and pigmentation, physiological and genetic characteristics

ROLES OF FUNGI

•       Adverse impact

–   Mycoses (fungal infections), allergies, toxin production

Fungal infections vary depending on the way the pathogen enters the body—skin, respiratory, gi

Fungi cell walls can give off toxins

•       Allergies,liver cancer (aflatoxin)

–   Destruction of crops and food storages

Beneficial impact

–   Decomposers of dead plants and animals

–   Sources of antibiotics, alcohol, vitamins

–   Used in making foods (yeast!)

FUNGI AND HUMAN DISEASE

•       Nearly 300 species of fungi can cause human disease

•       Three types of fungal disease in humans:

–   Community-acquired infections caused by environmental pathogens

•       Most human infections are accidental with contact with soil , water or dust

–   Hospital-associated infections caused by fungal pathogens in clinical settings

–   Opportunistic infections caused by low-virulence species infecting already-weakened individuals

PROTOZOA

•       - unicellular eukaryotes that lack tissues and share similarities in cell structure, nutrition, life cycle, and biochemistry, vary in shape

all are microscopic and most are motile

•       Most are harmless, free-living in a moist habitat

–   Fresh & salt water, plants,soil and animals

•       Some are animal parasites and can be spread by insect vectors

•       All are heterotrophic (lack chloroplasts for photosynthesis)

–   Feed by engulfing other microbes and organic matter

•       Parasitic species live on fluids from the human host

–   Plasma, digestive juices, or feed on tissue

•       Most have locomotor structures – pseudopods, flagella or cilia

LIFE CYCLE

•       Trophozoite: motile feeding stage requiring ample food and moisture to stay active

•       Cyst:

–   Dormant, resting stage when conditions in the environment become unfavorable

–   Resistant to heat, drying, and chemicals

–   Can be dispersed by air currents

–   Important factor in the spread of disease

•       Either stage can infect an individual

–   Some protozoan groups exist only in the trophozoite phase

–   Many alternate between the trophozoite and cyst stage, depending on the habitat

–   Trichomonas vaginalis, a common STD, does not form cysts and must be transmitted by intimate contact

–   Entamoeba histolytica and Giardia lamblia form cysts and are readily transmitted in contaminated water and foods

IDENTIFICATION of Protozoa

•       Classification is difficult because of diversity.

•       Simple grouping is based on method of motility, reproduction,

and life cycle.

4 groups of medically relevant protozoa:

1.      Mastigophora (flagellated)

2.      Sarcodina (pseudopod bearing)

3.      Ciliophora (ciliated)

4.      Apicomplexa (non-motile)

•       Evaluate blood , sputum, cerebral spinal fluid, feces are vaginal smears

•    Can id with or without stain microscopically

•    May need to culture

LIFE CYCLE AND REPRODUCTION

•       Complete life cycle includes the fertilized egg, larval, and adult stages

•       Adults derive nutrients and reproduce sexually in a host’s body

•       For survival, the worm must complete the life cycle by transmitting an infective egg or larva to another host

•    Intermediate host: larval development occurs

•    Definitive host: adulthood and mating occurs

•    Transport host: intermediate host with no parasitic development by needed for life cycle completion

•    Sources for human infection are contaminated food, soil, and water or infected animals

•    Some restricted to certain geographic regions with higher incidence in tropics

A Helminth Cycle: The Pinworm

•       Enterobius vermicularis:

–   Pinworm or seatworm

–   Common infestation of the large intestine

–   Range from 2 to 12 mm long with a tapered, curved cylindrical shape

•       Life cycle:

–   Microscopic eggs are swallowed: picked up from another infected person or objects they have touched

–   Eggs hatch in the intestine

–   Larvae mature into adults within 1 month

–   Male and female worms mate

–   Female migrates to the anus to deposit eggs

–   Intense itching ensues

–   Scratching spreads the eggs