5: ORGANISM THAT MAKE UP THE MICROBIAL WORLD

Eukaryotes

• algae

• fungi

• lichen

• slime molds

Algae

• produce 50% of oxygen

• no roots, leaves, stems, branches

• grows on wet areas

• absorb light to generate energy

• can be used as medicine

• can also be a source of toxin

Diversity of algae

• microscopic algae:

  • diatoms

  • dinoflagellates

• macroscopic algae:

  • green algae (ulva)

  • golden algae (golden brown algae)

  • brown algae (kelp, sargassum)

  • red algae (porphyra)

Structures and features of microscopic algae

• pellicle

• flagellum

• stigma (eyespot)

• contractile vacuole

• nucleus

• cytoplasm

• chloroplast

Pellicle

flexible, protective outer covering of algae

Flagellum

long whip like structure used for movement of algae

Stigma (eyeshot)

light sensitive organelle that helps detect light in algae

Contractile vacuole

expels excess water to maintain balance in algae

Nucleus

contains genetic material and controls actvities

Cytoplasm

jelly like substance where organelles are suspended

Chloroplast

contains chlorophyll for photosynthesis

Importance of algae

• food source

  • food

  • iodine

  • minerals

• industrial products

  • agar

  • alginic acid

• food industry

  • emulsifier

  • stabilizer

  • gelling agent

• healthcare and manufacturing

  • dental materials

  • paint thickeners

  • cosmetics

  • fabric printing

• primary producers

  • 80% of global photosynthesis

  • base of aquatic food chains

Paralytic shellfish poisoning (PSP)

dinoflagellates (alexandrium) > mussels/clams > human consumption > neurologic symptoms

Red tide

• large blooms may discolor seawater

• avoid harvesting shellfish during outbreaks

Ciguatera

dinoflagellates (gambierdiscus) > herbiverous fish > large reef fish > human consumption > GI + neurologic symptoms

• heat stable toxin

• cooking does not destroy toxin

Fungi

• can ferment wine

• can cause upset stomach, food poisoning, fungal infection

• divided into macroscopic fungi (mushrooms, puffballs, gill fungi) and microscopic fungi (molds, yeast)

• non photosynthetic (lacks chlorophyll and a vascular system)

• cell walls contain chitin

• sterols (ergosterol) are usually present in cell membrane

Macroscopic fungi

• mushrooms

• puffballs

• gill fungi

Microscopic fungi

• molds

• yeast

Puffballs

releases spores in a cloud when mature

Gill fungi

mushrooms with gills (lamellae) on the underside of the cap

Molds

grow as a network of hyphae

Yeast

• primarily unicellulr fungi

• oval or spherical in shape

Yeast (unicellular) and mold (filamentous)

2 primary forms of fungi

Yeast form

• unicellular

• reproduce by asexual budding

Pseudohyphae

buds remain attached in a row, forming a chain of yeast cells

Budding

produces progeny with unequal amounts of cellular content

Mold form

• multicellular, filamentous fungi

• made of long tubelike filaments called hyphae

• hyphase brancg and form an interconnected network called mycelium

Coenocytic (aseptate) hyphae

• lack septa (cross walls)

• continuous multinucleate cytoplasm

Septate hyphae

• have septa (incomplete cross wall with pores)

• most common in medically important fungi

Thermal dimorsphism

• certain pathogenic fungi can exist in 2 different forms depending on temperature:

  • mold/mycelial form (25C or 30C)

  • yeast form (37C)

Fungal habitat and nutrition

• habitat: found almost everywhere

• saprophytic (saprobes): decompse dead organic matter

• parasitic: live in or in living hosts

• nutrition: heterothrophic, absorb organic nutrients

Examples of thermally dimorphic fungi

• histoplasma capsulatum

• blastomyces dermatitidis

• coccidiodes spp

• paracoccidiodes brasiliensis

Ringworm (tinea)

• superficial infection of the skin

  • raused scaly border

  • central clearing

  • dermatophyte hyphae (microscopic)

• can be spread by:

  • direct contact (human to human, animal to human)

