Chapter 12 Microbiology

Structure of Prokaryotic cells

tiny, no nucleus (DNA floats around), no membrane-bound organelles, simple cells, peptidoglycan cell wall, asexual only (binary fission = split in 2), DNA = one circular loop

Examples of Prokaryotic cells

bacteria and algae

Structure of Eukaryotic cells

bigger, has nucleus (DNA inside a “bubble”), has organelles (mitochondria, etc.), complex cell, cell wall made of chitin, cellulose, or none, asexual (mitosis) or sexual (meiosis), linear DNA

Examples of Eukaryotic cells

Fungi, algae, protozoa, plants, animals

What caused the potato famine?

• water mold (fungus) not photosynthetic and lack chloroplasts

  • identified through genetic makeup

Fungi

heterotrophic organisms, chitin in cell wall, decomposers (eat dead stuff), some cause infections

Protozoa

unicellular heterotrophs, “animal-like”, some parasites

Algae

simple autotrophs (photosynthesis), make oxygen

Worms

parasites, can live inside humans

Arthropods (insects)

spread diseases (vectors)

mycology

study of fungi

What does fungi form?

yeast, mold, mushrooms

Yeast

single-celled fungi (bread)

Mold

multicellular filamentous fungi (fuzzy stuff)

Mushroom

reproductive structures of certain fungi (big and visible)

Heterotrophs

can’t make their own food

Saprotrophs (Fungi)

use nutrients from dead or decaying organic matter

Functions of Fungi

1. they decompose (break down dead things) to recycle nutrients

2. make medicine (penicillin)

3. make food (bread, beer)

What infections does fungi produce in humans?

1. athlete’s foot

2. yeast infections

How can some fungi be parasitic?

by absorbing nutrients from living tissue

How is fungus and algae associated with each other?

• algae provides food

• fungus provides support

• ex: lichens with algae

How do Fungi look?

• they have hyphae (long threads) that make a fuzzy ball called mycelium

• can’t move on their own, but grow toward food

• can live in salty, sugary, or cold places

How do fungi reproduce?

• Asexual (no partner needed): they make spores (tiny baby fungi) that float around in air or water 

• Sexual (two partners): hyphae fuse, mix DNA, and make new spores 

Describe the membrane of the fungi

have ergosterol

• animal cell membranes contain cholesterol

• target for many anti fungal medications

Why is cholesterol important?

for cell support

• wrong cholesterol = cell membrane can’t function

• too much cholesterol = interferes with circulatory system

What are the 3 big fungi groups?

1. ascomycetes

2. basidiomycetes 

3. mucoromycota

Ascomycetes (Sac Fungi)

• sexual reproduction 

• includes penicillium (makes penicillin)

• includes most of the medically important fungi

• morels and truffles

• plant pathogens 

Basidiomycetes (Club Fungi)

• sexual reproduction

• like mushrooms

Mucoromycota

• sexual reproduction

• produces zygospores

• black bread mold

Mycosis

fungal infection

Problems caused by fungi?

• cause serious disease in weakened immune systems

• can infect skin and lungs

• some make toxins

• some cause allergies

Advantages of fungi?

• antimicrobial medicines

• produce vaccines and insulin

• useful for studying eukaryotic cells

Systemic fungi

causes disease even to healthy people

Lichens

association of fungus and a photosynthesizer

Mycorrhizae

association of fungus with plant roots

• help plants get water

Why are Protozoa good to study?

because they are single celled so they’re less complex

Characteristics of Protozoa

• no cell walls

• many can move (with cilia, flagella, or pseudopods)

• can live in water, soil, or inside animals

Two stages of Protozoa

1. trophozoite (growing and eating)

2. cyst (survive harsh environmental conditions

What happens in the trophozoite stage?

1. feed and multiply in intestines

2. develop into cysts as they exit in feces

What happens in the cyst stage?

when ingested by a host, they survive passage through the stomach and excyst to release trophozoite

What are the protozoa types?