  • contaminated objects (towels, clothing, combs, etc)

Fungal reproduction

• vegetative reproduction

• asexual reproduction

• sexual reproduction

Vegetative reproductive

• no spores involved

• hyphal growth > fragmentation

• existing hyphae grow outward > a fragment of myceliym grows into a new fungus

• a piece breaks off and develops into a new colony

Asexual reproduction

• one parent

• mitosis

• rapid multiplication

• produces asexual spores

  • sporangiopores

  • conindiospores (conidia)

• fast reproduction of many genetically identical spores

Sporangiospores

• formed inside a sac (sporangium) on a stalk (sporangosphere)

• released when the sporangium ruptures

Conidiospores (conidia)

• formed externally on specialized hyphae

• not enclosed in a sac

Sexual reproduction

• 2 compatible fungi nuclei

• meiosis

• sexual spores

• genetic variation

• greater survival and adaptation

• fusion of compatibel hyphae or gametes > fusion of nuclei > meiosis occurs > sexual spores formed

• mushroom (fruiting body)

Mushroom (fruiting body)

the reproductive structure that protects and disseminates sexual spores

Function of spores

• genetic variation: increases adaptability

• reproduction: creates new fungi (multiplication)

• survival: resist hear, desiccation and other harsh conditions

• dispersal: spread through air, water, and living things

Fungal pathogens

• 2 types of host response: granulomatus or pyogenic response

• some can be detected by using skin tests for delayed hypersensitivity reaction

• reduced cell mediated immunity predisposes to disseminated disease

Granulomatous

acts as body's defense againstbacteria and foreign materials that are difficult to eliminate particularly intracellular pathogens

Pyogenic response

• pus producing response

• primary defense against extracellular bacteria that do not invade cells

Amanita spp.

amanitin and phalloidin > sever liver necrosis

Aspergillus flavus

Aflatoxin contaminated peanuts and grains > liver cancer (heptocellular carcinoma)

Aspergillus fumigatus

inhaled spores > allergic bronchopulmonary aspergillosis (ABPA) (IgE mediated)

Laboratory diagnosis of fungi

• micrsocopy of KOH preparation

• sabouraud agar

• DNA probes for early infection

• tests for fungal antigens or antibodies to fungal antigens

Potassium hydroxide (KOH)

dissolves human cells, allowing visualization

Sabouraud agar

low pH inhibits the growth of bacteria

Desirable effects of fungi

• decomposers

• for chemotherapy

• biotechnology, bread and wine industry

• protein supplements

• production of cellulase, herbicides

Undesirable effects of fungi

• spoilage of foods and grains

• plant pathogens

• cause of human diseases

  • hypersensitivity reactions

  • toxicosis (mycotoxicosis)

  • mycoses

Lichens

• a unique symbiotic partnership between a fungus, alga (or cyanobacterium), and sometimes a yeast

• used as food in traditional japanese and korean dishes

• produce useful compounds and pigments (litmus) some with antibacterial properties

• often mistaken for moses (moses are plants)

Lichens

• found on rockes, tree trunks, roofs, and concrete

• pioneer organisms - among the first to colonize bare rock or soil

• very slow growing organisms

Fungus

provides structure, protection, and absorbs water and minerals in lichens

Alga (or cyanobacterium)

performs photosynthesis and produces food

Yeast

May be present in the cortex; role not fully understood in lichens

Slime molds

• have both fungal and protozoal characteristics

• found in soil and on rotting logs

• life cycle begins as an ameba like cell and progress into multicellular organism

• moved from kingdom fungi to kingdom protista

• not known to cause human disease

Prokaryotes

• bacteria

• archaea

Bacteria

• prokaryotic organisms with petidoglycan cell walls

• exist everywhere no nucleus membrane

• can fight other bacteria

• some are good for our system

• some cause sickness

Eubacteria

“true" bacteria

bacterial morphology

• shape:

  • cocci

  • bacilli

  • spiral

  • pleomorphic

• arrangement:

  • coccus

  • diplococcus

  • streptococcus

  • tetrad

  • staphylococcus

  • sarcina

Cocci

• “berries"

• ex: Streptococcus pneumoniae,
  Staphylooccus aureus, Neisseria gonorrhoeae

bacilli

• rod shaped

• ex: Escherichia coli, Proteus vulgaris

Spiral

• have one or more twists

• ex: Leptospira
  interrogans, Treponema pallidum

Pleomorphic

• changes shape or size in response to environmental conditions (mycoplasma pneumoniae)

Coccus

single spherical cell

Diplococcus

2 cells, 1 plane of division

Streptococcus

many cells in a chains, 1 plane of division

Tetrad

4 cells in a square, 2 planes of division

Staphylococcus

irregular “grapelike” cluster, many cells in clusters

Sarcina

packet or cube of cells, 3 planes of division

Stepto

• one plane of division

• ex: streptobacillus

Vibrio

• one twist

• ex: vibrio cholerae

Spirillum

• many twists

• ex: spirillum voluntans

Coccobacillus

• thick, short type of bacilli, almost the same as diplococci

• ex: haemophilus influenzae

habitat of bacteria

• soil

• human

• plants

• animal

Binary fission

• reproduction of bacteria

• parent cell > DNA replication > cytokinesis begins > septum formation > 2 daughter cells

Pathogenicity

can cause a wide variety of diseases

Rickettsia

• cell wall: has peptidoglycan (gran negative like)

• gran stain reaction: gram negative

• obligate intracellular: yes

• energy reproduction: use host ATP (energy parasite)

• size: very small (0.3-0.5 um)

• replication site: cytoplasm

• mode of transmission: arthopods (ticks, lice)

• notable diseases: typhus, rocky mountain spotted fever

Chlamydia

• cell wall: no true peptidoglycan (gram negative like)

• gran stain reaction: gram negative

• obligate intracellular: yes

• energy reproduction: use host ATP (energy parasite)

• size: very small (0.3 um)

• replication site: insde host cell inclusion bodies

• mode of transmission: direct contact or secretions (STI)

• notable diseases: trachnoma, chlamydia STI, pneumonia

Mycoplasma

• cell wall: no cell wall

• gran stain reaction: not applicable

• obligate intracellular: no (can liver extracellularly)

• energy reproduction: produces its own ATP

• size: smallest free living organism (0.1-0.3 um)

• replication site: extracellular or intracellular (not obligate)

• mode of transmission: respiratory doplets, close contact

• notable diseases: atypical pneumonia urogenital infections

Rickettsia

replicates via binary fission directly within the host cell's cytoplasm

Chlamydia

undergoes a unique biphasic life cycle transitioning between 2 forms

mycoplasma

replicates via binary fission while attached to the surface of host cells

Elementary body

small dense infectious form. enters the host cell

Reticulate body

larger, metabolically active form. replicates inside host cell

Release

RB convert back to EBs and the host cell bursts releasing new infectious EBs

Archaea

• archae - ancient bacteria

• previously referred to as archaebacteria and archaeobacteria

• nonpathogenic

• morphologically active

• importance:

  • methanogens

  • recycle carbon, nitrogen, and sulfur through various habitats in the ecosystem

Methanogens

fuel production from sewage

Grand prismatic spring

• yellowstone national park, myoming, usa

• the bright colores come from tiny microbes inluding archaea that live in hot water

Acellular infectious agents

• viroids

• prions

• viruses

Viroids

• obligate intracellular parasites of plants

• accelular

• naked RNA

• no human disease known

Prions

• infectious proteins that can cause disease even though they do not contain DNA or RNA

• abnormal versions of normal proteins

• overtime,these abnormal proteins accumulate in the brain, leading to severe and fatal neurological diseases

Virus

• smallest infectious agents

• contain only either DNA or RNA as the genome

• inert in the extracellular environment

• replicate only in living cells

Bacteriophage

virus that infect bacteria

Viral structures

• caspid/protein coat

• nucleocaspid

• protein spikes

• virion

• membrane envelope

Caspid/protein coat

surround the center of the virion

Nucleocaspid

combination of the nucleic acid and the caspid

Protein spikes

helps the virus attach to the host cell