1. amoebas

2. apicomplexans

3. kinetoplastids

4. flagellates

5. slime molds

Ameobas

• some harmless, some dangerous

• reproduce using asexual binary fission

• cells lack mitochondria

• rely on fermentation (anaerobic respiration)

Intestinal Ameobas 

• entamoeba histolytica - affects digestive system (can cause mild diarrhea to severe dysentery)

• naegleria fowleri - live in waters, if it enters sinuses it can destroy brain tissue causing death in a day or so (can happen when swimming)

Apicomplexans

• alternate between sexual and asexual reproduction in different hosts 

• parasites like plasmodium causes malaria

Definitive host

when sexual reproduction occurs (mosquitoes)

Intermediate host

asexual reproduction (humans)

How do Plasmodium parasites undergo multiple rounds of asexual replication and how do it affect us?

1. they repeatedly infect and lyse red blood cells

2. red blood cells transport oxygen, when infected they reduce respiration = less energy = tired (symptom of malaria) 

Kinetoplastids

• a large mass of mitochondrial DNA

• useful target for medications

Flagellates

• colonize the lumen (organs) of the intestinal tract or genital tract, using flagella for movement

• reproduce asexually using binary fission

• causes diarrhea

• lacks mitochondria but forms a hydrogenosome

• produces ATP while generating H2

Slime molds

• composed of ameboid cells

• live on soil, leaf litter, decaying vegetation

• important link in the food chain (ingest microorganisms and serve as as food for larger predators)

Characteristics of Algae

• make their own food

• avascular 

• Some reproduce sexually and some asexually

• alternate between haploid generation (one set of chromosomes) and a diploid generation (2 sets)

Photosynthesis in Algae

• occurs within chloroplasts 

• symbiotic - 2 organisms benefit from each other

Primary endosymbiosis

a non-photosynthetic eukaryotic cell engulfed a cyanobacterium

Secondary endosymbiosis

a non-photosynthetic eukaryotic cell engulfed a photosynthetic eukaryotic cell, which came through primary endosymbiosis

What’s the importance of knowing the number of endosymbiotic events?

it determines the number of membranes surrounding the organelles

• 2 membranes: surround chloroplasts that originated through primary endosymbiosis

• 3 membranes: surround those that originated through secondary endosymbiosis

Structures of Alage

• can be unicellular (tiny)

• can be multicellular (seaweed) which have holdfasts that allow them to adhere to solid surfaces

• different colors depend on pigments (green - most common, red, brown)

What are the habitats of algae?

• found in fresh and saltwater and in moist soil

• aquatic algae are major producers of O2 and users of CO2

• form the base of aquatic food chains

Types of Algae

1. diatoms

2. brown algae

3. green algae

4. red algae

Diatoms

• single-celled organisms 

• found in salt and fresh water and in terrestrial environments

• have glassy shells

• golden brown color, due to pigment fucoxanthin

• when they die in the ocean, they sink to the bottom releasing natural gas

Brown algae

• multicellular algae that grow in cold salt water

• kelps (form big “underwater trees'“) provide food for other marine organisms

• brownish color

Green algae

• mostly single-celled, but some are multicellular

• grow in fresh and saltwater, and on rocks, trees, and other terrestrial surfaces

• closest to plants

• chlorophyll a (pigment found in green plants and cyanobacteria) and b

Red algae

• single-celled or multicellular 

• grow in warm salt water and tropical coastal areas

• live deep underwater

• reddish color due to accessory pigments that absorb wavelengths of light that reach great depths

• used in sushi

Worms (Helminths)

• type of animals

• looking at their eggs helps identify pathogens

• enter the body through food, feet, bug bites, or water

• some invade host tissue, rob host of nutrients 

Types of Worms

1. roundworms

2. tapeworms

3. flukes

Roundworm

• cylindrical, round body covered by a tough, flexible cuticle

• ascaris lumbricoides causes ascariasis, most common roundworm disease

Tapeworm

• long, flat body that absorbs your nutrients

• head end attaches to intestines of host

• segments (proglottids) contain male, female structures

• proglottids contain eggs eliminated in feces

• humans can get larvae in undercooked meat

Flukes (Trematodes)

• flat leaf shape with two suckers to attach or move along a surface

• mouth but no anus

• complex life cycle with at least two hosts

Schistosomiasis

• releases larval form called cercaria

• Cercaria burrow through human skin and mature in blood vessels

• male and female worms mate and female lay eggs

• causes inflammation that can rupture vessel and release eggs into intestines or urinary bladder

• eggs that are not released continue inflammatory response snd damage tissues

Arthropods

• insects and arachnids

• vectors that can carry and spread diseases (like malaria through mosquito bites)

• killing or controlling the bugs helps stop diseases